Adding upstream version 2.5.0.upstream/2.5.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

31 files changed, 5104 insertions, 0 deletions

diff --git a/src/ssh_audit/__init__.py b/src/ssh_audit/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/src/ssh_audit/__init__.py
diff --git a/src/ssh_audit/__main__.py b/src/ssh_audit/__main__.py
new file mode 100644
index 0000000..9ae64fa
--- /dev/null
+++ b/src/ssh_audit/__main__.py
@@ -0,0 +1,16 @@
+import sys
+import traceback
+
+from ssh_audit.ssh_audit import main
+from ssh_audit import exitcodes
+
+
+exit_code = exitcodes.GOOD
+
+try:
+    exit_code = main()
+except Exception:
+    exit_code = exitcodes.UNKNOWN_ERROR
+    print(traceback.format_exc())
+
+sys.exit(exit_code)
diff --git a/src/ssh_audit/algorithm.py b/src/ssh_audit/algorithm.py
new file mode 100644
index 0000000..e213264
--- /dev/null
+++ b/src/ssh_audit/algorithm.py
@@ -0,0 +1,61 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+# pylint: disable=unused-import
+from typing import Dict, List, Set, Sequence, Tuple, Iterable  # noqa: F401
+from typing import Callable, Optional, Union, Any  # noqa: F401
+
+from ssh_audit.product import Product
+
+
+class Algorithm:
+
+    @staticmethod
+    def get_ssh_version(version_desc: str) -> Tuple[str, str, bool]:
+        is_client = version_desc.endswith('C')
+        if is_client:
+            version_desc = version_desc[:-1]
+        if version_desc.startswith('d'):
+            return Product.DropbearSSH, version_desc[1:], is_client
+        elif version_desc.startswith('l1'):
+            return Product.LibSSH, version_desc[2:], is_client
+        else:
+            return Product.OpenSSH, version_desc, is_client
+
+    @classmethod
+    def get_since_text(cls, versions: List[Optional[str]]) -> Optional[str]:
+        tv = []
+        if len(versions) == 0 or versions[0] is None:
+            return None
+        for v in versions[0].split(','):
+            ssh_prod, ssh_ver, is_cli = cls.get_ssh_version(v)
+            if not ssh_ver:
+                continue
+            if ssh_prod in [Product.LibSSH]:
+                continue
+            if is_cli:
+                ssh_ver = '{} (client only)'.format(ssh_ver)
+            tv.append('{} {}'.format(ssh_prod, ssh_ver))
+        if len(tv) == 0:
+            return None
+        return 'available since ' + ', '.join(tv).rstrip(', ')
diff --git a/src/ssh_audit/algorithms.py b/src/ssh_audit/algorithms.py
new file mode 100644
index 0000000..7c9a850
--- /dev/null
+++ b/src/ssh_audit/algorithms.py
@@ -0,0 +1,223 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017-2021 Joe Testa (jtesta@positronsecurity.com)
+   Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+# pylint: disable=unused-import
+from typing import Dict, List, Set, Sequence, Tuple, Iterable  # noqa: F401
+from typing import Callable, Optional, Union, Any  # noqa: F401
+
+from ssh_audit.algorithm import Algorithm
+from ssh_audit.product import Product
+from ssh_audit.software import Software
+from ssh_audit.ssh1_kexdb import SSH1_KexDB
+from ssh_audit.ssh1_publickeymessage import SSH1_PublicKeyMessage
+from ssh_audit.ssh2_kex import SSH2_Kex
+from ssh_audit.ssh2_kexdb import SSH2_KexDB
+from ssh_audit.timeframe import Timeframe
+from ssh_audit.utils import Utils
+
+
+class Algorithms:
+    def __init__(self, pkm: Optional[SSH1_PublicKeyMessage], kex: Optional[SSH2_Kex]) -> None:
+        self.__ssh1kex = pkm
+        self.__ssh2kex = kex
+
+    @property
+    def ssh1kex(self) -> Optional[SSH1_PublicKeyMessage]:
+        return self.__ssh1kex
+
+    @property
+    def ssh2kex(self) -> Optional[SSH2_Kex]:
+        return self.__ssh2kex
+
+    @property
+    def ssh1(self) -> Optional['Algorithms.Item']:
+        if self.ssh1kex is None:
+            return None
+        item = Algorithms.Item(1, SSH1_KexDB.ALGORITHMS)
+        item.add('key', ['ssh-rsa1'])
+        item.add('enc', self.ssh1kex.supported_ciphers)
+        item.add('aut', self.ssh1kex.supported_authentications)
+        return item
+
+    @property
+    def ssh2(self) -> Optional['Algorithms.Item']:
+        if self.ssh2kex is None:
+            return None
+        item = Algorithms.Item(2, SSH2_KexDB.ALGORITHMS)
+        item.add('kex', self.ssh2kex.kex_algorithms)
+        item.add('key', self.ssh2kex.key_algorithms)
+        item.add('enc', self.ssh2kex.server.encryption)
+        item.add('mac', self.ssh2kex.server.mac)
+        return item
+
+    @property
+    def values(self) -> Iterable['Algorithms.Item']:
+        for item in [self.ssh1, self.ssh2]:
+            if item is not None:
+                yield item
+
+    @property
+    def maxlen(self) -> int:
+        def _ml(items: Sequence[str]) -> int:
+            return max(len(i) for i in items)
+        maxlen = 0
+        if self.ssh1kex is not None:
+            maxlen = max(_ml(self.ssh1kex.supported_ciphers),
+                         _ml(self.ssh1kex.supported_authentications),
+                         maxlen)
+        if self.ssh2kex is not None:
+            maxlen = max(_ml(self.ssh2kex.kex_algorithms),
+                         _ml(self.ssh2kex.key_algorithms),
+                         _ml(self.ssh2kex.server.encryption),
+                         _ml(self.ssh2kex.server.mac),
+                         maxlen)
+        return maxlen
+
+    def get_ssh_timeframe(self, for_server: Optional[bool] = None) -> 'Timeframe':
+        timeframe = Timeframe()
+        for alg_pair in self.values:
+            alg_db = alg_pair.db
+            for alg_type, alg_list in alg_pair.items():
+                for alg_name in alg_list:
+                    alg_name_native = Utils.to_text(alg_name)
+                    alg_desc = alg_db[alg_type].get(alg_name_native)
+                    if alg_desc is None:
+                        continue
+                    versions = alg_desc[0]
+                    timeframe.update(versions, for_server)
+        return timeframe
+
+    def get_recommendations(self, software: Optional['Software'], for_server: bool = True) -> Tuple[Optional['Software'], Dict[int, Dict[str, Dict[str, Dict[str, int]]]]]:
+        # pylint: disable=too-many-locals,too-many-statements
+        vproducts = [Product.OpenSSH,
+                     Product.DropbearSSH,
+                     Product.LibSSH,
+                     Product.TinySSH]
+        # Set to True if server is not one of vproducts, above.
+        unknown_software = False
+        if software is not None:
+            if software.product not in vproducts:
+                unknown_software = True
+
+        # The code below is commented out because it would try to guess what the server is,
+        # usually resulting in wild & incorrect recommendations.
+        # if software is None:
+        #     ssh_timeframe = self.get_ssh_timeframe(for_server)
+        #     for product in vproducts:
+        #         if product not in ssh_timeframe:
+        #             continue
+        #         version = ssh_timeframe.get_from(product, for_server)
+        #         if version is not None:
+        #             software = SSH.Software(None, product, version, None, None)
+        #             break
+        rec: Dict[int, Dict[str, Dict[str, Dict[str, int]]]] = {}
+        if software is None:
+            unknown_software = True
+        for alg_pair in self.values:
+            sshv, alg_db = alg_pair.sshv, alg_pair.db
+            rec[sshv] = {}
+            for alg_type, alg_list in alg_pair.items():
+                if alg_type == 'aut':
+                    continue
+                rec[sshv][alg_type] = {'add': {}, 'del': {}, 'chg': {}}
+                for n, alg_desc in alg_db[alg_type].items():
+                    versions = alg_desc[0]
+                    empty_version = False
+                    if len(versions) == 0 or versions[0] is None:
+                        empty_version = True
+                    else:
+                        matches = False
+                        if unknown_software:
+                            matches = True
+                        for v in versions[0].split(','):
+                            ssh_prefix, ssh_version, is_cli = Algorithm.get_ssh_version(v)
+                            if not ssh_version:
+                                continue
+                            if (software is not None) and (ssh_prefix != software.product):
+                                continue
+                            if is_cli and for_server:
+                                continue
+                            if (software is not None) and (software.compare_version(ssh_version) < 0):
+                                continue
+                            matches = True
+                            break
+                        if not matches:
+                            continue
+                    adl, faults = len(alg_desc), 0
+                    for i in range(1, 3):
+                        if not adl > i:
+                            continue
+                        fc = len(alg_desc[i])
+                        if fc > 0:
+                            faults += pow(10, 2 - i) * fc
+                    if n not in alg_list:
+                        # Don't recommend certificate or token types; these will only appear in the server's list if they are fully configured & functional on the server.
+                        if faults > 0 or (alg_type == 'key' and (('-cert-' in n) or (n.startswith('sk-')))) or empty_version:
+                            continue
+                        rec[sshv][alg_type]['add'][n] = 0
+                    else:
+                        if faults == 0:
+                            continue
+                        if n in ['diffie-hellman-group-exchange-sha256', 'rsa-sha2-256', 'rsa-sha2-512', 'rsa-sha2-256-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com']:
+                            rec[sshv][alg_type]['chg'][n] = faults
+                        else:
+                            rec[sshv][alg_type]['del'][n] = faults
+                # If we are working with unknown software, drop all add recommendations, because we don't know if they're valid.
+                if unknown_software:
+                    rec[sshv][alg_type]['add'] = {}
+                add_count = len(rec[sshv][alg_type]['add'])
+                del_count = len(rec[sshv][alg_type]['del'])
+                chg_count = len(rec[sshv][alg_type]['chg'])
+
+                if add_count == 0:
+                    del rec[sshv][alg_type]['add']
+                if del_count == 0:
+                    del rec[sshv][alg_type]['del']
+                if chg_count == 0:
+                    del rec[sshv][alg_type]['chg']
+                if len(rec[sshv][alg_type]) == 0:
+                    del rec[sshv][alg_type]
+            if len(rec[sshv]) == 0:
+                del rec[sshv]
+        return software, rec
+
+    class Item:
+        def __init__(self, sshv: int, db: Dict[str, Dict[str, List[List[Optional[str]]]]]) -> None:
+            self.__sshv = sshv
+            self.__db = db
+            self.__storage: Dict[str, List[str]] = {}
+
+        @property
+        def sshv(self) -> int:
+            return self.__sshv
+
+        @property
+        def db(self) -> Dict[str, Dict[str, List[List[Optional[str]]]]]:
+            return self.__db
+
+        def add(self, key: str, value: List[str]) -> None:
+            self.__storage[key] = value
+
+        def items(self) -> Iterable[Tuple[str, List[str]]]:
+            return self.__storage.items()
diff --git a/src/ssh_audit/auditconf.py b/src/ssh_audit/auditconf.py
new file mode 100644
index 0000000..1d51240
--- /dev/null
+++ b/src/ssh_audit/auditconf.py
@@ -0,0 +1,98 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017-2021 Joe Testa (jtesta@positronsecurity.com)
+   Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+# pylint: disable=unused-import
+from typing import Dict, List, Set, Sequence, Tuple, Iterable  # noqa: F401
+from typing import Callable, Optional, Union, Any  # noqa: F401
+
+from ssh_audit.policy import Policy
+from ssh_audit.utils import Utils
+
+
+class AuditConf:
+    # pylint: disable=too-many-instance-attributes
+    def __init__(self, host: str = '', port: int = 22) -> None:
+        self.host = host
+        self.port = port
+        self.ssh1 = True
+        self.ssh2 = True
+        self.batch = False
+        self.client_audit = False
+        self.colors = True
+        self.json = False
+        self.json_print_indent = False
+        self.verbose = False
+        self.level = 'info'
+        self.ip_version_preference: List[int] = []  # Holds only 5 possible values: [] (no preference), [4] (use IPv4 only), [6] (use IPv6 only), [46] (use both IPv4 and IPv6, but prioritize v4), and [64] (use both IPv4 and IPv6, but prioritize v6).
+        self.ipv4 = False
+        self.ipv6 = False
+        self.make_policy = False  # When True, creates a policy file from an audit scan.
+        self.policy_file: Optional[str] = None   # File system path to a policy
+        self.policy: Optional[Policy] = None  # Policy object
+        self.timeout = 5.0
+        self.timeout_set = False  # Set to True when the user explicitly sets it.
+        self.target_file: Optional[str] = None
+        self.target_list: List[str] = []
+        self.threads = 32
+        self.list_policies = False
+        self.lookup = ''
+        self.manual = False
+        self.debug = False
+
+    def __setattr__(self, name: str, value: Union[str, int, float, bool, Sequence[int]]) -> None:
+        valid = False
+        if name in ['batch', 'client_audit', 'colors', 'json', 'json_print_indent', 'list_policies', 'manual', 'make_policy', 'ssh1', 'ssh2', 'timeout_set', 'verbose', 'debug']:
+            valid, value = True, bool(value)
+        elif name in ['ipv4', 'ipv6']:
+            valid, value = True, bool(value)
+            if len(self.ip_version_preference) == 2:  # Being called more than twice is not valid.
+                valid = False
+            elif value:
+                self.ip_version_preference.append(4 if name == 'ipv4' else 6)
+        elif name == 'port':
+            valid, port = True, Utils.parse_int(value)
+            if port < 1 or port > 65535:
+                raise ValueError('invalid port: {}'.format(value))
+            value = port
+        elif name in ['level']:
+            if value not in ('info', 'warn', 'fail'):
+                raise ValueError('invalid level: {}'.format(value))
+            valid = True
+        elif name == 'host':
+            valid = True
+        elif name == 'timeout':
+            value = Utils.parse_float(value)
+            if value == -1.0:
+                raise ValueError('invalid timeout: {}'.format(value))
+            valid = True
+        elif name in ['ip_version_preference', 'lookup', 'policy_file', 'policy', 'target_file', 'target_list']:
+            valid = True
+        elif name == "threads":
+            valid, num_threads = True, Utils.parse_int(value)
+            if num_threads < 1:
+                raise ValueError('invalid number of threads: {}'.format(value))
+            value = num_threads
+
+        if valid:
+            object.__setattr__(self, name, value)
diff --git a/src/ssh_audit/banner.py b/src/ssh_audit/banner.py
new file mode 100644
index 0000000..da6ee17
--- /dev/null
+++ b/src/ssh_audit/banner.py
@@ -0,0 +1,92 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+import re
+
+# pylint: disable=unused-import
+from typing import Dict, List, Set, Sequence, Tuple, Iterable  # noqa: F401
+from typing import Callable, Optional, Union, Any  # noqa: F401
+
+from ssh_audit.utils import Utils
+
+
+class Banner:
+    _RXP, _RXR = r'SSH-\d\.\s*?\d+', r'(-\s*([^\s]*)(?:\s+(.*))?)?'
+    RX_PROTOCOL = re.compile(re.sub(r'\\d(\+?)', r'(\\d\g<1>)', _RXP))
+    RX_BANNER = re.compile(r'^({0}(?:(?:-{0})*)){1}$'.format(_RXP, _RXR))
+
+    def __init__(self, protocol: Tuple[int, int], software: Optional[str], comments: Optional[str], valid_ascii: bool) -> None:
+        self.__protocol = protocol
+        self.__software = software
+        self.__comments = comments
+        self.__valid_ascii = valid_ascii
+
+    @property
+    def protocol(self) -> Tuple[int, int]:
+        return self.__protocol
+
+    @property
+    def software(self) -> Optional[str]:
+        return self.__software
+
+    @property
+    def comments(self) -> Optional[str]:
+        return self.__comments
+
+    @property
+    def valid_ascii(self) -> bool:
+        return self.__valid_ascii
+
+    def __str__(self) -> str:
+        r = 'SSH-{}.{}'.format(self.protocol[0], self.protocol[1])
+        if self.software is not None:
+            r += '-{}'.format(self.software)
+        if bool(self.comments):
+            r += ' {}'.format(self.comments)
+        return r
+
+    def __repr__(self) -> str:
+        p = '{}.{}'.format(self.protocol[0], self.protocol[1])
+        r = 'protocol={}'.format(p)
+        if self.software is not None:
+            r += ', software={}'.format(self.software)
+        if bool(self.comments):
+            r += ', comments={}'.format(self.comments)
+        return '<{}({})>'.format(self.__class__.__name__, r)
+
+    @classmethod
+    def parse(cls, banner: str) -> Optional['Banner']:
+        valid_ascii = Utils.is_print_ascii(banner)
+        ascii_banner = Utils.to_print_ascii(banner)
+        mx = cls.RX_BANNER.match(ascii_banner)
+        if mx is None:
+            return None
+        protocol = min(re.findall(cls.RX_PROTOCOL, mx.group(1)))
+        protocol = (int(protocol[0]), int(protocol[1]))
+        software = (mx.group(3) or '').strip() or None
+        if software is None and (mx.group(2) or '').startswith('-'):
+            software = ''
+        comments = (mx.group(4) or '').strip() or None
+        if comments is not None:
+            comments = re.sub(r'\s+', ' ', comments)
+        return cls(protocol, software, comments, valid_ascii)
diff --git a/src/ssh_audit/exitcodes.py b/src/ssh_audit/exitcodes.py
new file mode 100644
index 0000000..5392f1d
--- /dev/null
+++ b/src/ssh_audit/exitcodes.py
@@ -0,0 +1,6 @@
+# The program return values corresponding to failure(s) encountered, warning(s) encountered, connection errors, and no problems found, respectively.
+FAILURE = 3
+WARNING = 2
+CONNECTION_ERROR = 1
+GOOD = 0
+UNKNOWN_ERROR = -1
diff --git a/src/ssh_audit/fingerprint.py b/src/ssh_audit/fingerprint.py
new file mode 100644
index 0000000..a9d2caf
--- /dev/null
+++ b/src/ssh_audit/fingerprint.py
@@ -0,0 +1,43 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017-2021 Joe Testa (jtesta@positronsecurity.com)
+   Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+import base64
+import hashlib
+
+
+class Fingerprint:
+    def __init__(self, fpd: bytes) -> None:
+        self.__fpd = fpd
+
+    @property
+    def md5(self) -> str:
+        h = hashlib.md5(self.__fpd).hexdigest()
+        r = ':'.join(h[i:i + 2] for i in range(0, len(h), 2))
+        return 'MD5:{}'.format(r)
+
+    @property
+    def sha256(self) -> str:
+        h = base64.b64encode(hashlib.sha256(self.__fpd).digest())
+        r = h.decode('ascii').rstrip('=')
+        return 'SHA256:{}'.format(r)
diff --git a/src/ssh_audit/gextest.py b/src/ssh_audit/gextest.py
new file mode 100644
index 0000000..f82a856
--- /dev/null
+++ b/src/ssh_audit/gextest.py
@@ -0,0 +1,162 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017-2021 Joe Testa (jtesta@positronsecurity.com)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+
+# pylint: disable=unused-import
+from typing import Dict, List, Set, Sequence, Tuple, Iterable  # noqa: F401
+from typing import Callable, Optional, Union, Any  # noqa: F401
+
+import traceback
+
+from ssh_audit.kexdh import KexGroupExchange_SHA1, KexGroupExchange_SHA256
+from ssh_audit.ssh2_kexdb import SSH2_KexDB
+from ssh_audit.ssh2_kex import SSH2_Kex
+from ssh_audit.ssh_socket import SSH_Socket
+from ssh_audit.outputbuffer import OutputBuffer
+
+
+# Performs DH group exchanges to find what moduli are supported, and checks
+# their size.
+class GEXTest:
+
+    # Creates a new connection to the server.  Returns True on success, or False.
+    @staticmethod
+    def reconnect(out: 'OutputBuffer', s: 'SSH_Socket', kex: 'SSH2_Kex', gex_alg: str) -> bool:
+        if s.is_connected():
+            return True
+
+        err = s.connect()
+        if err is not None:
+            out.v(err, write_now=True)
+            return False
+
+        _, _, err = s.get_banner()
+        if err is not None:
+            out.v(err, write_now=True)
+            s.close()
+            return False
+
+        # Send our KEX using the specified group-exchange and most of the
+        # server's own values.
+        s.send_kexinit(key_exchanges=[gex_alg], hostkeys=kex.key_algorithms, ciphers=kex.server.encryption, macs=kex.server.mac, compressions=kex.server.compression, languages=kex.server.languages)
+
+        try:
+            # Parse the server's KEX.
+            _, payload = s.read_packet(2)
+            SSH2_Kex.parse(payload)
+        except Exception:
+            out.v("Failed to parse server's kex.  Stack trace:\n%s" % str(traceback.format_exc()), write_now=True)
+            return False
+
+        return True
+
+    # Runs the DH moduli test against the specified target.
+    @staticmethod
+    def run(out: 'OutputBuffer', s: 'SSH_Socket', kex: 'SSH2_Kex') -> None:
+        GEX_ALGS = {
+            'diffie-hellman-group-exchange-sha1': KexGroupExchange_SHA1,
+            'diffie-hellman-group-exchange-sha256': KexGroupExchange_SHA256,
+        }
+
+        # The previous RSA tests put the server in a state we can't
+        # test.  So we need a new connection to start with a clean
+        # slate.
+        if s.is_connected():
+            s.close()
+
+        # Check if the server supports any of the group-exchange
+        # algorithms.  If so, test each one.
+        for gex_alg, kex_group_class in GEX_ALGS.items():
+            if gex_alg in kex.kex_algorithms:
+                out.d('Preparing to perform DH group exchange using ' + gex_alg + '...', write_now=True)
+
+                if GEXTest.reconnect(out, s, kex, gex_alg) is False:
+                    break
+
+                kex_group = kex_group_class()
+                smallest_modulus = -1
+
+                # First try a range of weak sizes.
+                try:
+                    kex_group.send_init_gex(s, 512, 1024, 1536)
+                    kex_group.recv_reply(s, False)
+
+                    # Its been observed that servers will return a group
+                    # larger than the requested max.  So just because we
+                    # got here, doesn't mean the server is vulnerable...
+                    smallest_modulus = kex_group.get_dh_modulus_size()
+
+                except Exception:
+                    pass
+                finally:
+                    s.close()
+
+                # Try an array of specific modulus sizes... one at a time.
+                reconnect_failed = False
+                for bits in [512, 768, 1024, 1536, 2048, 3072, 4096]:
+
+                    # If we found one modulus size already, but we're about
+                    # to test a larger one, don't bother.
+                    if bits >= smallest_modulus > 0:
+                        break
+
+                    out.d('Preparing to perform DH group exchange using ' + gex_alg + ' with modulus size ' + str(bits) + '...', write_now=True)
+
+                    if GEXTest.reconnect(out, s, kex, gex_alg) is False:
+                        reconnect_failed = True
+                        break
+
+                    try:
+                        kex_group.send_init_gex(s, bits, bits, bits)
+                        kex_group.recv_reply(s, False)
+                        smallest_modulus = kex_group.get_dh_modulus_size()
+                    except Exception:
+                        # import traceback
+                        # print(traceback.format_exc())
+                        pass
+                    finally:
+                        # The server is in a state that is not re-testable,
+                        # so there's nothing else to do with this open
+                        # connection.
+                        s.close()
+
+                if smallest_modulus > 0:
+                    kex.set_dh_modulus_size(gex_alg, smallest_modulus)
+
+                    # We flag moduli smaller than 2048 as a failure.
+                    if smallest_modulus < 2048:
+                        text = 'using small %d-bit modulus' % smallest_modulus
+                        lst = SSH2_KexDB.ALGORITHMS['kex'][gex_alg]
+                        # For 'diffie-hellman-group-exchange-sha256', add
+                        # a failure reason.
+                        if len(lst) == 1:
+                            lst.append([text])
+                        # For 'diffie-hellman-group-exchange-sha1', delete
+                        # the existing failure reason (which is vague), and
+                        # insert our own.
+                        else:
+                            del lst[1]
+                            lst.insert(1, [text])
+
+                if reconnect_failed:
+                    break
diff --git a/src/ssh_audit/globals.py b/src/ssh_audit/globals.py
new file mode 100644
index 0000000..c15359d
--- /dev/null
+++ b/src/ssh_audit/globals.py
@@ -0,0 +1,27 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017-2021 Joe Testa (jtesta@positronsecurity.com)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+VERSION = 'v2.5.0'
+SSH_HEADER = 'SSH-{0}-OpenSSH_8.2'  # SSH software to impersonate
+GITHUB_ISSUES_URL = 'https://github.com/jtesta/ssh-audit/issues'  # The URL to the Github issues tracker.
+WINDOWS_MAN_PAGE = ''
diff --git a/src/ssh_audit/hostkeytest.py b/src/ssh_audit/hostkeytest.py
new file mode 100644
index 0000000..6f87ac5
--- /dev/null
+++ b/src/ssh_audit/hostkeytest.py
@@ -0,0 +1,188 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017-2021 Joe Testa (jtesta@positronsecurity.com)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+
+# pylint: disable=unused-import
+from typing import Dict, List, Set, Sequence, Tuple, Iterable  # noqa: F401
+from typing import Callable, Optional, Union, Any  # noqa: F401
+
+import traceback
+
+from ssh_audit.kexdh import KexDH, KexGroup1, KexGroup14_SHA1, KexGroup14_SHA256, KexCurve25519_SHA256, KexGroup16_SHA512, KexGroup18_SHA512, KexGroupExchange_SHA1, KexGroupExchange_SHA256, KexNISTP256, KexNISTP384, KexNISTP521
+from ssh_audit.ssh2_kex import SSH2_Kex
+from ssh_audit.ssh2_kexdb import SSH2_KexDB
+from ssh_audit.ssh_socket import SSH_Socket
+from ssh_audit.outputbuffer import OutputBuffer
+
+
+# Obtains host keys, checks their size, and derives their fingerprints.
+class HostKeyTest:
+    # Tracks the RSA host key types.  As of this writing, testing one in this family yields valid results for the rest.
+    RSA_FAMILY = ['ssh-rsa', 'rsa-sha2-256', 'rsa-sha2-512']
+
+    # Dict holding the host key types we should extract & parse.  'cert' is True to denote that a host key type handles certificates (thus requires additional parsing).  'variable_key_len' is True for host key types that can have variable sizes (True only for RSA types, as the rest are of fixed-size).  After the host key type is fully parsed, the key 'parsed' is added with a value of True.
+    HOST_KEY_TYPES = {
+        'ssh-rsa':      {'cert': False, 'variable_key_len': True},
+        'rsa-sha2-256': {'cert': False, 'variable_key_len': True},
+        'rsa-sha2-512': {'cert': False, 'variable_key_len': True},
+
+        'ssh-rsa-cert-v01@openssh.com':      {'cert': True, 'variable_key_len': True},
+        'rsa-sha2-256-cert-v01@openssh.com': {'cert': True, 'variable_key_len': True},
+        'rsa-sha2-512-cert-v01@openssh.com': {'cert': True, 'variable_key_len': True},
+
+        'ssh-ed25519':                      {'cert': False, 'variable_key_len': False},
+        'ssh-ed25519-cert-v01@openssh.com': {'cert': True, 'variable_key_len': False},
+    }
+
+    @staticmethod
+    def run(out: 'OutputBuffer', s: 'SSH_Socket', server_kex: 'SSH2_Kex') -> None:
+        KEX_TO_DHGROUP = {
+            'diffie-hellman-group1-sha1': KexGroup1,
+            'diffie-hellman-group14-sha1': KexGroup14_SHA1,
+            'diffie-hellman-group14-sha256': KexGroup14_SHA256,
+            'curve25519-sha256': KexCurve25519_SHA256,
+            'curve25519-sha256@libssh.org': KexCurve25519_SHA256,
+            'diffie-hellman-group16-sha512': KexGroup16_SHA512,
+            'diffie-hellman-group18-sha512': KexGroup18_SHA512,
+            'diffie-hellman-group-exchange-sha1': KexGroupExchange_SHA1,
+            'diffie-hellman-group-exchange-sha256': KexGroupExchange_SHA256,
+            'ecdh-sha2-nistp256': KexNISTP256,
+            'ecdh-sha2-nistp384': KexNISTP384,
+            'ecdh-sha2-nistp521': KexNISTP521,
+            # 'kexguess2@matt.ucc.asn.au': ???
+        }
+
+        # Pick the first kex algorithm that the server supports, which we
+        # happen to support as well.
+        kex_str = None
+        kex_group = None
+        for server_kex_alg in server_kex.kex_algorithms:
+            if server_kex_alg in KEX_TO_DHGROUP:
+                kex_str = server_kex_alg
+                kex_group = KEX_TO_DHGROUP[kex_str]()
+                break
+
+        if kex_str is not None and kex_group is not None:
+            HostKeyTest.perform_test(out, s, server_kex, kex_str, kex_group, HostKeyTest.HOST_KEY_TYPES)
+
+    @staticmethod
+    def perform_test(out: 'OutputBuffer', s: 'SSH_Socket', server_kex: 'SSH2_Kex', kex_str: str, kex_group: 'KexDH', host_key_types: Dict[str, Dict[str, bool]]) -> None:
+        hostkey_modulus_size = 0
+        ca_modulus_size = 0
+
+        # If the connection still exists, close it so we can test
+        # using a clean slate (otherwise it may exist in a non-testable
+        # state).
+        if s.is_connected():
+            s.close()
+
+        # For each host key type...
+        for host_key_type in host_key_types:
+            # Skip those already handled (i.e.: those in the RSA family, as testing one tests them all).
+            if 'parsed' in host_key_types[host_key_type] and host_key_types[host_key_type]['parsed']:
+                continue
+
+            # If this host key type is supported by the server, we test it.
+            if host_key_type in server_kex.key_algorithms:
+                out.d('Preparing to obtain ' + host_key_type + ' host key...', write_now=True)
+
+                cert = host_key_types[host_key_type]['cert']
+                variable_key_len = host_key_types[host_key_type]['variable_key_len']
+
+                # If the connection is closed, re-open it and get the kex again.
+                if not s.is_connected():
+                    err = s.connect()
+                    if err is not None:
+                        out.v(err, write_now=True)
+                        return
+
+                    _, _, err = s.get_banner()
+                    if err is not None:
+                        out.v(err, write_now=True)
+                        s.close()
+                        return
+
+                    # Send our KEX using the specified group-exchange and most of the server's own values.
+                    s.send_kexinit(key_exchanges=[kex_str], hostkeys=[host_key_type], ciphers=server_kex.server.encryption, macs=server_kex.server.mac, compressions=server_kex.server.compression, languages=server_kex.server.languages)
+
+                    try:
+                        # Parse the server's KEX.
+                        _, payload = s.read_packet()
+                        SSH2_Kex.parse(payload)
+                    except Exception:
+                        out.v("Failed to parse server's kex.  Stack trace:\n%s" % str(traceback.format_exc()), write_now=True)
+                        return
+
+                # Do the initial DH exchange.  The server responds back
+                # with the host key and its length.  Bingo.  We also get back the host key fingerprint.
+                kex_group.send_init(s)
+                try:
+                    host_key = kex_group.recv_reply(s, variable_key_len)
+                    if host_key is not None:
+                        server_kex.set_host_key(host_key_type, host_key)
+                except Exception:
+                    pass
+
+                hostkey_modulus_size = kex_group.get_hostkey_size()
+                ca_modulus_size = kex_group.get_ca_size()
+
+                # Close the socket, as the connection has
+                # been put in a state that later tests can't use.
+                s.close()
+
+                # If the host key modulus or CA modulus was successfully parsed, check to see that its a safe size.
+                if hostkey_modulus_size > 0 or ca_modulus_size > 0:
+                    # Set the hostkey size for all RSA key types since 'ssh-rsa',
+                    # 'rsa-sha2-256', etc. are all using the same host key.
+                    # Note, however, that this may change in the future.
+                    if cert is False and host_key_type in HostKeyTest.RSA_FAMILY:
+                        for rsa_type in HostKeyTest.RSA_FAMILY:
+                            server_kex.set_rsa_key_size(rsa_type, hostkey_modulus_size)
+                    elif cert is True:
+                        server_kex.set_rsa_key_size(host_key_type, hostkey_modulus_size, ca_modulus_size)
+
+                    # Keys smaller than 2048 result in a failure.  Update the database accordingly.
+                    if (cert is False) and (hostkey_modulus_size < 2048):
+                        for rsa_type in HostKeyTest.RSA_FAMILY:
+                            alg_list = SSH2_KexDB.ALGORITHMS['key'][rsa_type]
+
+                            # If no failure list exists, add an empty failure list.
+                            if len(alg_list) < 2:
+                                alg_list.append([])
+                            alg_list[1].append('using small %d-bit modulus' % hostkey_modulus_size)
+                    elif (cert is True) and ((hostkey_modulus_size < 2048) or (ca_modulus_size > 0 and ca_modulus_size < 2048)):  # pylint: disable=chained-comparison
+                        alg_list = SSH2_KexDB.ALGORITHMS['key'][host_key_type]
+                        min_modulus = min(hostkey_modulus_size, ca_modulus_size)
+                        min_modulus = min_modulus if min_modulus > 0 else max(hostkey_modulus_size, ca_modulus_size)
+
+                        # If no failure list exists, add an empty failure list.
+                        if len(alg_list) < 2:
+                            alg_list.append([])
+                        alg_list[1].append('using small %d-bit modulus' % min_modulus)
+
+                # If this host key type is in the RSA family, then mark them all as parsed (since results in one are valid for them all).
+                if host_key_type in HostKeyTest.RSA_FAMILY:
+                    for rsa_type in HostKeyTest.RSA_FAMILY:
+                        host_key_types[rsa_type]['parsed'] = True
+                else:
+                    host_key_types[host_key_type]['parsed'] = True
diff --git a/src/ssh_audit/kexdh.py b/src/ssh_audit/kexdh.py
new file mode 100644
index 0000000..536f0a8
--- /dev/null
+++ b/src/ssh_audit/kexdh.py
@@ -0,0 +1,365 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017-2021 Joe Testa (jtesta@positronsecurity.com)
+   Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+import binascii
+import os
+import random
+import struct
+
+# pylint: disable=unused-import
+from typing import Dict, List, Set, Sequence, Tuple, Iterable  # noqa: F401
+from typing import Callable, Optional, Union, Any  # noqa: F401
+
+from ssh_audit.protocol import Protocol
+from ssh_audit.ssh_socket import SSH_Socket
+
+
+class KexDH:  # pragma: nocover
+    def __init__(self, kex_name: str, hash_alg: str, g: int, p: int) -> None:
+        self.__kex_name = kex_name  # pylint: disable=unused-private-member
+        self.__hash_alg = hash_alg  # pylint: disable=unused-private-member
+        self.__g = 0
+        self.__p = 0
+        self.__q = 0
+        self.__x = 0
+        self.__e = 0
+        self.set_params(g, p)
+
+        self.__ed25519_pubkey: Optional[bytes] = None  # pylint: disable=unused-private-member
+        self.__hostkey_type: Optional[bytes] = None
+        self.__hostkey_e = 0  # pylint: disable=unused-private-member
+        self.__hostkey_n = 0  # pylint: disable=unused-private-member
+        self.__hostkey_n_len = 0  # Length of the host key modulus.
+        self.__ca_n_len = 0  # Length of the CA key modulus (if hostkey is a cert).
+
+    def set_params(self, g: int, p: int) -> None:
+        self.__g = g
+        self.__p = p
+        self.__q = (self.__p - 1) // 2
+        self.__x = 0
+        self.__e = 0
+
+    def send_init(self, s: SSH_Socket, init_msg: int = Protocol.MSG_KEXDH_INIT) -> None:
+        r = random.SystemRandom()
+        self.__x = r.randrange(2, self.__q)
+        self.__e = pow(self.__g, self.__x, self.__p)
+        s.write_byte(init_msg)
+        s.write_mpint2(self.__e)
+        s.send_packet()
+
+    # Parse a KEXDH_REPLY or KEXDH_GEX_REPLY message from the server.  This
+    # contains the host key, among other things.  Function returns the host
+    # key blob (from which the fingerprint can be calculated).
+    def recv_reply(self, s: 'SSH_Socket', parse_host_key_size: bool = True) -> Optional[bytes]:
+        packet_type, payload = s.read_packet(2)
+
+        # Skip any & all MSG_DEBUG messages.
+        while packet_type == Protocol.MSG_DEBUG:
+            packet_type, payload = s.read_packet(2)
+
+        if packet_type != -1 and packet_type not in [Protocol.MSG_KEXDH_REPLY, Protocol.MSG_KEXDH_GEX_REPLY]:  # pylint: disable=no-else-raise
+            # TODO: change Exception to something more specific.
+            raise Exception('Expected MSG_KEXDH_REPLY (%d) or MSG_KEXDH_GEX_REPLY (%d), but got %d instead.' % (Protocol.MSG_KEXDH_REPLY, Protocol.MSG_KEXDH_GEX_REPLY, packet_type))
+        elif packet_type == -1:
+            # A connection error occurred.  We can't parse anything, so just
+            # return.  The host key modulus (and perhaps certificate modulus)
+            # will remain at length 0.
+            return None
+
+        hostkey_len = 0  # pylint: disable=unused-variable
+        hostkey_type_len = hostkey_e_len = 0  # pylint: disable=unused-variable
+        key_id_len = principles_len = 0  # pylint: disable=unused-variable
+        critical_options_len = extensions_len = 0  # pylint: disable=unused-variable
+        nonce_len = ca_key_len = ca_key_type_len = 0  # pylint: disable=unused-variable
+        ca_key_len = ca_key_type_len = ca_key_e_len = 0  # pylint: disable=unused-variable
+
+        key_id = principles = None  # pylint: disable=unused-variable
+        critical_options = extensions = None  # pylint: disable=unused-variable
+        nonce = ca_key = ca_key_type = None  # pylint: disable=unused-variable
+        ca_key_e = ca_key_n = None  # pylint: disable=unused-variable
+
+        # Get the host key blob, F, and signature.
+        ptr = 0
+        hostkey, hostkey_len, ptr = KexDH.__get_bytes(payload, ptr)
+
+        # If we are not supposed to parse the host key size (i.e.: it is a type that is of fixed size such as ed25519), then stop here.
+        if not parse_host_key_size:
+            return hostkey
+
+        _, _, ptr = KexDH.__get_bytes(payload, ptr)
+        _, _, ptr = KexDH.__get_bytes(payload, ptr)
+
+        # Now pick apart the host key blob.
+        # Get the host key type (i.e.: 'ssh-rsa', 'ssh-ed25519', etc).
+        ptr = 0
+        self.__hostkey_type, hostkey_type_len, ptr = KexDH.__get_bytes(hostkey, ptr)
+
+        # If this is an RSA certificate, skip over the nonce.
+        if self.__hostkey_type.startswith(b'ssh-rsa-cert-v0'):
+            nonce, nonce_len, ptr = KexDH.__get_bytes(hostkey, ptr)
+
+        # The public key exponent.
+        hostkey_e, hostkey_e_len, ptr = KexDH.__get_bytes(hostkey, ptr)
+        self.__hostkey_e = int(binascii.hexlify(hostkey_e), 16)  # pylint: disable=unused-private-member
+
+        # Here is the modulus size & actual modulus of the host key public key.
+        hostkey_n, self.__hostkey_n_len, ptr = KexDH.__get_bytes(hostkey, ptr)
+        self.__hostkey_n = int(binascii.hexlify(hostkey_n), 16)  # pylint: disable=unused-private-member
+
+        # If this is an RSA certificate, continue parsing to extract the CA
+        # key.
+        if self.__hostkey_type.startswith(b'ssh-rsa-cert-v0'):
+            # Skip over the serial number.
+            ptr += 8
+
+            # Get the certificate type.
+            cert_type = int(binascii.hexlify(hostkey[ptr:ptr + 4]), 16)
+            ptr += 4
+
+            # Only SSH2_CERT_TYPE_HOST (2) makes sense in this context.
+            if cert_type == 2:
+
+                # Skip the key ID (this is the serial number of the
+                # certificate).
+                key_id, key_id_len, ptr = KexDH.__get_bytes(hostkey, ptr)
+
+                # The principles, which are... I don't know what.
+                principles, principles_len, ptr = KexDH.__get_bytes(hostkey, ptr)
+
+                # Skip over the timestamp that this certificate is valid after.
+                ptr += 8
+
+                # Skip over the timestamp that this certificate is valid before.
+                ptr += 8
+
+                # TODO: validate the principles, and time range.
+
+                # The critical options.
+                critical_options, critical_options_len, ptr = KexDH.__get_bytes(hostkey, ptr)
+
+                # Certificate extensions.
+                extensions, extensions_len, ptr = KexDH.__get_bytes(hostkey, ptr)
+
+                # Another nonce.
+                nonce, nonce_len, ptr = KexDH.__get_bytes(hostkey, ptr)
+
+                # Finally, we get to the CA key.
+                ca_key, ca_key_len, ptr = KexDH.__get_bytes(hostkey, ptr)
+
+                # Last in the host key blob is the CA signature.  It isn't
+                # interesting to us, so we won't bother parsing any further.
+                # The CA key has the modulus, however...
+                ptr = 0
+
+                # 'ssh-rsa', 'rsa-sha2-256', etc.
+                ca_key_type, ca_key_type_len, ptr = KexDH.__get_bytes(ca_key, ptr)
+
+                # CA's public key exponent.
+                ca_key_e, ca_key_e_len, ptr = KexDH.__get_bytes(ca_key, ptr)
+
+                # CA's modulus.  Bingo.
+                ca_key_n, self.__ca_n_len, ptr = KexDH.__get_bytes(ca_key, ptr)
+
+        return hostkey
+
+    @staticmethod
+    def __get_bytes(buf: bytes, ptr: int) -> Tuple[bytes, int, int]:
+        num_bytes = struct.unpack('>I', buf[ptr:ptr + 4])[0]
+        ptr += 4
+        return buf[ptr:ptr + num_bytes], num_bytes, ptr + num_bytes
+
+    # Converts a modulus length in bytes to its size in bits, after some
+    # possible adjustments.
+    @staticmethod
+    def __adjust_key_size(size: int) -> int:
+        size = size * 8
+        # Actual keys are observed to be about 8 bits bigger than expected
+        # (i.e.: 1024-bit keys have a 1032-bit modulus).  Check if this is
+        # the case, and subtract 8 if so.  This simply improves readability
+        # in the UI.
+        if (size >> 3) % 2 != 0:
+            size = size - 8
+        return size
+
+    # Returns the size of the hostkey, in bits.
+    def get_hostkey_size(self) -> int:
+        return KexDH.__adjust_key_size(self.__hostkey_n_len)
+
+    # Returns the size of the CA key, in bits.
+    def get_ca_size(self) -> int:
+        return KexDH.__adjust_key_size(self.__ca_n_len)
+
+    # Returns the size of the DH modulus, in bits.
+    def get_dh_modulus_size(self) -> int:
+        # -2 to account for the '0b' prefix in the string.
+        return len(bin(self.__p)) - 2
+
+
+class KexGroup1(KexDH):  # pragma: nocover
+    def __init__(self) -> None:
+        # rfc2409: second oakley group
+        p = int('ffffffffffffffffc90fdaa22168c234c4c6628b80dc1cd129024e088a67cc74020bbea63b139b22514a08798e3404ddef9519b3cd3a431b302b0a6df25f14374fe1356d6d51c245e485b576625e7ec6f44c42e9a637ed6b0bff5cb6f406b7edee386bfb5a899fa5ae9f24117c4b1fe649286651ece65381ffffffffffffffff', 16)
+        super(KexGroup1, self).__init__('KexGroup1', 'sha1', 2, p)
+
+
+class KexGroup14(KexDH):  # pragma: nocover
+    def __init__(self, hash_alg: str) -> None:
+        # rfc3526: 2048-bit modp group
+        p = int('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', 16)
+        super(KexGroup14, self).__init__('KexGroup14', hash_alg, 2, p)
+
+
+class KexGroup14_SHA1(KexGroup14):
+    def __init__(self) -> None:
+        super(KexGroup14_SHA1, self).__init__('sha1')
+
+
+class KexGroup14_SHA256(KexGroup14):
+    def __init__(self) -> None:
+        super(KexGroup14_SHA256, self).__init__('sha256')
+
+
+class KexGroup16_SHA512(KexDH):
+    def __init__(self) -> None:
+        # rfc3526: 4096-bit modp group
+        p = int('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', 16)
+        super(KexGroup16_SHA512, self).__init__('KexGroup16_SHA512', 'sha512', 2, p)
+
+
+class KexGroup18_SHA512(KexDH):
+    def __init__(self) -> None:
+        # rfc3526: 8192-bit modp group
+        p = int('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', 16)
+        super(KexGroup18_SHA512, self).__init__('KexGroup18_SHA512', 'sha512', 2, p)
+
+
+class KexCurve25519_SHA256(KexDH):
+    def __init__(self) -> None:
+        super(KexCurve25519_SHA256, self).__init__('KexCurve25519_SHA256', 'sha256', 0, 0)
+
+    # To start an ED25519 kex, we simply send a random 256-bit number as the
+    # public key.
+    def send_init(self, s: 'SSH_Socket', init_msg: int = Protocol.MSG_KEXDH_INIT) -> None:
+        self.__ed25519_pubkey = os.urandom(32)
+        s.write_byte(init_msg)
+        s.write_string(self.__ed25519_pubkey)
+        s.send_packet()
+
+
+class KexNISTP256(KexDH):
+    def __init__(self) -> None:
+        super(KexNISTP256, self).__init__('KexNISTP256', 'sha256', 0, 0)
+
+    # Because the server checks that the value sent here is valid (i.e.: it lies
+    # on the curve, among other things), we would have to write a lot of code
+    # or import an elliptic curve library in order to randomly generate a
+    # valid elliptic point each time.  Hence, we will simply send a static
+    # value, which is enough for us to extract the server's host key.
+    def send_init(self, s: 'SSH_Socket', init_msg: int = Protocol.MSG_KEXDH_INIT) -> None:
+        s.write_byte(init_msg)
+        s.write_string(b'\x04\x0b\x60\x44\x9f\x8a\x11\x9e\xc7\x81\x0c\xa9\x98\xfc\xb7\x90\xaa\x6b\x26\x8c\x12\x4a\xc0\x09\xbb\xdf\xc4\x2c\x4c\x2c\x99\xb6\xe1\x71\xa0\xd4\xb3\x62\x47\x74\xb3\x39\x0c\xf2\x88\x4a\x84\x6b\x3b\x15\x77\xa5\x77\xd2\xa9\xc9\x94\xf9\xd5\x66\x19\xcd\x02\x34\xd1')
+        s.send_packet()
+
+
+class KexNISTP384(KexDH):
+    def __init__(self) -> None:
+        super(KexNISTP384, self).__init__('KexNISTP384', 'sha256', 0, 0)
+
+    # See comment for KexNISTP256.send_init().
+    def send_init(self, s: 'SSH_Socket', init_msg: int = Protocol.MSG_KEXDH_INIT) -> None:
+        s.write_byte(init_msg)
+        s.write_string(b'\x04\xe2\x9b\x84\xce\xa1\x39\x50\xfe\x1e\xa3\x18\x70\x1c\xe2\x7a\xe4\xb5\x6f\xdf\x93\x9f\xd4\xf4\x08\xcc\x9b\x02\x10\xa4\xca\x77\x9c\x2e\x51\x44\x1d\x50\x7a\x65\x4e\x7e\x2f\x10\x2d\x2d\x4a\x32\xc9\x8e\x18\x75\x90\x6c\x19\x10\xda\xcc\xa8\xe9\xf4\xc4\x3a\x53\x80\x35\xf4\x97\x9c\x04\x16\xf9\x5a\xdc\xcc\x05\x94\x29\xfa\xc4\xd6\x87\x4e\x13\x21\xdb\x3d\x12\xac\xbd\x20\x3b\x60\xff\xe6\x58\x42')
+        s.send_packet()
+
+
+class KexNISTP521(KexDH):
+    def __init__(self) -> None:
+        super(KexNISTP521, self).__init__('KexNISTP521', 'sha256', 0, 0)
+
+    # See comment for KexNISTP256.send_init().
+    def send_init(self, s: 'SSH_Socket', init_msg: int = Protocol.MSG_KEXDH_INIT) -> None:
+        s.write_byte(init_msg)
+        s.write_string(b'\x04\x01\x02\x90\x29\xe9\x8f\xa8\x04\xaf\x1c\x00\xf9\xc6\x29\xc0\x39\x74\x8e\xea\x47\x7e\x7c\xf7\x15\x6e\x43\x3b\x59\x13\x53\x43\xb0\xae\x0b\xe7\xe6\x7c\x55\x73\x52\xa5\x2a\xc1\x42\xde\xfc\xf4\x1f\x8b\x5a\x8d\xfa\xcd\x0a\x65\x77\xa8\xce\x68\xd2\xc6\x26\xb5\x3f\xee\x4b\x01\x7b\xd2\x96\x23\x69\x53\xc7\x01\xe1\x0d\x39\xe9\x87\x49\x3b\xc8\xec\xda\x0c\xf9\xca\xad\x89\x42\x36\x6f\x93\x78\x78\x31\x55\x51\x09\x51\xc0\x96\xd7\xea\x61\xbf\xc2\x44\x08\x80\x43\xed\xc6\xbb\xfb\x94\xbd\xf8\xdf\x2b\xd8\x0b\x2e\x29\x1b\x8c\xc4\x8a\x04\x2d\x3a')
+        s.send_packet()
+
+
+class KexGroupExchange(KexDH):
+    def __init__(self, classname: str, hash_alg: str) -> None:
+        super(KexGroupExchange, self).__init__(classname, hash_alg, 0, 0)
+
+    def send_init(self, s: 'SSH_Socket', init_msg: int = Protocol.MSG_KEXDH_GEX_REQUEST) -> None:
+        self.send_init_gex(s)
+
+    # The group exchange starts with sending a message to the server with
+    # the minimum, maximum, and preferred number of bits are for the DH group.
+    # The server responds with a generator and prime modulus that matches that,
+    # then the handshake continues on like a normal DH handshake (except the
+    # SSH message types differ).
+    def send_init_gex(self, s: 'SSH_Socket', minbits: int = 1024, prefbits: int = 2048, maxbits: int = 8192) -> None:
+
+        # Send the initial group exchange request.  Tell the server what range
+        # of modulus sizes we will accept, along with our preference.
+        s.write_byte(Protocol.MSG_KEXDH_GEX_REQUEST)
+        s.write_int(minbits)
+        s.write_int(prefbits)
+        s.write_int(maxbits)
+        s.send_packet()
+
+        packet_type, payload = s.read_packet(2)
+        if packet_type not in [Protocol.MSG_KEXDH_GEX_GROUP, Protocol.MSG_DEBUG]:
+            # TODO: replace with a better exception type.
+            raise Exception('Expected MSG_KEXDH_GEX_REPLY (%d), but got %d instead.' % (Protocol.MSG_KEXDH_GEX_REPLY, packet_type))
+
+        # Skip any & all MSG_DEBUG messages.
+        while packet_type == Protocol.MSG_DEBUG:
+            packet_type, payload = s.read_packet(2)
+
+        # Parse the modulus (p) and generator (g) values from the server.
+        ptr = 0
+        p_len = struct.unpack('>I', payload[ptr:ptr + 4])[0]
+        ptr += 4
+
+        p = int(binascii.hexlify(payload[ptr:ptr + p_len]), 16)
+        ptr += p_len
+
+        g_len = struct.unpack('>I', payload[ptr:ptr + 4])[0]
+        ptr += 4
+
+        g = int(binascii.hexlify(payload[ptr:ptr + g_len]), 16)
+        ptr += g_len
+
+        # Now that we got the generator and modulus, perform the DH exchange
+        # like usual.
+        super(KexGroupExchange, self).set_params(g, p)
+        super(KexGroupExchange, self).send_init(s, Protocol.MSG_KEXDH_GEX_INIT)
+
+
+class KexGroupExchange_SHA1(KexGroupExchange):
+    def __init__(self) -> None:
+        super(KexGroupExchange_SHA1, self).__init__('KexGroupExchange_SHA1', 'sha1')
+
+
+class KexGroupExchange_SHA256(KexGroupExchange):
+    def __init__(self) -> None:
+        super(KexGroupExchange_SHA256, self).__init__('KexGroupExchange_SHA256', 'sha256')
diff --git a/src/ssh_audit/outputbuffer.py b/src/ssh_audit/outputbuffer.py
new file mode 100644
index 0000000..38723e3
--- /dev/null
+++ b/src/ssh_audit/outputbuffer.py
@@ -0,0 +1,185 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2021 Joe Testa (jtesta@positronsecurity.com)
+   Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+import os
+import sys
+
+# pylint: disable=unused-import
+from typing import Dict, List, Set, Sequence, Tuple, Iterable  # noqa: F401
+from typing import Callable, Optional, Union, Any  # noqa: F401
+
+from ssh_audit.utils import Utils
+
+
+class OutputBuffer:
+    LEVELS: Sequence[str] = ('info', 'warn', 'fail')
+    COLORS = {'head': 36, 'good': 32, 'warn': 33, 'fail': 31}
+
+    # Use brighter colors on Windows for better readability.
+    if Utils.is_windows():
+        COLORS = {'head': 96, 'good': 92, 'warn': 93, 'fail': 91}
+
+    def __init__(self, buffer_output: bool = True) -> None:
+        self.buffer_output = buffer_output
+        self.buffer: List[str] = []
+        self.in_section = False
+        self.section: List[str] = []
+        self.batch = False
+        self.verbose = False
+        self.debug = False
+        self.use_colors = True
+        self.json = False
+        self.__level = 0
+        self.__is_color_supported = ('colorama' in sys.modules) or (os.name == 'posix')
+        self.line_ended = True
+
+    def _print(self, level: str, s: str = '', line_ended: bool = True) -> None:
+        '''Saves output to buffer (if in buffered mode), or immediately prints to stdout otherwise.'''
+
+        # If we're logging only 'warn' or above, and this is an 'info', ignore message.
+        if self.get_level(level) < self.__level:
+            return
+
+        if self.use_colors and self.colors_supported and len(s) > 0 and level != 'info':
+            s = "\033[0;%dm%s\033[0m" % (self.COLORS[level], s)
+
+        if self.buffer_output:
+            # Select which list to add to.  If we are in a 'with' statement, then this goes in the section buffer, otherwise the general buffer.
+            buf = self.section if self.in_section else self.buffer
+
+            # Determine if a new line should be added, or if the last line should be appended.
+            if not self.line_ended:
+                last_entry = -1 if len(buf) > 0 else 0
+                buf[last_entry] = buf[last_entry] + s
+            else:
+                buf.append(s)
+
+            # When False, this tells the next call to append to the last line we just added.
+            self.line_ended = line_ended
+        else:
+            print(s)
+
+    def get_buffer(self) -> str:
+        '''Returns all buffered output, then clears the buffer.'''
+        self.flush_section()
+
+        buffer_str = "\n".join(self.buffer)
+        self.buffer = []
+        return buffer_str
+
+    def write(self) -> None:
+        '''Writes the output to stdout.'''
+        self.flush_section()
+        print(self.get_buffer(), flush=True)
+
+    def reset(self) -> None:
+        self.flush_section()
+        self.get_buffer()
+
+    @property
+    def level(self) -> str:
+        '''Returns the minimum level for output.'''
+        if self.__level < len(self.LEVELS):
+            return self.LEVELS[self.__level]
+        return 'unknown'
+
+    @level.setter
+    def level(self, name: str) -> None:
+        '''Sets the minimum level for output (one of: 'info', 'warn', 'fail').'''
+        self.__level = self.get_level(name)
+
+    def get_level(self, name: str) -> int:
+        cname = 'info' if name == 'good' else name
+        if cname not in self.LEVELS:
+            return sys.maxsize
+        return self.LEVELS.index(cname)
+
+    @property
+    def colors_supported(self) -> bool:
+        '''Returns True if the system supports color output.'''
+        return self.__is_color_supported
+
+    # When used in a 'with' block, the output to goes into a section; this can be sorted separately when add_section_to_buffer() is later called.
+    def __enter__(self) -> 'OutputBuffer':
+        self.in_section = True
+        return self
+
+    def __exit__(self, *args: Any) -> None:
+        self.in_section = False
+
+    def flush_section(self, sort_section: bool = False) -> None:
+        '''Appends section output (optionally sorting it first) to the end of the buffer, then clears the section output.'''
+        if sort_section:
+            self.section.sort()
+
+        self.buffer.extend(self.section)
+        self.section = []
+
+    def is_section_empty(self) -> bool:
+        '''Returns True if the section buffer is empty, otherwise False.'''
+        return len(self.section) == 0
+
+    def head(self, s: str, line_ended: bool = True) -> 'OutputBuffer':
+        if not self.batch:
+            self._print('head', s, line_ended)
+        return self
+
+    def fail(self, s: str, line_ended: bool = True) -> 'OutputBuffer':
+        self._print('fail', s, line_ended)
+        return self
+
+    def warn(self, s: str, line_ended: bool = True) -> 'OutputBuffer':
+        self._print('warn', s, line_ended)
+        return self
+
+    def info(self, s: str, line_ended: bool = True) -> 'OutputBuffer':
+        self._print('info', s, line_ended)
+        return self
+
+    def good(self, s: str, line_ended: bool = True) -> 'OutputBuffer':
+        self._print('good', s, line_ended)
+        return self
+
+    def sep(self) -> 'OutputBuffer':
+        if not self.batch:
+            self._print('info')
+        return self
+
+    def v(self, s: str, write_now: bool = False) -> 'OutputBuffer':
+        '''Prints a message if verbose output is enabled.'''
+        if self.verbose or self.debug:
+            self.info(s)
+            if write_now:
+                self.write()
+
+        return self
+
+    def d(self, s: str, write_now: bool = False) -> 'OutputBuffer':
+        '''Prints a message if verbose output is enabled.'''
+        if self.debug:
+            self.info(s)
+            if write_now:
+                self.write()
+
+        return self
diff --git a/src/ssh_audit/policy.py b/src/ssh_audit/policy.py
new file mode 100644
index 0000000..fd9d2c7
--- /dev/null
+++ b/src/ssh_audit/policy.py
@@ -0,0 +1,521 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2020-2021 Joe Testa (jtesta@positronsecurity.com)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+import sys
+
+from typing import Dict, List, Tuple
+from typing import Optional, Any, Union, cast
+from datetime import date
+
+from ssh_audit import exitcodes
+from ssh_audit.ssh2_kex import SSH2_Kex  # pylint: disable=unused-import
+from ssh_audit.banner import Banner  # pylint: disable=unused-import
+
+
+# Validates policy files and performs policy testing
+class Policy:
+
+    # Each field maps directly to a private member variable of the Policy class.
+    BUILTIN_POLICIES: Dict[str, Dict[str, Union[Optional[str], Optional[List[str]], bool, Dict[str, int]]]] = {
+
+        # Ubuntu Server policies
+
+        'Hardened Ubuntu Server 16.04 LTS (version 1)': {'version': '1', 'banner': None, 'compressions': None, 'host_keys': ['ssh-ed25519'], 'optional_host_keys': ['ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-256-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com'], 'kex': ['curve25519-sha256@libssh.org', 'diffie-hellman-group-exchange-sha256'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes128-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-ctr'], 'macs': ['hmac-sha2-256-etm@openssh.com', 'hmac-sha2-512-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': None, 'cakey_sizes': None, 'dh_modulus_sizes': {'diffie-hellman-group-exchange-sha256': 2048}, 'server_policy': True},
+
+        'Hardened Ubuntu Server 18.04 LTS (version 1)': {'version': '1', 'banner': None, 'compressions': None, 'host_keys': ['ssh-ed25519'], 'optional_host_keys': ['ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-256-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com'], 'kex': ['curve25519-sha256', 'curve25519-sha256@libssh.org', 'diffie-hellman-group16-sha512', 'diffie-hellman-group18-sha512', 'diffie-hellman-group-exchange-sha256'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes128-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-ctr'], 'macs': ['hmac-sha2-256-etm@openssh.com', 'hmac-sha2-512-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': None, 'cakey_sizes': None, 'dh_modulus_sizes': {'diffie-hellman-group-exchange-sha256': 2048}, 'server_policy': True},
+
+        'Hardened Ubuntu Server 20.04 LTS (version 1)': {'version': '1', 'banner': None, 'compressions': None, 'host_keys': ['rsa-sha2-512', 'rsa-sha2-256', 'ssh-ed25519'], 'optional_host_keys': ['sk-ssh-ed25519@openssh.com', 'ssh-ed25519-cert-v01@openssh.com', 'sk-ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-256-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com'], 'kex': ['curve25519-sha256', 'curve25519-sha256@libssh.org', 'diffie-hellman-group16-sha512', 'diffie-hellman-group18-sha512', 'diffie-hellman-group-exchange-sha256'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes128-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-ctr'], 'macs': ['hmac-sha2-256-etm@openssh.com', 'hmac-sha2-512-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': {'rsa-sha2-256': 4096, 'rsa-sha2-512': 4096}, 'cakey_sizes': {'rsa-sha2-256-cert-v01@openssh.com': 4096, 'rsa-sha2-512-cert-v01@openssh.com': 4096}, 'dh_modulus_sizes': {'diffie-hellman-group-exchange-sha256': 2048}, 'server_policy': True},
+
+
+        # Generic OpenSSH Server policies
+
+        'Hardened OpenSSH Server v7.7 (version 1)': {'version': '1', 'banner': None, 'compressions': None, 'host_keys': ['rsa-sha2-512', 'rsa-sha2-256', 'ssh-ed25519'], 'optional_host_keys': ['ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-256-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com'], 'kex': ['curve25519-sha256', 'curve25519-sha256@libssh.org', 'diffie-hellman-group16-sha512', 'diffie-hellman-group18-sha512', 'diffie-hellman-group-exchange-sha256'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes128-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-ctr'], 'macs': ['hmac-sha2-256-etm@openssh.com', 'hmac-sha2-512-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': None, 'cakey_sizes': None, 'dh_modulus_sizes': {'diffie-hellman-group-exchange-sha256': 2048}, 'server_policy': True},
+
+        'Hardened OpenSSH Server v7.8 (version 1)': {'version': '1', 'banner': None, 'compressions': None, 'host_keys': ['rsa-sha2-512', 'rsa-sha2-256', 'ssh-ed25519'], 'optional_host_keys': ['ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-256-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com'], 'kex': ['curve25519-sha256', 'curve25519-sha256@libssh.org', 'diffie-hellman-group16-sha512', 'diffie-hellman-group18-sha512', 'diffie-hellman-group-exchange-sha256'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes128-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-ctr'], 'macs': ['hmac-sha2-256-etm@openssh.com', 'hmac-sha2-512-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': None, 'cakey_sizes': None, 'dh_modulus_sizes': {'diffie-hellman-group-exchange-sha256': 2048}, 'server_policy': True},
+
+        'Hardened OpenSSH Server v7.9 (version 1)': {'version': '1', 'banner': None, 'compressions': None, 'host_keys': ['rsa-sha2-512', 'rsa-sha2-256', 'ssh-ed25519'], 'optional_host_keys': ['ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-256-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com'], 'kex': ['curve25519-sha256', 'curve25519-sha256@libssh.org', 'diffie-hellman-group16-sha512', 'diffie-hellman-group18-sha512', 'diffie-hellman-group-exchange-sha256'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes128-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-ctr'], 'macs': ['hmac-sha2-256-etm@openssh.com', 'hmac-sha2-512-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': None, 'cakey_sizes': None, 'dh_modulus_sizes': {'diffie-hellman-group-exchange-sha256': 2048}, 'server_policy': True},
+
+        'Hardened OpenSSH Server v8.0 (version 1)': {'version': '1', 'banner': None, 'compressions': None, 'host_keys': ['rsa-sha2-512', 'rsa-sha2-256', 'ssh-ed25519'], 'optional_host_keys': ['ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-256-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com'], 'kex': ['curve25519-sha256', 'curve25519-sha256@libssh.org', 'diffie-hellman-group16-sha512', 'diffie-hellman-group18-sha512', 'diffie-hellman-group-exchange-sha256'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes128-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-ctr'], 'macs': ['hmac-sha2-256-etm@openssh.com', 'hmac-sha2-512-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': None, 'cakey_sizes': None, 'dh_modulus_sizes': {'diffie-hellman-group-exchange-sha256': 2048}, 'server_policy': True},
+
+        'Hardened OpenSSH Server v8.1 (version 1)': {'version': '1', 'banner': None, 'compressions': None, 'host_keys': ['rsa-sha2-512', 'rsa-sha2-256', 'ssh-ed25519'], 'optional_host_keys': ['sk-ssh-ed25519@openssh.com', 'ssh-ed25519-cert-v01@openssh.com', 'sk-ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-256-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com'], 'kex': ['curve25519-sha256', 'curve25519-sha256@libssh.org', 'diffie-hellman-group16-sha512', 'diffie-hellman-group18-sha512', 'diffie-hellman-group-exchange-sha256'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes128-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-ctr'], 'macs': ['hmac-sha2-256-etm@openssh.com', 'hmac-sha2-512-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': None, 'cakey_sizes': None, 'dh_modulus_sizes': {'diffie-hellman-group-exchange-sha256': 2048}, 'server_policy': True},
+
+        'Hardened OpenSSH Server v8.2 (version 1)': {'version': '1', 'banner': None, 'compressions': None, 'host_keys': ['rsa-sha2-512', 'rsa-sha2-256', 'ssh-ed25519'], 'optional_host_keys': ['sk-ssh-ed25519@openssh.com', 'ssh-ed25519-cert-v01@openssh.com', 'sk-ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-256-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com'], 'kex': ['curve25519-sha256', 'curve25519-sha256@libssh.org', 'diffie-hellman-group16-sha512', 'diffie-hellman-group18-sha512', 'diffie-hellman-group-exchange-sha256'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes128-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-ctr'], 'macs': ['hmac-sha2-256-etm@openssh.com', 'hmac-sha2-512-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': {'rsa-sha2-256': 4096, 'rsa-sha2-512': 4096}, 'cakey_sizes': {'rsa-sha2-256-cert-v01@openssh.com': 4096, 'rsa-sha2-512-cert-v01@openssh.com': 4096}, 'dh_modulus_sizes': {'diffie-hellman-group-exchange-sha256': 2048}, 'server_policy': True},
+
+        'Hardened OpenSSH Server v8.3 (version 1)': {'version': '1', 'banner': None, 'compressions': None, 'host_keys': ['rsa-sha2-512', 'rsa-sha2-256', 'ssh-ed25519'], 'optional_host_keys': ['sk-ssh-ed25519@openssh.com', 'ssh-ed25519-cert-v01@openssh.com', 'sk-ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-256-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com'], 'kex': ['curve25519-sha256', 'curve25519-sha256@libssh.org', 'diffie-hellman-group16-sha512', 'diffie-hellman-group18-sha512', 'diffie-hellman-group-exchange-sha256'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes128-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-ctr'], 'macs': ['hmac-sha2-256-etm@openssh.com', 'hmac-sha2-512-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': {'rsa-sha2-256': 4096, 'rsa-sha2-512': 4096}, 'cakey_sizes': {'rsa-sha2-256-cert-v01@openssh.com': 4096, 'rsa-sha2-512-cert-v01@openssh.com': 4096}, 'dh_modulus_sizes': {'diffie-hellman-group-exchange-sha256': 2048}, 'server_policy': True},
+
+        'Hardened OpenSSH Server v8.4 (version 1)': {'version': '1', 'banner': None, 'compressions': None, 'host_keys': ['rsa-sha2-512', 'rsa-sha2-256', 'ssh-ed25519'], 'optional_host_keys': ['sk-ssh-ed25519@openssh.com', 'ssh-ed25519-cert-v01@openssh.com', 'sk-ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-256-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com'], 'kex': ['curve25519-sha256', 'curve25519-sha256@libssh.org', 'diffie-hellman-group16-sha512', 'diffie-hellman-group18-sha512', 'diffie-hellman-group-exchange-sha256'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes128-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-ctr'], 'macs': ['hmac-sha2-256-etm@openssh.com', 'hmac-sha2-512-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': {'rsa-sha2-256': 4096, 'rsa-sha2-512': 4096}, 'cakey_sizes': {'rsa-sha2-256-cert-v01@openssh.com': 4096, 'rsa-sha2-512-cert-v01@openssh.com': 4096}, 'dh_modulus_sizes': {'diffie-hellman-group-exchange-sha256': 2048}, 'server_policy': True},
+
+        'Hardened OpenSSH Server v8.5 (version 1)': {'version': '1', 'banner': None, 'compressions': None, 'host_keys': ['rsa-sha2-512', 'rsa-sha2-256', 'ssh-ed25519'], 'optional_host_keys': ['sk-ssh-ed25519@openssh.com', 'ssh-ed25519-cert-v01@openssh.com', 'sk-ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-256-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com'], 'kex': ['curve25519-sha256', 'curve25519-sha256@libssh.org', 'diffie-hellman-group16-sha512', 'diffie-hellman-group18-sha512', 'diffie-hellman-group-exchange-sha256'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes128-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-ctr'], 'macs': ['hmac-sha2-256-etm@openssh.com', 'hmac-sha2-512-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': {'rsa-sha2-256': 4096, 'rsa-sha2-512': 4096}, 'cakey_sizes': {'rsa-sha2-256-cert-v01@openssh.com': 4096, 'rsa-sha2-512-cert-v01@openssh.com': 4096}, 'dh_modulus_sizes': {'diffie-hellman-group-exchange-sha256': 2048}, 'server_policy': True},
+
+        'Hardened OpenSSH Server v8.6 (version 1)': {'version': '1', 'banner': None, 'compressions': None, 'host_keys': ['rsa-sha2-512', 'rsa-sha2-256', 'ssh-ed25519'], 'optional_host_keys': ['sk-ssh-ed25519@openssh.com', 'ssh-ed25519-cert-v01@openssh.com', 'sk-ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-256-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com'], 'kex': ['curve25519-sha256', 'curve25519-sha256@libssh.org', 'diffie-hellman-group16-sha512', 'diffie-hellman-group18-sha512', 'diffie-hellman-group-exchange-sha256'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes128-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-ctr'], 'macs': ['hmac-sha2-256-etm@openssh.com', 'hmac-sha2-512-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': {'rsa-sha2-256': 4096, 'rsa-sha2-512': 4096}, 'cakey_sizes': {'rsa-sha2-256-cert-v01@openssh.com': 4096, 'rsa-sha2-512-cert-v01@openssh.com': 4096}, 'dh_modulus_sizes': {'diffie-hellman-group-exchange-sha256': 2048}, 'server_policy': True},
+
+        'Hardened OpenSSH Server v8.7 (version 1)': {'version': '1', 'banner': None, 'compressions': None, 'host_keys': ['rsa-sha2-512', 'rsa-sha2-256', 'ssh-ed25519'], 'optional_host_keys': ['sk-ssh-ed25519@openssh.com', 'ssh-ed25519-cert-v01@openssh.com', 'sk-ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-256-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com'], 'kex': ['curve25519-sha256', 'curve25519-sha256@libssh.org', 'diffie-hellman-group16-sha512', 'diffie-hellman-group18-sha512', 'diffie-hellman-group-exchange-sha256'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes128-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-ctr'], 'macs': ['hmac-sha2-256-etm@openssh.com', 'hmac-sha2-512-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': {'rsa-sha2-256': 4096, 'rsa-sha2-512': 4096}, 'cakey_sizes': {'rsa-sha2-256-cert-v01@openssh.com': 4096, 'rsa-sha2-512-cert-v01@openssh.com': 4096}, 'dh_modulus_sizes': {'diffie-hellman-group-exchange-sha256': 2048}, 'server_policy': True},
+
+
+        # Ubuntu Client policies
+
+        'Hardened Ubuntu Client 16.04 LTS (version 2)': {'version': '2', 'banner': None, 'compressions': None, 'host_keys': ['ssh-ed25519', 'ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-256', 'rsa-sha2-512'], 'optional_host_keys': None, 'kex': ['curve25519-sha256@libssh.org', 'diffie-hellman-group-exchange-sha256', 'ext-info-c'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes128-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-ctr'], 'macs': ['hmac-sha2-256-etm@openssh.com', 'hmac-sha2-512-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': None, 'cakey_sizes': None, 'dh_modulus_sizes': None, 'server_policy': False},
+
+        'Hardened Ubuntu Client 18.04 LTS (version 2)': {'version': '2', 'banner': None, 'compressions': None, 'host_keys': ['ssh-ed25519', 'ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-256', 'rsa-sha2-512'], 'optional_host_keys': None, 'kex': ['curve25519-sha256', 'curve25519-sha256@libssh.org', 'diffie-hellman-group16-sha512', 'diffie-hellman-group18-sha512', 'diffie-hellman-group-exchange-sha256', 'ext-info-c'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes128-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-ctr'], 'macs': ['hmac-sha2-256-etm@openssh.com', 'hmac-sha2-512-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': None, 'cakey_sizes': None, 'dh_modulus_sizes': None, 'server_policy': False},
+
+        'Hardened Ubuntu Client 20.04 LTS (version 2)': {'version': '2', 'banner': None, 'compressions': None, 'host_keys': ['ssh-ed25519', 'ssh-ed25519-cert-v01@openssh.com', 'sk-ssh-ed25519@openssh.com', 'sk-ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-256', 'rsa-sha2-256-cert-v01@openssh.com', 'rsa-sha2-512', 'rsa-sha2-512-cert-v01@openssh.com'], 'optional_host_keys': None, 'kex': ['curve25519-sha256', 'curve25519-sha256@libssh.org', 'diffie-hellman-group16-sha512', 'diffie-hellman-group18-sha512', 'diffie-hellman-group-exchange-sha256', 'ext-info-c'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes128-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-ctr'], 'macs': ['hmac-sha2-256-etm@openssh.com', 'hmac-sha2-512-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': None, 'cakey_sizes': None, 'dh_modulus_sizes': None, 'server_policy': False},
+
+    }
+
+
+    def __init__(self, policy_file: Optional[str] = None, policy_data: Optional[str] = None, manual_load: bool = False) -> None:
+        self._name: Optional[str] = None
+        self._version: Optional[str] = None
+        self._banner: Optional[str] = None
+        self._compressions: Optional[List[str]] = None
+        self._host_keys: Optional[List[str]] = None
+        self._optional_host_keys: Optional[List[str]] = None
+        self._kex: Optional[List[str]] = None
+        self._ciphers: Optional[List[str]] = None
+        self._macs: Optional[List[str]] = None
+        self._hostkey_sizes: Optional[Dict[str, int]] = None
+        self._cakey_sizes: Optional[Dict[str, int]] = None
+        self._dh_modulus_sizes: Optional[Dict[str, int]] = None
+        self._server_policy = True
+
+        self._name_and_version: str = ''
+
+        # Ensure that only one mode was specified.
+        num_modes = 0
+        if policy_file is not None:
+            num_modes += 1
+        if policy_data is not None:
+            num_modes += 1
+        if manual_load is True:
+            num_modes += 1
+
+        if num_modes != 1:
+            raise RuntimeError('Exactly one of the following can be specified only: policy_file, policy_data, or manual_load')
+
+        if manual_load:
+            return
+
+        if policy_file is not None:
+            try:
+                with open(policy_file, "r", encoding='utf-8') as f:
+                    policy_data = f.read()
+            except FileNotFoundError:
+                print("Error: policy file not found: %s" % policy_file)
+                sys.exit(exitcodes.UNKNOWN_ERROR)
+
+        lines = []
+        if policy_data is not None:
+            lines = policy_data.split("\n")
+
+        for line in lines:
+            line = line.strip()
+            if (len(line) == 0) or line.startswith('#'):
+                continue
+
+            key = None
+            val = None
+            try:
+                key, val = line.split('=')
+            except ValueError as ve:
+                raise ValueError("could not parse line: %s" % line) from ve
+
+            key = key.strip()
+            val = val.strip()
+
+            if key not in ['name', 'version', 'banner', 'compressions', 'host keys', 'optional host keys', 'key exchanges', 'ciphers', 'macs', 'client policy'] and not key.startswith('hostkey_size_') and not key.startswith('cakey_size_') and not key.startswith('dh_modulus_size_'):
+                raise ValueError("invalid field found in policy: %s" % line)
+
+            if key in ['name', 'banner']:
+
+                # If the banner value is blank, set it to "" so that the code below handles it.
+                if len(val) < 2:
+                    val = "\"\""
+
+                if (val[0] != '"') or (val[-1] != '"'):
+                    raise ValueError('the value for the %s field must be enclosed in quotes: %s' % (key, val))
+
+                # Remove the surrounding quotes, and unescape quotes & newlines.
+                val = val[1:-1]. replace("\\\"", "\"").replace("\\n", "\n")
+
+                if key == 'name':
+                    self._name = val
+                elif key == 'banner':
+                    self._banner = val
+            elif key == 'version':
+                self._version = val
+            elif key in ['compressions', 'host keys', 'optional host keys', 'key exchanges', 'ciphers', 'macs']:
+                try:
+                    algs = val.split(',')
+                except ValueError:
+                    # If the value has no commas, then set the algorithm list to just the value.
+                    algs = [val]
+
+                # Strip whitespace in each algorithm name.
+                algs = [alg.strip() for alg in algs]
+
+                if key == 'compressions':
+                    self._compressions = algs
+                elif key == 'host keys':
+                    self._host_keys = algs
+                elif key == 'optional host keys':
+                    self._optional_host_keys = algs
+                elif key == 'key exchanges':
+                    self._kex = algs
+                elif key == 'ciphers':
+                    self._ciphers = algs
+                elif key == 'macs':
+                    self._macs = algs
+            elif key.startswith('hostkey_size_'):
+                hostkey_type = key[13:]
+                if self._hostkey_sizes is None:
+                    self._hostkey_sizes = {}
+                self._hostkey_sizes[hostkey_type] = int(val)
+            elif key.startswith('cakey_size_'):
+                cakey_type = key[11:]
+                if self._cakey_sizes is None:
+                    self._cakey_sizes = {}
+                self._cakey_sizes[cakey_type] = int(val)
+            elif key.startswith('dh_modulus_size_'):
+                dh_modulus_type = key[16:]
+                if self._dh_modulus_sizes is None:
+                    self._dh_modulus_sizes = {}
+                self._dh_modulus_sizes[dh_modulus_type] = int(val)
+            elif key.startswith('client policy') and val.lower() == 'true':
+                self._server_policy = False
+
+
+        if self._name is None:
+            raise ValueError('The policy does not have a name field.')
+        if self._version is None:
+            raise ValueError('The policy does not have a version field.')
+
+        self._name_and_version = "%s (version %s)" % (self._name, self._version)
+
+
+    @staticmethod
+    def _append_error(errors: List[Any], mismatched_field: str, expected_required: Optional[List[str]], expected_optional: Optional[List[str]], actual: List[str]) -> None:
+        if expected_required is None:
+            expected_required = ['']
+        if expected_optional is None:
+            expected_optional = ['']
+        errors.append({'mismatched_field': mismatched_field, 'expected_required': expected_required, 'expected_optional': expected_optional, 'actual': actual})
+
+
+    @staticmethod
+    def create(source: Optional[str], banner: Optional['Banner'], kex: Optional['SSH2_Kex'], client_audit: bool) -> str:
+        '''Creates a policy based on a server configuration.  Returns a string.'''
+
+        today = date.today().strftime('%Y/%m/%d')
+        compressions = None
+        host_keys = None
+        kex_algs = None
+        ciphers = None
+        macs = None
+        rsa_hostkey_sizes_str = ''
+        rsa_cakey_sizes_str = ''
+        dh_modulus_sizes_str = ''
+        client_policy_str = ''
+
+        if client_audit:
+            client_policy_str = "\n# Set to true to signify this is a policy for clients, not servers.\nclient policy = true\n"
+
+        if kex is not None:
+            if kex.server.compression is not None:
+                compressions = ', '.join(kex.server.compression)
+            if kex.key_algorithms is not None:
+                host_keys = ', '.join(kex.key_algorithms)
+            if kex.kex_algorithms is not None:
+                kex_algs = ', '.join(kex.kex_algorithms)
+            if kex.server.encryption is not None:
+                ciphers = ', '.join(kex.server.encryption)
+            if kex.server.mac is not None:
+                macs = ', '.join(kex.server.mac)
+            if kex.rsa_key_sizes():
+                rsa_key_sizes_dict = kex.rsa_key_sizes()
+                for host_key_type in sorted(rsa_key_sizes_dict):
+                    hostkey_size, cakey_size = rsa_key_sizes_dict[host_key_type]
+
+                    rsa_hostkey_sizes_str = "%shostkey_size_%s = %d\n" % (rsa_hostkey_sizes_str, host_key_type, hostkey_size)
+                    if cakey_size != -1:
+                        rsa_cakey_sizes_str = "%scakey_size_%s = %d\n" % (rsa_cakey_sizes_str, host_key_type, cakey_size)
+
+                if len(rsa_hostkey_sizes_str) > 0:
+                    rsa_hostkey_sizes_str = "\n# RSA host key sizes.\n%s" % rsa_hostkey_sizes_str
+                if len(rsa_cakey_sizes_str) > 0:
+                    rsa_cakey_sizes_str = "\n# RSA CA key sizes.\n%s" % rsa_cakey_sizes_str
+            if kex.dh_modulus_sizes():
+                dh_modulus_sizes_dict = kex.dh_modulus_sizes()
+                for gex_type in sorted(dh_modulus_sizes_dict):
+                    modulus_size, _ = dh_modulus_sizes_dict[gex_type]
+                    dh_modulus_sizes_str = "%sdh_modulus_size_%s = %d\n" % (dh_modulus_sizes_str, gex_type, modulus_size)
+                if len(dh_modulus_sizes_str) > 0:
+                    dh_modulus_sizes_str = "\n# Group exchange DH modulus sizes.\n%s" % dh_modulus_sizes_str
+
+
+        policy_data = '''#
+# Custom policy based on %s (created on %s)
+#
+%s
+# The name of this policy (displayed in the output during scans).  Must be in quotes.
+name = "Custom Policy (based on %s on %s)"
+
+# The version of this policy (displayed in the output during scans).  Not parsed, and may be any value, including strings.
+version = 1
+
+# The banner that must match exactly.  Commented out to ignore banners, since minor variability in the banner is sometimes normal.
+# banner = "%s"
+
+# The compression options that must match exactly (order matters).  Commented out to ignore by default.
+# compressions = %s
+%s%s%s
+# The host key types that must match exactly (order matters).
+host keys = %s
+
+# Host key types that may optionally appear.
+#optional host keys = ssh-ed25519-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,sk-ssh-ed25519-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com
+
+# The key exchange algorithms that must match exactly (order matters).
+key exchanges = %s
+
+# The ciphers that must match exactly (order matters).
+ciphers = %s
+
+# The MACs that must match exactly (order matters).
+macs = %s
+''' % (source, today, client_policy_str, source, today, banner, compressions, rsa_hostkey_sizes_str, rsa_cakey_sizes_str, dh_modulus_sizes_str, host_keys, kex_algs, ciphers, macs)
+
+        return policy_data
+
+
+    def evaluate(self, banner: Optional['Banner'], kex: Optional['SSH2_Kex']) -> Tuple[bool, List[Dict[str, str]], str]:
+        '''Evaluates a server configuration against this policy.  Returns a tuple of a boolean (True if server adheres to policy) and an array of strings that holds error messages.'''
+
+        ret = True
+        errors: List[Any] = []
+
+        banner_str = str(banner)
+        if (self._banner is not None) and (banner_str != self._banner):
+            ret = False
+            self._append_error(errors, 'Banner', [self._banner], None, [banner_str])
+
+        # All subsequent tests require a valid kex, so end here if we don't have one.
+        if kex is None:
+            return ret, errors, self._get_error_str(errors)
+
+        if (self._compressions is not None) and (kex.server.compression != self._compressions):
+            ret = False
+            self._append_error(errors, 'Compression', self._compressions, None, kex.server.compression)
+
+        # If a list of optional host keys was given in the policy, remove any of its entries from the list retrieved from the server.  This allows us to do an exact comparison with the expected list below.
+        pruned_host_keys = kex.key_algorithms
+        if self._optional_host_keys is not None:
+            pruned_host_keys = [x for x in kex.key_algorithms if x not in self._optional_host_keys]
+
+        if (self._host_keys is not None) and (pruned_host_keys != self._host_keys):
+            ret = False
+            self._append_error(errors, 'Host keys', self._host_keys, self._optional_host_keys, kex.key_algorithms)
+
+        if self._hostkey_sizes is not None:
+            hostkey_types = list(self._hostkey_sizes.keys())
+            hostkey_types.sort()  # Sorted to make testing output repeatable.
+            for hostkey_type in hostkey_types:
+                expected_hostkey_size = self._hostkey_sizes[hostkey_type]
+                if hostkey_type in kex.rsa_key_sizes():
+                    actual_hostkey_size, actual_cakey_size = kex.rsa_key_sizes()[hostkey_type]
+                    if actual_hostkey_size != expected_hostkey_size:
+                        ret = False
+                        self._append_error(errors, 'RSA host key (%s) sizes' % hostkey_type, [str(expected_hostkey_size)], None, [str(actual_hostkey_size)])
+
+        if self._cakey_sizes is not None:
+            hostkey_types = list(self._cakey_sizes.keys())
+            hostkey_types.sort()  # Sorted to make testing output repeatable.
+            for hostkey_type in hostkey_types:
+                expected_cakey_size = self._cakey_sizes[hostkey_type]
+                if hostkey_type in kex.rsa_key_sizes():
+                    actual_hostkey_size, actual_cakey_size = kex.rsa_key_sizes()[hostkey_type]
+                    if actual_cakey_size != expected_cakey_size:
+                        ret = False
+                        self._append_error(errors, 'RSA CA key (%s) sizes' % hostkey_type, [str(expected_cakey_size)], None, [str(actual_cakey_size)])
+
+        if kex.kex_algorithms != self._kex:
+            ret = False
+            self._append_error(errors, 'Key exchanges', self._kex, None, kex.kex_algorithms)
+
+        if (self._ciphers is not None) and (kex.server.encryption != self._ciphers):
+            ret = False
+            self._append_error(errors, 'Ciphers', self._ciphers, None, kex.server.encryption)
+
+        if (self._macs is not None) and (kex.server.mac != self._macs):
+            ret = False
+            self._append_error(errors, 'MACs', self._macs, None, kex.server.mac)
+
+        if self._dh_modulus_sizes is not None:
+            dh_modulus_types = list(self._dh_modulus_sizes.keys())
+            dh_modulus_types.sort()  # Sorted to make testing output repeatable.
+            for dh_modulus_type in dh_modulus_types:
+                expected_dh_modulus_size = self._dh_modulus_sizes[dh_modulus_type]
+                if dh_modulus_type in kex.dh_modulus_sizes():
+                    actual_dh_modulus_size, _ = kex.dh_modulus_sizes()[dh_modulus_type]
+                    if expected_dh_modulus_size != actual_dh_modulus_size:
+                        ret = False
+                        self._append_error(errors, 'Group exchange (%s) modulus sizes' % dh_modulus_type, [str(expected_dh_modulus_size)], None, [str(actual_dh_modulus_size)])
+
+        return ret, errors, self._get_error_str(errors)
+
+
+    @staticmethod
+    def _get_error_str(errors: List[Any]) -> str:
+        '''Transforms an error struct to a flat string of error messages.'''
+
+        error_list = []
+        spacer = ''
+        for e in errors:
+            e_str = "  * %s did not match.\n" % e['mismatched_field']
+            if ('expected_optional' in e) and (e['expected_optional'] != ['']):
+                e_str += "    - Expected (required): %s\n    - Expected (optional): %s\n" % (Policy._normalize_error_field(e['expected_required']), Policy._normalize_error_field(e['expected_optional']))
+                spacer = '              '
+            else:
+                e_str += "    - Expected: %s\n" % Policy._normalize_error_field(e['expected_required'])
+                spacer = '   '
+            e_str += "    - Actual:%s%s\n" % (spacer, Policy._normalize_error_field(e['actual']))
+            error_list.append(e_str)
+
+        error_list.sort()  # To ensure repeatable results for testing.
+
+        error_str = ''
+        if len(error_list) > 0:
+            error_str = "\n".join(error_list)
+
+        return error_str
+
+
+    def get_name_and_version(self) -> str:
+        '''Returns a string of this Policy's name and version.'''
+        return self._name_and_version
+
+
+    def is_server_policy(self) -> bool:
+        '''Returns True if this is a server policy, or False if this is a client policy.'''
+        return self._server_policy
+
+
+    @staticmethod
+    def list_builtin_policies() -> Tuple[List[str], List[str]]:
+        '''Returns two lists: a list of names of built-in server policies, and a list of names of built-in client policies, respectively.'''
+        server_policy_names = []
+        client_policy_names = []
+
+        for policy_name, policy in Policy.BUILTIN_POLICIES.items():
+            if policy['server_policy']:
+                server_policy_names.append(policy_name)
+            else:
+                client_policy_names.append(policy_name)
+
+        server_policy_names.sort()
+        client_policy_names.sort()
+        return server_policy_names, client_policy_names
+
+
+    @staticmethod
+    def load_builtin_policy(policy_name: str) -> Optional['Policy']:
+        '''Returns a Policy with the specified built-in policy name loaded, or None if no policy of that name exists.'''
+        p = None
+        if policy_name in Policy.BUILTIN_POLICIES:
+            policy_struct = Policy.BUILTIN_POLICIES[policy_name]
+            p = Policy(manual_load=True)
+            policy_name_without_version = policy_name[0:policy_name.rfind(' (')]
+            p._name = policy_name_without_version  # pylint: disable=protected-access
+            p._version = cast(str, policy_struct['version'])  # pylint: disable=protected-access
+            p._banner = cast(Optional[str], policy_struct['banner'])  # pylint: disable=protected-access
+            p._compressions = cast(Optional[List[str]], policy_struct['compressions'])  # pylint: disable=protected-access
+            p._host_keys = cast(Optional[List[str]], policy_struct['host_keys'])  # pylint: disable=protected-access
+            p._optional_host_keys = cast(Optional[List[str]], policy_struct['optional_host_keys'])  # pylint: disable=protected-access
+            p._kex = cast(Optional[List[str]], policy_struct['kex'])  # pylint: disable=protected-access
+            p._ciphers = cast(Optional[List[str]], policy_struct['ciphers'])  # pylint: disable=protected-access
+            p._macs = cast(Optional[List[str]], policy_struct['macs'])  # pylint: disable=protected-access
+            p._hostkey_sizes = cast(Optional[Dict[str, int]], policy_struct['hostkey_sizes'])  # pylint: disable=protected-access
+            p._cakey_sizes = cast(Optional[Dict[str, int]], policy_struct['cakey_sizes'])  # pylint: disable=protected-access
+            p._dh_modulus_sizes = cast(Optional[Dict[str, int]], policy_struct['dh_modulus_sizes'])  # pylint: disable=protected-access
+            p._server_policy = cast(bool, policy_struct['server_policy'])  # pylint: disable=protected-access
+
+            p._name_and_version = "%s (version %s)" % (p._name, p._version)  # pylint: disable=protected-access
+
+        return p
+
+
+    @staticmethod
+    def _normalize_error_field(field: List[str]) -> Any:
+        '''If field is an array with a string parsable as an integer, return that integer.  Otherwise, return the field joined with commas.'''
+        if len(field) == 1:
+            try:
+                return int(field[0])
+            except ValueError:
+                return field[0]
+        else:
+            return ', '.join(field)
+
+
+    def __str__(self) -> str:
+        undefined = '{undefined}'
+
+        name = undefined
+        version = undefined
+        banner = undefined
+        compressions_str = undefined
+        host_keys_str = undefined
+        optional_host_keys_str = undefined
+        kex_str = undefined
+        ciphers_str = undefined
+        macs_str = undefined
+        hostkey_sizes_str = undefined
+        cakey_sizes_str = undefined
+        dh_modulus_sizes_str = undefined
+
+
+        if self._name is not None:
+            name = '[%s]' % self._name
+        if self._version is not None:
+            version = '[%s]' % self._version
+        if self._banner is not None:
+            banner = '[%s]' % self._banner
+
+        if self._compressions is not None:
+            compressions_str = ', '.join(self._compressions)
+        if self._host_keys is not None:
+            host_keys_str = ', '.join(self._host_keys)
+        if self._optional_host_keys is not None:
+            optional_host_keys_str = ', '.join(self._optional_host_keys)
+        if self._kex is not None:
+            kex_str = ', '.join(self._kex)
+        if self._ciphers is not None:
+            ciphers_str = ', '.join(self._ciphers)
+        if self._macs is not None:
+            macs_str = ', '.join(self._macs)
+        if self._hostkey_sizes is not None:
+            hostkey_sizes_str = str(self._hostkey_sizes)
+        if self._cakey_sizes is not None:
+            cakey_sizes_str = str(self._cakey_sizes)
+        if self._dh_modulus_sizes is not None:
+            dh_modulus_sizes_str = str(self._dh_modulus_sizes)
+
+        return "Name: %s\nVersion: %s\nBanner: %s\nCompressions: %s\nHost Keys: %s\nOptional Host Keys: %s\nKey Exchanges: %s\nCiphers: %s\nMACs: %s\nHost Key Sizes: %s\nCA Key Sizes: %s\nDH Modulus Sizes: %s\nServer Policy: %r" % (name, version, banner, compressions_str, host_keys_str, optional_host_keys_str, kex_str, ciphers_str, macs_str, hostkey_sizes_str, cakey_sizes_str, dh_modulus_sizes_str, self._server_policy)
diff --git a/src/ssh_audit/product.py b/src/ssh_audit/product.py
new file mode 100644
index 0000000..2d8ae06
--- /dev/null
+++ b/src/ssh_audit/product.py
@@ -0,0 +1,31 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+
+
+class Product:  # pylint: disable=too-few-public-methods
+    OpenSSH = 'OpenSSH'
+    DropbearSSH = 'Dropbear SSH'
+    LibSSH = 'libssh'
+    TinySSH = 'TinySSH'
+    PuTTY = 'PuTTY'
diff --git a/src/ssh_audit/protocol.py b/src/ssh_audit/protocol.py
new file mode 100644
index 0000000..1b1b216
--- /dev/null
+++ b/src/ssh_audit/protocol.py
@@ -0,0 +1,36 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+
+
+class Protocol:  # pylint: disable=too-few-public-methods
+    SMSG_PUBLIC_KEY = 2
+    MSG_DEBUG = 4
+    MSG_KEXINIT = 20
+    MSG_NEWKEYS = 21
+    MSG_KEXDH_INIT = 30
+    MSG_KEXDH_REPLY = 31
+    MSG_KEXDH_GEX_REQUEST = 34
+    MSG_KEXDH_GEX_GROUP = 31
+    MSG_KEXDH_GEX_INIT = 32
+    MSG_KEXDH_GEX_REPLY = 33
diff --git a/src/ssh_audit/readbuf.py b/src/ssh_audit/readbuf.py
new file mode 100644
index 0000000..c9405c4
--- /dev/null
+++ b/src/ssh_audit/readbuf.py
@@ -0,0 +1,92 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+import io
+import struct
+
+# pylint: disable=unused-import
+from typing import Dict, List, Set, Sequence, Tuple, Iterable  # noqa: F401
+from typing import Callable, Optional, Union, Any  # noqa: F401
+
+
+class ReadBuf:
+    def __init__(self, data: Optional[bytes] = None) -> None:
+        super(ReadBuf, self).__init__()
+        self._buf = io.BytesIO(data) if data is not None else io.BytesIO()
+        self._len = len(data) if data is not None else 0
+
+    @property
+    def unread_len(self) -> int:
+        return self._len - self._buf.tell()
+
+    def read(self, size: int) -> bytes:
+        return self._buf.read(size)
+
+    def read_byte(self) -> int:
+        v: int = struct.unpack('B', self.read(1))[0]
+        return v
+
+    def read_bool(self) -> bool:
+        return self.read_byte() != 0
+
+    def read_int(self) -> int:
+        v: int = struct.unpack('>I', self.read(4))[0]
+        return v
+
+    def read_list(self) -> List[str]:
+        list_size = self.read_int()
+        return self.read(list_size).decode('utf-8', 'replace').split(',')
+
+    def read_string(self) -> bytes:
+        n = self.read_int()
+        return self.read(n)
+
+    @classmethod
+    def _parse_mpint(cls, v: bytes, pad: bytes, f: str) -> int:
+        r = 0
+        if len(v) % 4 != 0:
+            v = pad * (4 - (len(v) % 4)) + v
+        for i in range(0, len(v), 4):
+            r = (r << 32) | struct.unpack(f, v[i:i + 4])[0]
+        return r
+
+    def read_mpint1(self) -> int:
+        # NOTE: Data Type Enc @ http://www.snailbook.com/docs/protocol-1.5.txt
+        bits = struct.unpack('>H', self.read(2))[0]
+        n = (bits + 7) // 8
+        return self._parse_mpint(self.read(n), b'\x00', '>I')
+
+    def read_mpint2(self) -> int:
+        # NOTE: Section 5 @ https://www.ietf.org/rfc/rfc4251.txt
+        v = self.read_string()
+        if len(v) == 0:
+            return 0
+        pad, f = (b'\xff', '>i') if ord(v[0:1]) & 0x80 != 0 else (b'\x00', '>I')
+        return self._parse_mpint(v, pad, f)
+
+    def read_line(self) -> str:
+        return self._buf.readline().rstrip().decode('utf-8', 'replace')
+
+    def reset(self) -> None:
+        self._buf = io.BytesIO()
+        self._len = 0
diff --git a/src/ssh_audit/software.py b/src/ssh_audit/software.py
new file mode 100644
index 0000000..f13ebeb
--- /dev/null
+++ b/src/ssh_audit/software.py
@@ -0,0 +1,227 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+import re
+
+# pylint: disable=unused-import
+from typing import Dict, List, Set, Sequence, Tuple, Iterable  # noqa: F401
+from typing import Callable, Optional, Union, Any  # noqa: F401
+
+from ssh_audit.banner import Banner
+from ssh_audit.product import Product
+
+
+class Software:
+    def __init__(self, vendor: Optional[str], product: str, version: str, patch: Optional[str], os_version: Optional[str]) -> None:
+        self.__vendor = vendor
+        self.__product = product
+        self.__version = version
+        self.__patch = patch
+        self.__os = os_version
+
+    @property
+    def vendor(self) -> Optional[str]:
+        return self.__vendor
+
+    @property
+    def product(self) -> str:
+        return self.__product
+
+    @property
+    def version(self) -> str:
+        return self.__version
+
+    @property
+    def patch(self) -> Optional[str]:
+        return self.__patch
+
+    @property
+    def os(self) -> Optional[str]:
+        return self.__os
+
+    def compare_version(self, other: Union[None, 'Software', str]) -> int:
+        # pylint: disable=too-many-branches,too-many-return-statements
+        if other is None:
+            return 1
+        if isinstance(other, Software):
+            other = '{}{}'.format(other.version, other.patch or '')
+        else:
+            other = str(other)
+        mx = re.match(r'^([\d\.]+\d+)(.*)$', other)
+        if mx is not None:
+            oversion, opatch = mx.group(1), mx.group(2).strip()
+        else:
+            oversion, opatch = other, ''
+        if self.version < oversion:
+            return -1
+        elif self.version > oversion:
+            return 1
+        spatch = self.patch or ''
+        if self.product == Product.DropbearSSH:
+            if not re.match(r'^test\d.*$', opatch):
+                opatch = 'z{}'.format(opatch)
+            if not re.match(r'^test\d.*$', spatch):
+                spatch = 'z{}'.format(spatch)
+        elif self.product == Product.OpenSSH:
+            mx1 = re.match(r'^p(\d).*', opatch)
+            mx2 = re.match(r'^p(\d).*', spatch)
+            if not (bool(mx1) and bool(mx2)):
+                if mx1 is not None:
+                    opatch = mx1.group(1)
+                if mx2 is not None:
+                    spatch = mx2.group(1)
+            # OpenBSD version and p1 versions are considered the same.
+            if ((spatch == '') and (opatch == '1')) or ((spatch == '1') and (opatch == '')):
+                return 0
+        if spatch < opatch:
+            return -1
+        elif spatch > opatch:
+            return 1
+        return 0
+
+    def between_versions(self, vfrom: str, vtill: str) -> bool:
+        if bool(vfrom) and self.compare_version(vfrom) < 0:
+            return False
+        if bool(vtill) and self.compare_version(vtill) > 0:
+            return False
+        return True
+
+    def display(self, full: bool = True) -> str:
+        r = '{} '.format(self.vendor) if bool(self.vendor) else ''
+        r += self.product
+        if bool(self.version):
+            r += ' {}'.format(self.version)
+        if full:
+            patch = self.patch or ''
+            if self.product == Product.OpenSSH:
+                mx = re.match(r'^(p\d)(.*)$', patch)
+                if mx is not None:
+                    r += mx.group(1)
+                    patch = mx.group(2).strip()
+            if bool(patch):
+                r += ' ({})'.format(patch)
+            if bool(self.os):
+                r += ' running on {}'.format(self.os)
+        return r
+
+    def __str__(self) -> str:
+        return self.display()
+
+    def __repr__(self) -> str:
+        r = 'vendor={}, '.format(self.vendor) if bool(self.vendor) else ''
+        r += 'product={}'.format(self.product)
+        if bool(self.version):
+            r += ', version={}'.format(self.version)
+        if bool(self.patch):
+            r += ', patch={}'.format(self.patch)
+        if bool(self.os):
+            r += ', os={}'.format(self.os)
+        return '<{}({})>'.format(self.__class__.__name__, r)
+
+    @staticmethod
+    def _fix_patch(patch: str) -> Optional[str]:
+        return re.sub(r'^[-_\.]+', '', patch) or None
+
+    @staticmethod
+    def _fix_date(d: Optional[str]) -> Optional[str]:
+        if d is not None and len(d) == 8:
+            return '{}-{}-{}'.format(d[:4], d[4:6], d[6:8])
+        else:
+            return None
+
+    @classmethod
+    def _extract_os_version(cls, c: Optional[str]) -> Optional[str]:
+        if c is None:
+            return None
+        mx = re.match(r'^NetBSD(?:_Secure_Shell)?(?:[\s-]+(\d{8})(.*))?$', c)
+        if mx is not None:
+            d = cls._fix_date(mx.group(1))
+            return 'NetBSD' if d is None else 'NetBSD ({})'.format(d)
+        mx = re.match(r'^FreeBSD(?:\slocalisations)?[\s-]+(\d{8})(.*)$', c)
+        if not bool(mx):
+            mx = re.match(r'^[^@]+@FreeBSD\.org[\s-]+(\d{8})(.*)$', c)
+        if mx is not None:
+            d = cls._fix_date(mx.group(1))
+            return 'FreeBSD' if d is None else 'FreeBSD ({})'.format(d)
+        w = ['RemotelyAnywhere', 'DesktopAuthority', 'RemoteSupportManager']
+        for win_soft in w:
+            mx = re.match(r'^in ' + win_soft + r' ([\d\.]+\d)$', c)
+            if mx is not None:
+                ver = mx.group(1)
+                return 'Microsoft Windows ({} {})'.format(win_soft, ver)
+        generic = ['NetBSD', 'FreeBSD']
+        for g in generic:
+            if c.startswith(g) or c.endswith(g):
+                return g
+        return None
+
+    @classmethod
+    def parse(cls, banner: 'Banner') -> Optional['Software']:
+        # pylint: disable=too-many-return-statements
+        software = str(banner.software)
+        mx = re.match(r'^dropbear_([\d\.]+\d+)(.*)', software)
+        v: Optional[str] = None
+        if mx is not None:
+            patch = cls._fix_patch(mx.group(2))
+            v, p = 'Matt Johnston', Product.DropbearSSH
+            v = None
+            return cls(v, p, mx.group(1), patch, None)
+        mx = re.match(r'^OpenSSH[_\.-]+([\d\.]+\d+)(.*)', software)
+        if mx is not None:
+            patch = cls._fix_patch(mx.group(2))
+            v, p = 'OpenBSD', Product.OpenSSH
+            v = None
+            os_version = cls._extract_os_version(banner.comments)
+            return cls(v, p, mx.group(1), patch, os_version)
+        mx = re.match(r'^libssh-([\d\.]+\d+)(.*)', software)
+        if mx is not None:
+            patch = cls._fix_patch(mx.group(2))
+            v, p = None, Product.LibSSH
+            os_version = cls._extract_os_version(banner.comments)
+            return cls(v, p, mx.group(1), patch, os_version)
+        mx = re.match(r'^libssh_([\d\.]+\d+)(.*)', software)
+        if mx is not None:
+            patch = cls._fix_patch(mx.group(2))
+            v, p = None, Product.LibSSH
+            os_version = cls._extract_os_version(banner.comments)
+            return cls(v, p, mx.group(1), patch, os_version)
+        mx = re.match(r'^RomSShell_([\d\.]+\d+)(.*)', software)
+        if mx is not None:
+            patch = cls._fix_patch(mx.group(2))
+            v, p = 'Allegro Software', 'RomSShell'
+            return cls(v, p, mx.group(1), patch, None)
+        mx = re.match(r'^mpSSH_([\d\.]+\d+)', software)
+        if mx is not None:
+            v, p = 'HP', 'iLO (Integrated Lights-Out) sshd'
+            return cls(v, p, mx.group(1), None, None)
+        mx = re.match(r'^Cisco-([\d\.]+\d+)', software)
+        if mx is not None:
+            v, p = 'Cisco', 'IOS/PIX sshd'
+            return cls(v, p, mx.group(1), None, None)
+        mx = re.match(r'^tinyssh_(.*)', software)
+        if mx is not None:
+            return cls(None, Product.TinySSH, mx.group(1), None, None)
+        mx = re.match(r'^PuTTY_Release_(.*)', software)
+        if mx:
+            return cls(None, Product.PuTTY, mx.group(1), None, None)
+        return None
diff --git a/src/ssh_audit/ssh1.py b/src/ssh_audit/ssh1.py
new file mode 100644
index 0000000..f966b74
--- /dev/null
+++ b/src/ssh_audit/ssh1.py
@@ -0,0 +1,40 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+# pylint: disable=unused-import
+from typing import Dict, List, Set, Sequence, Tuple, Iterable  # noqa: F401
+from typing import Callable, Optional, Union, Any  # noqa: F401
+
+from ssh_audit.ssh1_crc32 import SSH1_CRC32
+
+
+class SSH1:
+    _crc32: Optional[SSH1_CRC32] = None
+    CIPHERS = ['none', 'idea', 'des', '3des', 'tss', 'rc4', 'blowfish']
+    AUTHS = ['none', 'rhosts', 'rsa', 'password', 'rhosts_rsa', 'tis', 'kerberos']
+
+    @classmethod
+    def crc32(cls, v: bytes) -> int:
+        if cls._crc32 is None:
+            cls._crc32 = SSH1_CRC32()
+        return cls._crc32.calc(v)
diff --git a/src/ssh_audit/ssh1_crc32.py b/src/ssh_audit/ssh1_crc32.py
new file mode 100644
index 0000000..55089ed
--- /dev/null
+++ b/src/ssh_audit/ssh1_crc32.py
@@ -0,0 +1,47 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+# pylint: disable=unused-import
+from typing import Dict, List, Set, Sequence, Tuple, Iterable  # noqa: F401
+from typing import Callable, Optional, Union, Any  # noqa: F401
+
+
+class SSH1_CRC32:
+    def __init__(self) -> None:
+        self._table = [0] * 256
+        for i in range(256):
+            crc = 0
+            n = i
+            for _ in range(8):
+                x = (crc ^ n) & 1
+                crc = (crc >> 1) ^ (x * 0xedb88320)
+                n = n >> 1
+                self._table[i] = crc
+
+    def calc(self, v: bytes) -> int:
+        crc, length = 0, len(v)
+        for i in range(length):
+            n = ord(v[i:i + 1])
+            n = n ^ (crc & 0xff)
+            crc = (crc >> 8) ^ self._table[n]
+        return crc
diff --git a/src/ssh_audit/ssh1_kexdb.py b/src/ssh_audit/ssh1_kexdb.py
new file mode 100644
index 0000000..c9810ce
--- /dev/null
+++ b/src/ssh_audit/ssh1_kexdb.py
@@ -0,0 +1,58 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+# pylint: disable=unused-import
+from typing import Dict, List, Set, Sequence, Tuple, Iterable  # noqa: F401
+from typing import Callable, Optional, Union, Any  # noqa: F401
+
+
+class SSH1_KexDB:  # pylint: disable=too-few-public-methods
+
+    FAIL_PLAINTEXT = 'no encryption/integrity'
+    FAIL_OPENSSH37_REMOVE = 'removed since OpenSSH 3.7'
+    FAIL_NA_BROKEN = 'not implemented in OpenSSH, broken algorithm'
+    FAIL_NA_UNSAFE = 'not implemented in OpenSSH (server), unsafe algorithm'
+    TEXT_CIPHER_IDEA = 'cipher used by commercial SSH'
+
+    ALGORITHMS: Dict[str, Dict[str, List[List[Optional[str]]]]] = {
+        'key': {
+            'ssh-rsa1': [['1.2.2']],
+        },
+        'enc': {
+            'none': [['1.2.2'], [FAIL_PLAINTEXT]],
+            'idea': [[None], [], [], [TEXT_CIPHER_IDEA]],
+            'des': [['2.3.0C'], [FAIL_NA_UNSAFE]],
+            '3des': [['1.2.2']],
+            'tss': [[''], [FAIL_NA_BROKEN]],
+            'rc4': [[], [FAIL_NA_BROKEN]],
+            'blowfish': [['1.2.2']],
+        },
+        'aut': {
+            'rhosts': [['1.2.2', '3.6'], [FAIL_OPENSSH37_REMOVE]],
+            'rsa': [['1.2.2']],
+            'password': [['1.2.2']],
+            'rhosts_rsa': [['1.2.2']],
+            'tis': [['1.2.2']],
+            'kerberos': [['1.2.2', '3.6'], [FAIL_OPENSSH37_REMOVE]],
+        }
+    }
diff --git a/src/ssh_audit/ssh1_publickeymessage.py b/src/ssh_audit/ssh1_publickeymessage.py
new file mode 100644
index 0000000..67c4dec
--- /dev/null
+++ b/src/ssh_audit/ssh1_publickeymessage.py
@@ -0,0 +1,144 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+# pylint: disable=unused-import
+from typing import Dict, List, Set, Sequence, Tuple, Iterable  # noqa: F401
+from typing import Callable, Optional, Union, Any  # noqa: F401
+
+from ssh_audit.ssh1 import SSH1
+from ssh_audit.readbuf import ReadBuf
+from ssh_audit.utils import Utils
+from ssh_audit.writebuf import WriteBuf
+
+
+class SSH1_PublicKeyMessage:
+    def __init__(self, cookie: bytes, skey: Tuple[int, int, int], hkey: Tuple[int, int, int], pflags: int, cmask: int, amask: int) -> None:
+        if len(skey) != 3:
+            raise ValueError('invalid server key pair: {}'.format(skey))
+        if len(hkey) != 3:
+            raise ValueError('invalid host key pair: {}'.format(hkey))
+        self.__cookie = cookie
+        self.__server_key = skey
+        self.__host_key = hkey
+        self.__protocol_flags = pflags
+        self.__supported_ciphers_mask = cmask
+        self.__supported_authentications_mask = amask
+
+    @property
+    def cookie(self) -> bytes:
+        return self.__cookie
+
+    @property
+    def server_key_bits(self) -> int:
+        return self.__server_key[0]
+
+    @property
+    def server_key_public_exponent(self) -> int:
+        return self.__server_key[1]
+
+    @property
+    def server_key_public_modulus(self) -> int:
+        return self.__server_key[2]
+
+    @property
+    def host_key_bits(self) -> int:
+        return self.__host_key[0]
+
+    @property
+    def host_key_public_exponent(self) -> int:
+        return self.__host_key[1]
+
+    @property
+    def host_key_public_modulus(self) -> int:
+        return self.__host_key[2]
+
+    @property
+    def host_key_fingerprint_data(self) -> bytes:
+        # pylint: disable=protected-access
+        mod = WriteBuf._create_mpint(self.host_key_public_modulus, False)
+        e = WriteBuf._create_mpint(self.host_key_public_exponent, False)
+        return mod + e
+
+    @property
+    def protocol_flags(self) -> int:
+        return self.__protocol_flags
+
+    @property
+    def supported_ciphers_mask(self) -> int:
+        return self.__supported_ciphers_mask
+
+    @property
+    def supported_ciphers(self) -> List[str]:
+        ciphers = []
+        for i in range(len(SSH1.CIPHERS)):  # pylint: disable=consider-using-enumerate
+            if self.__supported_ciphers_mask & (1 << i) != 0:
+                ciphers.append(Utils.to_text(SSH1.CIPHERS[i]))
+        return ciphers
+
+    @property
+    def supported_authentications_mask(self) -> int:
+        return self.__supported_authentications_mask
+
+    @property
+    def supported_authentications(self) -> List[str]:
+        auths = []
+        for i in range(1, len(SSH1.AUTHS)):
+            if self.__supported_authentications_mask & (1 << i) != 0:
+                auths.append(Utils.to_text(SSH1.AUTHS[i]))
+        return auths
+
+    def write(self, wbuf: 'WriteBuf') -> None:
+        wbuf.write(self.cookie)
+        wbuf.write_int(self.server_key_bits)
+        wbuf.write_mpint1(self.server_key_public_exponent)
+        wbuf.write_mpint1(self.server_key_public_modulus)
+        wbuf.write_int(self.host_key_bits)
+        wbuf.write_mpint1(self.host_key_public_exponent)
+        wbuf.write_mpint1(self.host_key_public_modulus)
+        wbuf.write_int(self.protocol_flags)
+        wbuf.write_int(self.supported_ciphers_mask)
+        wbuf.write_int(self.supported_authentications_mask)
+
+    @property
+    def payload(self) -> bytes:
+        wbuf = WriteBuf()
+        self.write(wbuf)
+        return wbuf.write_flush()
+
+    @classmethod
+    def parse(cls, payload: bytes) -> 'SSH1_PublicKeyMessage':
+        buf = ReadBuf(payload)
+        cookie = buf.read(8)
+        server_key_bits = buf.read_int()
+        server_key_exponent = buf.read_mpint1()
+        server_key_modulus = buf.read_mpint1()
+        skey = (server_key_bits, server_key_exponent, server_key_modulus)
+        host_key_bits = buf.read_int()
+        host_key_exponent = buf.read_mpint1()
+        host_key_modulus = buf.read_mpint1()
+        hkey = (host_key_bits, host_key_exponent, host_key_modulus)
+        pflags = buf.read_int()
+        cmask = buf.read_int()
+        amask = buf.read_int()
+        pkm = cls(cookie, skey, hkey, pflags, cmask, amask)
+        return pkm
diff --git a/src/ssh_audit/ssh2_kex.py b/src/ssh_audit/ssh2_kex.py
new file mode 100644
index 0000000..0c31f3d
--- /dev/null
+++ b/src/ssh_audit/ssh2_kex.py
@@ -0,0 +1,136 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017-2020 Joe Testa (jtesta@positronsecurity.com)
+   Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+# pylint: disable=unused-import
+from typing import Dict, List, Set, Sequence, Tuple, Iterable  # noqa: F401
+from typing import Callable, Optional, Union, Any  # noqa: F401
+
+from ssh_audit.ssh2_kexparty import SSH2_KexParty
+from ssh_audit.readbuf import ReadBuf
+from ssh_audit.writebuf import WriteBuf
+
+
+class SSH2_Kex:
+    def __init__(self, cookie: bytes, kex_algs: List[str], key_algs: List[str], cli: 'SSH2_KexParty', srv: 'SSH2_KexParty', follows: bool, unused: int = 0) -> None:
+        self.__cookie = cookie
+        self.__kex_algs = kex_algs
+        self.__key_algs = key_algs
+        self.__client = cli
+        self.__server = srv
+        self.__follows = follows
+        self.__unused = unused
+
+        self.__rsa_key_sizes: Dict[str, Tuple[int, int]] = {}
+        self.__dh_modulus_sizes: Dict[str, Tuple[int, int]] = {}
+        self.__host_keys: Dict[str, bytes] = {}
+
+    @property
+    def cookie(self) -> bytes:
+        return self.__cookie
+
+    @property
+    def kex_algorithms(self) -> List[str]:
+        return self.__kex_algs
+
+    @property
+    def key_algorithms(self) -> List[str]:
+        return self.__key_algs
+
+    # client_to_server
+    @property
+    def client(self) -> 'SSH2_KexParty':
+        return self.__client
+
+    # server_to_client
+    @property
+    def server(self) -> 'SSH2_KexParty':
+        return self.__server
+
+    @property
+    def follows(self) -> bool:
+        return self.__follows
+
+    @property
+    def unused(self) -> int:
+        return self.__unused
+
+    def set_rsa_key_size(self, rsa_type: str, hostkey_size: int, ca_size: int = -1) -> None:
+        self.__rsa_key_sizes[rsa_type] = (hostkey_size, ca_size)
+
+    def rsa_key_sizes(self) -> Dict[str, Tuple[int, int]]:
+        return self.__rsa_key_sizes
+
+    def set_dh_modulus_size(self, gex_alg: str, modulus_size: int) -> None:
+        self.__dh_modulus_sizes[gex_alg] = (modulus_size, -1)
+
+    def dh_modulus_sizes(self) -> Dict[str, Tuple[int, int]]:
+        return self.__dh_modulus_sizes
+
+    def set_host_key(self, key_type: str, hostkey: bytes) -> None:
+        self.__host_keys[key_type] = hostkey
+
+    def host_keys(self) -> Dict[str, bytes]:
+        return self.__host_keys
+
+    def write(self, wbuf: 'WriteBuf') -> None:
+        wbuf.write(self.cookie)
+        wbuf.write_list(self.kex_algorithms)
+        wbuf.write_list(self.key_algorithms)
+        wbuf.write_list(self.client.encryption)
+        wbuf.write_list(self.server.encryption)
+        wbuf.write_list(self.client.mac)
+        wbuf.write_list(self.server.mac)
+        wbuf.write_list(self.client.compression)
+        wbuf.write_list(self.server.compression)
+        wbuf.write_list(self.client.languages)
+        wbuf.write_list(self.server.languages)
+        wbuf.write_bool(self.follows)
+        wbuf.write_int(self.__unused)
+
+    @property
+    def payload(self) -> bytes:
+        wbuf = WriteBuf()
+        self.write(wbuf)
+        return wbuf.write_flush()
+
+    @classmethod
+    def parse(cls, payload: bytes) -> 'SSH2_Kex':
+        buf = ReadBuf(payload)
+        cookie = buf.read(16)
+        kex_algs = buf.read_list()
+        key_algs = buf.read_list()
+        cli_enc = buf.read_list()
+        srv_enc = buf.read_list()
+        cli_mac = buf.read_list()
+        srv_mac = buf.read_list()
+        cli_compression = buf.read_list()
+        srv_compression = buf.read_list()
+        cli_languages = buf.read_list()
+        srv_languages = buf.read_list()
+        follows = buf.read_bool()
+        unused = buf.read_int()
+        cli = SSH2_KexParty(cli_enc, cli_mac, cli_compression, cli_languages)
+        srv = SSH2_KexParty(srv_enc, srv_mac, srv_compression, srv_languages)
+        kex = cls(cookie, kex_algs, key_algs, cli, srv, follows, unused)
+        return kex
diff --git a/src/ssh_audit/ssh2_kexdb.py b/src/ssh_audit/ssh2_kexdb.py
new file mode 100644
index 0000000..643d9c6
--- /dev/null
+++ b/src/ssh_audit/ssh2_kexdb.py
@@ -0,0 +1,280 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017-2021 Joe Testa (jtesta@positronsecurity.com)
+   Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+# pylint: disable=unused-import
+from typing import Dict, List, Set, Sequence, Tuple, Iterable  # noqa: F401
+from typing import Callable, Optional, Union, Any  # noqa: F401
+
+
+class SSH2_KexDB:  # pylint: disable=too-few-public-methods
+    WARN_OPENSSH74_UNSAFE = 'disabled (in client) since OpenSSH 7.4, unsafe algorithm'
+    WARN_OPENSSH72_LEGACY = 'disabled (in client) since OpenSSH 7.2, legacy algorithm'
+    FAIL_OPENSSH70_LEGACY = 'removed since OpenSSH 7.0, legacy algorithm'
+    FAIL_OPENSSH70_WEAK = 'removed (in server) and disabled (in client) since OpenSSH 7.0, weak algorithm'
+    FAIL_OPENSSH70_LOGJAM = 'disabled (in client) since OpenSSH 7.0, logjam attack'
+    INFO_OPENSSH69_CHACHA = 'default cipher since OpenSSH 6.9.'
+    FAIL_OPENSSH67_UNSAFE = 'removed (in server) since OpenSSH 6.7, unsafe algorithm'
+    FAIL_OPENSSH61_REMOVE = 'removed since OpenSSH 6.1, removed from specification'
+    FAIL_OPENSSH31_REMOVE = 'removed since OpenSSH 3.1'
+    INFO_OPENSSH82_FUTURE_DEPRECATION = 'a future deprecation notice has been issued in OpenSSH 8.2: https://www.openssh.com/txt/release-8.2'
+    FAIL_DBEAR67_DISABLED = 'disabled since Dropbear SSH 2015.67'
+    FAIL_DBEAR53_DISABLED = 'disabled since Dropbear SSH 0.53'
+    FAIL_DEPRECATED_CIPHER = 'deprecated cipher'
+    FAIL_WEAK_CIPHER = 'using weak cipher'
+    FAIL_WEAK_ALGORITHM = 'using weak/obsolete algorithm'
+    FAIL_PLAINTEXT = 'no encryption/integrity'
+    FAIL_DEPRECATED_MAC = 'deprecated MAC'
+    FAIL_1024BIT_MODULUS = 'using small 1024-bit modulus'
+    FAIL_UNPROVEN = 'using unproven algorithm'
+    FAIL_HASH_WEAK = 'using weak hashing algorithm'
+    WARN_CURVES_WEAK = 'using weak elliptic curves'
+    WARN_RNDSIG_KEY = 'using weak random number generator could reveal the key'
+    WARN_HASH_WEAK = 'using weak hashing algorithm'
+    WARN_CIPHER_MODE = 'using weak cipher mode'
+    WARN_BLOCK_SIZE = 'using small 64-bit block size'
+    WARN_CIPHER_WEAK = 'using weak cipher'
+    WARN_ENCRYPT_AND_MAC = 'using encrypt-and-MAC mode'
+    WARN_TAG_SIZE = 'using small 64-bit tag size'
+    WARN_TAG_SIZE_96 = 'using small 96-bit tag size'
+    WARN_EXPERIMENTAL = 'using experimental algorithm'
+    WARN_OBSOLETE = 'using obsolete algorithm'
+    WARN_UNTRUSTED = 'using untrusted algorithm'
+
+    ALGORITHMS: Dict[str, Dict[str, List[List[Optional[str]]]]] = {
+        # Format: 'algorithm_name': [['version_first_appeared_in'], [reason_for_failure1, reason_for_failure2, ...], [warning1, warning2, ...]]
+        'kex': {
+            'diffie-hellman-group1-sha1': [['2.3.0,d0.28,l10.2', '6.6', '6.9'], [FAIL_1024BIT_MODULUS, FAIL_OPENSSH67_UNSAFE, FAIL_OPENSSH70_LOGJAM], [WARN_HASH_WEAK]],
+            'gss-group1-sha1-toWM5Slw5Ew8Mqkay+al2g==': [[], [FAIL_1024BIT_MODULUS, FAIL_OPENSSH67_UNSAFE, FAIL_OPENSSH70_LOGJAM], [WARN_HASH_WEAK]],
+            'gss-gex-sha1-eipGX3TCiQSrx573bT1o1Q==': [[], [], [WARN_HASH_WEAK]],
+            'gss-gex-sha1-toWM5Slw5Ew8Mqkay+al2g==': [[], [], [WARN_HASH_WEAK]],
+            'gss-gex-sha1-': [[], [], [WARN_HASH_WEAK]],
+            'gss-group1-sha1-eipGX3TCiQSrx573bT1o1Q==': [[], [FAIL_1024BIT_MODULUS], [WARN_HASH_WEAK]],
+            'gss-group1-sha1-': [[], [FAIL_1024BIT_MODULUS], [WARN_HASH_WEAK]],
+            'gss-group14-sha1-': [[], [], [WARN_HASH_WEAK]],
+            'gss-group14-sha1-eipGX3TCiQSrx573bT1o1Q==': [[], [], [WARN_HASH_WEAK]],
+            'gss-group14-sha1-toWM5Slw5Ew8Mqkay+al2g==': [[], [], [WARN_HASH_WEAK]],
+            'gss-group14-sha256-': [[]],
+            'gss-group14-sha256-toWM5Slw5Ew8Mqkay+al2g==': [[]],
+            'gss-group15-sha512-': [[]],
+            'gss-group15-sha512-toWM5Slw5Ew8Mqkay+al2g==': [[]],
+            'gss-group16-sha512-': [[]],
+            'gss-nistp256-sha256-': [[], [WARN_CURVES_WEAK]],
+            'gss-curve25519-sha256-': [[]],
+            'diffie-hellman-group1-sha256': [[], [FAIL_1024BIT_MODULUS]],
+            'diffie-hellman-group14-sha1': [['3.9,d0.53,l10.6.0'], [], [WARN_HASH_WEAK]],
+            'diffie-hellman-group14-sha256': [['7.3,d2016.73']],
+            'diffie-hellman-group14-sha256@ssh.com': [[]],
+            'diffie-hellman-group15-sha256': [[]],
+            'diffie-hellman-group15-sha256@ssh.com': [[]],
+            'diffie-hellman-group15-sha384@ssh.com': [[]],
+            'diffie-hellman-group15-sha512': [[]],
+            'diffie-hellman-group16-sha256': [[]],
+            'diffie-hellman-group16-sha384@ssh.com': [[]],
+            'diffie-hellman-group16-sha512': [['7.3,d2016.73']],
+            'diffie-hellman-group16-sha512@ssh.com': [[]],
+            'diffie-hellman-group17-sha512': [[]],
+            'diffie-hellman-group18-sha512': [['7.3']],
+            'diffie-hellman-group18-sha512@ssh.com': [[]],
+            'diffie-hellman-group-exchange-sha1': [['2.3.0', '6.6', None], [FAIL_OPENSSH67_UNSAFE], [WARN_HASH_WEAK]],
+            'diffie-hellman-group-exchange-sha256': [['4.4']],
+            'diffie-hellman-group-exchange-sha256@ssh.com': [[]],
+            'diffie-hellman-group-exchange-sha512@ssh.com': [[]],
+            'ecdh-sha2-curve25519': [[], []],
+            'ecdh-sha2-nistb233': [[], [WARN_CURVES_WEAK]],
+            'ecdh-sha2-nistb409': [[], [WARN_CURVES_WEAK]],
+            'ecdh-sha2-nistk163': [[], [WARN_CURVES_WEAK]],
+            'ecdh-sha2-nistk233': [[], [WARN_CURVES_WEAK]],
+            'ecdh-sha2-nistk283': [[], [WARN_CURVES_WEAK]],
+            'ecdh-sha2-nistk409': [[], [WARN_CURVES_WEAK]],
+            'ecdh-sha2-nistp192': [[], [WARN_CURVES_WEAK]],
+            'ecdh-sha2-nistp224': [[], [WARN_CURVES_WEAK]],
+            'ecdh-sha2-nistp256': [['5.7,d2013.62,l10.6.0'], [WARN_CURVES_WEAK]],
+            'ecdh-sha2-nistp384': [['5.7,d2013.62'], [WARN_CURVES_WEAK]],
+            'ecdh-sha2-nistp521': [['5.7,d2013.62'], [WARN_CURVES_WEAK]],
+            'ecdh-sha2-nistt571': [[], [WARN_CURVES_WEAK]],
+            'ecdh-sha2-1.3.132.0.10': [[]],  # ECDH over secp256k1 (i.e.: the Bitcoin curve)
+            'curve25519-sha256@libssh.org': [['6.5,d2013.62,l10.6.0']],
+            'curve25519-sha256': [['7.4,d2018.76']],
+            'curve448-sha512': [[]],
+            'kexguess2@matt.ucc.asn.au': [['d2013.57']],
+            'rsa1024-sha1': [[], [FAIL_1024BIT_MODULUS], [WARN_HASH_WEAK]],
+            'rsa2048-sha256': [[]],
+            'sntrup4591761x25519-sha512@tinyssh.org': [['8.0', '8.4'], [], [WARN_EXPERIMENTAL]],
+            'sntrup761x25519-sha512@openssh.com': [['8.5'], [], [WARN_EXPERIMENTAL]],
+            'kexAlgoCurve25519SHA256': [[]],
+            'Curve25519SHA256': [[]],
+            'ext-info-c': [[]],  # Extension negotiation (RFC 8308)
+            'ext-info-s': [[]],  # Extension negotiation (RFC 8308)
+        },
+        'key': {
+            'ssh-rsa1': [[], [FAIL_WEAK_ALGORITHM]],
+            'rsa-sha2-256': [['7.2']],
+            'rsa-sha2-512': [['7.2']],
+            'ssh-ed25519': [['6.5,l10.7.0']],
+            'ssh-ed25519-cert-v01@openssh.com': [['6.5']],
+            'ssh-rsa': [['2.5.0,d0.28,l10.2'], [FAIL_HASH_WEAK], [], [INFO_OPENSSH82_FUTURE_DEPRECATION]],
+            'ssh-dss': [['2.1.0,d0.28,l10.2', '6.9'], [FAIL_1024BIT_MODULUS, FAIL_OPENSSH70_WEAK], [WARN_RNDSIG_KEY]],
+            'ecdsa-sha2-nistp256': [['5.7,d2013.62,l10.6.4'], [WARN_CURVES_WEAK], [WARN_RNDSIG_KEY]],
+            'ecdsa-sha2-nistp384': [['5.7,d2013.62,l10.6.4'], [WARN_CURVES_WEAK], [WARN_RNDSIG_KEY]],
+            'ecdsa-sha2-nistp521': [['5.7,d2013.62,l10.6.4'], [WARN_CURVES_WEAK], [WARN_RNDSIG_KEY]],
+            'ecdsa-sha2-1.3.132.0.10': [[], [], [WARN_RNDSIG_KEY]],  # ECDSA over secp256k1 (i.e.: the Bitcoin curve)
+            'x509v3-sign-dss': [[], [FAIL_1024BIT_MODULUS, FAIL_OPENSSH70_WEAK], [WARN_RNDSIG_KEY]],
+            'x509v3-sign-rsa': [[], [FAIL_HASH_WEAK], [], [INFO_OPENSSH82_FUTURE_DEPRECATION]],
+            'x509v3-sign-rsa-sha256@ssh.com': [[]],
+            'x509v3-ssh-dss': [[], [FAIL_1024BIT_MODULUS, FAIL_OPENSSH70_WEAK], [WARN_RNDSIG_KEY]],
+            'x509v3-ssh-rsa': [[], [FAIL_HASH_WEAK], [], [INFO_OPENSSH82_FUTURE_DEPRECATION]],
+            'ssh-rsa-cert-v00@openssh.com': [['5.4', '6.9'], [FAIL_OPENSSH70_LEGACY, FAIL_HASH_WEAK], [], [INFO_OPENSSH82_FUTURE_DEPRECATION]],
+            'ssh-dss-cert-v00@openssh.com': [['5.4', '6.9'], [FAIL_1024BIT_MODULUS, FAIL_OPENSSH70_LEGACY], [WARN_RNDSIG_KEY]],
+            'ssh-rsa-cert-v01@openssh.com': [['5.6'], [FAIL_HASH_WEAK], [], [INFO_OPENSSH82_FUTURE_DEPRECATION]],
+            'ssh-dss-cert-v01@openssh.com': [['5.6', '6.9'], [FAIL_1024BIT_MODULUS, FAIL_OPENSSH70_WEAK], [WARN_RNDSIG_KEY]],
+            'ecdsa-sha2-nistp256-cert-v01@openssh.com': [['5.7'], [WARN_CURVES_WEAK], [WARN_RNDSIG_KEY]],
+            'ecdsa-sha2-nistp384-cert-v01@openssh.com': [['5.7'], [WARN_CURVES_WEAK], [WARN_RNDSIG_KEY]],
+            'ecdsa-sha2-nistp521-cert-v01@openssh.com': [['5.7'], [WARN_CURVES_WEAK], [WARN_RNDSIG_KEY]],
+            'rsa-sha2-256-cert-v01@openssh.com': [['7.8']],
+            'rsa-sha2-512-cert-v01@openssh.com': [['7.8']],
+            'ssh-rsa-sha256@ssh.com': [[]],
+            'ssh-dss-sha256@ssh.com': [[], [FAIL_1024BIT_MODULUS]],
+            'sk-ecdsa-sha2-nistp256-cert-v01@openssh.com': [['8.2'], [WARN_CURVES_WEAK], [WARN_RNDSIG_KEY]],
+            'sk-ecdsa-sha2-nistp256@openssh.com': [['8.2'], [WARN_CURVES_WEAK], [WARN_RNDSIG_KEY]],
+            'sk-ssh-ed25519-cert-v01@openssh.com': [['8.2']],
+            'sk-ssh-ed25519@openssh.com': [['8.2']],
+            'ssh-gost2001': [[], [], [WARN_UNTRUSTED]],
+            'ssh-gost2012-256': [[], [], [WARN_UNTRUSTED]],
+            'ssh-gost2012-512': [[], [], [WARN_UNTRUSTED]],
+            'spi-sign-rsa': [[]],
+            'ssh-ed448': [[]],
+            'x509v3-ecdsa-sha2-nistp256': [[], [WARN_CURVES_WEAK]],
+            'x509v3-ecdsa-sha2-nistp384': [[], [WARN_CURVES_WEAK]],
+            'x509v3-ecdsa-sha2-nistp521': [[], [WARN_CURVES_WEAK]],
+            'x509v3-rsa2048-sha256': [[]],
+        },
+        'enc': {
+            'none': [['1.2.2,d2013.56,l10.2'], [FAIL_PLAINTEXT]],
+            'des': [[], [FAIL_WEAK_CIPHER], [WARN_CIPHER_MODE, WARN_BLOCK_SIZE]],
+            'des-cbc': [[], [FAIL_WEAK_CIPHER], [WARN_CIPHER_MODE, WARN_BLOCK_SIZE]],
+            'des-cbc@ssh.com': [[], [FAIL_WEAK_CIPHER], [WARN_CIPHER_MODE, WARN_BLOCK_SIZE]],
+            'des-cbc-ssh1': [[], [FAIL_WEAK_CIPHER], [WARN_CIPHER_MODE, WARN_BLOCK_SIZE]],
+            '3des': [[], [FAIL_OPENSSH67_UNSAFE], [WARN_OPENSSH74_UNSAFE, WARN_CIPHER_WEAK, WARN_CIPHER_MODE, WARN_BLOCK_SIZE]],
+            '3des-cbc': [['1.2.2,d0.28,l10.2', '6.6', None], [FAIL_OPENSSH67_UNSAFE], [WARN_OPENSSH74_UNSAFE, WARN_CIPHER_WEAK, WARN_CIPHER_MODE, WARN_BLOCK_SIZE]],
+            '3des-ctr': [['d0.52'], [FAIL_WEAK_CIPHER]],
+            'blowfish': [[], [FAIL_WEAK_ALGORITHM], [WARN_BLOCK_SIZE]],
+            'blowfish-cbc': [['1.2.2,d0.28,l10.2', '6.6,d0.52', '7.1,d0.52'], [FAIL_OPENSSH67_UNSAFE, FAIL_DBEAR53_DISABLED], [WARN_OPENSSH72_LEGACY, WARN_CIPHER_MODE, WARN_BLOCK_SIZE]],
+            'blowfish-ctr': [[], [FAIL_OPENSSH67_UNSAFE, FAIL_DBEAR53_DISABLED], [WARN_OPENSSH72_LEGACY, WARN_CIPHER_MODE, WARN_BLOCK_SIZE]],
+            'twofish-cbc': [['d0.28', 'd2014.66'], [FAIL_DBEAR67_DISABLED], [WARN_CIPHER_MODE]],
+            'twofish128-cbc': [['d0.47', 'd2014.66'], [FAIL_DBEAR67_DISABLED], [WARN_CIPHER_MODE]],
+            'twofish192-cbc': [[], [], [WARN_CIPHER_MODE]],
+            'twofish256-cbc': [['d0.47', 'd2014.66'], [FAIL_DBEAR67_DISABLED], [WARN_CIPHER_MODE]],
+            'twofish-ctr': [[]],
+            'twofish128-ctr': [['d2015.68']],
+            'twofish192-ctr': [[]],
+            'twofish256-ctr': [['d2015.68']],
+            'serpent128-cbc': [[], [FAIL_DEPRECATED_CIPHER], [WARN_CIPHER_MODE]],
+            'serpent192-cbc': [[], [FAIL_DEPRECATED_CIPHER], [WARN_CIPHER_MODE]],
+            'serpent256-cbc': [[], [FAIL_DEPRECATED_CIPHER], [WARN_CIPHER_MODE]],
+            'serpent128-ctr': [[], [FAIL_DEPRECATED_CIPHER]],
+            'serpent192-ctr': [[], [FAIL_DEPRECATED_CIPHER]],
+            'serpent256-ctr': [[], [FAIL_DEPRECATED_CIPHER]],
+            'idea-cbc': [[], [FAIL_DEPRECATED_CIPHER], [WARN_CIPHER_MODE]],
+            'idea-ctr': [[], [FAIL_DEPRECATED_CIPHER]],
+            'cast128-ctr': [[], [FAIL_DEPRECATED_CIPHER]],
+            'cast128-cbc': [['2.1.0', '6.6', '7.1'], [FAIL_OPENSSH67_UNSAFE], [WARN_OPENSSH72_LEGACY, WARN_CIPHER_MODE, WARN_BLOCK_SIZE]],
+            'arcfour': [['2.1.0', '6.6', '7.1'], [FAIL_OPENSSH67_UNSAFE], [WARN_OPENSSH72_LEGACY, WARN_CIPHER_WEAK]],
+            'arcfour128': [['4.2', '6.6', '7.1'], [FAIL_OPENSSH67_UNSAFE], [WARN_OPENSSH72_LEGACY, WARN_CIPHER_WEAK]],
+            'arcfour256': [['4.2', '6.6', '7.1'], [FAIL_OPENSSH67_UNSAFE], [WARN_OPENSSH72_LEGACY, WARN_CIPHER_WEAK]],
+            'aes128-cbc': [['2.3.0,d0.28,l10.2', '6.6', None], [FAIL_OPENSSH67_UNSAFE], [WARN_CIPHER_MODE]],
+            'aes192-cbc': [['2.3.0,l10.2', '6.6', None], [FAIL_OPENSSH67_UNSAFE], [WARN_CIPHER_MODE]],
+            'aes256-cbc': [['2.3.0,d0.47,l10.2', '6.6', None], [FAIL_OPENSSH67_UNSAFE], [WARN_CIPHER_MODE]],
+            'rijndael128-cbc': [['2.3.0', '3.0.2'], [FAIL_OPENSSH31_REMOVE], [WARN_CIPHER_MODE]],
+            'rijndael192-cbc': [['2.3.0', '3.0.2'], [FAIL_OPENSSH31_REMOVE], [WARN_CIPHER_MODE]],
+            'rijndael256-cbc': [['2.3.0', '3.0.2'], [FAIL_OPENSSH31_REMOVE], [WARN_CIPHER_MODE]],
+            'rijndael-cbc@lysator.liu.se': [['2.3.0', '6.6', '7.1'], [FAIL_OPENSSH67_UNSAFE], [WARN_OPENSSH72_LEGACY, WARN_CIPHER_MODE]],
+            'aes128-ctr': [['3.7,d0.52,l10.4.1']],
+            'aes192-ctr': [['3.7,l10.4.1']],
+            'aes256-ctr': [['3.7,d0.52,l10.4.1']],
+            'aes128-gcm': [[]],
+            'aes256-gcm': [[]],
+            'AEAD_AES_128_GCM': [[]],
+            'AEAD_AES_256_GCM': [[]],
+            'aes128-gcm@openssh.com': [['6.2']],
+            'aes256-gcm@openssh.com': [['6.2']],
+            'chacha20-poly1305': [[], [], [], [INFO_OPENSSH69_CHACHA]],
+            'chacha20-poly1305@openssh.com': [['6.5'], [], [], [INFO_OPENSSH69_CHACHA]],
+            'camellia128-cbc': [[], [], [WARN_CIPHER_MODE]],
+            'camellia128-ctr': [[]],
+            'camellia192-cbc': [[], [], [WARN_CIPHER_MODE]],
+            'camellia192-ctr': [[]],
+            'camellia256-cbc': [[], [], [WARN_CIPHER_MODE]],
+            'camellia256-ctr': [[]],
+            'crypticore128@ssh.com': [[], [FAIL_UNPROVEN]],
+            'seed-cbc@ssh.com': [[], [], [WARN_OBSOLETE, WARN_CIPHER_MODE]],
+        },
+        'mac': {
+            'none': [['d2013.56'], [FAIL_PLAINTEXT]],
+            'hmac-sha1': [['2.1.0,d0.28,l10.2'], [], [WARN_ENCRYPT_AND_MAC, WARN_HASH_WEAK]],
+            'hmac-sha1-96': [['2.5.0,d0.47', '6.6', '7.1'], [FAIL_OPENSSH67_UNSAFE], [WARN_OPENSSH72_LEGACY, WARN_ENCRYPT_AND_MAC, WARN_HASH_WEAK]],
+            'hmac-sha2-56': [[], [], [WARN_TAG_SIZE, WARN_ENCRYPT_AND_MAC]],
+            'hmac-sha2-224': [[], [], [WARN_TAG_SIZE, WARN_ENCRYPT_AND_MAC]],
+            'hmac-sha2-256': [['5.9,d2013.56,l10.7.0'], [], [WARN_ENCRYPT_AND_MAC]],
+            'hmac-sha2-256-96': [['5.9', '6.0'], [FAIL_OPENSSH61_REMOVE], [WARN_ENCRYPT_AND_MAC]],
+            'hmac-sha2-384': [[], [], [WARN_ENCRYPT_AND_MAC]],
+            'hmac-sha2-512': [['5.9,d2013.56,l10.7.0'], [], [WARN_ENCRYPT_AND_MAC]],
+            'hmac-sha2-512-96': [['5.9', '6.0'], [FAIL_OPENSSH61_REMOVE], [WARN_ENCRYPT_AND_MAC]],
+            'hmac-sha3-224': [[], [], [WARN_ENCRYPT_AND_MAC]],
+            'hmac-sha3-256': [[], [], [WARN_ENCRYPT_AND_MAC]],
+            'hmac-sha3-384': [[], [], [WARN_ENCRYPT_AND_MAC]],
+            'hmac-sha3-512': [[], [], [WARN_ENCRYPT_AND_MAC]],
+            'hmac-sha256': [[], [], [WARN_ENCRYPT_AND_MAC]],
+            'hmac-sha256-96@ssh.com': [[], [], [WARN_ENCRYPT_AND_MAC, WARN_TAG_SIZE]],
+            'hmac-sha256@ssh.com': [[], [], [WARN_ENCRYPT_AND_MAC]],
+            'hmac-sha512': [[], [], [WARN_ENCRYPT_AND_MAC]],
+            'hmac-sha512@ssh.com': [[], [], [WARN_ENCRYPT_AND_MAC]],
+            'hmac-md5': [['2.1.0,d0.28', '6.6', '7.1'], [FAIL_OPENSSH67_UNSAFE], [WARN_OPENSSH72_LEGACY, WARN_ENCRYPT_AND_MAC, WARN_HASH_WEAK]],
+            'hmac-md5-96': [['2.5.0', '6.6', '7.1'], [FAIL_OPENSSH67_UNSAFE], [WARN_OPENSSH72_LEGACY, WARN_ENCRYPT_AND_MAC, WARN_HASH_WEAK]],
+            'hmac-ripemd': [[], [FAIL_DEPRECATED_MAC], [WARN_OPENSSH72_LEGACY, WARN_ENCRYPT_AND_MAC]],
+            'hmac-ripemd160': [['2.5.0', '6.6', '7.1'], [FAIL_OPENSSH67_UNSAFE], [WARN_OPENSSH72_LEGACY, WARN_ENCRYPT_AND_MAC]],
+            'hmac-ripemd160-96': [[], [FAIL_DEPRECATED_MAC], [WARN_ENCRYPT_AND_MAC, WARN_TAG_SIZE]],
+            'hmac-ripemd160@openssh.com': [['2.1.0', '6.6', '7.1'], [FAIL_OPENSSH67_UNSAFE], [WARN_OPENSSH72_LEGACY, WARN_ENCRYPT_AND_MAC]],
+            'umac-64@openssh.com': [['4.7'], [], [WARN_ENCRYPT_AND_MAC, WARN_TAG_SIZE]],
+            'umac-128@openssh.com': [['6.2'], [], [WARN_ENCRYPT_AND_MAC]],
+            'hmac-sha1-etm@openssh.com': [['6.2'], [], [WARN_HASH_WEAK]],
+            'hmac-sha1-96-etm@openssh.com': [['6.2', '6.6', None], [FAIL_OPENSSH67_UNSAFE], [WARN_HASH_WEAK]],
+            'hmac-sha2-256-96-etm@openssh.com': [[], [], [WARN_TAG_SIZE_96]],  # Despite the @openssh.com tag, it doesn't appear that this was ever shipped with OpenSSH; it is only implemented in AsyncSSH (?).
+            'hmac-sha2-512-96-etm@openssh.com': [[], [], [WARN_TAG_SIZE_96]],  # Despite the @openssh.com tag, it doesn't appear that this was ever shipped with OpenSSH; it is only implemented in AsyncSSH (?).
+            'hmac-sha2-256-etm@openssh.com': [['6.2']],
+            'hmac-sha2-512-etm@openssh.com': [['6.2']],
+            'hmac-md5-etm@openssh.com': [['6.2', '6.6', '7.1'], [FAIL_OPENSSH67_UNSAFE], [WARN_OPENSSH72_LEGACY, WARN_HASH_WEAK]],
+            'hmac-md5-96-etm@openssh.com': [['6.2', '6.6', '7.1'], [FAIL_OPENSSH67_UNSAFE], [WARN_OPENSSH72_LEGACY, WARN_HASH_WEAK]],
+            'hmac-ripemd160-etm@openssh.com': [['6.2', '6.6', '7.1'], [FAIL_OPENSSH67_UNSAFE], [WARN_OPENSSH72_LEGACY]],
+            'umac-32@openssh.com': [[], [], [WARN_ENCRYPT_AND_MAC, WARN_TAG_SIZE]],  # Despite having the @openssh.com suffix, this may never have shipped with OpenSSH (!).
+            'umac-64-etm@openssh.com': [['6.2'], [], [WARN_TAG_SIZE]],
+            'umac-96@openssh.com': [[], [], [WARN_ENCRYPT_AND_MAC]],  # Despite having the @openssh.com suffix, this may never have shipped with OpenSSH (!).
+            'umac-128-etm@openssh.com': [['6.2']],
+            'aes128-gcm': [[]],
+            'aes256-gcm': [[]],
+            'chacha20-poly1305@openssh.com': [[]],  # Despite the @openssh.com tag, this was never shipped as a MAC in OpenSSH (only as a cipher); it is only implemented as a MAC in Syncplify.
+            'crypticore-mac@ssh.com': [[], [FAIL_UNPROVEN]],
+            'AEAD_AES_128_GCM': [[]],
+            'AEAD_AES_256_GCM': [[]],
+        }
+    }
diff --git a/src/ssh_audit/ssh2_kexparty.py b/src/ssh_audit/ssh2_kexparty.py
new file mode 100644
index 0000000..52b5ac5
--- /dev/null
+++ b/src/ssh_audit/ssh2_kexparty.py
@@ -0,0 +1,50 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+# pylint: disable=unused-import
+from typing import Dict, List, Set, Sequence, Tuple, Iterable  # noqa: F401
+from typing import Callable, Optional, Union, Any  # noqa: F401
+
+
+class SSH2_KexParty:
+    def __init__(self, enc: List[str], mac: List[str], compression: List[str], languages: List[str]) -> None:
+        self.__enc = enc
+        self.__mac = mac
+        self.__compression = compression
+        self.__languages = languages
+
+    @property
+    def encryption(self) -> List[str]:
+        return self.__enc
+
+    @property
+    def mac(self) -> List[str]:
+        return self.__mac
+
+    @property
+    def compression(self) -> List[str]:
+        return self.__compression
+
+    @property
+    def languages(self) -> List[str]:
+        return self.__languages
diff --git a/src/ssh_audit/ssh_audit.py b/src/ssh_audit/ssh_audit.py
new file mode 100755
index 0000000..38b5095
--- /dev/null
+++ b/src/ssh_audit/ssh_audit.py
@@ -0,0 +1,1132 @@
+#!/usr/bin/env python3
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017-2021 Joe Testa (jtesta@positronsecurity.com)
+   Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+import concurrent.futures
+import copy
+import getopt
+import json
+import os
+import re
+import sys
+import traceback
+
+# pylint: disable=unused-import
+from typing import Dict, List, Set, Sequence, Tuple, Iterable  # noqa: F401
+from typing import Callable, Optional, Union, Any  # noqa: F401
+
+from ssh_audit.globals import VERSION
+from ssh_audit.globals import WINDOWS_MAN_PAGE
+from ssh_audit.algorithm import Algorithm
+from ssh_audit.algorithms import Algorithms
+from ssh_audit.auditconf import AuditConf
+from ssh_audit.banner import Banner
+from ssh_audit import exitcodes
+from ssh_audit.fingerprint import Fingerprint
+from ssh_audit.gextest import GEXTest
+from ssh_audit.hostkeytest import HostKeyTest
+from ssh_audit.outputbuffer import OutputBuffer
+from ssh_audit.policy import Policy
+from ssh_audit.product import Product
+from ssh_audit.protocol import Protocol
+from ssh_audit.software import Software
+from ssh_audit.ssh1_kexdb import SSH1_KexDB
+from ssh_audit.ssh1_publickeymessage import SSH1_PublicKeyMessage
+from ssh_audit.ssh2_kex import SSH2_Kex
+from ssh_audit.ssh2_kexdb import SSH2_KexDB
+from ssh_audit.ssh_socket import SSH_Socket
+from ssh_audit.utils import Utils
+from ssh_audit.versionvulnerabilitydb import VersionVulnerabilityDB
+
+# Only import colorama under Windows.  Other OSes can natively handle terminal colors.
+if sys.platform == 'win32':
+    try:
+        from colorama import init as colorama_init
+        colorama_init()
+    except ImportError:
+        pass
+
+
+def usage(err: Optional[str] = None) -> None:
+    retval = exitcodes.GOOD
+    uout = OutputBuffer()
+    p = os.path.basename(sys.argv[0])
+    uout.head('# {} {}, https://github.com/jtesta/ssh-audit\n'.format(p, VERSION))
+    if err is not None and len(err) > 0:
+        uout.fail('\n' + err)
+        retval = exitcodes.UNKNOWN_ERROR
+    uout.info('usage: {0} [options] <host>\n'.format(p))
+    uout.info('   -h,  --help             print this help')
+    uout.info('   -1,  --ssh1             force ssh version 1 only')
+    uout.info('   -2,  --ssh2             force ssh version 2 only')
+    uout.info('   -4,  --ipv4             enable IPv4 (order of precedence)')
+    uout.info('   -6,  --ipv6             enable IPv6 (order of precedence)')
+    uout.info('   -b,  --batch            batch output')
+    uout.info('   -c,  --client-audit     starts a server on port 2222 to audit client\n                               software config (use -p to change port;\n                               use -t to change timeout)')
+    uout.info('   -d,  --debug            debug output')
+    uout.info('   -j,  --json             JSON output (use -jj to enable indents)')
+    uout.info('   -l,  --level=<level>    minimum output level (info|warn|fail)')
+    uout.info('   -L,  --list-policies    list all the official, built-in policies')
+    uout.info('        --lookup=<alg1,alg2,...>    looks up an algorithm(s) without\n                                    connecting to a server')
+    uout.info('   -M,  --make-policy=<policy.txt>  creates a policy based on the target server\n                                    (i.e.: the target server has the ideal\n                                    configuration that other servers should\n                                    adhere to)')
+    uout.info('   -m,  --manual           print the man page (Windows only)')
+    uout.info('   -n,  --no-colors        disable colors')
+    uout.info('   -p,  --port=<port>      port to connect')
+    uout.info('   -P,  --policy=<policy.txt>  run a policy test using the specified policy')
+    uout.info('   -t,  --timeout=<secs>   timeout (in seconds) for connection and reading\n                               (default: 5)')
+    uout.info('   -T,  --targets=<hosts.txt>  a file containing a list of target hosts (one\n                                   per line, format HOST[:PORT]).  Use --threads\n                                   to control concurrent scans.')
+    uout.info('        --threads=<threads>    number of threads to use when scanning multiple\n                                   targets (-T/--targets) (default: 32)')
+    uout.info('   -v,  --verbose          verbose output')
+    uout.sep()
+    uout.write()
+    sys.exit(retval)
+
+
+def output_algorithms(out: OutputBuffer, title: str, alg_db: Dict[str, Dict[str, List[List[Optional[str]]]]], alg_type: str, algorithms: List[str], unknown_algs: List[str], is_json_output: bool, program_retval: int, maxlen: int = 0, alg_sizes: Optional[Dict[str, Tuple[int, int]]] = None) -> int:  # pylint: disable=too-many-arguments
+    with out:
+        for algorithm in algorithms:
+            program_retval = output_algorithm(out, alg_db, alg_type, algorithm, unknown_algs, program_retval, maxlen, alg_sizes)
+    if not out.is_section_empty() and not is_json_output:
+        out.head('# ' + title)
+        out.flush_section()
+        out.sep()
+
+    return program_retval
+
+
+def output_algorithm(out: OutputBuffer, alg_db: Dict[str, Dict[str, List[List[Optional[str]]]]], alg_type: str, alg_name: str, unknown_algs: List[str], program_retval: int, alg_max_len: int = 0, alg_sizes: Optional[Dict[str, Tuple[int, int]]] = None) -> int:
+    prefix = '(' + alg_type + ') '
+    if alg_max_len == 0:
+        alg_max_len = len(alg_name)
+    padding = '' if out.batch else ' ' * (alg_max_len - len(alg_name))
+
+    # If this is an RSA host key or DH GEX, append the size to its name and fix
+    # the padding.
+    alg_name_with_size = None
+    if (alg_sizes is not None) and (alg_name in alg_sizes):
+        hostkey_size, ca_size = alg_sizes[alg_name]
+        if ca_size > 0:
+            alg_name_with_size = '%s (%d-bit cert/%d-bit CA)' % (alg_name, hostkey_size, ca_size)
+            padding = padding[0:-15]
+        else:
+            alg_name_with_size = '%s (%d-bit)' % (alg_name, hostkey_size)
+            padding = padding[0:-11]
+
+    texts = []
+    if len(alg_name.strip()) == 0:
+        return program_retval
+    alg_name_native = Utils.to_text(alg_name)
+    if alg_name_native in alg_db[alg_type]:
+        alg_desc = alg_db[alg_type][alg_name_native]
+        ldesc = len(alg_desc)
+        for idx, level in enumerate(['fail', 'warn', 'info']):
+            if level == 'info':
+                versions = alg_desc[0]
+                since_text = Algorithm.get_since_text(versions)
+                if since_text is not None and len(since_text) > 0:
+                    texts.append((level, since_text))
+            idx = idx + 1
+            if ldesc > idx:
+                for t in alg_desc[idx]:
+                    if t is None:
+                        continue
+                    texts.append((level, t))
+        if len(texts) == 0:
+            texts.append(('info', ''))
+    else:
+        texts.append(('warn', 'unknown algorithm'))
+        unknown_algs.append(alg_name)
+
+    alg_name = alg_name_with_size if alg_name_with_size is not None else alg_name
+    first = True
+    for level, text in texts:
+        if level == 'fail':
+            program_retval = exitcodes.FAILURE
+        elif level == 'warn' and program_retval != exitcodes.FAILURE:  # If a failure was found previously, don't downgrade to warning.
+            program_retval = exitcodes.WARNING
+
+        f = getattr(out, level)
+        comment = (padding + ' -- [' + level + '] ' + text) if text != '' else ''
+        if first:
+            if first and level == 'info':
+                f = out.good
+            f(prefix + alg_name + comment)
+            first = False
+        else:  # pylint: disable=else-if-used
+            if out.verbose:
+                f(prefix + alg_name + comment)
+            elif text != '':
+                comment = (padding + ' `- [' + level + '] ' + text)
+                f(' ' * len(prefix + alg_name) + comment)
+
+    return program_retval
+
+
+def output_compatibility(out: OutputBuffer, algs: Algorithms, client_audit: bool, for_server: bool = True) -> None:
+
+    # Don't output any compatibility info if we're doing a client audit.
+    if client_audit:
+        return
+
+    ssh_timeframe = algs.get_ssh_timeframe(for_server)
+    comp_text = []
+    for ssh_prod in [Product.OpenSSH, Product.DropbearSSH]:
+        if ssh_prod not in ssh_timeframe:
+            continue
+        v_from = ssh_timeframe.get_from(ssh_prod, for_server)
+        v_till = ssh_timeframe.get_till(ssh_prod, for_server)
+        if v_from is None:
+            continue
+        if v_till is None:
+            comp_text.append('{} {}+'.format(ssh_prod, v_from))
+        elif v_from == v_till:
+            comp_text.append('{} {}'.format(ssh_prod, v_from))
+        else:
+            software = Software(None, ssh_prod, v_from, None, None)
+            if software.compare_version(v_till) > 0:
+                tfmt = '{0} {1}+ (some functionality from {2})'
+            else:
+                tfmt = '{0} {1}-{2}'
+            comp_text.append(tfmt.format(ssh_prod, v_from, v_till))
+    if len(comp_text) > 0:
+        out.good('(gen) compatibility: ' + ', '.join(comp_text))
+
+
+def output_security_sub(out: OutputBuffer, sub: str, software: Optional[Software], client_audit: bool, padlen: int) -> None:
+    secdb = VersionVulnerabilityDB.CVE if sub == 'cve' else VersionVulnerabilityDB.TXT
+    if software is None or software.product not in secdb:
+        return
+    for line in secdb[software.product]:
+        vfrom: str = ''
+        vtill: str = ''
+        vfrom, vtill = line[0:2]
+        if not software.between_versions(vfrom, vtill):
+            continue
+        target: int = 0
+        name: str = ''
+        target, name = line[2:4]
+        is_server = target & 1 == 1
+        is_client = target & 2 == 2
+        # is_local = target & 4 == 4
+
+        # If this security entry applies only to servers, but we're testing a client, then skip it.  Similarly, skip entries that apply only to clients, but we're testing a server.
+        if (is_server and not is_client and client_audit) or (is_client and not is_server and not client_audit):
+            continue
+        p = '' if out.batch else ' ' * (padlen - len(name))
+        if sub == 'cve':
+            cvss: float = 0.0
+            descr: str = ''
+            cvss, descr = line[4:6]
+
+            # Critical CVSS scores (>= 8.0) are printed as a fail, otherwise they are printed as a warning.
+            out_func = out.warn
+            if cvss >= 8.0:
+                out_func = out.fail
+            out_func('(cve) {}{} -- (CVSSv2: {}) {}'.format(name, p, cvss, descr))
+        else:
+            descr = line[4]
+            out.fail('(sec) {}{} -- {}'.format(name, p, descr))
+
+
+def output_security(out: OutputBuffer, banner: Optional[Banner], client_audit: bool, padlen: int, is_json_output: bool) -> None:
+    with out:
+        if banner is not None:
+            software = Software.parse(banner)
+            output_security_sub(out, 'cve', software, client_audit, padlen)
+            output_security_sub(out, 'txt', software, client_audit, padlen)
+            if banner.protocol[0] == 1:
+                p = '' if out.batch else ' ' * (padlen - 14)
+                out.fail('(sec) SSH v1 enabled{} -- SSH v1 can be exploited to recover plaintext passwords'.format(p))
+    if not out.is_section_empty() and not is_json_output:
+        out.head('# security')
+        out.flush_section()
+        out.sep()
+
+
+def output_fingerprints(out: OutputBuffer, algs: Algorithms, is_json_output: bool) -> None:
+    with out:
+        fps = []
+        if algs.ssh1kex is not None:
+            name = 'ssh-rsa1'
+            fp = Fingerprint(algs.ssh1kex.host_key_fingerprint_data)
+            # bits = algs.ssh1kex.host_key_bits
+            fps.append((name, fp))
+        if algs.ssh2kex is not None:
+            host_keys = algs.ssh2kex.host_keys()
+            for host_key_type in algs.ssh2kex.host_keys():
+                if host_keys[host_key_type] is None:
+                    continue
+
+                fp = Fingerprint(host_keys[host_key_type])
+
+                # Workaround for Python's order-indifference in dicts.  We might get a random RSA type (ssh-rsa, rsa-sha2-256, or rsa-sha2-512), so running the tool against the same server three times may give three different host key types here.  So if we have any RSA type, we will simply hard-code it to 'ssh-rsa'.
+                if host_key_type in HostKeyTest.RSA_FAMILY:
+                    host_key_type = 'ssh-rsa'
+
+                # Skip over certificate host types (or we would return invalid fingerprints).
+                if '-cert-' not in host_key_type:
+                    fps.append((host_key_type, fp))
+        # Similarly, the host keys can be processed in random order due to Python's order-indifference in dicts.  So we sort this list before printing; this makes automated testing possible.
+        fps = sorted(fps)
+        for fpp in fps:
+            name, fp = fpp
+            out.good('(fin) {}: {}'.format(name, fp.sha256))
+
+            # Output the MD5 hash too if verbose mode is enabled.
+            if out.verbose:
+                out.info('(fin) {}: {} -- [info] do not rely on MD5 fingerprints for server identification; it is insecure for this use case'.format(name, fp.md5))
+
+    if not out.is_section_empty() and not is_json_output:
+        out.head('# fingerprints')
+        out.flush_section()
+        out.sep()
+
+
+# Returns True if no warnings or failures encountered in configuration.
+def output_recommendations(out: OutputBuffer, algs: Algorithms, software: Optional[Software], is_json_output: bool, padlen: int = 0) -> bool:
+
+    ret = True
+    # PuTTY's algorithms cannot be modified, so there's no point in issuing recommendations.
+    if (software is not None) and (software.product == Product.PuTTY):
+        max_vuln_version = 0.0
+        max_cvssv2_severity = 0.0
+        # Search the CVE database for the most recent vulnerable version and the max CVSSv2 score.
+        for cve_list in VersionVulnerabilityDB.CVE['PuTTY']:
+            vuln_version = float(cve_list[1])
+            cvssv2_severity = cve_list[4]
+
+            if vuln_version > max_vuln_version:
+                max_vuln_version = vuln_version
+            if cvssv2_severity > max_cvssv2_severity:
+                max_cvssv2_severity = cvssv2_severity
+
+        fn = out.warn
+        if max_cvssv2_severity > 8.0:
+            fn = out.fail
+
+        # Assuming that PuTTY versions will always increment by 0.01, we can calculate the first safe version by adding 0.01 to the latest vulnerable version.
+        current_version = float(software.version)
+        upgrade_to_version = max_vuln_version + 0.01
+        if current_version < upgrade_to_version:
+            out.head('# recommendations')
+            fn('(rec) Upgrade to PuTTY v%.2f' % upgrade_to_version)
+            out.sep()
+            ret = False
+        return ret
+
+    for_server = True
+    with out:
+        software, alg_rec = algs.get_recommendations(software, for_server)
+        for sshv in range(2, 0, -1):
+            if sshv not in alg_rec:
+                continue
+            for alg_type in ['kex', 'key', 'enc', 'mac']:
+                if alg_type not in alg_rec[sshv]:
+                    continue
+                for action in ['del', 'add', 'chg']:
+                    if action not in alg_rec[sshv][alg_type]:
+                        continue
+                    for name in alg_rec[sshv][alg_type][action]:
+                        p = '' if out.batch else ' ' * (padlen - len(name))
+                        chg_additional_info = ''
+                        if action == 'del':
+                            an, sg, fn = 'remove', '-', out.warn
+                            ret = False
+                            if alg_rec[sshv][alg_type][action][name] >= 10:
+                                fn = out.fail
+                        elif action == 'add':
+                            an, sg, fn = 'append', '+', out.good
+                        elif action == 'chg':
+                            an, sg, fn = 'change', '!', out.fail
+                            ret = False
+                            chg_additional_info = ' (increase modulus size to 2048 bits or larger)'
+                        b = '(SSH{})'.format(sshv) if sshv == 1 else ''
+                        fm = '(rec) {0}{1}{2}-- {3} algorithm to {4}{5} {6}'
+                        fn(fm.format(sg, name, p, alg_type, an, chg_additional_info, b))
+    if not out.is_section_empty() and not is_json_output:
+        if software is not None:
+            title = '(for {})'.format(software.display(False))
+        else:
+            title = ''
+        out.head('# algorithm recommendations {}'.format(title))
+        out.flush_section(sort_section=True)  # Sort the output so that it is always stable (needed for repeatable testing).
+        out.sep()
+    return ret
+
+
+# Output additional information & notes.
+def output_info(out: OutputBuffer, software: Optional['Software'], client_audit: bool, any_problems: bool, is_json_output: bool) -> None:
+    with out:
+        # Tell user that PuTTY cannot be hardened at the protocol-level.
+        if client_audit and (software is not None) and (software.product == Product.PuTTY):
+            out.warn('(nfo) PuTTY does not have the option of restricting any algorithms during the SSH handshake.')
+
+        # If any warnings or failures were given, print a link to the hardening guides.
+        if any_problems:
+            out.warn('(nfo) For hardening guides on common OSes, please see: <https://www.ssh-audit.com/hardening_guides.html>')
+
+    if not out.is_section_empty() and not is_json_output:
+        out.head('# additional info')
+        out.flush_section()
+        out.sep()
+
+
+# Returns a exitcodes.* flag to denote if any failures or warnings were encountered.
+def output(out: OutputBuffer, aconf: AuditConf, banner: Optional[Banner], header: List[str], client_host: Optional[str] = None, kex: Optional[SSH2_Kex] = None, pkm: Optional[SSH1_PublicKeyMessage] = None, print_target: bool = False) -> int:
+
+    program_retval = exitcodes.GOOD
+    client_audit = client_host is not None  # If set, this is a client audit.
+    sshv = 1 if pkm is not None else 2
+    algs = Algorithms(pkm, kex)
+    with out:
+        if print_target:
+            host = aconf.host
+
+            # Print the port if it's not the default of 22.
+            if aconf.port != 22:
+
+                # Check if this is an IPv6 address, as that is printed in a different format.
+                if Utils.is_ipv6_address(aconf.host):
+                    host = '[%s]:%d' % (aconf.host, aconf.port)
+                else:
+                    host = '%s:%d' % (aconf.host, aconf.port)
+
+            out.good('(gen) target: {}'. format(host))
+        if client_audit:
+            out.good('(gen) client IP: {}'.format(client_host))
+        if len(header) > 0:
+            out.info('(gen) header: ' + '\n'.join(header))
+        if banner is not None:
+            banner_line = '(gen) banner: {}'.format(banner)
+            if sshv == 1 or banner.protocol[0] == 1:
+                out.fail(banner_line)
+                out.fail('(gen) protocol SSH1 enabled')
+            else:
+                out.good(banner_line)
+
+            if not banner.valid_ascii:
+                # NOTE: RFC 4253, Section 4.2
+                out.warn('(gen) banner contains non-printable ASCII')
+
+            software = Software.parse(banner)
+            if software is not None:
+                out.good('(gen) software: {}'.format(software))
+        else:
+            software = None
+        output_compatibility(out, algs, client_audit)
+        if kex is not None:
+            compressions = [x for x in kex.server.compression if x != 'none']
+            if len(compressions) > 0:
+                cmptxt = 'enabled ({})'.format(', '.join(compressions))
+            else:
+                cmptxt = 'disabled'
+            out.good('(gen) compression: {}'.format(cmptxt))
+    if not out.is_section_empty() and not aconf.json:  # Print output when it exists and JSON output isn't requested.
+        out.head('# general')
+        out.flush_section()
+        out.sep()
+    maxlen = algs.maxlen + 1
+    output_security(out, banner, client_audit, maxlen, aconf.json)
+    # Filled in by output_algorithms() with unidentified algs.
+    unknown_algorithms: List[str] = []
+    if pkm is not None:
+        adb = SSH1_KexDB.ALGORITHMS
+        ciphers = pkm.supported_ciphers
+        auths = pkm.supported_authentications
+        title, atype = 'SSH1 host-key algorithms', 'key'
+        program_retval = output_algorithms(out, title, adb, atype, ['ssh-rsa1'], unknown_algorithms, aconf.json, program_retval, maxlen)
+        title, atype = 'SSH1 encryption algorithms (ciphers)', 'enc'
+        program_retval = output_algorithms(out, title, adb, atype, ciphers, unknown_algorithms, aconf.json, program_retval, maxlen)
+        title, atype = 'SSH1 authentication types', 'aut'
+        program_retval = output_algorithms(out, title, adb, atype, auths, unknown_algorithms, aconf.json, program_retval, maxlen)
+    if kex is not None:
+        adb = SSH2_KexDB.ALGORITHMS
+        title, atype = 'key exchange algorithms', 'kex'
+        program_retval = output_algorithms(out, title, adb, atype, kex.kex_algorithms, unknown_algorithms, aconf.json, program_retval, maxlen, kex.dh_modulus_sizes())
+        title, atype = 'host-key algorithms', 'key'
+        program_retval = output_algorithms(out, title, adb, atype, kex.key_algorithms, unknown_algorithms, aconf.json, program_retval, maxlen, kex.rsa_key_sizes())
+        title, atype = 'encryption algorithms (ciphers)', 'enc'
+        program_retval = output_algorithms(out, title, adb, atype, kex.server.encryption, unknown_algorithms, aconf.json, program_retval, maxlen)
+        title, atype = 'message authentication code algorithms', 'mac'
+        program_retval = output_algorithms(out, title, adb, atype, kex.server.mac, unknown_algorithms, aconf.json, program_retval, maxlen)
+    output_fingerprints(out, algs, aconf.json)
+    perfect_config = output_recommendations(out, algs, software, aconf.json, maxlen)
+    output_info(out, software, client_audit, not perfect_config, aconf.json)
+
+    if aconf.json:
+        out.reset()
+        # Build & write the JSON struct.
+        out.info(json.dumps(build_struct(aconf.host, banner, kex=kex, client_host=client_host), indent=4 if aconf.json_print_indent else None, sort_keys=True))
+    elif len(unknown_algorithms) > 0:  # If we encountered any unknown algorithms, ask the user to report them.
+        out.warn("\n\n!!! WARNING: unknown algorithm(s) found!: %s.  Please email the full output above to the maintainer (jtesta@positronsecurity.com), or create a Github issue at <https://github.com/jtesta/ssh-audit/issues>.\n" % ','.join(unknown_algorithms))
+
+    return program_retval
+
+
+def evaluate_policy(out: OutputBuffer, aconf: AuditConf, banner: Optional['Banner'], client_host: Optional[str], kex: Optional['SSH2_Kex'] = None) -> bool:
+
+    if aconf.policy is None:
+        raise RuntimeError('Internal error: cannot evaluate against null Policy!')
+
+    passed, error_struct, error_str = aconf.policy.evaluate(banner, kex)
+    if aconf.json:
+        json_struct = {'host': aconf.host, 'policy': aconf.policy.get_name_and_version(), 'passed': passed, 'errors': error_struct}
+        out.info(json.dumps(json_struct, indent=4 if aconf.json_print_indent else None, sort_keys=True))
+    else:
+        spacing = ''
+        if aconf.client_audit:
+            out.info("Client IP: %s" % client_host)
+            spacing = "   "  # So the fields below line up with 'Client IP: '.
+        else:
+            host = aconf.host
+            if aconf.port != 22:
+                # Check if this is an IPv6 address, as that is printed in a different format.
+                if Utils.is_ipv6_address(aconf.host):
+                    host = '[%s]:%d' % (aconf.host, aconf.port)
+                else:
+                    host = '%s:%d' % (aconf.host, aconf.port)
+
+            out.info("Host:   %s" % host)
+        out.info("Policy: %s%s" % (spacing, aconf.policy.get_name_and_version()))
+        out.info("Result: %s" % spacing, line_ended=False)
+
+        # Use these nice unicode characters in the result message, unless we're on Windows (the cmd.exe terminal doesn't display them properly).
+        icon_good = "✔ "
+        icon_fail = "❌ "
+        if Utils.is_windows():
+            icon_good = ""
+            icon_fail = ""
+
+        if passed:
+            out.good("%sPassed" % icon_good)
+        else:
+            out.fail("%sFailed!" % icon_fail)
+            out.warn("\nErrors:\n%s" % error_str)
+
+    return passed
+
+
+def list_policies(out: OutputBuffer) -> None:
+    '''Prints a list of server & client policies.'''
+
+    server_policy_names, client_policy_names = Policy.list_builtin_policies()
+
+    if len(server_policy_names) > 0:
+        out.head('\nServer policies:\n')
+        out.info("  * \"%s\"" % "\"\n  * \"".join(server_policy_names))
+
+    if len(client_policy_names) > 0:
+        out.head('\nClient policies:\n')
+        out.info("  * \"%s\"" % "\"\n  * \"".join(client_policy_names))
+
+    out.sep()
+    if len(server_policy_names) == 0 and len(client_policy_names) == 0:
+        out.fail("Error: no built-in policies found!")
+    else:
+        out.info("\nHint: Use -P and provide the full name of a policy to run a policy scan with.\n")
+    out.write()
+
+
+def make_policy(aconf: AuditConf, banner: Optional['Banner'], kex: Optional['SSH2_Kex'], client_host: Optional[str]) -> None:
+
+    # Set the source of this policy to the server host if this is a server audit, otherwise set it to the client address.
+    source: Optional[str] = aconf.host
+    if aconf.client_audit:
+        source = client_host
+
+    policy_data = Policy.create(source, banner, kex, aconf.client_audit)
+
+    if aconf.policy_file is None:
+        raise RuntimeError('Internal error: cannot write policy file since filename is None!')
+
+    # Open with mode 'x' (creates the file, or fails if it already exist).
+    succeeded = True
+    try:
+        with open(aconf.policy_file, 'x', encoding='utf-8') as f:
+            f.write(policy_data)
+    except FileExistsError:
+        succeeded = False
+
+    if succeeded:
+        print("Wrote policy to %s.  Customize as necessary, then run a policy scan with -P option." % aconf.policy_file)
+    else:
+        print("Error: file already exists: %s" % aconf.policy_file)
+
+
+def process_commandline(out: OutputBuffer, args: List[str], usage_cb: Callable[..., None]) -> 'AuditConf':  # pylint: disable=too-many-statements
+    # pylint: disable=too-many-branches
+    aconf = AuditConf()
+    try:
+        sopts = 'h1246M:p:P:jbcnvl:t:T:Lmd'
+        lopts = ['help', 'ssh1', 'ssh2', 'ipv4', 'ipv6', 'make-policy=', 'port=', 'policy=', 'json', 'batch', 'client-audit', 'no-colors', 'verbose', 'level=', 'timeout=', 'targets=', 'list-policies', 'lookup=', 'threads=', 'manual', 'debug']
+        opts, args = getopt.gnu_getopt(args, sopts, lopts)
+    except getopt.GetoptError as err:
+        usage_cb(str(err))
+    aconf.ssh1, aconf.ssh2 = False, False
+    host: str = ''
+    oport: Optional[str] = None
+    port: int = 0
+    for o, a in opts:
+        if o in ('-h', '--help'):
+            usage_cb()
+        elif o in ('-1', '--ssh1'):
+            aconf.ssh1 = True
+        elif o in ('-2', '--ssh2'):
+            aconf.ssh2 = True
+        elif o in ('-4', '--ipv4'):
+            aconf.ipv4 = True
+        elif o in ('-6', '--ipv6'):
+            aconf.ipv6 = True
+        elif o in ('-p', '--port'):
+            oport = a
+        elif o in ('-b', '--batch'):
+            aconf.batch = True
+            aconf.verbose = True
+        elif o in ('-c', '--client-audit'):
+            aconf.client_audit = True
+        elif o in ('-n', '--no-colors'):
+            aconf.colors = False
+            out.use_colors = False
+        elif o in ('-j', '--json'):
+            if aconf.json:  # If specified twice, enable indent printing.
+                aconf.json_print_indent = True
+            else:
+                aconf.json = True
+        elif o in ('-v', '--verbose'):
+            aconf.verbose = True
+            out.verbose = True
+        elif o in ('-l', '--level'):
+            if a not in ('info', 'warn', 'fail'):
+                usage_cb('level {} is not valid'.format(a))
+            aconf.level = a
+        elif o in ('-t', '--timeout'):
+            aconf.timeout = float(a)
+            aconf.timeout_set = True
+        elif o in ('-M', '--make-policy'):
+            aconf.make_policy = True
+            aconf.policy_file = a
+        elif o in ('-P', '--policy'):
+            aconf.policy_file = a
+        elif o in ('-T', '--targets'):
+            aconf.target_file = a
+        elif o == '--threads':
+            aconf.threads = int(a)
+        elif o in ('-L', '--list-policies'):
+            aconf.list_policies = True
+        elif o == '--lookup':
+            aconf.lookup = a
+        elif o in ('-m', '--manual'):
+            aconf.manual = True
+        elif o in ('-d', '--debug'):
+            aconf.debug = True
+            out.debug = True
+
+    if len(args) == 0 and aconf.client_audit is False and aconf.target_file is None and aconf.list_policies is False and aconf.lookup == '' and aconf.manual is False:
+        usage_cb()
+
+    if aconf.manual:
+        return aconf
+
+    if aconf.lookup != '':
+        return aconf
+
+    if aconf.list_policies:
+        list_policies(out)
+        sys.exit(exitcodes.GOOD)
+
+    if aconf.client_audit is False and aconf.target_file is None:
+        if oport is not None:
+            host = args[0]
+        else:
+            host, port = Utils.parse_host_and_port(args[0])
+        if not host and aconf.target_file is None:
+            usage_cb('host is empty')
+
+    if port == 0 and oport is None:
+        if aconf.client_audit:  # The default port to listen on during a client audit is 2222.
+            port = 2222
+        else:
+            port = 22
+
+    if oport is not None:
+        port = Utils.parse_int(oport)
+        if port <= 0 or port > 65535:
+            usage_cb('port {} is not valid'.format(oport))
+
+    aconf.host = host
+    aconf.port = port
+    if not (aconf.ssh1 or aconf.ssh2):
+        aconf.ssh1, aconf.ssh2 = True, True
+
+    # If a file containing a list of targets was given, read it.
+    if aconf.target_file is not None:
+        with open(aconf.target_file, 'r', encoding='utf-8') as f:
+            aconf.target_list = f.readlines()
+
+        # Strip out whitespace from each line in target file, and skip empty lines.
+        aconf.target_list = [target.strip() for target in aconf.target_list if target not in ("", "\n")]
+
+    # If a policy file was provided, validate it.
+    if (aconf.policy_file is not None) and (aconf.make_policy is False):
+
+        # First, see if this is a built-in policy name.  If not, assume a file path was provided, and try to load it from disk.
+        aconf.policy = Policy.load_builtin_policy(aconf.policy_file)
+        if aconf.policy is None:
+            try:
+                aconf.policy = Policy(policy_file=aconf.policy_file)
+            except Exception as e:
+                out.fail("Error while loading policy file: %s: %s" % (str(e), traceback.format_exc()))
+                out.write()
+                sys.exit(exitcodes.UNKNOWN_ERROR)
+
+        # If the user wants to do a client audit, but provided a server policy, terminate.
+        if aconf.client_audit and aconf.policy.is_server_policy():
+            out.fail("Error: client audit selected, but server policy provided.")
+            out.write()
+            sys.exit(exitcodes.UNKNOWN_ERROR)
+
+        # If the user wants to do a server audit, but provided a client policy, terminate.
+        if aconf.client_audit is False and aconf.policy.is_server_policy() is False:
+            out.fail("Error: server audit selected, but client policy provided.")
+            out.write()
+            sys.exit(exitcodes.UNKNOWN_ERROR)
+
+    return aconf
+
+
+def build_struct(target_host: str, banner: Optional['Banner'], kex: Optional['SSH2_Kex'] = None, pkm: Optional['SSH1_PublicKeyMessage'] = None, client_host: Optional[str] = None) -> Any:
+
+    banner_str = ''
+    banner_protocol = None
+    banner_software = None
+    banner_comments = None
+    if banner is not None:
+        banner_str = str(banner)
+        banner_protocol = banner.protocol
+        banner_software = banner.software
+        banner_comments = banner.comments
+
+    res: Any = {
+        "banner": {
+            "raw": banner_str,
+            "protocol": banner_protocol,
+            "software": banner_software,
+            "comments": banner_comments,
+        },
+    }
+
+    # If we're scanning a client host, put the client's IP into the results.  Otherwise, include the target host.
+    if client_host is not None:
+        res['client_ip'] = client_host
+    else:
+        res['target'] = target_host
+
+    if kex is not None:
+        res['compression'] = kex.server.compression
+
+        res['kex'] = []
+        alg_sizes = kex.dh_modulus_sizes()
+        for algorithm in kex.kex_algorithms:
+            entry: Any = {
+                'algorithm': algorithm,
+            }
+            if algorithm in alg_sizes:
+                hostkey_size, ca_size = alg_sizes[algorithm]
+                entry['keysize'] = hostkey_size
+                if ca_size > 0:
+                    entry['casize'] = ca_size
+            res['kex'].append(entry)
+
+        res['key'] = []
+        alg_sizes = kex.rsa_key_sizes()
+        for algorithm in kex.key_algorithms:
+            entry = {
+                'algorithm': algorithm,
+            }
+            if algorithm in alg_sizes:
+                hostkey_size, ca_size = alg_sizes[algorithm]
+                entry['keysize'] = hostkey_size
+                if ca_size > 0:
+                    entry['casize'] = ca_size
+            res['key'].append(entry)
+
+        res['enc'] = kex.server.encryption
+        res['mac'] = kex.server.mac
+        res['fingerprints'] = []
+        host_keys = kex.host_keys()
+
+        # Normalize all RSA key types to 'ssh-rsa'.  Otherwise, due to Python's order-indifference dictionary types, we would iterate key types in unpredictable orders, which interferes with the docker testing framework (i.e.: tests would fail because elements are reported out of order, even though the output is semantically the same).
+        for host_key_type in list(host_keys.keys())[:]:
+            if host_key_type in HostKeyTest.RSA_FAMILY:
+                val = host_keys[host_key_type]
+                del host_keys[host_key_type]
+                host_keys['ssh-rsa'] = val
+
+        for host_key_type in sorted(host_keys):
+            if host_keys[host_key_type] is None:
+                continue
+
+            fp = Fingerprint(host_keys[host_key_type])
+
+            # Skip over certificate host types (or we would return invalid fingerprints).
+            if '-cert-' in host_key_type:
+                continue
+
+            # Add the SHA256 and MD5 fingerprints.
+            res['fingerprints'].append({
+                'hostkey': host_key_type,
+                'hash_alg': 'SHA256',
+                'hash': fp.sha256[7:]
+            })
+            res['fingerprints'].append({
+                'hostkey': host_key_type,
+                'hash_alg': 'MD5',
+                'hash': fp.md5[4:]
+            })
+    else:
+        pkm_supported_ciphers = None
+        pkm_supported_authentications = None
+        pkm_fp = None
+        if pkm is not None:
+            pkm_supported_ciphers = pkm.supported_ciphers
+            pkm_supported_authentications = pkm.supported_authentications
+            pkm_fp = Fingerprint(pkm.host_key_fingerprint_data).sha256
+
+        res['key'] = ['ssh-rsa1']
+        res['enc'] = pkm_supported_ciphers
+        res['aut'] = pkm_supported_authentications
+        res['fingerprints'] = [{
+            'type': 'ssh-rsa1',
+            'fp': pkm_fp,
+        }]
+
+    return res
+
+
+# Returns one of the exitcodes.* flags.
+def audit(out: OutputBuffer, aconf: AuditConf, sshv: Optional[int] = None, print_target: bool = False) -> int:
+    program_retval = exitcodes.GOOD
+    out.batch = aconf.batch
+    out.verbose = aconf.verbose
+    out.debug = aconf.debug
+    out.level = aconf.level
+    out.use_colors = aconf.colors
+    s = SSH_Socket(out, aconf.host, aconf.port, aconf.ip_version_preference, aconf.timeout, aconf.timeout_set)
+
+    if aconf.client_audit:
+        out.v("Listening for client connection on port %d..." % aconf.port, write_now=True)
+        s.listen_and_accept()
+    else:
+        out.v("Starting audit of %s:%d..." % ('[%s]' % aconf.host if Utils.is_ipv6_address(aconf.host) else aconf.host, aconf.port), write_now=True)
+        err = s.connect()
+
+        if err is not None:
+            out.fail(err)
+
+            # If we're running against multiple targets, return a connection error to the calling worker thread.  Otherwise, write the error message to the console and exit.
+            if len(aconf.target_list) > 0:
+                return exitcodes.CONNECTION_ERROR
+            else:
+                out.write()
+                sys.exit(exitcodes.CONNECTION_ERROR)
+
+    if sshv is None:
+        sshv = 2 if aconf.ssh2 else 1
+    err = None
+    banner, header, err = s.get_banner(sshv)
+    if banner is None:
+        if err is None:
+            err = '[exception] did not receive banner.'
+        else:
+            err = '[exception] did not receive banner: {}'.format(err)
+    if err is None:
+        s.send_kexinit()  # Send the algorithms we support (except we don't since this isn't a real SSH connection).
+
+        packet_type, payload = s.read_packet(sshv)
+        if packet_type < 0:
+            try:
+                if len(payload) > 0:
+                    payload_txt = payload.decode('utf-8')
+                else:
+                    payload_txt = 'empty'
+            except UnicodeDecodeError:
+                payload_txt = '"{}"'.format(repr(payload).lstrip('b')[1:-1])
+            if payload_txt == 'Protocol major versions differ.':
+                if sshv == 2 and aconf.ssh1:
+                    ret = audit(out, aconf, 1)
+                    out.write()
+                    return ret
+            err = '[exception] error reading packet ({})'.format(payload_txt)
+        else:
+            err_pair = None
+            if sshv == 1 and packet_type != Protocol.SMSG_PUBLIC_KEY:
+                err_pair = ('SMSG_PUBLIC_KEY', Protocol.SMSG_PUBLIC_KEY)
+            elif sshv == 2 and packet_type != Protocol.MSG_KEXINIT:
+                err_pair = ('MSG_KEXINIT', Protocol.MSG_KEXINIT)
+            if err_pair is not None:
+                fmt = '[exception] did not receive {0} ({1}), ' + \
+                      'instead received unknown message ({2})'
+                err = fmt.format(err_pair[0], err_pair[1], packet_type)
+    if err is not None:
+        output(out, aconf, banner, header)
+        out.fail(err)
+        return exitcodes.CONNECTION_ERROR
+    if sshv == 1:
+        program_retval = output(out, aconf, banner, header, pkm=SSH1_PublicKeyMessage.parse(payload))
+    elif sshv == 2:
+        try:
+            kex = SSH2_Kex.parse(payload)
+        except Exception:
+            out.fail("Failed to parse server's kex.  Stack trace:\n%s" % str(traceback.format_exc()))
+            return exitcodes.CONNECTION_ERROR
+
+        if aconf.client_audit is False:
+            HostKeyTest.run(out, s, kex)
+            GEXTest.run(out, s, kex)
+
+        # This is a standard audit scan.
+        if (aconf.policy is None) and (aconf.make_policy is False):
+            program_retval = output(out, aconf, banner, header, client_host=s.client_host, kex=kex, print_target=print_target)
+
+        # This is a policy test.
+        elif (aconf.policy is not None) and (aconf.make_policy is False):
+            program_retval = exitcodes.GOOD if evaluate_policy(out, aconf, banner, s.client_host, kex=kex) else exitcodes.FAILURE
+
+        # A new policy should be made from this scan.
+        elif (aconf.policy is None) and (aconf.make_policy is True):
+            make_policy(aconf, banner, kex, s.client_host)
+
+        else:
+            raise RuntimeError('Internal error while handling output: %r %r' % (aconf.policy is None, aconf.make_policy))
+
+    return program_retval
+
+
+def algorithm_lookup(out: OutputBuffer, alg_names: str) -> int:
+    '''Looks up a comma-separated list of algorithms and outputs their security properties.  Returns an exitcodes.* flag.'''
+    retval = exitcodes.GOOD
+    alg_types = {
+        'kex': 'key exchange algorithms',
+        'key': 'host-key algorithms',
+        'mac': 'message authentication code algorithms',
+        'enc': 'encryption algorithms (ciphers)'
+    }
+
+    algorithm_names = alg_names.split(",")
+    adb = SSH2_KexDB.ALGORITHMS
+
+    # Use nested dictionary comprehension to iterate an outer dictionary where
+    # each key is an alg type that consists of a value (which is itself a
+    # dictionary) of alg names. Filter the alg names against the user supplied
+    # list of names.
+    algorithms_dict = {
+        outer_k: {
+            inner_k
+            for (inner_k, inner_v) in outer_v.items()
+            if inner_k in algorithm_names
+        }
+        for (outer_k, outer_v) in adb.items()
+    }
+
+    unknown_algorithms: List[str] = []
+    padding = len(max(algorithm_names, key=len))
+
+    for alg_type in alg_types:
+        if len(algorithms_dict[alg_type]) > 0:
+            title = str(alg_types.get(alg_type))
+            retval = output_algorithms(out, title, adb, alg_type, list(algorithms_dict[alg_type]), unknown_algorithms, False, retval, padding)
+
+    algorithms_dict_flattened = [
+        alg_name
+        for val in algorithms_dict.values()
+        for alg_name in val
+    ]
+
+    algorithms_not_found = [
+        alg_name
+        for alg_name in algorithm_names
+        if alg_name not in algorithms_dict_flattened
+    ]
+
+    similar_algorithms = [
+        alg_unknown + " --> (" + alg_type + ") " + alg_name
+        for alg_unknown in algorithms_not_found
+        for alg_type, alg_names in adb.items()
+        for alg_name in alg_names
+        # Perform a case-insensitive comparison using 'casefold'
+        # and match substrings using the 'in' operator.
+        if alg_unknown.casefold() in alg_name.casefold()
+    ]
+
+    if len(algorithms_not_found) > 0:
+        retval = exitcodes.FAILURE
+        out.head('# unknown algorithms')
+        for algorithm_not_found in algorithms_not_found:
+            out.fail(algorithm_not_found)
+
+    out.sep()
+
+    if len(similar_algorithms) > 0:
+        retval = exitcodes.FAILURE
+        out.head('# suggested similar algorithms')
+        for similar_algorithm in similar_algorithms:
+            out.warn(similar_algorithm)
+
+    return retval
+
+
+# Worker thread for scanning multiple targets concurrently.
+def target_worker_thread(host: str, port: int, shared_aconf: AuditConf) -> Tuple[int, str]:
+    ret = -1
+    string_output = ''
+
+    out = OutputBuffer()
+    out.verbose = shared_aconf.verbose
+    my_aconf = copy.deepcopy(shared_aconf)
+    my_aconf.host = host
+    my_aconf.port = port
+
+    # If we're outputting JSON, turn off colors and ensure 'info' level messages go through.
+    if my_aconf.json:
+        out.json = True
+        out.use_colors = False
+
+    out.v("Running against: %s:%d..." % (my_aconf.host, my_aconf.port), write_now=True)
+    try:
+        ret = audit(out, my_aconf, print_target=True)
+        string_output = out.get_buffer()
+    except Exception:
+        ret = -1
+        string_output = "An exception occurred while scanning %s:%d:\n%s" % (host, port, str(traceback.format_exc()))
+
+    return ret, string_output
+
+
+def windows_manual(out: OutputBuffer) -> int:
+    '''Prints the man page on Windows.  Returns an exitcodes.* flag.'''
+
+    retval = exitcodes.GOOD
+
+    if sys.platform != 'win32':
+        out.fail("The '-m' and '--manual' parameters are reserved for use on Windows only.\nUsers of other operating systems should read the man page.")
+        retval = exitcodes.FAILURE
+        return retval
+
+    # If colors are disabled, strip the ANSI color codes from the man page.
+    windows_man_page = WINDOWS_MAN_PAGE
+    if not out.use_colors:
+        windows_man_page = re.sub(r'\x1b\[\d+?m', '', windows_man_page)
+
+    out.info(windows_man_page)
+    return retval
+
+
+def main() -> int:
+    out = OutputBuffer()
+    aconf = process_commandline(out, sys.argv[1:], usage)
+
+    # If we're on Windows, but the colorama module could not be imported, print a warning if we're in verbose mode.
+    if (sys.platform == 'win32') and ('colorama' not in sys.modules):
+        out.v("WARNING: colorama module not found.  Colorized output will be disabled.", write_now=True)
+
+    # If we're outputting JSON, turn off colors and ensure 'info' level messages go through.
+    if aconf.json:
+        out.json = True
+        out.use_colors = False
+
+    if aconf.manual:
+        # If the colorama module was not be imported, turn off colors in order
+        # to output a plain text version of the man page.
+        if (sys.platform == 'win32') and ('colorama' not in sys.modules):
+            out.use_colors = False
+        retval = windows_manual(out)
+        out.write()
+        sys.exit(retval)
+
+    if aconf.lookup != '':
+        retval = algorithm_lookup(out, aconf.lookup)
+        out.write()
+        sys.exit(retval)
+
+    # If multiple targets were specified...
+    if len(aconf.target_list) > 0:
+        ret = exitcodes.GOOD
+
+        # If JSON output is desired, each target's results will be reported in its own list entry.
+        if aconf.json:
+            print('[', end='')
+
+        # Loop through each target in the list.
+        target_servers = []
+        for _, target in enumerate(aconf.target_list):
+            host, port = Utils.parse_host_and_port(target, default_port=22)
+            target_servers.append((host, port))
+
+        # A ranked list of return codes.  Those with higher indices will take precendence over lower ones.  For example, if three servers are scanned, yielding WARNING, GOOD, and UNKNOWN_ERROR, the overall result will be UNKNOWN_ERROR, since its index is the highest.  Errors have highest priority, followed by failures, then warnings.
+        ranked_return_codes = [exitcodes.GOOD, exitcodes.WARNING, exitcodes.FAILURE, exitcodes.CONNECTION_ERROR, exitcodes.UNKNOWN_ERROR]
+
+        # Queue all worker threads.
+        num_target_servers = len(target_servers)
+        num_processed = 0
+        out.v("Scanning %u targets with %s%u threads..." % (num_target_servers, '(at most) ' if aconf.threads > num_target_servers else '',  aconf.threads), write_now=True)
+        with concurrent.futures.ThreadPoolExecutor(max_workers=aconf.threads) as executor:
+            future_to_server = {executor.submit(target_worker_thread, target_server[0], target_server[1], aconf): target_server for target_server in target_servers}
+            for future in concurrent.futures.as_completed(future_to_server):
+                worker_ret, worker_output = future.result()
+
+                # If this worker's return code is ranked higher that what we've cached so far, update our cache.
+                if ranked_return_codes.index(worker_ret) > ranked_return_codes.index(ret):
+                    ret = worker_ret
+
+                # print("Worker for %s:%d returned %d: [%s]" % (target_server[0], target_server[1], worker_ret, worker_output))
+                print(worker_output, end='' if aconf.json else "\n")
+
+                # Don't print a delimiter after the last target was handled.
+                num_processed += 1
+                if num_processed < num_target_servers:
+                    if aconf.json:
+                        print(", ", end='')
+                    else:
+                        print(("-" * 80) + "\n")
+
+        if aconf.json:
+            print(']')
+
+    else:  # Just a scan against a single target.
+        ret = audit(out, aconf)
+        out.write()
+
+    return ret
+
+
+if __name__ == '__main__':  # pragma: nocover
+    exit_code = exitcodes.GOOD
+
+    try:
+        exit_code = main()
+    except Exception:
+        exit_code = exitcodes.UNKNOWN_ERROR
+        print(traceback.format_exc())
+
+    sys.exit(exit_code)
diff --git a/src/ssh_audit/ssh_socket.py b/src/ssh_audit/ssh_socket.py
new file mode 100644
index 0000000..6853c1c
--- /dev/null
+++ b/src/ssh_audit/ssh_socket.py
@@ -0,0 +1,343 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017-2021 Joe Testa (jtesta@positronsecurity.com)
+   Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+import errno
+import os
+import select
+import socket
+import struct
+import sys
+
+# pylint: disable=unused-import
+from typing import Dict, List, Set, Sequence, Tuple, Iterable  # noqa: F401
+from typing import Callable, Optional, Union, Any  # noqa: F401
+
+from ssh_audit import exitcodes
+from ssh_audit.banner import Banner
+from ssh_audit.globals import SSH_HEADER
+from ssh_audit.outputbuffer import OutputBuffer
+from ssh_audit.protocol import Protocol
+from ssh_audit.readbuf import ReadBuf
+from ssh_audit.ssh1 import SSH1
+from ssh_audit.ssh2_kex import SSH2_Kex
+from ssh_audit.ssh2_kexparty import SSH2_KexParty
+from ssh_audit.utils import Utils
+from ssh_audit.writebuf import WriteBuf
+
+
+class SSH_Socket(ReadBuf, WriteBuf):
+    class InsufficientReadException(Exception):
+        pass
+
+    SM_BANNER_SENT = 1
+
+    def __init__(self, outputbuffer: 'OutputBuffer', host: Optional[str], port: int, ip_version_preference: List[int] = [], timeout: Union[int, float] = 5, timeout_set: bool = False) -> None:  # pylint: disable=dangerous-default-value
+        super(SSH_Socket, self).__init__()
+        self.__outputbuffer = outputbuffer
+        self.__sock: Optional[socket.socket] = None
+        self.__sock_map: Dict[int, socket.socket] = {}
+        self.__block_size = 8
+        self.__state = 0
+        self.__header: List[str] = []
+        self.__banner: Optional[Banner] = None
+        if host is None:
+            raise ValueError('undefined host')
+        nport = Utils.parse_int(port)
+        if nport < 1 or nport > 65535:
+            raise ValueError('invalid port: {}'.format(port))
+        self.__host = host
+        self.__port = nport
+        self.__ip_version_preference = ip_version_preference  # Holds only 5 possible values: [] (no preference), [4] (use IPv4 only), [6] (use IPv6 only), [46] (use both IPv4 and IPv6, but prioritize v4), and [64] (use both IPv4 and IPv6, but prioritize v6).
+        self.__timeout = timeout
+        self.__timeout_set = timeout_set
+        self.client_host: Optional[str] = None
+        self.client_port = None
+
+    def _resolve(self) -> Iterable[Tuple[int, Tuple[Any, ...]]]:
+        # If __ip_version_preference has only one entry, then it means that ONLY that IP version should be used.
+        if len(self.__ip_version_preference) == 1:
+            family = socket.AF_INET if self.__ip_version_preference[0] == 4 else socket.AF_INET6
+        else:
+            family = socket.AF_UNSPEC
+        try:
+            stype = socket.SOCK_STREAM
+            r = socket.getaddrinfo(self.__host, self.__port, family, stype)
+
+            # If the user has a preference for using IPv4 over IPv6 (or vice-versa), then sort the list returned by getaddrinfo() so that the preferred address type comes first.
+            if len(self.__ip_version_preference) == 2:
+                r = sorted(r, key=lambda x: x[0], reverse=(self.__ip_version_preference[0] == 6))
+            for af, socktype, _proto, _canonname, addr in r:
+                if socktype == socket.SOCK_STREAM:
+                    yield af, addr
+        except socket.error as e:
+            self.__outputbuffer.fail('[exception] {}'.format(e)).write()
+            sys.exit(exitcodes.CONNECTION_ERROR)
+
+    # Listens on a server socket and accepts one connection (used for
+    # auditing client connections).
+    def listen_and_accept(self) -> None:
+
+        try:
+            # Socket to listen on all IPv4 addresses.
+            s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+            s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+            s.bind(('0.0.0.0', self.__port))
+            s.listen()
+            self.__sock_map[s.fileno()] = s
+        except Exception:
+            print("Warning: failed to listen on any IPv4 interfaces.")
+
+        try:
+            # Socket to listen on all IPv6 addresses.
+            s = socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
+            s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+            s.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_V6ONLY, 1)
+            s.bind(('::', self.__port))
+            s.listen()
+            self.__sock_map[s.fileno()] = s
+        except Exception:
+            print("Warning: failed to listen on any IPv6 interfaces.")
+
+        # If we failed to listen on any interfaces, terminate.
+        if len(self.__sock_map.keys()) == 0:
+            print("Error: failed to listen on any IPv4 and IPv6 interfaces!")
+            sys.exit(exitcodes.CONNECTION_ERROR)
+
+        # Wait for an incoming connection.  If a timeout was explicitly
+        # set by the user, terminate when it elapses.
+        fds = None
+        time_elapsed = 0.0
+        interval = 1.0
+        while True:
+            # Wait for a connection on either socket.
+            fds = select.select(self.__sock_map.keys(), [], [], interval)
+            time_elapsed += interval
+
+            # We have incoming data on at least one of the sockets.
+            if len(fds[0]) > 0:
+                break
+
+            if self.__timeout_set and time_elapsed >= self.__timeout:
+                print("Timeout elapsed.  Terminating...")
+                sys.exit(exitcodes.CONNECTION_ERROR)
+
+        # Accept the connection.
+        c, addr = self.__sock_map[fds[0][0]].accept()
+        self.client_host = addr[0]
+        self.client_port = addr[1]
+        c.settimeout(self.__timeout)
+        self.__sock = c
+
+    def connect(self) -> Optional[str]:
+        '''Returns None on success, or an error string.'''
+        err = None
+        for af, addr in self._resolve():
+            s = None
+            try:
+                s = socket.socket(af, socket.SOCK_STREAM)
+                s.settimeout(self.__timeout)
+                self.__outputbuffer.d(("Connecting to %s:%d..." % ('[%s]' % addr[0] if Utils.is_ipv6_address(addr[0]) else addr[0], addr[1])), write_now=True)
+                s.connect(addr)
+                self.__sock = s
+                return None
+            except socket.error as e:
+                err = e
+                self._close_socket(s)
+        if err is None:
+            errm = 'host {} has no DNS records'.format(self.__host)
+        else:
+            errt = (self.__host, self.__port, err)
+            errm = 'cannot connect to {} port {}: {}'.format(*errt)
+        return '[exception] {}'.format(errm)
+
+    def get_banner(self, sshv: int = 2) -> Tuple[Optional['Banner'], List[str], Optional[str]]:
+        self.__outputbuffer.d('Getting banner...', write_now=True)
+
+        if self.__sock is None:
+            return self.__banner, self.__header, 'not connected'
+        if self.__banner is not None:
+            return self.__banner, self.__header, None
+
+        banner = SSH_HEADER.format('1.5' if sshv == 1 else '2.0')
+        if self.__state < self.SM_BANNER_SENT:
+            self.send_banner(banner)
+
+        s = 0
+        e = None
+        while s >= 0:
+            s, e = self.recv()
+            if s < 0:
+                continue
+            while self.unread_len > 0:
+                line = self.read_line()
+                if len(line.strip()) == 0:
+                    continue
+                self.__banner = Banner.parse(line)
+                if self.__banner is not None:
+                    return self.__banner, self.__header, None
+                self.__header.append(line)
+
+        return self.__banner, self.__header, e
+
+    def recv(self, size: int = 2048) -> Tuple[int, Optional[str]]:
+        if self.__sock is None:
+            return -1, 'not connected'
+        try:
+            data = self.__sock.recv(size)
+        except socket.timeout:
+            return -1, 'timed out'
+        except socket.error as e:
+            if e.args[0] in (errno.EAGAIN, errno.EWOULDBLOCK):
+                return 0, 'retry'
+            return -1, str(e.args[-1])
+        if len(data) == 0:
+            return -1, None
+        pos = self._buf.tell()
+        self._buf.seek(0, 2)
+        self._buf.write(data)
+        self._len += len(data)
+        self._buf.seek(pos, 0)
+        return len(data), None
+
+    def send(self, data: bytes) -> Tuple[int, Optional[str]]:
+        if self.__sock is None:
+            return -1, 'not connected'
+        try:
+            self.__sock.send(data)
+            return 0, None
+        except socket.error as e:
+            return -1, str(e.args[-1])
+
+    # Send a KEXINIT with the lists of key exchanges, hostkeys, ciphers, MACs, compressions, and languages that we "support".
+    def send_kexinit(self, key_exchanges: List[str] = ['curve25519-sha256', 'curve25519-sha256@libssh.org', 'ecdh-sha2-nistp256', 'ecdh-sha2-nistp384', 'ecdh-sha2-nistp521', 'diffie-hellman-group-exchange-sha256', 'diffie-hellman-group16-sha512', 'diffie-hellman-group18-sha512', 'diffie-hellman-group14-sha256'], hostkeys: List[str] = ['rsa-sha2-512', 'rsa-sha2-256', 'ssh-rsa', 'ecdsa-sha2-nistp256', 'ssh-ed25519'], ciphers: List[str] = ['chacha20-poly1305@openssh.com', 'aes128-ctr', 'aes192-ctr', 'aes256-ctr', 'aes128-gcm@openssh.com', 'aes256-gcm@openssh.com'], macs: List[str] = ['umac-64-etm@openssh.com', 'umac-128-etm@openssh.com', 'hmac-sha2-256-etm@openssh.com', 'hmac-sha2-512-etm@openssh.com', 'hmac-sha1-etm@openssh.com', 'umac-64@openssh.com', 'umac-128@openssh.com', 'hmac-sha2-256', 'hmac-sha2-512', 'hmac-sha1'], compressions: List[str] = ['none', 'zlib@openssh.com'], languages: List[str] = ['']) -> None:  # pylint: disable=dangerous-default-value
+        '''Sends the list of supported host keys, key exchanges, ciphers, and MACs.  Emulates OpenSSH v8.2.'''
+
+        self.__outputbuffer.d('KEX initialisation...', write_now=True)
+
+        kexparty = SSH2_KexParty(ciphers, macs, compressions, languages)
+        kex = SSH2_Kex(os.urandom(16), key_exchanges, hostkeys, kexparty, kexparty, False, 0)
+
+        self.write_byte(Protocol.MSG_KEXINIT)
+        kex.write(self)
+        self.send_packet()
+
+    def send_banner(self, banner: str) -> None:
+        self.send(banner.encode() + b'\r\n')
+        if self.__state < self.SM_BANNER_SENT:
+            self.__state = self.SM_BANNER_SENT
+
+    def ensure_read(self, size: int) -> None:
+        while self.unread_len < size:
+            s, e = self.recv()
+            if s < 0:
+                raise SSH_Socket.InsufficientReadException(e)
+
+    def read_packet(self, sshv: int = 2) -> Tuple[int, bytes]:
+        try:
+            header = WriteBuf()
+            self.ensure_read(4)
+            packet_length = self.read_int()
+            header.write_int(packet_length)
+            # XXX: validate length
+            if sshv == 1:
+                padding_length = 8 - packet_length % 8
+                self.ensure_read(padding_length)
+                padding = self.read(padding_length)
+                header.write(padding)
+                payload_length = packet_length
+                check_size = padding_length + payload_length
+            else:
+                self.ensure_read(1)
+                padding_length = self.read_byte()
+                header.write_byte(padding_length)
+                payload_length = packet_length - padding_length - 1
+                check_size = 4 + 1 + payload_length + padding_length
+            if check_size % self.__block_size != 0:
+                self.__outputbuffer.fail('[exception] invalid ssh packet (block size)').write()
+                sys.exit(exitcodes.CONNECTION_ERROR)
+            self.ensure_read(payload_length)
+            if sshv == 1:
+                payload = self.read(payload_length - 4)
+                header.write(payload)
+                crc = self.read_int()
+                header.write_int(crc)
+            else:
+                payload = self.read(payload_length)
+                header.write(payload)
+            packet_type = ord(payload[0:1])
+            if sshv == 1:
+                rcrc = SSH1.crc32(padding + payload)
+                if crc != rcrc:
+                    self.__outputbuffer.fail('[exception] packet checksum CRC32 mismatch.').write()
+                    sys.exit(exitcodes.CONNECTION_ERROR)
+            else:
+                self.ensure_read(padding_length)
+                padding = self.read(padding_length)
+            payload = payload[1:]
+            return packet_type, payload
+        except SSH_Socket.InsufficientReadException as ex:
+            if ex.args[0] is None:
+                header.write(self.read(self.unread_len))
+                e = header.write_flush().strip()
+            else:
+                e = ex.args[0].encode('utf-8')
+            return -1, e
+
+    def send_packet(self) -> Tuple[int, Optional[str]]:
+        payload = self.write_flush()
+        padding = -(len(payload) + 5) % 8
+        if padding < 4:
+            padding += 8
+        plen = len(payload) + padding + 1
+        pad_bytes = b'\x00' * padding
+        data = struct.pack('>Ib', plen, padding) + payload + pad_bytes
+        return self.send(data)
+
+    def is_connected(self) -> bool:
+        """Returns true if this Socket is connected, False otherwise."""
+        return self.__sock is not None
+
+    def close(self) -> None:
+        self.__cleanup()
+        self.reset()
+        self.__state = 0
+        self.__header = []
+        self.__banner = None
+
+    def _close_socket(self, s: Optional[socket.socket]) -> None:  # pylint: disable=no-self-use
+        try:
+            if s is not None:
+                s.shutdown(socket.SHUT_RDWR)
+                s.close()  # pragma: nocover
+        except Exception:
+            pass
+
+    def __del__(self) -> None:
+        self.__cleanup()
+
+    def __cleanup(self) -> None:
+        self._close_socket(self.__sock)
+        for sock in self.__sock_map.values():
+            self._close_socket(sock)
+        self.__sock = None
diff --git a/src/ssh_audit/timeframe.py b/src/ssh_audit/timeframe.py
new file mode 100644
index 0000000..cb98d9b
--- /dev/null
+++ b/src/ssh_audit/timeframe.py
@@ -0,0 +1,77 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+# pylint: disable=unused-import
+from typing import Dict, List, Set, Sequence, Tuple, Iterable  # noqa: F401
+from typing import Callable, Optional, Union, Any  # noqa: F401
+
+from ssh_audit.algorithm import Algorithm
+
+
+class Timeframe:
+    def __init__(self) -> None:
+        self.__storage: Dict[str, List[Optional[str]]] = {}
+
+    def __contains__(self, product: str) -> bool:
+        return product in self.__storage
+
+    def __getitem__(self, product: str) -> Sequence[Optional[str]]:
+        return tuple(self.__storage.get(product, [None] * 4))
+
+    def __str__(self) -> str:
+        return self.__storage.__str__()
+
+    def __repr__(self) -> str:
+        return self.__str__()
+
+    def get_from(self, product: str, for_server: bool = True) -> Optional[str]:
+        return self[product][0 if bool(for_server) else 2]
+
+    def get_till(self, product: str, for_server: bool = True) -> Optional[str]:
+        return self[product][1 if bool(for_server) else 3]
+
+    def _update(self, versions: Optional[str], pos: int) -> None:
+        ssh_versions: Dict[str, str] = {}
+        for_srv, for_cli = pos < 2, pos > 1
+        for v in (versions or '').split(','):
+            ssh_prod, ssh_ver, is_cli = Algorithm.get_ssh_version(v)
+            if not ssh_ver or (is_cli and for_srv) or (not is_cli and for_cli and ssh_prod in ssh_versions):
+                continue
+            ssh_versions[ssh_prod] = ssh_ver
+        for ssh_product, ssh_version in ssh_versions.items():
+            if ssh_product not in self.__storage:
+                self.__storage[ssh_product] = [None] * 4
+            prev = self[ssh_product][pos]
+            if (prev is None or (prev < ssh_version and pos % 2 == 0) or (prev > ssh_version and pos % 2 == 1)):
+                self.__storage[ssh_product][pos] = ssh_version
+
+    def update(self, versions: List[Optional[str]], for_server: Optional[bool] = None) -> 'Timeframe':
+        for_cli = for_server is None or for_server is False
+        for_srv = for_server is None or for_server is True
+        vlen = len(versions)
+        for i in range(min(3, vlen)):
+            if for_srv and i < 2:
+                self._update(versions[i], i)
+            if for_cli and (i % 2 == 0 or vlen == 2):
+                self._update(versions[i], 3 - 0**i)
+        return self
diff --git a/src/ssh_audit/utils.py b/src/ssh_audit/utils.py
new file mode 100644
index 0000000..a17ecb6
--- /dev/null
+++ b/src/ssh_audit/utils.py
@@ -0,0 +1,165 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017-2020 Joe Testa (jtesta@positronsecurity.com)
+   Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+import ipaddress
+import re
+import sys
+
+# pylint: disable=unused-import
+from typing import Dict, List, Set, Sequence, Tuple, Iterable  # noqa: F401
+from typing import Callable, Optional, Union, Any  # noqa: F401
+
+
+class Utils:
+    @classmethod
+    def _type_err(cls, v: Any, target: str) -> TypeError:
+        return TypeError('cannot convert {} to {}'.format(type(v), target))
+
+    @classmethod
+    def to_bytes(cls, v: Union[bytes, str], enc: str = 'utf-8') -> bytes:
+        if isinstance(v, bytes):
+            return v
+        elif isinstance(v, str):
+            return v.encode(enc)
+        raise cls._type_err(v, 'bytes')
+
+    @classmethod
+    def to_text(cls, v: Union[str, bytes], enc: str = 'utf-8') -> str:
+        if isinstance(v, str):
+            return v
+        elif isinstance(v, bytes):
+            return v.decode(enc)
+        raise cls._type_err(v, 'unicode text')
+
+    @classmethod
+    def _is_ascii(cls, v: str, char_filter: Callable[[int], bool] = lambda x: x <= 127) -> bool:
+        r = False
+        if isinstance(v, str):
+            for c in v:
+                i = cls.ctoi(c)
+                if not char_filter(i):
+                    return r
+            r = True
+        return r
+
+    @classmethod
+    def _to_ascii(cls, v: str, char_filter: Callable[[int], bool] = lambda x: x <= 127, errors: str = 'replace') -> str:
+        if isinstance(v, str):
+            r = bytearray()
+            for c in v:
+                i = cls.ctoi(c)
+                if char_filter(i):
+                    r.append(i)
+                else:
+                    if errors == 'ignore':
+                        continue
+                    r.append(63)
+            return cls.to_text(r.decode('ascii'))
+        raise cls._type_err(v, 'ascii')
+
+    @classmethod
+    def is_ascii(cls, v: str) -> bool:
+        return cls._is_ascii(v)
+
+    @classmethod
+    def to_ascii(cls, v: str, errors: str = 'replace') -> str:
+        return cls._to_ascii(v, errors=errors)
+
+    @classmethod
+    def is_print_ascii(cls, v: str) -> bool:
+        return cls._is_ascii(v, lambda x: 126 >= x >= 32)
+
+    @classmethod
+    def to_print_ascii(cls, v: str, errors: str = 'replace') -> str:
+        return cls._to_ascii(v, lambda x: 126 >= x >= 32, errors)
+
+    @classmethod
+    def unique_seq(cls, seq: Sequence[Any]) -> Sequence[Any]:
+        seen: Set[Any] = set()
+
+        def _seen_add(x: Any) -> bool:
+            seen.add(x)
+            return False
+
+        if isinstance(seq, tuple):
+            return tuple(x for x in seq if x not in seen and not _seen_add(x))
+        else:
+            return [x for x in seq if x not in seen and not _seen_add(x)]
+
+    @classmethod
+    def ctoi(cls, c: Union[str, int]) -> int:
+        if isinstance(c, str):
+            return ord(c[0])
+        else:
+            return c
+
+    @staticmethod
+    def parse_int(v: Any) -> int:
+        try:
+            return int(v)
+        except ValueError:
+            return 0
+
+    @staticmethod
+    def parse_float(v: Any) -> float:
+        try:
+            return float(v)
+        except ValueError:
+            return -1.0
+
+    @staticmethod
+    def parse_host_and_port(host_and_port: str, default_port: int = 0) -> Tuple[str, int]:
+        '''Parses a string into a tuple of its host and port.  The port is 0 if not specified.'''
+        host = host_and_port
+        port = default_port
+
+        mx = re.match(r'^\[([^\]]+)\](?::(\d+))?$', host_and_port)
+        if mx is not None:
+            host = mx.group(1)
+            port_str = mx.group(2)
+            if port_str is not None:
+                port = int(port_str)
+        else:
+            s = host_and_port.split(':')
+            if len(s) == 2:
+                host = s[0]
+                if len(s[1]) > 0:
+                    port = int(s[1])
+
+        return host, port
+
+    @staticmethod
+    def is_ipv6_address(address: str) -> bool:
+        '''Returns True if address is an IPv6 address, otherwise False.'''
+        is_ipv6 = True
+        try:
+            ipaddress.IPv6Address(address)
+        except ipaddress.AddressValueError:
+            is_ipv6 = False
+
+        return is_ipv6
+
+    @staticmethod
+    def is_windows() -> bool:
+        return sys.platform in ['win32', 'cygwin']
diff --git a/src/ssh_audit/versionvulnerabilitydb.py b/src/ssh_audit/versionvulnerabilitydb.py
new file mode 100644
index 0000000..7f02c71
--- /dev/null
+++ b/src/ssh_audit/versionvulnerabilitydb.py
@@ -0,0 +1,151 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017-2020 Joe Testa (jtesta@positronsecurity.com)
+   Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+# pylint: disable=unused-import
+from typing import Dict, List, Set, Sequence, Tuple, Iterable  # noqa: F401
+from typing import Callable, Optional, Union, Any  # noqa: F401
+
+
+class VersionVulnerabilityDB:  # pylint: disable=too-few-public-methods
+    # Format: [starting_vuln_version, last_vuln_version, affected, CVE_ID, CVSSv2, description]
+    #   affected: 1 = server, 2 = client, 4 = local
+    #   Example:  if it affects servers, both remote & local, then affected
+    #             = 1.  If it affects servers, but is a local issue only,
+    #             then affected = 1 + 4 = 5.
+    CVE: Dict[str, List[List[Any]]] = {
+        'Dropbear SSH': [
+            ['0.0', '2018.76', 1, 'CVE-2018-15599', 5.0, 'remote users may enumerate users on the system'],
+            ['0.0', '2017.74', 5, 'CVE-2017-9079', 4.7, 'local users can read certain files as root'],
+            ['0.0', '2017.74', 5, 'CVE-2017-9078', 9.3, 'local users may elevate privileges to root under certain conditions'],
+            ['0.0', '2016.73', 5, 'CVE-2016-7409', 2.1, 'local users can read process memory under limited conditions'],
+            ['0.0', '2016.73', 1, 'CVE-2016-7408', 6.5, 'remote users can execute arbitrary code'],
+            ['0.0', '2016.73', 5, 'CVE-2016-7407', 10.0, 'local users can execute arbitrary code'],
+            ['0.0', '2016.73', 1, 'CVE-2016-7406', 10.0, 'remote users can execute arbitrary code'],
+            ['0.44', '2015.71', 1, 'CVE-2016-3116', 5.5, 'bypass command restrictions via xauth command injection'],
+            ['0.28', '2013.58', 1, 'CVE-2013-4434', 5.0, 'discover valid usernames through different time delays'],
+            ['0.28', '2013.58', 1, 'CVE-2013-4421', 5.0, 'cause DoS via a compressed packet (memory consumption)'],
+            ['0.52', '2011.54', 1, 'CVE-2012-0920', 7.1, 'execute arbitrary code or bypass command restrictions'],
+            ['0.40', '0.48.1',  1, 'CVE-2007-1099', 7.5, 'conduct a MitM attack (no warning for hostkey mismatch)'],
+            ['0.28', '0.47',    1, 'CVE-2006-1206', 7.5, 'cause DoS via large number of connections (slot exhaustion)'],
+            ['0.39', '0.47',    1, 'CVE-2006-0225', 4.6, 'execute arbitrary commands via scp with crafted filenames'],
+            ['0.28', '0.46',    1, 'CVE-2005-4178', 6.5, 'execute arbitrary code via buffer overflow vulnerability'],
+            ['0.28', '0.42',    1, 'CVE-2004-2486', 7.5, 'execute arbitrary code via DSS verification code']],
+        'libssh': [
+            ['0.6.4',   '0.6.4',  1, 'CVE-2018-10933', 6.4, 'authentication bypass'],
+            ['0.7.0',   '0.7.5',  1, 'CVE-2018-10933', 6.4, 'authentication bypass'],
+            ['0.8.0',   '0.8.3',  1, 'CVE-2018-10933', 6.4, 'authentication bypass'],
+            ['0.1',   '0.7.2',  1, 'CVE-2016-0739', 4.3, 'conduct a MitM attack (weakness in DH key generation)'],
+            ['0.5.1', '0.6.4',  1, 'CVE-2015-3146', 5.0, 'cause DoS via kex packets (null pointer dereference)'],
+            ['0.5.1', '0.6.3',  1, 'CVE-2014-8132', 5.0, 'cause DoS via kex init packet (dangling pointer)'],
+            ['0.4.7', '0.6.2',  1, 'CVE-2014-0017', 1.9, 'leak data via PRNG state reuse on forking servers'],
+            ['0.4.7', '0.5.3',  1, 'CVE-2013-0176', 4.3, 'cause DoS via kex packet (null pointer dereference)'],
+            ['0.4.7', '0.5.2',  1, 'CVE-2012-6063', 7.5, 'cause DoS or execute arbitrary code via sftp (double free)'],
+            ['0.4.7', '0.5.2',  1, 'CVE-2012-4562', 7.5, 'cause DoS or execute arbitrary code (overflow check)'],
+            ['0.4.7', '0.5.2',  1, 'CVE-2012-4561', 5.0, 'cause DoS via unspecified vectors (invalid pointer)'],
+            ['0.4.7', '0.5.2',  1, 'CVE-2012-4560', 7.5, 'cause DoS or execute arbitrary code (buffer overflow)'],
+            ['0.4.7', '0.5.2',  1, 'CVE-2012-4559', 6.8, 'cause DoS or execute arbitrary code (double free)']],
+        'OpenSSH': [
+            ['1.0',     '7.7',     1, 'CVE-2018-15473', 5.3, 'enumerate usernames due to timing discrepencies'],
+            ['7.2',     '7.2p2',   1, 'CVE-2016-6515',  7.8, 'cause DoS via long password string (crypt CPU consumption)'],
+            ['1.2.2',   '7.2',     1, 'CVE-2016-3115',  5.5, 'bypass command restrictions via crafted X11 forwarding data'],
+            ['5.4',     '7.1',     1, 'CVE-2016-1907',  5.0, 'cause DoS via crafted network traffic (out of bounds read)'],
+            ['5.4',     '7.1p1',   2, 'CVE-2016-0778',  4.6, 'cause DoS via requesting many forwardings (heap based buffer overflow)'],
+            ['5.0',     '7.1p1',   2, 'CVE-2016-0777',  4.0, 'leak data via allowing transfer of entire buffer'],
+            ['6.0',     '7.2p2',   5, 'CVE-2015-8325',  7.2, 'privilege escalation via triggering crafted environment'],
+            ['6.8',     '6.9',     5, 'CVE-2015-6565',  7.2, 'cause DoS via writing to a device (terminal disruption)'],
+            ['5.0',     '6.9',     5, 'CVE-2015-6564',  6.9, 'privilege escalation via leveraging sshd uid'],
+            ['5.0',     '6.9',     5, 'CVE-2015-6563',  1.9, 'conduct impersonation attack'],
+            ['6.9p1',   '6.9p1',   1, 'CVE-2015-5600',  8.5, 'cause Dos or aid in conduct brute force attack (CPU consumption)'],
+            ['6.0',     '6.6',     1, 'CVE-2015-5352',  4.3, 'bypass access restrictions via a specific connection'],
+            ['6.0',     '6.6',     2, 'CVE-2014-2653',  5.8, 'bypass SSHFP DNS RR check via unacceptable host certificate'],
+            ['5.0',     '6.5',     1, 'CVE-2014-2532',  5.8, 'bypass environment restrictions via specific string before wildcard'],
+            ['1.2',     '6.4',     1, 'CVE-2014-1692',  7.5, 'cause DoS via triggering error condition (memory corruption)'],
+            ['6.2',     '6.3',     1, 'CVE-2013-4548',  6.0, 'bypass command restrictions via crafted packet data'],
+            ['1.2',     '5.6',     1, 'CVE-2012-0814',  3.5, 'leak data via debug messages'],
+            ['1.2',     '5.8',     1, 'CVE-2011-5000',  3.5, 'cause DoS via large value in certain length field (memory consumption)'],
+            ['5.6',     '5.7',     2, 'CVE-2011-0539',  5.0, 'leak data or conduct hash collision attack'],
+            ['1.2',     '6.1',     1, 'CVE-2010-5107',  5.0, 'cause DoS via large number of connections (slot exhaustion)'],
+            ['1.2',     '5.8',     1, 'CVE-2010-4755',  4.0, 'cause DoS via crafted glob expression (CPU and memory consumption)'],
+            ['1.2',     '5.6',     1, 'CVE-2010-4478',  7.5, 'bypass authentication check via crafted values'],
+            ['4.3',     '4.8',     1, 'CVE-2009-2904',  6.9, 'privilege escalation via hard links to setuid programs'],
+            ['4.0',     '5.1',     1, 'CVE-2008-5161',  2.6, 'recover plaintext data from ciphertext'],
+            ['1.2',     '4.6',     1, 'CVE-2008-4109',  5.0, 'cause DoS via multiple login attempts (slot exhaustion)'],
+            ['1.2',     '4.8',     1, 'CVE-2008-1657',  6.5, 'bypass command restrictions via modifying session file'],
+            ['1.2.2',   '4.9',     1, 'CVE-2008-1483',  6.9, 'hijack forwarded X11 connections'],
+            ['4.0',     '4.6',     1, 'CVE-2007-4752',  7.5, 'privilege escalation via causing an X client to be trusted'],
+            ['4.3p2',   '4.3p2',   1, 'CVE-2007-3102',  4.3, 'allow attacker to write random data to audit log'],
+            ['1.2',     '4.6',     1, 'CVE-2007-2243',  5.0, 'discover valid usernames through different responses'],
+            ['4.4',     '4.4',     1, 'CVE-2006-5794',  7.5, 'bypass authentication'],
+            ['4.1',     '4.1p1',   1, 'CVE-2006-5229',  2.6, 'discover valid usernames through different time delays'],
+            ['1.2',     '4.3p2',   1, 'CVE-2006-5052',  5.0, 'discover valid usernames through different responses'],
+            ['1.2',     '4.3p2',   1, 'CVE-2006-5051',  9.3, 'cause DoS or execute arbitrary code (double free)'],
+            ['4.5',     '4.5',     1, 'CVE-2006-4925',  5.0, 'cause DoS via invalid protocol sequence (crash)'],
+            ['1.2',     '4.3p2',   1, 'CVE-2006-4924',  7.8, 'cause DoS via crafted packet (CPU consumption)'],
+            ['3.8.1p1', '3.8.1p1', 1, 'CVE-2006-0883',  5.0, 'cause DoS via connecting multiple times (client connection refusal)'],
+            ['3.0',     '4.2p1',   1, 'CVE-2006-0225',  4.6, 'execute arbitrary code'],
+            ['2.1',     '4.1p1',   1, 'CVE-2005-2798',  5.0, 'leak data about authentication credentials'],
+            ['3.5',     '3.5p1',   1, 'CVE-2004-2760',  6.8, 'leak data through different connection states'],
+            ['2.3',     '3.7.1p2', 1, 'CVE-2004-2069',  5.0, 'cause DoS via large number of connections (slot exhaustion)'],
+            ['3.0',     '3.4p1',   1, 'CVE-2004-0175',  4.3, 'leak data through directoy traversal'],
+            ['1.2',     '3.9p1',   1, 'CVE-2003-1562',  7.6, 'leak data about authentication credentials'],
+            ['3.1p1',   '3.7.1p1', 1, 'CVE-2003-0787',  7.5, 'privilege escalation via modifying stack'],
+            ['3.1p1',   '3.7.1p1', 1, 'CVE-2003-0786', 10.0, 'privilege escalation via bypassing authentication'],
+            ['1.0',     '3.7.1',   1, 'CVE-2003-0695',  7.5, 'cause DoS or execute arbitrary code'],
+            ['1.0',     '3.7',     1, 'CVE-2003-0693', 10.0, 'execute arbitrary code'],
+            ['3.0',     '3.6.1p2', 1, 'CVE-2003-0386',  7.5, 'bypass address restrictions for connection'],
+            ['3.1p1',   '3.6.1p1', 1, 'CVE-2003-0190',  5.0, 'discover valid usernames through different time delays'],
+            ['3.2.2',   '3.2.2',   1, 'CVE-2002-0765',  7.5, 'bypass authentication'],
+            ['1.2.2',   '3.3p1',   1, 'CVE-2002-0640', 10.0, 'execute arbitrary code'],
+            ['1.2.2',   '3.3p1',   1, 'CVE-2002-0639', 10.0, 'execute arbitrary code'],
+            ['2.1',     '3.2',     1, 'CVE-2002-0575',  7.5, 'privilege escalation'],
+            ['2.1',     '3.0.2p1', 2, 'CVE-2002-0083', 10.0, 'privilege escalation'],
+            ['3.0',     '3.0p1',   1, 'CVE-2001-1507',  7.5, 'bypass authentication'],
+            ['1.2.3',   '3.0.1p1', 5, 'CVE-2001-0872',  7.2, 'privilege escalation via crafted environment variables'],
+            ['1.2.3',   '2.1.1',   1, 'CVE-2001-0361',  4.0, 'recover plaintext from ciphertext'],
+            ['1.2',     '2.1',     1, 'CVE-2000-0525', 10.0, 'execute arbitrary code (improper privileges)']],
+        'PuTTY': [
+            ['0.54', '0.73', 2, 'CVE-2020-XXXX', 5.0, 'out of bounds memory read'],
+            ['0.0', '0.72', 2, 'CVE-2019-17069', 5.0, 'potential DOS by remote SSHv1 server'],
+            ['0.71', '0.72', 2, 'CVE-2019-17068', 5.0, 'xterm bracketed paste mode command injection'],
+            ['0.52', '0.72', 2, 'CVE-2019-17067', 7.5, 'port rebinding weakness in port forward tunnel handling'],
+            ['0.0', '0.71', 2, 'CVE-2019-XXXX', 5.0, 'undefined vulnerability in obsolete SSHv1 protocol handling'],
+            ['0.0', '0.71', 6, 'CVE-2019-XXXX', 5.0, 'local privilege escalation in Pageant'],
+            ['0.0', '0.70', 2, 'CVE-2019-9898', 7.5, 'potential recycling of random numbers'],
+            ['0.0', '0.70', 2, 'CVE-2019-9897', 5.0, 'multiple denial-of-service issues from writing to the terminal'],
+            ['0.0', '0.70', 6, 'CVE-2019-9896', 4.6, 'local application hijacking through malicious Windows help file'],
+            ['0.0', '0.70', 2, 'CVE-2019-9894', 6.4, 'buffer overflow in RSA key exchange'],
+            ['0.0', '0.69', 6, 'CVE-2016-6167', 4.4, 'local application hijacking through untrusted DLL loading'],
+            ['0.0', '0.67', 2, 'CVE-2017-6542', 7.5, 'buffer overflow in UNIX client that can result in privilege escalation or denial-of-service'],
+            ['0.0', '0.66', 2, 'CVE-2016-2563', 7.5, 'buffer overflow in SCP command-line utility'],
+            ['0.0', '0.65', 2, 'CVE-2015-5309', 4.3, 'integer overflow in terminal-handling code'],
+        ]
+    }
+    TXT: Dict[str, List[List[Any]]] = {
+        'Dropbear SSH': [
+            ['0.28', '0.34', 1, 'remote root exploit', 'remote format string buffer overflow exploit (exploit-db#387)']],
+        'libssh': [
+            ['0.3.3', '0.3.3', 1, 'null pointer check', 'missing null pointer check in "crypt_set_algorithms_server"'],
+            ['0.3.3', '0.3.3', 1, 'integer overflow',   'integer overflow in "buffer_get_data"'],
+            ['0.3.3', '0.3.3', 3, 'heap overflow',      'heap overflow in "packet_decrypt"']]
+    }
diff --git a/src/ssh_audit/writebuf.py b/src/ssh_audit/writebuf.py
new file mode 100644
index 0000000..5f25d8c
--- /dev/null
+++ b/src/ssh_audit/writebuf.py
@@ -0,0 +1,108 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+import io
+import struct
+
+# pylint: disable=unused-import
+from typing import Dict, List, Set, Sequence, Tuple, Iterable  # noqa: F401
+from typing import Callable, Optional, Union, Any  # noqa: F401
+
+
+class WriteBuf:
+    def __init__(self, data: Optional[bytes] = None) -> None:
+        super(WriteBuf, self).__init__()
+        self._wbuf = io.BytesIO(data) if data is not None else io.BytesIO()
+
+    def write(self, data: bytes) -> 'WriteBuf':
+        self._wbuf.write(data)
+        return self
+
+    def write_byte(self, v: int) -> 'WriteBuf':
+        return self.write(struct.pack('B', v))
+
+    def write_bool(self, v: bool) -> 'WriteBuf':
+        return self.write_byte(1 if v else 0)
+
+    def write_int(self, v: int) -> 'WriteBuf':
+        return self.write(struct.pack('>I', v))
+
+    def write_string(self, v: Union[bytes, str]) -> 'WriteBuf':
+        if not isinstance(v, bytes):
+            v = bytes(bytearray(v, 'utf-8'))
+        self.write_int(len(v))
+        return self.write(v)
+
+    def write_list(self, v: List[str]) -> 'WriteBuf':
+        return self.write_string(','.join(v))
+
+    @classmethod
+    def _bitlength(cls, n: int) -> int:
+        try:
+            return n.bit_length()
+        except AttributeError:
+            return len(bin(n)) - (2 if n > 0 else 3)
+
+    @classmethod
+    def _create_mpint(cls, n: int, signed: bool = True, bits: Optional[int] = None) -> bytes:
+        if bits is None:
+            bits = cls._bitlength(n)
+        length = bits // 8 + (1 if n != 0 else 0)
+        ql = (length + 7) // 8
+        fmt, v2 = '>{}Q'.format(ql), [0] * ql
+        for i in range(ql):
+            v2[ql - i - 1] = n & 0xffffffffffffffff
+            n >>= 64
+        data = bytes(struct.pack(fmt, *v2)[-length:])
+        if not signed:
+            data = data.lstrip(b'\x00')
+        elif data.startswith(b'\xff\x80'):
+            data = data[1:]
+        return data
+
+    def write_mpint1(self, n: int) -> 'WriteBuf':
+        # NOTE: Data Type Enc @ http://www.snailbook.com/docs/protocol-1.5.txt
+        bits = self._bitlength(n)
+        data = self._create_mpint(n, False, bits)
+        self.write(struct.pack('>H', bits))
+        return self.write(data)
+
+    def write_mpint2(self, n: int) -> 'WriteBuf':
+        # NOTE: Section 5 @ https://www.ietf.org/rfc/rfc4251.txt
+        data = self._create_mpint(n)
+        return self.write_string(data)
+
+    def write_line(self, v: Union[bytes, str]) -> 'WriteBuf':
+        if not isinstance(v, bytes):
+            v = bytes(bytearray(v, 'utf-8'))
+        v += b'\r\n'
+        return self.write(v)
+
+    def write_flush(self) -> bytes:
+        payload = self._wbuf.getvalue()
+        self._wbuf.truncate(0)
+        self._wbuf.seek(0)
+        return payload
+
+    def reset(self) -> None:
+        self._wbuf = io.BytesIO()