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Diffstat (limited to 'src/ssh_audit/ssh_socket.py')
| -rw-r--r-- | src/ssh_audit/ssh_socket.py | 343 |
1 files changed, 343 insertions, 0 deletions
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 |