1 files changed, 212 insertions, 0 deletions
diff --git a/scripts/ssh2-enum-algos.nse b/scripts/ssh2-enum-algos.nse
new file mode 100644
index 0000000..fda9f0e
--- /dev/null
+++ b/scripts/ssh2-enum-algos.nse
@@ -0,0 +1,212 @@
+local nmap = require "nmap"
+local shortport = require "shortport"
+local stdnse = require "stdnse"
+local string = require "string"
+local stringaux = require "stringaux"
+local table = require "table"
+
+local openssl = stdnse.silent_require "openssl"
+local ssh2 = stdnse.silent_require "ssh2"
+
+description = [[
+Reports the number of algorithms (for encryption, compression, etc.) that
+the target SSH2 server offers. If verbosity is set, the offered algorithms
+are each listed by type.
+
+If the "client to server" and "server to client" algorithm lists are identical
+(order specifies preference) then the list is shown only once under a combined
+type.
+]]
+
+---
+-- @usage
+-- nmap --script ssh2-enum-algos target
+--
+-- @output
+-- PORT   STATE SERVICE
+-- 22/tcp open  ssh
+-- | ssh2-enum-algos:
+-- |   kex_algorithms (4)
+-- |       diffie-hellman-group-exchange-sha256
+-- |       diffie-hellman-group-exchange-sha1
+-- |       diffie-hellman-group14-sha1
+-- |       diffie-hellman-group1-sha1
+-- |   server_host_key_algorithms (2)
+-- |       ssh-rsa
+-- |       ssh-dss
+-- |   encryption_algorithms (13)
+-- |       aes128-ctr
+-- |       aes192-ctr
+-- |       aes256-ctr
+-- |       arcfour256
+-- |       arcfour128
+-- |       aes128-cbc
+-- |       3des-cbc
+-- |       blowfish-cbc
+-- |       cast128-cbc
+-- |       aes192-cbc
+-- |       aes256-cbc
+-- |       arcfour
+-- |       rijndael-cbc@lysator.liu.se
+-- |   mac_algorithms (6)
+-- |       hmac-md5
+-- |       hmac-sha1
+-- |       hmac-ripemd160
+-- |       hmac-ripemd160@openssh.com
+-- |       hmac-sha1-96
+-- |       hmac-md5-96
+-- |   compression_algorithms (2)
+-- |       none
+-- |_      zlib@openssh.com
+--
+-- @xmloutput
+-- <table key="kex_algorithms">
+--   <elem>ecdh-sha2-nistp256</elem>
+--   <elem>ecdh-sha2-nistp384</elem>
+--   <elem>ecdh-sha2-nistp521</elem>
+--   <elem>diffie-hellman-group-exchange-sha256</elem>
+--   <elem>diffie-hellman-group-exchange-sha1</elem>
+--   <elem>diffie-hellman-group14-sha1</elem>
+--   <elem>diffie-hellman-group1-sha1</elem>
+-- </table>
+-- <table key="server_host_key_algorithms">
+--   <elem>ssh-rsa</elem>
+--   <elem>ecdsa-sha2-nistp256</elem>
+-- </table>
+-- <table key="encryption_algorithms">
+--   <elem>aes128-ctr</elem>
+--   <elem>aes192-ctr</elem>
+--   <elem>aes256-ctr</elem>
+--   <elem>aes128-cbc</elem>
+--   <elem>3des-cbc</elem>
+--   <elem>blowfish-cbc</elem>
+--   <elem>cast128-cbc</elem>
+--   <elem>aes192-cbc</elem>
+--   <elem>aes256-cbc</elem>
+-- </table>
+-- <table key="mac_algorithms">
+--   <elem>hmac-sha1</elem>
+--   <elem>umac-64@openssh.com</elem>
+--   <elem>hmac-ripemd160</elem>
+--   <elem>hmac-sha2-256</elem>
+--   <elem>hmac-sha2-512</elem>
+-- </table>
+-- <table key="compression_algorithms">
+--   <elem>none</elem>
+--   <elem>zlib@openssh.com</elem>
+-- </table>
+
+author = "Kris Katterjohn"
+
+license = "Same as Nmap--See https://nmap.org/book/man-legal.html"
+
+categories = {"safe", "discovery"}
+
+
+portrule = shortport.ssh
+
+-- Build onto lists{} and possibly modify parsed{} based on whether the
+-- algorithm name-lists are identical between the server-to-client and
+-- client-to-server types.  Note that this simply modifies the passed tables.
+local combine_types = function(parsed, lists)
+  local doubles = {
+    "encryption_algorithms",
+    "mac_algorithms",
+    "compression_algorithms"
+  }
+
+  for _, i in ipairs(doubles) do
+    local c2s = i .. "_client_to_server"
+    local s2c = i .. "_server_to_client"
+
+    if parsed[c2s] == parsed[s2c] then
+      parsed[i] = parsed[c2s]
+      parsed[c2s] = nil
+      parsed[s2c] = nil
+      table.insert(lists, i)
+    else
+      table.insert(lists, c2s)
+      table.insert(lists, s2c)
+    end
+  end
+end
+
+-- Build and return the output table
+local output = function(parsed, lists)
+  local out = stdnse.output_table()
+
+  for _, l in ipairs(lists) do
+    local v = parsed[l]
+    local a = v:len() > 0 and stringaux.strsplit(",", v) or {}
+    if nmap.verbosity() > 0 then
+      setmetatable(a, {
+        __tostring = function(t)
+          return string.format("(%d)\n      %s", #t, table.concat(t, "\n      "))
+        end
+      })
+    else
+      setmetatable(a, {
+        __tostring = function(t)
+          return string.format("(%d)", #t)
+        end
+      })
+    end
+    out[l] = a
+  end
+
+  return out
+end
+
+action = function(host, port)
+  local sock = nmap.new_socket()
+  local status = sock:connect(host, port)
+  if not status then
+    return
+  end
+
+  -- send the client banner
+  -- NB: The protocol does not prescribe which side sends the banner first
+  status = sock:send("SSH-2.0-Nmap_SSH2_Enum_Algos\r\n")
+  if not status then
+    sock:close()
+    return
+  end
+
+  -- slurp the server banner
+  status = sock:receive_buf("\r?\n", false)
+  if not status then
+    sock:close()
+    return
+  end
+
+  local ssh = ssh2.transport
+
+  -- send the client key exchange
+  -- NB: The protocol does not prescribe which side sends the kex init first
+  status = sock:send(ssh.build(ssh.kex_init()))
+  if not status then
+    sock:close()
+    return
+  end
+
+  local response
+  status, response = ssh.receive_packet(sock)
+  sock:close()
+  if not status then
+    return
+  end
+
+  local parsed = ssh.parse_kex_init(ssh.payload(response))
+
+  local lists = {
+    "kex_algorithms",
+    "server_host_key_algorithms"
+    -- Other types will be added below in combine_types()
+  }
+
+  -- Modifies tables
+  combine_types(parsed, lists)
+
+  return output(parsed, lists)
+end
+