o [NSE] Added the script smtp-brute that performs brute force password

auditing against SMTP servers. [Patrik]

o [NSE] Updated SMTP library to support authentication using both plain-text
  and the SASL library. [Patrik]

CHANGELOG

@@ -1,5 +1,11 @@
 # Nmap Changelog ($Id$); -*-text-*-
 
+o [NSE] Added the script smtp-brute that performs brute force password
+  auditing against SMTP servers. [Patrik]
+
+o [NSE] Updated SMTP library to support authentication using both plain-text
+  and the SASL library. [Patrik]
+
 o [NSE] Added the script imap-brute that performs brute force password
   auditing against IMAP servers. [Patrik]
 

nselib/smtp.lua

@@ -8,6 +8,8 @@ module(... or "smtp", package.seeall)
 local comm    = require 'comm'
 local nmap    = require 'nmap'
 local stdnse  = require 'stdnse'
+local base64  = require 'base64'
+local sasl    = require 'sasl'
 
 local ERROR_MESSAGES = {
   ["EOF"]     = "connection closed",
@@ -580,3 +582,80 @@ quit = function(socket)
   socket:send("QUIT\r\n")
   socket:close()
 end
+
+login = function(socket, username, password, mech)
+	assert(mech == "LOGIN" or mech == "PLAIN" or mech == "CRAM-MD5" 
+			or mech == "DIGEST-MD5" or mech == "NTLM",
+			("Unsupported authentication mechanism (%s)"):format(mech or "nil"))
+	local status, response = query(socket, "AUTH", mech)
+	if ( not(status) ) then
+		return false, "ERROR: Failed to send AUTH to server"
+	end
+
+	if ( mech == "LOGIN" ) then
+		local tmp = response:match("334 (.*)")
+		if ( not(tmp) ) then
+			return false, "ERROR: Failed to decode LOGIN response"
+		end
+		tmp = base64.dec(tmp):lower()
+		if ( not(tmp:match("^username")) ) then
+			return false, ("ERROR: Expected \"Username\", but received (%s)"):format(tmp)
+		end
+		status, response = query(socket, base64.enc(username))
+		if ( not(status) ) then
+			return false, "ERROR: Failed to read LOGIN response"
+		end
+		tmp = response:match("334 (.*)")
+		if ( not(tmp) ) then
+			return false, "ERROR: Failed to decode LOGIN response"
+		end
+		tmp = base64.dec(tmp):lower()
+		if ( not(tmp:match("^password")) ) then
+			return false, ("ERROR: Expected \"password\", but received (%s)"):format(tmp)
+		end
+		status, response = query(socket, base64.enc(password))
+		if ( not(status) ) then
+			return false, "ERROR: Failed to read LOGIN response"
+		end
+		if ( response:match("^235") ) then
+			return true, "Login success"
+		end
+		return false, response
+	end
+	
+	
+	if ( mech == "NTLM" ) then
+		-- sniffed of the wire, seems to always be the same
+		-- decodes to some NTLMSSP blob greatness
+		status, response = query(socket, "TlRMTVNTUAABAAAAB7IIogYABgA3AAAADwAPACgAAAAFASgKAAAAD0FCVVNFLUFJUi5MT0NBTERPTUFJTg==")
+		if ( not(status) ) then return false, "ERROR: Failed to receieve NTLM challenge" end 
+	end
+	
+	
+	local chall = response:match("^334 (.*)")
+	chall = (chall and base64.dec(chall))
+	if (not(chall)) then return false, "ERROR: Failed to retrieve challenge" end
+
+	-- All mechanisms expect username and pass
+	-- add the otheronce for those who need them
+	local mech_params = { username, password, chall, "smtp" }
+	local auth_data = sasl.Helper:new(mech):encode(unpack(mech_params))
+	auth_data = base64.enc(auth_data)
+	
+	status, response = query(socket, auth_data)
+	if ( not(status) ) then
+		return false, ("ERROR: Failed to authenticate using SASL %s"):format(mech)
+	end
+	
+	if ( mech == "DIGEST-MD5" ) then
+		local rspauth = response:match("^334 (.*)")
+		if ( rspauth ) then
+			rspauth = base64.dec(rspauth)
+			status, response = query(socket,"")
+		end
+	end
+	
+	if ( response:match("^235") ) then return true, "Login success"	end
+		
+	return false, response
+end

scripts/script.db

@@ -184,6 +184,7 @@ Entry { filename = "smb-security-mode.nse", categories = { "discovery", "safe",
 Entry { filename = "smb-server-stats.nse", categories = { "discovery", "intrusive", } }
 Entry { filename = "smb-system-info.nse", categories = { "discovery", "intrusive", } }
 Entry { filename = "smbv2-enabled.nse", categories = { "default", "safe", } }
+Entry { filename = "smtp-brute.nse", categories = { "brute", "intrusive", } }
 Entry { filename = "smtp-commands.nse", categories = { "default", "discovery", "safe", } }
 Entry { filename = "smtp-enum-users.nse", categories = { "discovery", "external", "intrusive", } }
 Entry { filename = "smtp-open-relay.nse", categories = { "discovery", "external", "intrusive", } }

scripts/smtp-brute.nse

@@ -0,0 +1,136 @@
+description = [[
+Performs password guessing against SMTP servers using either LOGIN, PLAIN,
+CRAM-MD5, DIGEST-MD5 or NTLM authentication.
+]]
+
+---
+-- @usage
+-- nmap -p 25 --script smtp-brute <host>
+--
+-- @output
+-- PORT    STATE SERVICE REASON
+-- 25/tcp  open  stmp    syn-ack
+-- | smtp-brute: 
+-- |   Accounts
+-- |     braddock:jules - Account is valid
+-- |     lane:sniper - Account is valid
+-- |     parker:scorpio - Account is valid
+-- |   Statistics
+-- |_    Performed 1160 guesses in 41 seconds, average tps: 33
+--
+-- @args smtp-brute.auth authentication mechanism to use LOGIN, PLAIN, 
+--		 CRAM-MD5, DIGEST-MD5 or NTLM
+
+-- Version 0.1
+-- Created 07/15/2011 - v0.1 - created by Patrik Karlsson <patrik@cqure.net>
+
+require 'creds'
+require 'brute'
+require 'shortport'
+require 'smtp'
+
+author = "Patrik Karlsson"
+license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
+categories = {"brute", "intrusive"}
+
+portrule = shortport.port_or_service({ 25, 465, 587 },
+                { "smtp", "smtps", "submission" })
+
+local mech
+
+-- By using this connectionpool we don't need to reconnect the socket
+-- for each attempt.
+ConnectionPool = {}
+
+Driver = 
+{
+
+	-- Creates a new driver instance
+	-- @param host table as received by the action method
+	-- @param port table as received by the action method
+	-- @param pool an instance of the ConnectionPool
+	new = function(self, host, port)
+		local o = { host = host, port = port }
+       	setmetatable(o, self)
+        self.__index = self
+		return o
+	end,
+	
+	-- Connects to the server (retrieves a connection from the pool)
+	connect = function( self )
+		self.socket = ConnectionPool[coroutine.running()]
+		if ( not(self.socket) ) then
+			self.socket = smtp.connect(self.host, self.port, { ssl = true, recv_before = true })
+			if ( not(self.socket) ) then return false end
+			ConnectionPool[coroutine.running()] = self.socket
+		end
+		return true
+	end,
+
+	-- Attempts to login to the server
+	-- @param username string containing the username
+	-- @param password string containing the password
+	-- @return status true on success, false on failure
+	-- @return brute.Error on failure and brute.Account on success
+	login = function( self, username, password )
+		local status, err = smtp.login( self.socket, username, password, mech )
+		if ( status ) then
+			smtp.quit(self.socket)
+			ConnectionPool[coroutine.running()] = nil
+			return true, brute.Account:new(username, password, creds.State.VALID)
+		end
+		if ( err:match("^ERROR: Failed to .*") ) then
+			self.socket:close()
+			ConnectionPool[coroutine.running()] = nil
+			local err = brute.Error:new( err )
+			-- This might be temporary, set the retry flag
+			err:setRetry( true )
+			return false, err			
+		end
+		return false, brute.Error:new( "Incorrect password" )
+	end,
+	
+	-- Disconnects from the server (release the connection object back to
+	-- the pool)
+	disconnect = function( self )
+		return true
+	end,
+		
+}
+
+
+action = function(host, port)
+
+	local socket, response = smtp.connect(host, port, { ssl = true, recv_before = true })
+	if ( not(socket) ) then return "\n  ERROR: Failed to connect to SMTP server" end
+	local status, response = smtp.ehlo(socket, smtp.get_domain(host))
+	if ( not(status) ) then return "\n  ERROR: EHLO command failed, aborting ..." end
+	local mechs = smtp.get_auth_mech(response)
+	if ( not(mechs) ) then 
+		return "\n  ERROR: Failed to retrieve authentication mechanisms form server"
+	end
+	smtp.quit(socket)
+		
+	local mech_prio = stdnse.get_script_args("smtp-brute.auth") 
+	mech_prio = ( mech_prio and { mech_prio } ) or 
+					{ "LOGIN", "PLAIN", "CRAM-MD5", "DIGEST-MD5", "NTLM" }
+	
+	for _, mp in ipairs(mech_prio) do
+		for _, m in pairs(mechs) do 
+			if ( mp == m ) then
+				mech = m
+				break
+			end
+		end
+		if ( mech ) then break end
+	end
+		
+	local engine = brute.Engine:new(Driver, host, port)
+	
+	engine.options.script_name = SCRIPT_NAME	
+	status, result = engine:start()
+	
+	for _, sock in pairs(ConnectionPool) do sock:close() end
+	
+	return result
+end