local comm = require "comm"
local creds = require "creds"
local ldap = require "ldap"
local nmap = require "nmap"
local shortport = require "shortport"
local stdnse = require "stdnse"
local string = require "string"
local table = require "table"
local unpwdb = require "unpwdb"

description = [[
Attempts to brute-force LDAP authentication. By default
it uses the built-in username and password lists. In order to use your
own lists use the <code>userdb</code> and <code>passdb</code> script arguments.

This script does not make any attempt to prevent account lockout!
If the number of passwords in the dictionary exceed the amount of
allowed tries, accounts will be locked out. This usually happens
very quickly.

Authenticating against Active Directory using LDAP does not use the
Windows user name but the user accounts distinguished name. LDAP on Windows
2003 allows authentication using a simple user name rather than using the
fully distinguished name. E.g., "Patrik Karlsson" vs.
"cn=Patrik Karlsson,cn=Users,dc=cqure,dc=net"
This type of authentication is not supported on e.g. OpenLDAP.

This script uses some AD-specific support and optimizations:
* LDAP on Windows 2003/2008 reports different error messages depending on whether an account exists or not. If the script receives an error indicating that the username does not exist it simply stops guessing passwords for this account and moves on to the next.
* The script attempts to authenticate with the username only if no LDAP base is specified. The benefit of authenticating this way is that the LDAP path of each account does not need to be known in advance as it's looked up by the server.  This technique will only find a match if the account Display Name matches the username being attempted.
]]

---
-- @usage
-- nmap -p 389 --script ldap-brute --script-args ldap.base='"cn=users,dc=cqure,dc=net"' <host>
--
-- @output
-- 389/tcp open  ldap
-- | ldap-brute:
-- |_  ldaptest:ldaptest => Valid credentials
-- |   restrict.ws:restricted1 => Valid credentials, account cannot log in from current host
-- |   restrict.time:restricted1 => Valid credentials, account cannot log in at current time
-- |   valid.user:valid1 => Valid credentials
-- |   expired.user:expired1 => Valid credentials, account expired
-- |   disabled.user:disabled1 => Valid credentials, account disabled
-- |_  must.change:need2change => Valid credentials, password must be changed at next logon
--
-- @args ldap.base If set, the script will use it as a base for the password
--       guessing attempts. If both ldap.base and ldap.upnsuffix are unset the user
--       list must either contain the distinguished name of each user or the server
--       must support authentication using a simple user name. See the AD discussion
--       in the description.  DO NOT use ldap.upnsuffix in conjunction with ldap.base
--       as attempts to login will fail.
--
-- @args ldap.upnsuffix  If set, the script will append this suffix value to the username
--       to create a User Principle Name (UPN).  For example if the ldap.upnsuffix value were
--       'mycompany.com' and the username being tested was 'pete' then this script would
--       attempt to login as 'pete@mycompany.com'.  This setting should only have value
--       when running the script against a Microsoft Active Directory LDAP implementation.
--       When the UPN is known using this setting should provide more reliable results
--       against domains that have been organized into various OUs or child domains.
--       If both ldap.base and ldap.upnsuffix are unset the user list must either contain
--       the distinguished name of each user or the server must support authentication
--       using a simple user name. See the AD discussion in the description.
--       DO NOT use ldap.upnsuffix in conjunction with ldap.base as attempts to login
--       will fail.
--
-- @args ldap.saveprefix  If set, the script will save the output to a file
--       beginning with the specified path and name.  The file suffix will automatically
--       be added based on the output type selected.
--
-- @args ldap.savetype  If set, the script will save the passwords in the specified
--       format.  The current formats are CSV, verbose and plain. In both verbose and plain
--       records are separated by colons.  The difference between the two is that verbose
--       includes the credential state.  When ldap.savetype is used without ldap.saveprefix
--       then ldap-brute will be prefixed to all output filenames.
--

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


-- Version 0.6
-- Created 01/20/2010 - v0.1 - created by Patrik Karlsson
-- Revised 01/26/2010 - v0.2 - cleaned up unpwdb related code, fixed ssl stuff
-- Revised 02/17/2010 - v0.3 - added AD specific checks and fixed bugs related to LDAP base
-- Revised 08/07/2011 - v0.4 - adjusted AD match strings to be level independent, added additional account condition checks
-- Revised 09/04/2011 - v0.5 - added support for creds library, saving output to file
-- Revised 09/09/2011 - v0.6 - added support specifying a UPN suffix via ldap.upnsuffx, changed account status text for consistency.

portrule = shortport.port_or_service({389,636}, {"ldap","ldapssl"})

--- Tries to determine a valid naming context to use to validate credentials
--
-- @param socket socket already connected to LDAP server
-- @return string containing a valid naming context
function get_naming_context( socket )

  local req = { baseObject = "", scope = ldap.SCOPE.base, derefPolicy = ldap.DEREFPOLICY.default, attributes = { "defaultNamingContext", "namingContexts" } }
  local status, searchResEntries = ldap.searchRequest( socket, req )

  if not status then
    return nil
  end

  local contexts = ldap.extractAttribute( searchResEntries, "defaultNamingContext" )

  -- OpenLDAP does not have a defaultNamingContext
  if not contexts then
    contexts = ldap.extractAttribute( searchResEntries, "namingContexts" )
  end

  if contexts and #contexts > 0 then
    return contexts[1]
  end

  return nil
end

--- Attempts to validate the credentials by requesting the base object of the supplied context
--
-- @param socket socket already connected to the LDAP server
-- @param context string containing the context to search
-- @return true if credentials are valid and search was a success, false if not.
function is_valid_credential( socket, context )
  local req = { baseObject = context, scope = ldap.SCOPE.base, derefPolicy = ldap.DEREFPOLICY.default, attributes = nil }
  local status, searchResEntries = ldap.searchRequest( socket, req )

  return status
end

action = function( host, port )

  local result, response, status, err, context, output, valid_accounts = {}, nil, nil, nil, nil, nil, {}
  local usernames, passwords, username, password, fq_username
  local user_cnt, invalid_account_cnt, tot_tries = 0, 0, 0

  local clock_start = nmap.clock_ms()

  local ldap_anonymous_bind = "\x30\x0c\x02\x01\x01\x60\x07\x02\x01\x03\x04\x00\x80\x00"
  local socket, _, opt = comm.tryssl( host, port, ldap_anonymous_bind, nil )

  local base_dn = stdnse.get_script_args('ldap.base')
  local upn_suffix = stdnse.get_script_args('ldap.upnsuffix')

  local output_type = stdnse.get_script_args('ldap.savetype')

  local output_prefix = nil
  if ( stdnse.get_script_args('ldap.saveprefix') ) then
    output_prefix = stdnse.get_script_args('ldap.saveprefix')
  elseif ( output_type ) then
    output_prefix = "ldap-brute"
  end

  local credTable = creds.Credentials:new(SCRIPT_NAME, host, port)

  if not socket then
    return
  end

  -- We close and re-open the socket so that the anonymous bind does not distract us
  socket:close()
  -- set a reasonable timeout value
  socket:set_timeout(5000)
  status = socket:connect(host, port, opt)
  if not status then
    return
  end

  context = get_naming_context(socket)

  if not context then
    stdnse.debug1("Failed to retrieve namingContext")
    socket:close()
    return
  end

  status, usernames = unpwdb.usernames()
  if not status then
    return
  end

  status, passwords = unpwdb.passwords()
  if not status then
    return
  end

  for username in usernames do
    -- if a base DN was set append our username (CN) to the base
    if base_dn then
      fq_username = ("cn=%s,%s"):format(username, base_dn)
    elseif upn_suffix then
      fq_username = ("%s@%s"):format(username, upn_suffix)
    else
      fq_username = username
    end


    user_cnt = user_cnt + 1
    for password in passwords do
      tot_tries = tot_tries + 1

      -- handle special case where we want to guess the username as password
      if password == "%username%" then
        password = username
      end

      stdnse.debug1( "Trying %s/%s ...", fq_username, password )
      status, response = ldap.bindRequest( socket, { version=3, ['username']=fq_username, ['password']=password} )

      -- if the DN (username) does not exist, break loop
      if not status and response:match("invalid DN") then
        stdnse.debug1( "%s returned: \"Invalid DN\"", fq_username )
        invalid_account_cnt = invalid_account_cnt + 1
        break
      end

      -- Is AD telling us the account does not exist?
      if not status and response:match("AcceptSecurityContext error, data 525,") then
        invalid_account_cnt = invalid_account_cnt + 1
        break
      end

      -- Account Locked Out
      if not status and response:match("AcceptSecurityContext error, data 775,") then
        table.insert( valid_accounts, string.format("%s => Valid credentials, account locked", fq_username ) )
        stdnse.verbose2("%s => Valid credentials, account locked", fq_username)
        credTable:add(fq_username,password, creds.State.LOCKED_VALID)
        break
      end

      -- Login correct, account disabled
      if not status and response:match("AcceptSecurityContext error, data 533,") then
        table.insert( valid_accounts, string.format("%s:%s => Valid credentials, account disabled", fq_username, password:len()>0 and password or "<empty>" ) )
        stdnse.verbose2("%s:%s => Valid credentials, account disabled", fq_username, password:len()>0 and password or "<empty>" )
        credTable:add(fq_username,password, creds.State.DISABLED_VALID)
        break
      end

      -- Login correct, user must change password
      if not status and response:match("AcceptSecurityContext error, data 773,") then
        table.insert( valid_accounts, string.format("%s:%s => Valid credentials, password must be changed at next logon", fq_username, password:len()>0 and password or "<empty>" ) )
        stdnse.verbose2("%s:%s => Valid credentials, password must be changed at next logon", fq_username, password:len()>0 and password or "<empty>")
        credTable:add(fq_username,password, creds.State.CHANGEPW)
        break
      end

      -- Login correct, user account expired
      if not status and response:match("AcceptSecurityContext error, data 701,") then
        table.insert( valid_accounts, string.format("%s:%s => Valid credentials, account expired", fq_username, password:len()>0 and password or "<empty>" ) )
        stdnse.verbose2("%s:%s => Valid credentials, account expired", fq_username, password:len()>0 and password or "<empty>")
        credTable:add(fq_username,password, creds.State.EXPIRED)
        break
      end

      -- Login correct, user account logon time restricted
      if not status and response:match("AcceptSecurityContext error, data 530,") then
        table.insert( valid_accounts, string.format("%s:%s => Valid credentials, account cannot log in at current time", fq_username, password:len()>0 and password or "<empty>" ) )
        stdnse.verbose2("%s:%s => Valid credentials, account cannot log in at current time", fq_username, password:len()>0 and password or "<empty>")
        credTable:add(fq_username,password, creds.State.TIME_RESTRICTED)
        break
      end

      -- Login correct, user account can only log in from certain workstations
      if not status and response:match("AcceptSecurityContext error, data 531,") then
        table.insert( valid_accounts, string.format("%s:%s => Valid credentials, account cannot log in from current host", fq_username, password:len()>0 and password or "<empty>" ) )
        stdnse.verbose2("%s:%s => Valid credentials, account cannot log in from current host", fq_username, password:len()>0 and password or "<empty>")
        credTable:add(fq_username,password, creds.State.HOST_RESTRICTED)
        break
      end

      --Login, correct
      if status then
        status = is_valid_credential( socket, context )
        if status then
          table.insert( valid_accounts, string.format("%s:%s => Valid credentials", fq_username, password:len()>0 and password or "<empty>" ) )
          stdnse.verbose2("%s:%s => Valid credentials", fq_username, password:len()>0 and password or "<empty>")
          -- Add credentials for other ldap scripts to use
          if nmap.registry.ldapaccounts == nil then
            nmap.registry.ldapaccounts = {}
          end
          nmap.registry.ldapaccounts[fq_username]=password
          credTable:add(fq_username,password, creds.State.VALID)

          break
        end
      end
    end
    passwords("reset")
  end

  stdnse.debug1( "Finished brute against LDAP, total tries: %d, tps: %.f", tot_tries, ( tot_tries / ( ( nmap.clock_ms() - clock_start ) / 1000 ) ) )

  if ( invalid_account_cnt == user_cnt and base_dn ~= nil ) then
    return "WARNING: All usernames were invalid. Invalid LDAP base?"
  end



  if output_prefix then
    local output_file = output_prefix .. "_" .. host.ip .. "_" .. port.number
    status, err = credTable:saveToFile(output_file,output_type)
    if not status then
      stdnse.debug1("%s", err)
    end
  end

  output = stdnse.format_output(true, valid_accounts)
  if err then
    output = (output or "") .. stdnse.format_output(true, err)
  end

  return output

end
