--- Attempts to enumerate the users on a remote Windows system, with as much information as possible, 
--  through a variety of techniques (over SMB + MSRPC, which uses port 445 or 139). \n
--\n
-- Will first attempt to call the QueryDisplayInfo() MSRPC function. If NULL sessions are enabled, 
-- this will succeed and pull back a detailed list of users. Unfortunately, this likely won't succeed
-- unless we're scanning Windows 2000. When this test is performed, the following MSRPC functions
-- are called:\n
--\n
-- Bind() -- bind to the SAMR service\n
-- Connect4() -- get a connect_handle\n
-- EnumDomains() -- get a list of the domains\n
-- QueryDomain() -- get the sid for the domain\n
-- OpenDomain() -- get a handle for each domain\n
-- QueryDisplayInfo() -- get the list of users in the domain\n
-- Close() -- Close the domain handle\n
-- Close() -- Close the connect handle\n
--\n
-- Credit goes out to the enum.exe program, the code I wrote for this is largely due to packetlogs 
-- I took of its operations. \n
--\n
-- Regardless of whether or not this succeeds, a second technique is used to pull user accounts. 
-- This one is apparently successful against more machines, although I haven't found a machine
-- that this only works against. However, I did find that this will turn up more users for certain
-- systems (although I haven't figured out why). \n
-- \n
-- Each user on a Windows system has an RID. The RID of 500 is the Administrator account (even if 
-- it's renamed), 501 is the Guest account, and 1000+ are the user accounts. This technique, which
-- was originally used in the sid2user/user2sid programs, will attempt to convert common RID numbers
-- to names to discover users. \n
-- \n
-- First, the SID of the server has to be determined. This is done by looking up any name present on
-- the server using a technique like user2sid. For this code, we try and convert as many names as we
-- can find -- all we need is one valid name for this to succeed. In this code, I use:\n
-- - The computer name / domain name, returned in SMB_COM_NEGOTIATE\n
-- - An nbstat query to get the server name and the currently loggeed in user\n
-- - Some common names ("administrator", "guest", and "test")\n
--\n
-- In theory, the computer name should be sufficient for this to always work, and the rest of the \n
-- names are in there for good measure. \n
--\n
-- Once that's completed, the RIDs 500 - 505 are requested, and any responses are displayed. Then,
-- starting at 1000, we take small groups of RIDs which are requestd. I break them into
-- smaller groups because if too many are requested at once, we get a STATUS_BUFFER_OVERFLOW 
-- error. We try every RID up to 1100, then, as soon as we get an empty group (5 RIDs in a row 
-- without a result), we stop. \n
--\n
-- It might be a good idea to modify this, in the future, with some more intelligence. For example,
-- have it run until it get 5 groups in a row with no results instead of going up to 1100. I 
-- performed a test on an old server we have here with a lot of accounts, and I got these results:
-- 500, 501, 1000, 1030, 1031, 1053, 1054, 1055, 1056, 1057, 1058, 1059, 1060, 1061, 1062, 1063, 
-- 1064, 1065, 1066, 1067, 1070, 1075, 1081, 1088, 1090. The jump from 1000 to 1030 is quite large
-- and can easily result in missing accounts.\n
--\n
-- The disadvantage of using the user2sid/sid2user technique is that less information is returned 
-- about the user. \n
--\n
-- The names and details from both of these techniques are merged and displayed. If the output is
-- verbose, then as many details as possible are displayed, otherwise only the list of usernames
-- are displayed. The names are ordered alphabetically.\n
--
--@usage
-- nmap --script smb-enumusers.nse -p445 <host>\n
-- sudo nmap -sU -sS --script smb-enumusers.nse -p U:137,T:139 <host>\n
--
--@output
-- TODO
-----------------------------------------------------------------------

id = "MSRPC: List of user accounts"
description = "Tries calling SAMR and LSA functions to get a list of user accounts."
author = "Ron Bowes"
copyright = "Ron Bowes"
license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
categories = {"discovery","intrusive"}

require 'msrpc'
require 'smb'
require 'stdnse'

hostrule = function(host)

	local port = smb.get_port(host)

	if(port == nil) then
		return false
	else
		return true
	end

end

---Attempt to enumerate users through SAMR methods. See the file description for more information. 
--
--@param host The host object. 
--@return (status, result) If status is false, result is an error message. Otherwise, result is an
--        array of tables. Each table contains a 'name', 'domain', 'fullname', 'rid', and 'description'. 
local function enum_samr(host)

	local bind_result, connect4_result, enumdomains_result
	local connect_handle
	local status, socket
	local uid, tid, fid
	local response = {}

	-- Create the SMB session
	status, socket, uid, tid, fid = msrpc.start_smb(host, msrpc.SAMR_PATH)
	if(status == false) then
		return false, socket
	end

	-- Bind to SAMR service
	status, bind_result = msrpc.bind(socket, msrpc.SAMR_UUID, msrpc.SAMR_VERSION, nil, uid, tid, fid)
	if(status == false) then
		msrpc.stop_smb(socket, uid, tid)
		return false, bind_result
	end

	-- Call connect4()
	status, connect4_result = msrpc.samr_connect4(socket, host.ip, uid, tid, fid)
	if(status == false) then
		msrpc.stop_smb(socket, uid, tid)
		return false, connect4_result
	end

	-- Save the connect_handle
	connect_handle = connect4_result['connect_handle']

	-- Call EnumDomains()
	status, enumdomains_result = msrpc.samr_enumdomains(socket, connect_handle, uid, tid, fid)
	if(status == false) then
		msrpc.stop_smb(socket, uid, tid)
		return false, enumdomains_result
	end

	-- If no domains were returned, go back with an error
	if(#enumdomains_result['domains'] == 0) then
		msrpc.stop_smb(socket, uid, tid)
		return false, "Couldn't find any domains"
	end

	for i = 1, #enumdomains_result['domains'], 1 do

		local domain = enumdomains_result['domains'][i]
		-- We don't care about the 'builtin' domain
		if(domain ~= 'Builtin') then
			local sid
			local domain_handle
			local opendomain_result, querydisplayinfo_result

			-- Call LookupDomain()
			status, lookupdomain_result = msrpc.samr_lookupdomain(socket, connect_handle, domain, uid, tid, fid)
			if(status == false) then
				msrpc.stop_smb(socket, uid, tid)
				return false, lookupdomain_result
			end

			-- Save the sid
			sid = lookupdomain_result['sid']
	
			-- Call OpenDomain()
			status, opendomain_result = msrpc.samr_opendomain(socket, connect_handle, sid, uid, tid, fid)
			if(status == false) then
				msrpc.stop_smb(socket, uid, tid)
				return false, opendomain_result
			end

			-- Save the domain handle
			domain_handle = opendomain_result['domain_handle']
	
			-- Call QueryDisplayInfo()
			status, querydisplayinfo_result = msrpc.samr_querydisplayinfo(socket, domain_handle, uid, tid, fid)
			if(status == false) then
				msrpc.stop_smb(socket, uid, tid)
				return false, querydisplayinfo_result
			end

			-- Close the domain handle
			msrpc.samr_close(socket, domain_handle,  uid, tid, fid)

			-- Finally, fill in the response!
			for i = 1, #querydisplayinfo_result['details'], 1 do
				querydisplayinfo_result['details'][i]['domain'] = domain
				response[#response + 1] = querydisplayinfo_result['details'][i]
			end
		end -- Checking for 'builtin'
	end -- Domain loop

	-- Close the connect handle
	msrpc.samr_close(socket, connect_handle, uid, tid, fid)

	-- Stop the SAMR SMB
	msrpc.stop_smb(socket, uid, tid)

	return true, response
end

---Attempt to enumerate users through LSA methods. See the file description for more information. 
--
--@param host The host object. 
--@return (status, result) If status is false, result is an error message. Otherwise, result is an
--        array of tables. Each table contains a 'name', 'domain', and 'rid'. 
local function enum_lsa(host)

	local status, socket
	local uid, tid, fid
	local response = {}

    -- Create the SMB session
    status, socket, uid, tid, fid, negotiate_result = msrpc.start_smb(host, msrpc.LSA_PATH)
    if(status == false) then
        return false, socket
    end

    -- Bind to LSA service
    status, bind_result = msrpc.bind(socket, msrpc.LSA_UUID, msrpc.LSA_VERSION, nil, uid, tid, fid)
    if(status == false) then
        msrpc.stop_smb(socket, uid, tid)
        return false, bind_result
    end

    -- Open the LSA policy
    status, openpolicy2_result = msrpc.lsa_openpolicy2(socket, host.ip, uid, tid, fid)
    if(status == false) then
        msrpc.stop_smb(socket, uid, tid)
        return false, openpolicy2_result
    end

    -- Start with some common names, as well as the name returned by the negotiate call
    names = {"administrator", "guest", "test", negotiate_result['domain'], negotiate_result['server'] }

    -- Get the server's name from nbstat
    local result, server_name = netbios.get_server_name(host.ip)
    if(result == true) then
        names[#names + 1] = server_name
    end

    -- Get the logged in user from nbstat
    local result, user_name = netbios.get_user_name(host.ip)
    if(result == true) then
        names[#names + 1] = user_name
    end

    -- Look up the names, if any are valid than the server's SID will be returned
    status, lookupnames2_result = msrpc.lsa_lookupnames2(socket, openpolicy2_result['policy_handle'], names, uid, tid, fid)
    if(status == false) then
        msrpc.stop_smb(socket, uid, tid)
        return false, lookupnames2_result
    end

    -- Loop through the domains returned and find teh users in each
    for i = 1, #lookupnames2_result['domains'], 1 do
        local domain = lookupnames2_result['domains'][i]['name']
        local sid    = lookupnames2_result['domains'][i]['sid']
        local rids   = { }
        local start  = 1000

        -- Start by looking up 500 - 505 (will likely be Administrator + guest)
        for j = 500, 505, 1 do 
			rids[#rids + 1] = j 
		end

        status, lookupsids2_result = msrpc.lsa_lookupsids2(socket, openpolicy2_result['policy_handle'], sid, rids, uid, tid, fid)
        if(status == false) then
            msrpc.stop_smb(socket, uid, tid)
            return false, lookupsids2_result
        end

		-- Put the details for each name into an array
		for j = 1, #lookupsids2_result['details'], 1 do
			if(lookupsids2_result['details'][j]['name'] ~= nil) then
				local result = {}
				result['name']   = lookupsids2_result['details'][j]['name']
				result['rid']    = 500 + j - 1
				result['domain'] = domain
				response[#response + 1] = result
			end
		end

        -- Now do groups of 5 users, until we get past 1100 and have an empty group
        repeat
            rids = {}
            for j = start, start + 4, 1 do 
				rids[#rids + 1] = j 
			end

			-- Try converting this group of RIDs into names
            status, lookupsids2_result = msrpc.lsa_lookupsids2(socket, openpolicy2_result['policy_handle'], sid, rids, uid, tid, fid)
            if(status == false) then
                msrpc.stop_smb(socket, uid, tid)
                return false, lookupsids2_result
            end

			-- Put the details for each name into an array
			for j = 1, #lookupsids2_result['details'], 1 do
				if(lookupsids2_result['details'][j]['name'] ~= nil) then
					local result = {}
					result['name']   = lookupsids2_result['details'][j]['name']
					result['rid']    = start + j - 1
					result['domain'] = domain
					response[#response + 1] = result
				end
			end

			-- Go to the next set of RIDs
            start = start + 5
        until #lookupsids2_result['names'] == 0 and start > 1100

    end

    -- Close the handle
    msrpc.lsa_close(socket, openpolicy2_result['policy_handle'], uid, tid, fid)

    msrpc.stop_smb(socket, uid, tid)

	return true, response
end



action = function(host)
	local i, j
	local status
	local samr_result, lsa_result
	local names = {}
	local name_strings = {}
	local response = " \n"

	-- Try enumerating through SAMR
	status, samr_result = enum_samr(host)
	if(status == false) then
		response = response .. "Enum via SAMR error: " .. samr_result .. "\n"
	else
		-- Copy the returned array into the names[] table, using the name as the key
		stdnse.print_debug("EnumUsers: Received %d names from SAMR", #samr_result)
		for i = 1, #samr_result, 1 do
			names[string.upper(samr_result[i]['name'])] = samr_result[i]
		end
	end

	-- Try enumerating through LSA
	status, lsa_result  = enum_lsa(host)
	if(status == false) then
		response = response .. "Enum via LSA error: " .. lsa_result .. "\n"
	else
		-- Copy the returned array into the names[] table, using the name as the key
		stdnse.print_debug("EnumUsers: Received %d names from LSA", #samr_result)
		for i = 1, #lsa_result, 1 do
			if(names[lsa_result[i]['name']] == nil) then
				names[string.upper(lsa_result[i]['name'])] = lsa_result[i]
			end
		end
	end

	-- Put the names into an array of strings, so we can sort them
	for name, details in pairs(names) do
		name_strings[#name_strings + 1] = name
	end
	-- Sort them
	table.sort(name_strings, function (a, b) return string.lower(a) < string.lower(b) end)

	-- Check if we actually got any names back
	if(#name_strings == 0) then
		response = response .. "Sorry, couldn't find any account names anonymously!"
	else
		-- If we're not verbose, just print out the names. Otherwise, print out everything we can
		if(nmap.verbosity() < 1) then
			response = response .. stdnse.strjoin(", ", name_strings)
		else
			for i = 1, #name_strings, 1 do
				local name = name_strings[i]
				response = response .. string.format("%s\n", names[name]['name'])
				if(names[name]['domain'] ~= nil)      then response = response .. string.format("  |_ Domain: %s\n",      names[name]['domain'])      end
				if(names[name]['rid'] ~= nil)         then response = response .. string.format("  |_ RID: %s\n",         names[name]['rid'])         end
				if(names[name]['fullname'] ~= nil)    then response = response .. string.format("  |_ Full name: %s\n",   names[name]['fullname'])    end
				if(names[name]['description'] ~= nil) then response = response .. string.format("  |_ Description: %s\n", names[name]['description']) end
				if(names[name]['flags'] ~= nil)       then response = response .. string.format("  |_ Flags: %s\n",       stdnse.strjoin(", ", names[name]['flags_list'])) end
			end
		end
	end

	return response
end