description = [[
Enumerates the users logged into a system either locally or through an SMB share. The local users 
can be logged on either physically on the machine, or through a terminal services session. 
Connections to a SMB share are, for example, people connected to fileshares or making RPC calls. 
Nmap's connection will also show up, and is generally identified by the one that connected "0 
seconds ago". 

From the perspective of a penetration tester, the SMB Sessions is probably the most useful
part of this program, especially because it doesn't require a high level of access. On, for 
example, a file server, there might be a dozen or more users connected at the same time. Based 
on the usernames, it might tell the tester what types of files are stored on the share. 

Since the IP they're connected from and the account is revealed, the information here can also
provide extra targets to test, as well as a username that's likely valid on that target. Additionally,
since a strong username to ip correlation is given, it can be a boost to a social engineering 
attack. 

Enumerating the logged in users is done by reading the remote registry (and therefore won't 
work against Vista, which disables it by default). Keys stored under <code>HKEY_USERS</code> are 
SIDs that represent the connected users, and those SIDs can be converted to proper names by using 
the <code>lsar.LsaLookupSids</code> function. Doing this requires any access higher than 
anonymous; guests, users, or administrators are all able to perform this request on Windows 2000,
XP, 2003, and Vista. 

Enumerating SMB connections is done using the <code>srvsvc.netsessenum</code> function, which 
returns the usernames that are logged in, when they logged in, and how long they've been idle 
for. The level of access required for this varies between Windows versions, but in Windows 
2000 anybody (including the anonymous account) can access this, and in Windows 2003 a user 
or administrator account is required.

I learned the idea and technique for this from sysinternals' tool, PsLoggedOn.exe. I (Ron 
Bowes) use similar function calls to what they use (although I didn't use their source), 
so thanks go out to them. Thanks also to Matt Gardenghi, for requesting this script.  

WARNING: I have experienced crashes in regsvc.exe while making registry calls
against a fully patched Windows 2000 system; I've fixed the issue that caused it,
but there's no guarantee that it (or a similar vuln in the same code) won't show
up again. Since the process automatically restarts, it doesn't negatively impact
the system, besides showing a message box to the user.
]]

---
--@usage
-- nmap --script smb-enum-sessions.nse -p445 <host>
-- sudo nmap -sU -sS --script smb-enum-sessions.nse -p U:137,T:139 <host>
--
--@output
-- Host script results:
-- |  smb-enum-sessions:
-- |  Users logged in:
-- |  |  TESTBOX\Administrator since 2008-10-21 08:17:14
-- |  |_ DOMAIN\rbowes since 2008-10-20 09:03:23
-- |  Active SMB Sessions:
-- |_ |_ ADMINISTRATOR is connected from 10.100.254.138 for [just logged in, it's probably you], idle for [not idle]
-----------------------------------------------------------------------

author = "Ron Bowes"
copyright = "Ron Bowes"
license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
categories = {"discovery","intrusive"}
dependencies = {"smb-brute"}

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

hostrule = function(host)
	return smb.get_port(host) ~= nil
end

---Attempts to enumerate the sessions on a remote system using MSRPC calls. This will likely fail 
-- against a modern system, but will succeed against Windows 2000. 
--
--@param host The host object. 
--@return Status (true or false).
--@return List of sessions (if status is true) or an an error string (if status is false).
local function srvsvc_enum_sessions(host)
	local i
	local status, smbstate
	local bind_result, netsessenum_result

	-- Create the SMB session
	status, smbstate = msrpc.start_smb(host, msrpc.SRVSVC_PATH)
	if(status == false) then
		return false, smbstate
	end

	-- Bind to SRVSVC service
	status, bind_result = msrpc.bind(smbstate, msrpc.SRVSVC_UUID, msrpc.SRVSVC_VERSION, nil)
	if(status == false) then
		msrpc.stop_smb(smbstate)
		return false, bind_result
	end

	-- Call netsessenum
	status, netsessenum_result = msrpc.srvsvc_netsessenum(smbstate, host.ip)
	if(status == false) then
		msrpc.stop_smb(smbstate)
		return false, netsessenum_result
	end

	-- Stop the SMB session
	msrpc.stop_smb(smbstate)

	return true, netsessenum_result['ctr']['array']
end

---Enumerates the users logged in locally (or through terminal services) by using functions
-- that access the registry. To perform this check, guest access or higher is required. 
--
-- The way this works is based on the registry. HKEY_USERS is enumerated, and every key in it
-- that looks like a SID is converted to a username using the LSA lookup function lsa_lookupsids2(). 
--
--@param host The host object. 
--@return An array of user tables, each with the keys <code>name</code>, <code>domain</code>, and <code>changed_date</code> (representing
--        when they logged in). 
local function winreg_enum_rids(host)
	local i, j
	local elements = {}

	-- Create the SMB session
	status, smbstate = msrpc.start_smb(host, msrpc.WINREG_PATH)
	if(status == false) then
		return false, smbstate
	end

	-- Bind to WINREG service
	status, bind_result = msrpc.bind(smbstate, msrpc.WINREG_UUID, msrpc.WINREG_VERSION, nil)
	if(status == false) then
		msrpc.stop_smb(smbstate)
		return false, bind_result
	end

	status, openhku_result = msrpc.winreg_openhku(smbstate)
	if(status == false) then
		msrpc.stop_smb(smbstate)
		return false, openhku_result
	end

	-- Loop through the keys under HKEY_USERS and grab the names
	i = 0
	repeat 
		status, enumkey_result = msrpc.winreg_enumkey(smbstate, openhku_result['handle'], i, "")

		if(status == true) then
			local status, openkey_result

			local element = {}
			element['name'] = enumkey_result['name']

			-- To get the time the user logged in, we check the 'Volatile Environment' key
			-- This can fail with the 'guest' account due to access restrictions
			status, openkey_result = msrpc.winreg_openkey(smbstate, openhku_result['handle'], element['name'] .. "\\Volatile Environment")
			if(status ~= false) then
				local queryinfokey_result, closekey_result

				-- Query the info about this key. The response will tell us when the user logged into the server. 
				status, queryinfokey_result = msrpc.winreg_queryinfokey(smbstate, openkey_result['handle'])
				if(status == false) then
					msrpc.stop_smb(smbstate)
					return false, queryinfokey_result
				end

				status, closekey_result = msrpc.winreg_closekey(smbstate, openkey_result['handle'])
				if(status == false) then
					msrpc.stop_smb(smbstate)
					return false, closekey_result
				end

				element['changed_date'] = queryinfokey_result['last_changed_date']
			else
				-- Getting extra details failed, but we can still handle this
				element['changed_date'] = "<unknown>"
			end
			elements[#elements + 1] = element
		end

		i = i + 1
	until status ~= true

	status, closekey_result = msrpc.winreg_closekey(smbstate, openhku_result['handle'])
	if(status == false) then
		msrpc.stop_smb(smbstate)
		return false, closekey_result
	end

	msrpc.stop_smb(smbstate)

	-- Start a new SMB session
	status, smbstate = msrpc.start_smb(host, msrpc.LSA_PATH)
	if(status == false) then
		return false, smbstate
	end

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

	-- Get a policy handle
	status, openpolicy2_result = msrpc.lsa_openpolicy2(smbstate, host.ip)
	if(status == false) then
		msrpc.stop_smb(smbstate)
		return false, openpolicy2_result
	end

	-- Convert the SID to the name of the user
	local results = {}
	stdnse.print_debug(3, "MSRPC: Found %d SIDs that might be logged in", #elements)
	for i = 1, #elements, 1 do
		if(elements[i]['name'] ~= nil) then
			local sid = elements[i]['name']
		    if(string.find(sid, "^S-") ~= nil and string.find(sid, "-%d+$") ~= nil) then
				-- The rid is the last digits before the end of the string
				local rid = string.sub(sid, string.find(sid, "%d+$"))

				status, lookupsids2_result = msrpc.lsa_lookupsids2(smbstate, openpolicy2_result['policy_handle'], {elements[i]['name']})

				if(status == false) then
					-- It may not succeed, if it doesn't that's ok
					stdnse.print_debug(3, "MSRPC: Lookup failed")
				else
					-- Create the result array
					local result = {}
					result['changed_date'] = elements[i]['changed_date']
					result['rid'] = rid
		
					-- Fill in the result from the response
					if(lookupsids2_result['names']['names'][1] == nil) then
						result['name'] = "<unknown>"
						result['type'] = "<unknown>"
						result['domain'] = ""
					else
						result['name'] = lookupsids2_result['names']['names'][1]['name']
						result['type'] = lookupsids2_result['names']['names'][1]['sid_type']
						if(lookupsids2_result['domains'] ~= nil and lookupsids2_result['domains']['domains'] ~= nil and lookupsids2_result['domains']['domains'][1] ~= nil) then
							result['domain'] = lookupsids2_result['domains']['domains'][1]['name']
						else
							result['domain'] = ""
						end
					end
	
					if(result['type'] ~= "SID_NAME_WKN_GRP") then -- Don't show "well known" accounts
						-- Add it to the results
						results[#results + 1] = result
					end
				end
			end
		end
	end

	-- Close the policy
	msrpc.lsa_close(smbstate, openpolicy2_result['policy_handle'])

	-- Stop the session
	msrpc.stop_smb(smbstate)

	return true, results
end


--_G.TRACEBACK = TRACEBACK or {}
action = function(host)
--    TRACEBACK[coroutine.running()] = true;

	local response = {}

	local status1, status2

	-- Enumerate the logged in users
	local logged_in = {}
	logged_in['name'] = "Users logged in"
	status1, users = winreg_enum_rids(host)
	if(status1 == false) then
		logged_in['warning'] = "Couldn't enumerate login sessions: " .. users
	else
		if(#users == 0) then
			table.insrt(response, "<nobody>")
		else
			for i = 1, #users, 1 do
				if(users[i]['name'] ~= nil) then
					table.insert(logged_in, string.format("%s\\%s since %s", users[i]['domain'], users[i]['name'], users[i]['changed_date']))
				end
			end
		end
	end
	table.insert(response, logged_in)

	-- Get the connected sessions
	local sessions_output = {}
	sessions_output['name'] = "Active SMB sessions"
	status2, sessions = srvsvc_enum_sessions(host)
	if(status2 == false) then
		sessions_output['warning'] = "Couldn't enumerate network sessions: " .. sessions
	else
		if(#sessions == 0) then
			table.insert(sessions_output, "<none>")
		else
			-- Format the result
			for i = 1, #sessions, 1 do
				local time = sessions[i]['time']
				if(time == 0) then
					time = "[just logged in, it's probably you]"
				elseif(time > 60 * 60 * 24) then
					time = string.format("%dd%dh%02dm%02ds", time / (60*60*24), (time % (60*60*24)) / 3600, (time % 3600) / 60, time % 60)
				elseif(time > 60 * 60) then
					time = string.format("%dh%02dm%02ds", time / 3600, (time % 3600) / 60, time % 60)
				else
					time = string.format("%02dm%02ds", time / 60, time % 60)
				end
		
				local idle_time = sessions[i]['idle_time']
				if(idle_time == 0) then
					idle_time = "[not idle]"
				elseif(idle_time > 60 * 60 * 24) then
					idle_time = string.format("%dd%dh%02dm%02ds", idle_time / (60*60*24), (idle_time % (60*60*24)) / 3600, (idle_time % 3600) / 60, idle_time % 60)
				elseif(idle_time > 60 * 60) then
					idle_time = string.format("%dh%02dm%02ds", idle_time / 3600, (idle_time % 3600) / 60, idle_time % 60)
				else
					idle_time = string.format("%02dm%02ds", idle_time / 60, idle_time % 60)
				end

				table.insert(sessions_output, string.format("%s is connected from %s for %s, idle for %s", sessions[i]['user'], sessions[i]['client'], time, idle_time))
			end
		end
	end
	table.insert(response, sessions_output)

	return stdnse.format_output(true, response)
end