import string, sys, traceback

# Read a single line of input from standard input
input=sys.stdin.readline()
input=string.strip(input)

# The input looks like 1234,789 where 1234 and 789 are the port
# numbers of the sockets on the foreign and the local machine.  The
# ident daemon can then look up the user who owns that socket and
# return the user's ID. (These days, when anyone can be running their
# own Linux box, it's not much of a protection, but many MUDs and IRC
# servers still use it.)

# Enclose everything in a try...except block, since this server must
# produce some output no matter what.

try:
    # Write the input to a log file, so I can track what requests
    # have been made.  (/scratch is a directory that gets erased on
    # every bootup.)
    f=open('/scratch/identd.calls', 'a')
    f.write(input+'\n')
    f.close()

    # Break the input line apart to get the server and client ports,
    # and remove any whitespace.
    L=string.split(input, ',')
    L=map(string.strip, L)
    server_port, client_port = string.atoi(L[0]), string.atoi(L[1])

    # Open /proc/net/tcp, and scan each line.  Lines in /proc/net/tcp
    # look like:
    # 79: 00000000:004F 00000000:0000 0A 00000000:00000000 00:FFBE3990 00000000 0 0 1287
    #              ^==local port ^==remote port                                   ^=numeric user ID

    f=open('/proc/net/tcp', 'r')
    f.readline()                        # The first line is just headers

    while (1):
        # Read a single line
        L=f.readline()

        # If we reach the end of the file, exit this loop
        if L=="": break

        # Break the line into a list, splitting at the whitespace.
        L=string.split(L)

        # Break the local and remote addresses into the IP address
        # and the port number.
        [localaddr, localport] = string.split(L[1], ':')
        [remoteaddr, remoteport] = string.split(L[2], ':')

        # Convert the hexadecimal port numbers into integers.
        localport=string.atoi(localport, 16)
        remoteport=string.atoi(remoteport, 16)

        # If they match the requested port numbers, get the
        # corresponding user name.
        if (localport==server_port and
            remoteport==client_port):
            import pwd
            uid=string.atoi(L[7])
            userid=pwd.getpwuid(uid)[0]
            # Output a string containing the port numbers and the user ID.
            sys.stdout.write('%s,%s:USERID:UNIX %s\r\n' %
                             (server_port, client_port, userid) )
            sys.exit(0)

    # No match for the local and remote port numbers was found, so
    # we'll output an error
    sys.stdout.write(input+':ERROR:NO-USER\r\n')

# The sys.exit(0) call raises the SystemExit exception.  We don't want
# to do anything when sys.exit() is called, so its handler is simply a
# "pass" statement (which does nothing).
except SystemExit: pass

# All other exceptions will be caught by this handler.  An error
# response has to be returned to the client.
except:
    sys.stdout.write(input+':ERROR:UNKNOWN-ERROR'+ CRLF)