Microsoft Comic Chat Helper for Freenode V0.02b

# Microsoft Comic Chat Helper for Freenode V0.02b
#
# README:
# This script allows Microsoft Comic Chat 2.5 (4.71.2302) to be used with
# Freenode.
#
# Freenode does not use some formatting that MSCC depends on for operation. As
# a result, MSCC will crash upon joining Freenode channels. This script
# provides a fix by creating a ``server socket'' on loclhost. Once MSCC
# connects to it, the script establishes a connection with Freenode. It begins
# forwarding MSCC's input to Freenode and sanitizing Freenode's responses
# before sending them back to MSCC.
#
# USAGE:
# Run this script, enter Freenode username and password, leave it running in background.
# Connect MSCC to the address '127.0.0.1:6660' or whatever options are set.
# If you are a terrible person, hard-code Freenode username and password into this script.
#
# CHANGES:
# 7/1/2014 - V0.01  - Initial Release. Raleigh NC to Little Rock AK
# 7/2/2014 - V0.02  - Disabled removing channel mode list (not necessary)
#                   - Added SSL support
#                   - Made passwords secure
#                   - Little Rock AK to the middle of nowhere in Oklahoma
#            V0.02a - Made use numeral cues (as opposed to language cues) for control
#                   - Added some more exception handling
# 7/3/2014 - V0.02b - Fixed greedy sanitation bug (deleting too many chars)
#                   - Made empty recv()s throw ConnectionAbortedError
#                   - Restructured exception handling
#                   - Fixed abort on MSCC disconnect or connection lost
# KNOWN ISSUES:
# - Can't send messages containing ` JOIN #'
# - Blocking operations (connect, waitign for client connect) cause hang that can't be aborted with ^C ^X ^Z.
# - After a connection dies, sockets stay alive for a long time. Can only be
#   'solved' by: 1) Lowering socket TCP timeout (non-fix)
#                2) Checking for TCP pings/aknowlegements (nasty)
#                3) Sending IRC pings in paralell (ineffective)
# - Can't run headless with logging.
#------------------------------------------------------------------------------
# (c) 2014 Christian Chapman under the 1988 MIT license

import sys;
import string;
import base64;
import getpass;
import errno;

import socket;
import ssl;
import select;

# Options for IRC Server
host = 'irc.freenode.net';
port = 7000;

# If you choose to hardcode remember to comment out 'getCreds()' line.
#str_username = '';
#str_pass = '';
#str_authident = str_username;

# Options for MSCC connection
str_localAddr = '127.0.0.1';
n_localPort = 6660;

str_msccBuf = '';
str_ircBuf = '';

# Sanitizes raw Freenode message so that it won't crash MSCC. Currently
# performs 4 manipulations, all related to joining channels:
# 1) Add `:' to initial `JOIN' message.
# 2) (DISABLED) Remove channel MODE message.
# 3) Change channel user list delimiter from `@' to `='.
# 4) Prefix channel user list with a `:'.
#
# Inputs:
# str_in: UTF-8 string of raw messages from Freenode terminated by '\r\n.'
# str_usr: String containing username
# Returns: Sanitized messages in the same format.
def sanitizeMscc(str_in, str_usr):
    # Add `:' to initial `JOIN' message.
    str_san = str_in.replace('JOIN #','JOIN :#');

    # Remove channel MODE message.
    #if ' MODE #' in str_san:
    #   idx = str_san.find(' MODE #');
    #   # We expect all input to be terminated.
    #   en  = str_san.find('\r\n', idx);
    #   st  = str_san.rfind('\r\n', idx);
    #   if st < 0:
    #       str_san = str_san[en + 4:]; # It's at the very beginning
    #   else:
    #       str_san = str_san[0:st + 4] + str_san[en + 4:];

    # Change channel user list delimiter from `@' to `='.
    # Prefix channel user list with a `:'.
    idx = str_san.find('353' + str_usr + ' @ #');
    while idx > 0:
        idx = str_san.find(' @ #', idx);
        str_end = str_san[idx + 2:];
        li = str_end.split(None, 1);
        str_san = str_san[0:idx] + ' = #' + li[0] + ' :' + li[1];
        idx = str_san.find('353' + str_usr + ' @ #');

    # Removes garbage response about MSCC's `ISIRCX' query
    idx = str_san.find('ISIRCX :No such channel');
    while idx > 0:
        # We expect all input to be terminated.
        en  = str_san.find('\r\n', idx);
        st  = str_san.rfind('\r\n', 0, idx);
        if st < 0:
            str_san = str_san[en + 2:]; # It's at the very beginning
        else:
            str_san = str_san[0:st + 2] + str_san[en + 2:];
        idx = str_san.find('ISIRCX :No such channel');

    return str_san;

# Get info
def getCreds():
    str_usr = input('Username: ');
    str_auth = str_usr;
    str_pass = getpass.getpass();
    return (str_usr, str_auth, str_pass);

(str_username, str_authident, str_pass) = getCreds();

# Outer loop makes sockets. If some connection is lost, it will restart to here.
while(True):
    try:
        # Create a server for MSCC to connect.
        try:
            skt_server = socket.socket(socket.AF_INET, socket.SOCK_STREAM);
            skt_server.bind((str_localAddr, n_localPort));
            skt_server.listen(5);
        except socket.error as msg:
            print('Failed to create socket. Error code: ' + str(msg[0]) + \
                  ' , Error message : ' + msg[1]);
            sys.exit();
        print('Created server socket. Waiting for MSCC to connect...');

        # Get MSCC's connection to skt_server.
        (skt_mscc, addr_mscc) = skt_server.accept();
        print('Client Connected.');

        # Connect to IRC. (SSL)
        skt_irc = socket.socket(socket.AF_INET, socket.SOCK_STREAM);
        skt_irc = ssl.wrap_socket(skt_irc);
        try:
            print('Resolving host...');
            remote_ip = socket.gethostbyname( host );
        except socket.gaierror:
            # Could not resolve.
            print('Hostname could not be resolved. Exiting.');
            sys.exit();

        # Connect, wait until socket is connected.
        print('Connecting to IRC...');
        skt_irc.connect((remote_ip , port));

        print('Connected to ' + host + ' on ip ' + remote_ip);

        skt_irc.setblocking(False);

        # Request SASL.
        skt_irc.sendall(bytes('CAP REQ :sasl\r\n','utf-8'));
        # Send client info
        skt_irc.sendall(bytes('NICK ' + str_username + '\r\n','utf-8'));
        skt_irc.sendall(bytes('USER ' + str_username + ' MSCC 1 :'
                           + str_authident + '\r\n','utf-8'));
        print('Sent client info.');

        # Receive into backup buffer to forward to MSCC after SASL is done.
        # If MSCC does not receive the server's initial messages, it will think
        # that it isn't connected.
        # 'ACK :sasl' *SHOULD* arrive after all these messages.
        str_ircBuf = '';
        while('ACK :sasl' not in str_ircBuf):
            select.select([skt_irc],[],[]);
            b = skt_irc.recv(4096);
            if(len(b)==0):
                raise ConnectionAbortedError('No more data in socket..');
            str_ircBuf = str_ircBuf + b.decode('utf-8', errors='replace');
            print(b.decode(sys.stdout.encoding, errors='replace'));

        skt_irc.sendall(('AUTHENTICATE PLAIN \r\n').encode('utf-8', errors='replace'));
        print('AUTHENTICATE PLAIN');

        # Wait until 'AUTHENTICATE +' to send SASL auth string.
        str_buf = '';
        while('AUTHENTICATE +' not in str_buf):
            select.select([skt_irc],[],[]);
            print('recv');
            print(b);
            b = skt_irc.recv(4096);
            if(len(b)==0):
                raise ConnectionAbortedError('No more data in socket.');
            str_buf = str_buf + b.decode('utf-8', errors='replace');
            print(b.decode(sys.stdout.encoding, errors='replace'));

        # Make and send SASL auth string.
        str_sasl = str_username + '\u0000' + str_authident + '\u0000' + str_pass;
        b_sasl = str_sasl.encode('utf-8', errors='replace');

        str_saslText = 'AUTHENTICATE ' + \
                        base64.b64encode(b_sasl).decode('utf-8', errors='replace') + \
                        '\r\n';
        b_saslText = str_saslText.encode('utf-8', errors='replace');

        skt_irc.sendall(b_saslText);
        print('AUTHENTICATE ****');

        # Wait until you receive 'authentication successful'
        str_buf = '';
        while(' :SASL authentication successful' not in str_buf):
            select.select([skt_irc],[],[]);
            b = skt_irc.recv(4096);
            if(len(b)==0):
                raise ConnectionAbortedError('No more data in socket.');
            str_buf = str_buf + b.decode('utf-8', errors='replace');
            print(b.decode(sys.stdout.encoding, errors='replace'));
            if('904 ' + str_username in str_buf or
               '905 ' + str_username in str_buf ):
               print('SASL authentication failed! Please reenter credentials.');
               (str_username, str_authident, str_pass) = getCreds();
               raise ConnectionAbortedError('SASL auth failed.');

        # End SASL communication
        skt_irc.sendall(('CAP END\r\n').encode('utf-8', errors='replace'));
        print('SASL authenticated successfully!');

        # Recall that we earlier initialized our buffer with Freenode's initial messages.
        # (Freenode will (mostly) ignore MSCC's attempt to reauth)
        # In case we stopped in the middle of a message, add a delimiter.
        str_ircBuf = str_ircBuf + '\r\n';

        # main loop
        # Forward IRC socket received data to MSCC & vice-versa.
        while(True):
            (li_rready, _, _) = select.select([skt_mscc, skt_irc],[],[]);
            try:
                # Forward MSCC to Freenode
                if skt_mscc in li_rready:
                    b_msccBuf = skt_mscc.recv(4096);
                    if(len(b_msccBuf)==0):
                        raise ConnectionAbortedError('No more data in socket.');
                    skt_irc.sendall(b_msccBuf);
                    print( ' > ' + b_msccBuf.decode(sys.stdout.encoding, errors='replace'));
                    b_msccBuf = b'';

                    # Forward IRC to MSCC
                if skt_irc in li_rready:
                    b = skt_irc.recv(4096);
                    if(len(b)==0):
                        raise ConnectionAbortedError('No more data in socket.');
                    str_ircBuf = str_ircBuf + b.decode('utf-8', errors='replace');

                    # Sometimes the buffer will chop a message in the middle.
                    if '\r\n' in str_ircBuf:
                        li = str_ircBuf.rsplit('\r\n', 1);
                        str_ircBuf = li[0];
                        str_ircBuf = str_ircBuf + '\r\n';
                        str_ircBufCutOff = li[1];
                    # If there's no carriage return in the buffer, it's a really long message. We need to finish loading at least all of one message into str_ircBuf, so go back to beginning.
                    else:
                        continue;

                    # Sanitize the buffer for MSCC and send
                    str_ircBuf = sanitizeMscc(str_ircBuf, str_username);
                    skt_mscc.sendall(str_ircBuf.encode('utf-8', errors='replace'));
                    print(bytes(str_ircBuf,'utf-8').decode(sys.stdout.encoding, errors='replace'));

                    # Include the beginning of the cut off message to be sent next time.
                    str_ircBuf = str_ircBufCutOff;
                    str_ircBufCutOff = '';
            except (ssl.SSLWantReadError, ssl.SSLWantWriteError) as e:
                # Not enough TLS packets have come in for us to read any SSL data.
                continue;
            except (ConnectionAbortedError, ConnectionResetError):
                raise;
            except socket.error as e:
                error = e.args[0];
                if e != errno.EAGAIN and e != errno.EWOULDBLOCK:
                    raise e;
                else:
                    # No data to read.
                    continue;
            except (ssl.SSLWantReadError, ssl.SSLWantWriteError) as e:
                # Not enough TLS packets have come in for us to read any SSL data.
                continue;

    except (ConnectionAbortedError, ConnectionResetError) as e:
        skt_mscc.close();
        skt_irc.close();
        error = e.args[0];
        print(error);
        print('Connection aborted.');
        continue;
    except socket.error as e:
        error = e.args[0];
        if error != errno.EAGAIN and error != errno.EWOULDBLOCK:
            # a "real" error occurred
            print('Socket error: ');
            print(error);
            print(type(e));
            raise ;
        else:
            # No data to read.
            pass;