Simple Python HTTP Proxy

Some time ago my company announced that they will start capturing and logging all HTTP traffic to and from the company. While I definitely don’t spend my time at work surfing the web, I don’t appreciate them looking over my shoulder and checking up on everything that I visit and read on the web.

So I wrote a small application which is a very simple, rudementary HTTP proxy server. It handles most HTTP traffic and some very simple FTP traffic (clicking on FTP links from web pages). The code is based on Suzuki Hisao’s Tiny HTTP Proxy module. I enhanced it to make it a standalone application.

#!/usr/bin/python

__doc__ = """Tiny HTTP Proxy.

This module implements GET, HEAD, POST, PUT and DELETE methods
on BaseHTTPServer, and behaves as an HTTP proxy.  The CONNECT
method is also implemented experimentally, but has not been
tested yet.

Any help will be greatly appreciated.		SUZUKI Hisao

2009/11/23 - Modified by Mitko Haralanov
             * Added very simple FTP file retrieval
             * Added custom logging methods
             * Added code to make this a standalone application
"""

__version__ = "0.3.1"

import BaseHTTPServer, select, socket, SocketServer, urlparse
import logging
import logging.handlers
import getopt
import sys
import os
import signal
import threading
from types import FrameType, CodeType
from time import sleep
import ftplib

DEFAULT_LOG_FILENAME = "proxy.log"

class ProxyHandler (BaseHTTPServer.BaseHTTPRequestHandler):
    __base = BaseHTTPServer.BaseHTTPRequestHandler
    __base_handle = __base.handle

    server_version = "TinyHTTPProxy/" + __version__
    rbufsize = 0                        # self.rfile Be unbuffered

    def handle(self):
        (ip, port) =  self.client_address
        self.server.logger.log (logging.INFO, "Request from '%s'", ip)
        if hasattr(self, 'allowed_clients') and ip not in self.allowed_clients:
            self.raw_requestline = self.rfile.readline()
            if self.parse_request(): self.send_error(403)
        else:
            self.__base_handle()

    def _connect_to(self, netloc, soc):
        i = netloc.find(':')
        if i >= 0:
            host_port = netloc[:i], int(netloc[i+1:])
        else:
            host_port = netloc, 80
        self.server.logger.log (logging.INFO, "connect to %s:%d", host_port[0], host_port[1])
        try: soc.connect(host_port)
        except socket.error, arg:
            try: msg = arg[1]
            except: msg = arg
            self.send_error(404, msg)
            return 0
        return 1

    def do_CONNECT(self):
        soc = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        try:
            if self._connect_to(self.path, soc):
                self.log_request(200)
                self.wfile.write(self.protocol_version +
                                 " 200 Connection established\r\n")
                self.wfile.write("Proxy-agent: %s\r\n" % self.version_string())
                self.wfile.write("\r\n")
                self._read_write(soc, 300)
        finally:
            soc.close()
            self.connection.close()

    def do_GET(self):
        (scm, netloc, path, params, query, fragment) = urlparse.urlparse(
            self.path, 'http')
        if scm not in ('http', 'ftp') or fragment or not netloc:
            self.send_error(400, "bad url %s" % self.path)
            return
        soc = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        try:
            if scm == 'http':
                if self._connect_to(netloc, soc):
                    self.log_request()
                    soc.send("%s %s %s\r\n" % (self.command,
                                               urlparse.urlunparse(('', '', path,
                                                                    params, query,
                                                                    '')),
                                               self.request_version))
                    self.headers['Connection'] = 'close'
                    del self.headers['Proxy-Connection']
                    for key_val in self.headers.items():
                        soc.send("%s: %s\r\n" % key_val)
                    soc.send("\r\n")
                    self._read_write(soc)
            elif scm == 'ftp':
                # fish out user and password information
                i = netloc.find ('@')
                if i >= 0:
                    login_info, netloc = netloc[:i], netloc[i+1:]
                    try: user, passwd = login_info.split (':', 1)
                    except ValueError: user, passwd = "anonymous", None
                else: user, passwd ="anonymous", None
                self.log_request ()
                try:
                    ftp = ftplib.FTP (netloc)
                    ftp.login (user, passwd)
                    if self.command == "GET":
                        ftp.retrbinary ("RETR %s"%path, self.connection.send)
                    ftp.quit ()
                except Exception, e:
                    self.server.logger.log (logging.WARNING, "FTP Exception: %s",
                                            e)
        finally:
            soc.close()
            self.connection.close()

    def _read_write(self, soc, max_idling=20, local=False):
        iw = [self.connection, soc]
        local_data = ""
        ow = []
        count = 0
        while 1:
            count += 1
            (ins, _, exs) = select.select(iw, ow, iw, 1)
            if exs: break
            if ins:
                for i in ins:
                    if i is soc: out = self.connection
                    else: out = soc
                    data = i.recv(8192)
                    if data:
                        if local: local_data += data
                        else: out.send(data)
                        count = 0
            if count == max_idling: break
        if local: return local_data
        return None

    do_HEAD = do_GET
    do_POST = do_GET
    do_PUT  = do_GET
    do_DELETE=do_GET

    def log_message (self, format, *args):
        self.server.logger.log (logging.INFO, "%s %s", self.address_string (),
                                format % args)

    def log_error (self, format, *args):
        self.server.logger.log (logging.ERROR, "%s %s", self.address_string (),
                                format % args)

class ThreadingHTTPServer (SocketServer.ThreadingMixIn,
                           BaseHTTPServer.HTTPServer):
    def __init__ (self, server_address, RequestHandlerClass, logger=None):
        BaseHTTPServer.HTTPServer.__init__ (self, server_address,
                                            RequestHandlerClass)
        self.logger = logger

def logSetup (filename, log_size, daemon):
    logger = logging.getLogger ("TinyHTTPProxy")
    logger.setLevel (logging.INFO)
    if not filename:
        if not daemon:
            # display to the screen
            handler = logging.StreamHandler ()
        else:
            handler = logging.handlers.RotatingFileHandler (DEFAULT_LOG_FILENAME,
                                                            maxBytes=(log_size*(1<<20)),
                                                            backupCount=5)
    else:
        handler = logging.handlers.RotatingFileHandler (filename,
                                                        maxBytes=(log_size*(1<<20)),
                                                        backupCount=5)
    fmt = logging.Formatter ("[%(asctime)-12s.%(msecs)03d] "
                             "%(levelname)-8s {%(name)s %(threadName)s}"
                             " %(message)s",
                             "%Y-%m-%d %H:%M:%S")
    handler.setFormatter (fmt)

    logger.addHandler (handler)
    return logger

def usage (msg=None):
    if msg: print msg
    print sys.argv[0], "[-p port] [-l logfile] [-dh] [allowed_client_name ...]]"
    print
    print "   -p       - Port to bind to"
    print "   -l       - Path to logfile. If not specified, STDOUT is used"
    print "   -d       - Run in the background"
    print

def handler (signo, frame):
    while frame and isinstance (frame, FrameType):
        if frame.f_code and isinstance (frame.f_code, CodeType):
            if "run_event" in frame.f_code.co_varnames:
                frame.f_locals["run_event"].set ()
                return
        frame = frame.f_back

def daemonize (logger):
    class DevNull (object):
        def __init__ (self): self.fd = os.open ("/dev/null", os.O_WRONLY)
        def write (self, *args, **kwargs): return 0
        def read (self, *args, **kwargs): return 0
        def fileno (self): return self.fd
        def close (self): os.close (self.fd)
    class ErrorLog:
        def __init__ (self, obj): self.obj = obj
        def write (self, string): self.obj.log (logging.ERROR, string)
        def read (self, *args, **kwargs): return 0
        def close (self): pass

    if os.fork () != 0:
        ## allow the child pid to instanciate the server
        ## class
        sleep (1)
        sys.exit (0)
    os.setsid ()
    fd = os.open ('/dev/null', os.O_RDONLY)
    if fd != 0:
        os.dup2 (fd, 0)
        os.close (fd)
    null = DevNull ()
    log = ErrorLog (logger)
    sys.stdout = null
    sys.stderr = log
    sys.stdin = null
    fd = os.open ('/dev/null', os.O_WRONLY)
    #if fd != 1: os.dup2 (fd, 1)
    os.dup2 (sys.stdout.fileno (), 1)
    if fd != 2: os.dup2 (fd, 2)
    if fd not in (1, 2): os.close (fd)

def main ():
    logfile = None
    daemon  = False
    max_log_size = 20
    port = 8000
    allowed = []
    run_event = threading.Event ()
    local_hostname = socket.gethostname ()

    try: opts, args = getopt.getopt (sys.argv[1:], "l:dhp:", [])
    except getopt.GetoptError, e:
        usage (str (e))
        return 1

    for opt, value in opts:
        if opt == "-p": port = int (value)
        if opt == "-l": logfile = value
        if opt == "-d": daemon = not daemon
        if opt == "-h":
            usage ()
            return 0

    # setup the log file
    logger = logSetup (logfile, max_log_size, daemon)

    if daemon:
        daemonize (logger)
    signal.signal (signal.SIGINT, handler)

    if args:
        allowed = []
        for name in args:
            client = socket.gethostbyname(name)
            allowed.append(client)
            logger.log (logging.INFO, "Accept: %s (%s)" % (client, name))
        ProxyHandler.allowed_clients = allowed
    else:
        logger.log (logging.INFO, "Any clients will be served...")

    server_address = (socket.gethostbyname (local_hostname), port)
    ProxyHandler.protocol = "HTTP/1.0"
    httpd = ThreadingHTTPServer (server_address, ProxyHandler, logger)
    sa = httpd.socket.getsockname ()
    print "Servering HTTP on", sa[0], "port", sa[1]
    req_count = 0
    while not run_event.isSet ():
        try:
            httpd.handle_request ()
            req_count += 1
            if req_count == 1000:
                logger.log (logging.INFO, "Number of active threads: %s",
                            threading.activeCount ())
                req_count = 0
        except select.error, e:
            if e[0] == 4 and run_event.isSet (): pass
            else:
                logger.log (logging.CRITICAL, "Errno: %d - %s", e[0], e[1])
    logger.log (logging.INFO, "Server shutdown")
    return 0

if __name__ == '__main__':
    sys.exit (main ())

Usage Examples

Below is the script’s help text which shows the accepted options and command line format:

proxy [-p port] [-l logfile] [-dh] [allowed_client_name ...]]

   -p       - Port to bind to
   -l       - Path to logfile. If not specified, STDOUT is used
   -d       - Run in the background

To start the proxy server and bind it to port 22222 (the port on which it will listen and accept connections):

proxy -p 22222

To start the proxy server, bind it to port 22222 and tell it to log all requests to the file proxy.log:

proxy -p 22222 -l proxy.log

To start the proxy server where it only allows connections from IP 123.123.123.123:

proxy 123.123.123.123

To start the proxy server bound to port 22222, log to file proxy.log and run the server in the background (as a daemon):

proxy -p 22222 -l proxy.log -d

TinyHTTPProxy
Version: 0.3.1

Categories:	Code
Posted on:	Jan 18th, 2010 17:32
Description:

3.49 KB
2486 Downloads

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