privoxy-tls/src/proxy.py

#!/usr/bin/env python3

"HTTP Proxy utilities, pyOpenSSL version"

__author__ = 'phoenix'
__version__ = '1.0'

from datetime import datetime
import logging
import threading
import cgi
import socket
import select
import ssl
import string
import pathlib

from http.server import HTTPServer, BaseHTTPRequestHandler
from socketserver import ThreadingMixIn
from cert import get_cert

_name = 'proxy'
logger = logging.getLogger('__main__')

static = pathlib.Path(__file__).parents[1] / 'static'
error_template = string.Template(open(static / 'error.html').read())


def walk_traceback(e, n=0):
    '''
    Produce an HTML formatted stack trace
    given an exception.
    '''
    partial = []
    ul = lambda xs: ('<ul><li>'
                     + '</li>\n<li>'.join(xs)
                     + '</li></ul>')

    for i, arg in enumerate(e.args):
        name = (('<strong>'
            + type(e).__name__
            + '</strong>') if i == 0 else '')
        if isinstance(arg, str):
            partial.append(
                name + ' -  '
                + arg.replace('<', '&lt;').replace('>', '&gt;'))
        else:
            partial.append(name)

        if isinstance(arg, Exception):
            partial.append(walk_traceback(arg, n+1))
    if n == 0:
        partial.append(walk_traceback(e.reason, n+1))
    return ul(partial)


def read_write(socket1, socket2, max_idling=10):
    '''
    Read and Write contents between 2 sockets
    '''
    iw = [socket1, socket2]
    ow = []
    count = 0
    while True:
        count += 1
        (ins, _, exs) = select.select(iw, ow, iw, 1)
        if exs:
            break
        if ins:
            for reader in ins:
                writer = socket2 if reader is socket1 else socket1
                try:
                    data = reader.recv(1024)
                    if data:
                        writer.send(data)
                        count = 0
                except (ConnectionAbortedError,
                        ConnectionResetError,
                        BrokenPipeError):
                    pass
        if count == max_idling:
            break


class Counter:
    reset_value = 999

    def __init__(self, start=0):
        self.lock = threading.Lock()
        self.value = start

    def increment_and_set(self, obj, attr):
        with self.lock:
            self.value = self.value + 1 if self.value < self.reset_value else 1
            setattr(obj, attr, self.value)


class ProxyRequestHandler(BaseHTTPRequestHandler):
    '''
    RequestHandler with do_CONNECT method defined
    '''
    server_version = f'{_name}/{__version__}'
    # do_CONNECT() will set self.ssltunnel to override this
    ssltunnel = False
    # Override default value 'HTTP/1.0'
    protocol_version = 'HTTP/1.1'
    # To be set in each request
    reqNum = 0

    def do_CONNECT(self):
        '''
        Descrypt https request and dispatch to http handler
        '''
        # request line: CONNECT www.example.com:443 HTTP/1.1
        self.host, self.port = self.path.split(':')
        # TLS MITM
        self.wfile.write(
            ('HTTP/1.1 200 Connection established\r\n'
             + f'Proxy-agent: {self.version_string()}\r\n'
             + '\r\n').encode('ascii'))

        if self.host.count('.') >= 2:
            commonname = '.' + self.host.partition('.')[-1]
        else:
            commonname = self.host
        dummycert = get_cert(commonname, self.config)
        # set a flag for do_METHOD
        self.ssltunnel = True

        ssl_sock = ssl.wrap_socket(self.connection, keyfile=dummycert,
                                   certfile=dummycert, server_side=True)
        # Ref: Lib/socketserver.py#StreamRequestHandler.setup()
        self.connection = ssl_sock
        self.rfile = self.connection.makefile('rb', self.rbufsize)
        self.wfile = self.connection.makefile('wb', self.wbufsize)
        # dispatch to do_METHOD()
        self.handle_one_request()

    def handle_one_request(self):
        '''Catch more exceptions than default

        Intend to catch exceptions on local side
        Exceptions on remote side should be handled in do_*()
        '''
        try:
            BaseHTTPRequestHandler.handle_one_request(self)
            return
        except (ConnectionError, FileNotFoundError) as e:
            logger.warning('{:03d} {} {}'.format(
                           self.reqNum, self.server_version, e))
        except (ssl.SSLEOFError, ssl.SSLError) as e:
            if hasattr(self, 'url'):
                # Happens after the tunnel is established
                logger.warning(f'{self.reqNum:03d} "{e}" while operating'
                               f' on established local TSL tunnel for'
                               f' [{self.url}]')
            else:
                logger.warning(f'{self.reqNum:03d} "{e}" while trying to'
                               ' establish local TLS tunnel for'
                               f'[{self.path}]')
        self.close_connection = 1

    def sendout_error(self, url, code, message=None, explain=None):
        '''
        Modified from http.server.send_error() for customized display
        '''
        try:
            shortmsg, longmsg = self.responses[code]
        except KeyError:
            shortmsg, longmsg = '???', '???'
        if message is None:
            message = shortmsg
        if explain is None:
            explain = longmsg

        content = error_template.substitute(
            code=code, message=message,
            explain=walk_traceback(explain),
            url=url,
            hostname=self.server.server_name,
            address=self.server.server_address[0],
            port=self.server.server_port,
            now=datetime.today().isoformat(sep=' ', timespec='seconds'),
            server=self.server_version)
        body = content.encode('UTF-8', 'replace')
        self.send_response_only(code, message)
        self.send_header('Content-Type', self.error_content_type)
        self.send_header('Content-Length', int(len(body)))
        self.end_headers()
        if self.command != 'HEAD' and code >= 200 and code not in (204, 304):
            self.wfile.write(body)

    def deny_request(self):
        self.send_response_only(403)
        self.send_header('Content-Length', 0)
        self.end_headers()

    def redirect(self, url):
        self.send_response_only(302)
        self.send_header('Content-Length', 0)
        self.send_header('Location', url)
        self.end_headers()

    def forward_to_https_proxy(self):
        '''
        Forward https request to upstream https proxy
        '''
        logger.debug(f'Using Proxy - {self.proxy}')
        proxy_host, proxy_port = self.proxy.split('//')[1].split(':')
        server_conn = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        try:
            server_conn.connect((proxy_host, int(proxy_port)))
            server_conn.send((
                f'CONNECT {self.path} HTTP/1.1\r\n\r\n').encode('ascii'))
            server_conn.settimeout(0.1)
            datas = b''
            while True:
                try:
                    data = server_conn.recv(4096)
                except socket.timeout:
                    break
                if data:
                    datas += data
                else:
                    break
            server_conn.setblocking(True)
            if b'200' in datas and b'established' in datas.lower():
                logger.info('{:03d} [P] TLS passthru: https://{}/'.format(
                            self.reqNum, self.path))
                self.wfile.write(('HTTP/1.1 200 Connection established\r\n' +
                                  'Proxy-agent: {}\r\n\r\n'.format(
                                   self.version_string()).encode('ascii')))
                read_write(self.connection, server_conn)
            else:
                logger.warning('{:03d} Proxy {} failed.'.format(
                               self.reqNum, self.proxy))
                if datas:
                    logger.debug(datas)
                    self.wfile.write(datas)
        finally:
            # We don't maintain a connection reuse pool,
            # so close the connection anyway
            server_conn.close()

    def forward_to_socks5_proxy(self):
        '''
        Forward https request to upstream socks5 proxy
        '''
        logger.warning('Socks5 proxy not implemented yet, '
                       'please use https proxy')

    def tunnel_traffic(self):
        '''
        Tunnel traffic to remote host:port
        '''
        logger.info('{:03d} [D] TLS passthru: https://{}/'.format(
                    self.reqNum, self.path))
        server_conn = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        try:
            server_conn.connect((self.host, int(self.port)))
            self.wfile.write(('HTTP/1.1 200 Connection established\r\n'
                              + 'Proxy-agent: {}\r\n'.format(
                                self.version_string())
                              + '\r\n').encode('ascii'))
            read_write(self.connection, server_conn)
        except TimeoutError:
            self.wfile.write(b'HTTP/1.1 504 Gateway Timeout\r\n\r\n')
            logger.warning('{:03d} Timed Out: https://{}:{}/'.format(
                           self.reqNum, self.host, self.port))
        except socket.gaierror as e:
            self.wfile.write(b'HTTP/1.1 503 Service Unavailable\r\n\r\n')
            logger.warning('{:03d} {}: https://{}:{}/'.format(
                           self.reqNum, e, self.host, self.port))
        finally:
            # We don't maintain a connection reuse pool,
            # so close the connection anyway
            server_conn.close()

    def ssl_get_response(self, conn):
        try:
            server_conn = ssl.wrap_socket(
                conn, cert_reqs=ssl.CERT_REQUIRED,
                ca_certs="cacert.pem",
                ssl_version=ssl.PROTOCOL_TLSv1)
            server_conn.sendall(
                ('{} {} HTTP/1.1\r\n'.format(
                 self.command, self.path)).encode('ascii'))
            server_conn.sendall(self.headers.as_bytes())
            if self.postdata:
                server_conn.sendall(self.postdata)
            while True:
                data = server_conn.recv(4096)
                if data:
                    self.wfile.write(data)
                else:
                    break
        except (ssl.SSLEOFError, ssl.SSLError) as e:
            logger.error("[SSLError]")
            self.send_error(417, message="Exception "
                            + str(e.__class__), explain=str(e))

    def purge_headers(self, headers):
        '''
        Remove hop-by-hop headers that shouldn't pass through a Proxy
        '''
        for name in ['Connection', 'Keep-Alive', 'Upgrade',
                     'Proxy-Connection', 'Proxy-Authenticate']:
            del headers[name]

    def purge_write_headers(self, headers):
        self.purge_headers(headers)
        for key, value in headers.items():
            self.send_header(key, value)
        self.end_headers()

    def stream_to_client(self, response):
        bufsize = 1024 * 64
        need_chunked = 'Transfer-Encoding' in response.headers
        written = 0
        while True:
            data = response.read(bufsize)
            if not data:
                if need_chunked:
                    self.wfile.write(b'0\r\n\r\n')
                break
            if need_chunked:
                self.wfile.write((f'{len(data):x}\r\n').encode('ascii'))
            self.wfile.write(data)
            if need_chunked:
                self.wfile.write(b'\r\n')
            written += len(data)
        return written

    def http_request_info(self):
        '''
        Return HTTP request information in bytes
        '''
        context = ['CLIENT VALUES:',
                   f'client_address = {self.client_address}',
                   f'requestline = {self.requestline}',
                   f'command = {self.command}',
                   f'path = {self.path}',
                   f'request_version = {self.request_version}',
                   '',
                   'SERVER VALUES:',
                   'server_version = {self.server_version}',
                   'sys_version = {self.sys_version}',
                   'protocol_version = {self.protocol_version}',
                   '',
                   'HEADER RECEIVED:']
        for name, value in sorted(self.headers.items()):
            context.append(f'{name} = {value.rstrip()}')

        if self.command == 'POST':
            context.append('\r\nPOST VALUES:')
            form = cgi.FieldStorage(fp=self.rfile,
                                    headers=self.headers,
                                    environ={'REQUEST_METHOD': 'POST'})
            for field in form.keys():
                fielditem = form[field]
                if fielditem.filename:
                    # The field contains an uploaded file
                    file_data = fielditem.file.read()
                    file_len = len(file_data)
                    context.append('Uploaded {} as "{}" ({} bytes)'.format(
                                   field, fielditem.filename, file_len))
                else:
                    # Regular form value
                    context.append(f'{field} = {fielditem.value}')

        return('\r\n'.join(context).encode('ascii'))


def demo():
    PORT = 8000

    class ProxyServer(ThreadingMixIn, HTTPServer):
        '''Handle requests in a separate thread.'''
        pass

    class RequestHandler(ProxyRequestHandler):
        'Displaying HTTP request information'
        server_version = 'DemoProxy/0.1'

        def do_METHOD(self):
            'Universal method for GET, POST, HEAD, PUT and DELETE'
            message = self.http_request_info()
            self.send_response(200)
            # 'Content-Length' is important for HTTP/1.1
            self.send_header('Content-Length', len(message))
            self.end_headers()
            self.wfile.write(message)

        do_GET = do_POST = do_HEAD = do_METHOD
        do_PUT = do_DELETE = do_OPTIONS = do_METHOD

    print(RequestHandler.server_version, 'serving now, <Ctrl-C> to stop ...')
    print(f'Listen Addr  : localhost:{PORT}')
    print('-' * 10)
    server = ProxyServer(('', PORT), RequestHandler)
    server.serve_forever()


if __name__ == '__main__':
    try:
        demo()
    except KeyboardInterrupt:
        print('Quitting...')