The Tor Browser / file revision

 # Copyright 2011, Google Inc.

 # All rights reserved.

 #

 # Redistribution and use in source and binary forms, with or without

 # modification, are permitted provided that the following conditions are

 # met:

 #

 #     * Redistributions of source code must retain the above copyright

 # notice, this list of conditions and the following disclaimer.

 #     * Redistributions in binary form must reproduce the above

 # copyright notice, this list of conditions and the following disclaimer

 # in the documentation and/or other materials provided with the

 # distribution.

 #     * Neither the name of Google Inc. nor the names of its

 # contributors may be used to endorse or promote products derived from

 # this software without specific prior written permission.

 #

 # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

 # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

 # A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

 # OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

 # SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

 # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 """WebSocket utilities.

 """

 import array

 import errno

 # Import hash classes from a module available and recommended for each Python

 # version and re-export those symbol. Use sha and md5 module in Python 2.4, and

 # hashlib module in Python 2.6.

 try:

     import hashlib

     md5_hash = hashlib.md5

     sha1_hash = hashlib.sha1

 except ImportError:

     import md5

     import sha

     md5_hash = md5.md5

     sha1_hash = sha.sha

 import StringIO

 import logging

 import os

 import re

 import socket

 import traceback

 import zlib

 def get_stack_trace():

     """Get the current stack trace as string.

     This is needed to support Python 2.3.

     TODO: Remove this when we only support Python 2.4 and above.

           Use traceback.format_exc instead.

     """

     out = StringIO.StringIO()

     traceback.print_exc(file=out)

     return out.getvalue()

 def prepend_message_to_exception(message, exc):

     """Prepend message to the exception."""

     exc.args = (message + str(exc),)

     return

 def __translate_interp(interp, cygwin_path):

     """Translate interp program path for Win32 python to run cygwin program

     (e.g. perl).  Note that it doesn't support path that contains space,

     which is typically true for Unix, where #!-script is written.

     For Win32 python, cygwin_path is a directory of cygwin binaries.

     Args:

       interp: interp command line

       cygwin_path: directory name of cygwin binary, or None

     Returns:

       translated interp command line.

     """

     if not cygwin_path:

         return interp

     m = re.match('^[^ ]*/([^ ]+)( .*)?', interp)

     if m:

         cmd = os.path.join(cygwin_path, m.group(1))

         return cmd + m.group(2)

     return interp

 def get_script_interp(script_path, cygwin_path=None):

     """Gets #!-interpreter command line from the script.

     It also fixes command path.  When Cygwin Python is used, e.g. in WebKit,

     it could run "/usr/bin/perl -wT hello.pl".

     When Win32 Python is used, e.g. in Chromium, it couldn't.  So, fix

     "/usr/bin/perl" to "<cygwin_path>\perl.exe".

     Args:

       script_path: pathname of the script

       cygwin_path: directory name of cygwin binary, or None

     Returns:

       #!-interpreter command line, or None if it is not #!-script.

     """

     fp = open(script_path)

     line = fp.readline()

     fp.close()

     m = re.match('^#!(.*)', line)

     if m:

         return __translate_interp(m.group(1), cygwin_path)

     return None

 def wrap_popen3_for_win(cygwin_path):

     """Wrap popen3 to support #!-script on Windows.

     Args:

       cygwin_path:  path for cygwin binary if command path is needed to be

                     translated.  None if no translation required.

     """

     __orig_popen3 = os.popen3

     def __wrap_popen3(cmd, mode='t', bufsize=-1):

         cmdline = cmd.split(' ')

         interp = get_script_interp(cmdline[0], cygwin_path)

         if interp:

             cmd = interp + ' ' + cmd

         return __orig_popen3(cmd, mode, bufsize)

     os.popen3 = __wrap_popen3

 def hexify(s):

     return ' '.join(map(lambda x: '%02x' % ord(x), s))

 def get_class_logger(o):

     return logging.getLogger(

         '%s.%s' % (o.__class__.__module__, o.__class__.__name__))

 class NoopMasker(object):

     """A masking object that has the same interface as RepeatedXorMasker but

     just returns the string passed in without making any change.

     """

     def __init__(self):

         pass

     def mask(self, s):

         return s

 class RepeatedXorMasker(object):

     """A masking object that applies XOR on the string given to mask method

     with the masking bytes given to the constructor repeatedly. This object

     remembers the position in the masking bytes the last mask method call

     ended and resumes from that point on the next mask method call.

     """

     def __init__(self, mask):

         self._mask = map(ord, mask)

         self._mask_size = len(self._mask)

         self._count = 0

     def mask(self, s):

         result = array.array('B')

         result.fromstring(s)

         # Use temporary local variables to eliminate the cost to access

         # attributes

         count = self._count

         mask = self._mask

         mask_size = self._mask_size

         for i in xrange(len(result)):

             result[i] ^= mask[count]

             count = (count + 1) % mask_size

         self._count = count

         return result.tostring()

 class DeflateRequest(object):

     """A wrapper class for request object to intercept send and recv to perform

     deflate compression and decompression transparently.

     """

     def __init__(self, request):

         self._request = request

         self.connection = DeflateConnection(request.connection)

     def __getattribute__(self, name):

         if name in ('_request', 'connection'):

             return object.__getattribute__(self, name)

         return self._request.__getattribute__(name)

     def __setattr__(self, name, value):

         if name in ('_request', 'connection'):

             return object.__setattr__(self, name, value)

         return self._request.__setattr__(name, value)

 # By making wbits option negative, we can suppress CMF/FLG (2 octet) and

 # ADLER32 (4 octet) fields of zlib so that we can use zlib module just as

 # deflate library. DICTID won't be added as far as we don't set dictionary.

 # LZ77 window of 32K will be used for both compression and decompression.

 # For decompression, we can just use 32K to cover any windows size. For

 # compression, we use 32K so receivers must use 32K.

 #

 # Compression level is Z_DEFAULT_COMPRESSION. We don't have to match level

 # to decode.

 #

 # See zconf.h, deflate.cc, inflate.cc of zlib library, and zlibmodule.c of

 # Python. See also RFC1950 (ZLIB 3.3).

 class _Deflater(object):

     def __init__(self, window_bits):

         self._logger = get_class_logger(self)

         self._compress = zlib.compressobj(

             zlib.Z_DEFAULT_COMPRESSION, zlib.DEFLATED, -window_bits)

     def compress_and_flush(self, bytes):

         compressed_bytes = self._compress.compress(bytes)

         compressed_bytes += self._compress.flush(zlib.Z_SYNC_FLUSH)

         self._logger.debug('Compress input %r', bytes)

         self._logger.debug('Compress result %r', compressed_bytes)

         return compressed_bytes

 class _Inflater(object):

     def __init__(self):

         self._logger = get_class_logger(self)

         self._unconsumed = ''

         self.reset()

     def decompress(self, size):

         if not (size == -1 or size > 0):

             raise Exception('size must be -1 or positive')

         data = ''

         while True:

             if size == -1:

                 data += self._decompress.decompress(self._unconsumed)

                 # See Python bug http://bugs.python.org/issue12050 to

                 # understand why the same code cannot be used for updating

                 # self._unconsumed for here and else block.

                 self._unconsumed = ''

             else:

                 data += self._decompress.decompress(

                     self._unconsumed, size - len(data))

                 self._unconsumed = self._decompress.unconsumed_tail

             if self._decompress.unused_data:

                 # Encountered a last block (i.e. a block with BFINAL = 1) and

                 # found a new stream (unused_data). We cannot use the same

                 # zlib.Decompress object for the new stream. Create a new

                 # Decompress object to decompress the new one.

                 #

                 # It's fine to ignore unconsumed_tail if unused_data is not

                 # empty.

                 self._unconsumed = self._decompress.unused_data

                 self.reset()

                 if size >= 0 and len(data) == size:

                     # data is filled. Don't call decompress again.

                     break

                 else:

                     # Re-invoke Decompress.decompress to try to decompress all

                     # available bytes before invoking read which blocks until

                     # any new byte is available.

                     continue

             else:

                 # Here, since unused_data is empty, even if unconsumed_tail is

                 # not empty, bytes of requested length are already in data. We

                 # don't have to "continue" here.

                 break

         if data:

             self._logger.debug('Decompressed %r', data)

         return data

     def append(self, data):

         self._logger.debug('Appended %r', data)

         self._unconsumed += data

     def reset(self):

         self._logger.debug('Reset')

         self._decompress = zlib.decompressobj(-zlib.MAX_WBITS)

 # Compresses/decompresses given octets using the method introduced in RFC1979.

 class _RFC1979Deflater(object):

     """A compressor class that applies DEFLATE to given byte sequence and

     flushes using the algorithm described in the RFC1979 section 2.1.

     """

     def __init__(self, window_bits, no_context_takeover):

         self._deflater = None

         if window_bits is None:

             window_bits = zlib.MAX_WBITS

         self._window_bits = window_bits

         self._no_context_takeover = no_context_takeover

     def filter(self, bytes):

         if self._deflater is None or self._no_context_takeover:

             self._deflater = _Deflater(self._window_bits)

         # Strip last 4 octets which is LEN and NLEN field of a non-compressed

         # block added for Z_SYNC_FLUSH.

         return self._deflater.compress_and_flush(bytes)[:-4]

 class _RFC1979Inflater(object):

     """A decompressor class for byte sequence compressed and flushed following

     the algorithm described in the RFC1979 section 2.1.

     """

     def __init__(self):

         self._inflater = _Inflater()

     def filter(self, bytes):

         # Restore stripped LEN and NLEN field of a non-compressed block added

         # for Z_SYNC_FLUSH.

         self._inflater.append(bytes + '\x00\x00\xff\xff')

         return self._inflater.decompress(-1)

 class DeflateSocket(object):

     """A wrapper class for socket object to intercept send and recv to perform

     deflate compression and decompression transparently.

     """

     # Size of the buffer passed to recv to receive compressed data.

     _RECV_SIZE = 4096

     def __init__(self, socket):

         self._socket = socket

         self._logger = get_class_logger(self)

         self._deflater = _Deflater(zlib.MAX_WBITS)

         self._inflater = _Inflater()

     def recv(self, size):

         """Receives data from the socket specified on the construction up

         to the specified size. Once any data is available, returns it even

         if it's smaller than the specified size.

         """

         # TODO(tyoshino): Allow call with size=0. It should block until any

         # decompressed data is available.

         if size <= 0:

             raise Exception('Non-positive size passed')

         while True:

             data = self._inflater.decompress(size)

             if len(data) != 0:

                 return data

             read_data = self._socket.recv(DeflateSocket._RECV_SIZE)

             if not read_data:

                 return ''

             self._inflater.append(read_data)

     def sendall(self, bytes):

         self.send(bytes)

     def send(self, bytes):

         self._socket.sendall(self._deflater.compress_and_flush(bytes))

         return len(bytes)

 class DeflateConnection(object):

     """A wrapper class for request object to intercept write and read to

     perform deflate compression and decompression transparently.

     """

     def __init__(self, connection):

         self._connection = connection

         self._logger = get_class_logger(self)

         self._deflater = _Deflater(zlib.MAX_WBITS)

         self._inflater = _Inflater()

     def get_remote_addr(self):

         return self._connection.remote_addr

     remote_addr = property(get_remote_addr)

     def put_bytes(self, bytes):

         self.write(bytes)

     def read(self, size=-1):

         """Reads at most size bytes. Blocks until there's at least one byte

         available.

         """

         # TODO(tyoshino): Allow call with size=0.

         if not (size == -1 or size > 0):

             raise Exception('size must be -1 or positive')

         data = ''

         while True:

             if size == -1:

                 data += self._inflater.decompress(-1)

             else:

                 data += self._inflater.decompress(size - len(data))

             if size >= 0 and len(data) != 0:

                 break

             # TODO(tyoshino): Make this read efficient by some workaround.

             #

             # In 3.0.3 and prior of mod_python, read blocks until length bytes

             # was read. We don't know the exact size to read while using

             # deflate, so read byte-by-byte.

             #

             # _StandaloneRequest.read that ultimately performs

             # socket._fileobject.read also blocks until length bytes was read

             read_data = self._connection.read(1)

             if not read_data:

                 break

             self._inflater.append(read_data)

         return data

     def write(self, bytes):

         self._connection.write(self._deflater.compress_and_flush(bytes))

 def _is_ewouldblock_errno(error_number):

     """Returns True iff error_number indicates that receive operation would

     block. To make this portable, we check availability of errno and then

     compare them.

     """

     for error_name in ['WSAEWOULDBLOCK', 'EWOULDBLOCK', 'EAGAIN']:

         if (error_name in dir(errno) and

             error_number == getattr(errno, error_name)):

             return True

     return False

 def drain_received_data(raw_socket):

     # Set the socket non-blocking.

     original_timeout = raw_socket.gettimeout()

     raw_socket.settimeout(0.0)

     drained_data = []

     # Drain until the socket is closed or no data is immediately

     # available for read.

     while True:

         try:

             data = raw_socket.recv(1)

             if not data:

                 break

             drained_data.append(data)

         except socket.error, e:

             # e can be either a pair (errno, string) or just a string (or

             # something else) telling what went wrong. We suppress only

             # the errors that indicates that the socket blocks. Those

             # exceptions can be parsed as a pair (errno, string).

             try:

                 error_number, message = e

             except:

                 # Failed to parse socket.error.

                 raise e

             if _is_ewouldblock_errno(error_number):

                 break

             else:

                 raise e

     # Rollback timeout value.

     raw_socket.settimeout(original_timeout)

     return ''.join(drained_data)

 # vi:sts=4 sw=4 et