# -*- coding: utf-8 -*-
from struct import pack, unpack
from ws4py.exc import FrameTooLargeException, ProtocolException
from ws4py.compat import py3k, ord, range
# Frame opcodes defined in the spec.
OPCODE_CONTINUATION = 0x0
OPCODE_TEXT = 0x1
OPCODE_BINARY = 0x2
OPCODE_CLOSE = 0x8
OPCODE_PING = 0x9
OPCODE_PONG = 0xa
__all__ = ['Frame']
[docs]class Frame(object):
def __init__(self, opcode=None, body=b'', masking_key=None, fin=0, rsv1=0, rsv2=0, rsv3=0):
"""
Implements the framing protocol as defined by RFC 6455.
.. code-block:: python
:linenos:
>>> test_mask = 'XXXXXX' # perhaps from os.urandom(4)
>>> f = Frame(OPCODE_TEXT, 'hello world', masking_key=test_mask, fin=1)
>>> bytes = f.build()
>>> bytes.encode('hex')
'818bbe04e66ad6618a06d1249105cc6882'
>>> f = Frame()
>>> f.parser.send(bytes[0])
1
>>> f.parser.send(bytes[1])
4
.. seealso:: Data Framing http://tools.ietf.org/html/rfc6455#section-5.2
"""
if not isinstance(body, bytes):
raise TypeError("The body must be properly encoded")
self.opcode = opcode
self.body = body
self.masking_key = masking_key
self.fin = fin
self.rsv1 = rsv1
self.rsv2 = rsv2
self.rsv3 = rsv3
self.payload_length = len(body)
self._parser = None
@property
def parser(self):
if self._parser is None:
self._parser = self._parsing()
# Python generators must be initialized once.
next(self.parser)
return self._parser
def _cleanup(self):
if self._parser:
self._parser.close()
self._parser = None
[docs] def build(self):
"""
Builds a frame from the instance's attributes and returns
its bytes representation.
"""
header = b''
if self.fin > 0x1:
raise ValueError('FIN bit parameter must be 0 or 1')
if 0x3 <= self.opcode <= 0x7 or 0xB <= self.opcode:
raise ValueError('Opcode cannot be a reserved opcode')
## +-+-+-+-+-------+
## |F|R|R|R| opcode|
## |I|S|S|S| (4) |
## |N|V|V|V| |
## | |1|2|3| |
## +-+-+-+-+-------+
header = pack('!B', ((self.fin << 7)
| (self.rsv1 << 6)
| (self.rsv2 << 5)
| (self.rsv3 << 4)
| self.opcode))
## +-+-------------+-------------------------------+
## |M| Payload len | Extended payload length |
## |A| (7) | (16/63) |
## |S| | (if payload len==126/127) |
## |K| | |
## +-+-+-+-+-------+-+-------------+ - - - - - - - - - - - - - - - +
## | Extended payload length continued, if payload len == 127 |
## + - - - - - - - - - - - - - - - +-------------------------------+
if self.masking_key: mask_bit = 1 << 7
else: mask_bit = 0
length = self.payload_length
if length < 126:
header += pack('!B', (mask_bit | length))
elif length < (1 << 16):
header += pack('!B', (mask_bit | 126)) + pack('!H', length)
elif length < (1 << 63):
header += pack('!B', (mask_bit | 127)) + pack('!Q', length)
else:
raise FrameTooLargeException()
## + - - - - - - - - - - - - - - - +-------------------------------+
## | |Masking-key, if MASK set to 1 |
## +-------------------------------+-------------------------------+
## | Masking-key (continued) | Payload Data |
## +-------------------------------- - - - - - - - - - - - - - - - +
## : Payload Data continued ... :
## + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - +
## | Payload Data continued ... |
## +---------------------------------------------------------------+
body = self.body
if not self.masking_key:
return bytes(header + body)
return bytes(header + self.masking_key + self.mask(body))
def _parsing(self):
"""
Generator to parse bytes into a frame. Yields until
enough bytes have been read or an error is met.
"""
buf = b''
some_bytes = b''
# yield until we get the first header's byte
while not some_bytes:
some_bytes = (yield 1)
first_byte = some_bytes[0] if isinstance(some_bytes, bytearray) else ord(some_bytes[0])
# frame-fin = %x0 ; more frames of this message follow
# / %x1 ; final frame of this message
self.fin = (first_byte >> 7) & 1
self.rsv1 = (first_byte >> 6) & 1
self.rsv2 = (first_byte >> 5) & 1
self.rsv3 = (first_byte >> 4) & 1
self.opcode = first_byte & 0xf
# frame-rsv1 = %x0 ; 1 bit, MUST be 0 unless negotiated otherwise
# frame-rsv2 = %x0 ; 1 bit, MUST be 0 unless negotiated otherwise
# frame-rsv3 = %x0 ; 1 bit, MUST be 0 unless negotiated otherwise
if self.rsv1 or self.rsv2 or self.rsv3:
raise ProtocolException()
# control frames between 3 and 7 as well as above 0xA are currently reserved
if 2 < self.opcode < 8 or self.opcode > 0xA:
raise ProtocolException()
# control frames cannot be fragmented
if self.opcode > 0x7 and self.fin == 0:
raise ProtocolException()
# do we already have enough some_bytes to continue?
some_bytes = some_bytes[1:] if some_bytes and len(some_bytes) > 1 else b''
# Yield until we get the second header's byte
while not some_bytes:
some_bytes = (yield 1)
second_byte = some_bytes[0] if isinstance(some_bytes, bytearray) else ord(some_bytes[0])
mask = (second_byte >> 7) & 1
self.payload_length = second_byte & 0x7f
# All control frames MUST have a payload length of 125 some_bytes or less
if self.opcode > 0x7 and self.payload_length > 125:
raise FrameTooLargeException()
if some_bytes and len(some_bytes) > 1:
buf = some_bytes[1:]
some_bytes = buf
else:
buf = b''
some_bytes = b''
if self.payload_length == 127:
# This will compute the actual application data size
if len(buf) < 8:
nxt_buf_size = 8 - len(buf)
some_bytes = (yield nxt_buf_size)
some_bytes = buf + (some_bytes or b'')
while len(some_bytes) < 8:
b = (yield 8 - len(some_bytes))
if b is not None:
some_bytes = some_bytes + b
if len(some_bytes) > 8:
buf = some_bytes[8:]
some_bytes = some_bytes[:8]
else:
some_bytes = buf[:8]
buf = buf[8:]
extended_payload_length = some_bytes
self.payload_length = unpack(
'!Q', extended_payload_length)[0]
if self.payload_length > 0x7FFFFFFFFFFFFFFF:
raise FrameTooLargeException()
elif self.payload_length == 126:
if len(buf) < 2:
nxt_buf_size = 2 - len(buf)
some_bytes = (yield nxt_buf_size)
some_bytes = buf + (some_bytes or b'')
while len(some_bytes) < 2:
b = (yield 2 - len(some_bytes))
if b is not None:
some_bytes = some_bytes + b
if len(some_bytes) > 2:
buf = some_bytes[2:]
some_bytes = some_bytes[:2]
else:
some_bytes = buf[:2]
buf = buf[2:]
extended_payload_length = some_bytes
self.payload_length = unpack(
'!H', extended_payload_length)[0]
if mask:
if len(buf) < 4:
nxt_buf_size = 4 - len(buf)
some_bytes = (yield nxt_buf_size)
some_bytes = buf + (some_bytes or b'')
while not some_bytes or len(some_bytes) < 4:
b = (yield 4 - len(some_bytes))
if b is not None:
some_bytes = some_bytes + b
if len(some_bytes) > 4:
buf = some_bytes[4:]
else:
some_bytes = buf[:4]
buf = buf[4:]
self.masking_key = some_bytes
if len(buf) < self.payload_length:
nxt_buf_size = self.payload_length - len(buf)
some_bytes = (yield nxt_buf_size)
some_bytes = buf + (some_bytes or b'')
while len(some_bytes) < self.payload_length:
l = self.payload_length - len(some_bytes)
b = (yield l)
if b is not None:
some_bytes = some_bytes + b
else:
if self.payload_length == len(buf):
some_bytes = buf
else:
some_bytes = buf[:self.payload_length]
self.body = some_bytes
yield
[docs] def mask(self, data):
"""
Performs the masking or unmasking operation on data
using the simple masking algorithm:
..
j = i MOD 4
transformed-octet-i = original-octet-i XOR masking-key-octet-j
"""
masked = bytearray(data)
if py3k: key = self.masking_key
else: key = map(ord, self.masking_key)
for i in range(len(data)):
masked[i] = masked[i] ^ key[i%4]
return masked
unmask = mask