mirror of
https://github.com/Grasscutters/mitmproxy.git
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379 lines
12 KiB
Python
379 lines
12 KiB
Python
from __future__ import absolute_import
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import base64
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import hashlib
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import os
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import struct
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import io
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from . import utils, odict, tcp
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# Colleciton of utility functions that implement small portions of the RFC6455
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# WebSockets Protocol Useful for building WebSocket clients and servers.
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#
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# Emphassis is on readabilty, simplicity and modularity, not performance or
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# completeness
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#
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# This is a work in progress and does not yet contain all the utilites need to
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# create fully complient client/servers #
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# Spec: https://tools.ietf.org/html/rfc6455
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# The magic sha that websocket servers must know to prove they understand
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# RFC6455
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websockets_magic = '258EAFA5-E914-47DA-95CA-C5AB0DC85B11'
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VERSION = "13"
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MAX_16_BIT_INT = (1 << 16)
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MAX_64_BIT_INT = (1 << 64)
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OPCODE = utils.BiDi(
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CONTINUE=0x00,
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TEXT=0x01,
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BINARY=0x02,
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CLOSE=0x08,
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PING=0x09,
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PONG=0x0a
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)
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class Masker:
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"""
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Data sent from the server must be masked to prevent malicious clients
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from sending data over the wire in predictable patterns
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Servers do not have to mask data they send to the client.
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https://tools.ietf.org/html/rfc6455#section-5.3
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"""
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def __init__(self, key):
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self.key = key
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self.masks = [utils.bytes_to_int(byte) for byte in key]
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self.offset = 0
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def mask(self, offset, data):
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result = ""
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for c in data:
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result += chr(ord(c) ^ self.masks[offset % 4])
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offset += 1
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return result
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def __call__(self, data):
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ret = self.mask(self.offset, data)
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self.offset += len(ret)
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return ret
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def client_handshake_headers(key=None, version=VERSION):
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"""
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Create the headers for a valid HTTP upgrade request. If Key is not
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specified, it is generated, and can be found in sec-websocket-key in
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the returned header set.
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Returns an instance of ODictCaseless
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"""
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if not key:
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key = base64.b64encode(os.urandom(16)).decode('utf-8')
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return odict.ODictCaseless([
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('Connection', 'Upgrade'),
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('Upgrade', 'websocket'),
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('Sec-WebSocket-Key', key),
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('Sec-WebSocket-Version', version)
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])
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def server_handshake_headers(key):
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"""
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The server response is a valid HTTP 101 response.
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"""
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return odict.ODictCaseless(
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[
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('Connection', 'Upgrade'),
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('Upgrade', 'websocket'),
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('Sec-WebSocket-Accept', create_server_nonce(key))
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]
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)
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def make_length_code(len):
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"""
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A websockets frame contains an initial length_code, and an optional
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extended length code to represent the actual length if length code is
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larger than 125
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"""
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if len <= 125:
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return len
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elif len >= 126 and len <= 65535:
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return 126
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else:
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return 127
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def check_client_handshake(headers):
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if headers.get_first("upgrade", None) != "websocket":
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return
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return headers.get_first('sec-websocket-key')
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def check_server_handshake(headers):
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if headers.get_first("upgrade", None) != "websocket":
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return
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return headers.get_first('sec-websocket-accept')
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def create_server_nonce(client_nonce):
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return base64.b64encode(
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hashlib.sha1(client_nonce + websockets_magic).hexdigest().decode('hex')
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)
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DEFAULT = object()
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class FrameHeader:
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def __init__(
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self,
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opcode=OPCODE.TEXT,
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payload_length=0,
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fin=False,
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rsv1=False,
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rsv2=False,
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rsv3=False,
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masking_key=DEFAULT,
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mask=DEFAULT,
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length_code=DEFAULT
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):
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if not 0 <= opcode < 2 ** 4:
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raise ValueError("opcode must be 0-16")
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self.opcode = opcode
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self.payload_length = payload_length
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self.fin = fin
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self.rsv1 = rsv1
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self.rsv2 = rsv2
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self.rsv3 = rsv3
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if length_code is DEFAULT:
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self.length_code = make_length_code(self.payload_length)
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else:
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self.length_code = length_code
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if mask is DEFAULT and masking_key is DEFAULT:
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self.mask = False
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self.masking_key = ""
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elif mask is DEFAULT:
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self.mask = 1
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self.masking_key = masking_key
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elif masking_key is DEFAULT:
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self.mask = mask
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self.masking_key = os.urandom(4)
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else:
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self.mask = mask
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self.masking_key = masking_key
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if self.masking_key and len(self.masking_key) != 4:
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raise ValueError("Masking key must be 4 bytes.")
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def human_readable(self):
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vals = [
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"ws frame:",
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OPCODE.get_name(self.opcode, hex(self.opcode)).lower()
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]
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flags = []
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for i in ["fin", "rsv1", "rsv2", "rsv3", "mask"]:
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if getattr(self, i):
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flags.append(i)
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if flags:
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vals.extend([":", "|".join(flags)])
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if self.masking_key:
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vals.append(":key=%s" % repr(self.masking_key))
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if self.payload_length:
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vals.append(" %s" % utils.pretty_size(self.payload_length))
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return "".join(vals)
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def to_bytes(self):
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first_byte = utils.setbit(0, 7, self.fin)
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first_byte = utils.setbit(first_byte, 6, self.rsv1)
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first_byte = utils.setbit(first_byte, 5, self.rsv2)
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first_byte = utils.setbit(first_byte, 4, self.rsv3)
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first_byte = first_byte | self.opcode
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second_byte = utils.setbit(self.length_code, 7, self.mask)
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b = chr(first_byte) + chr(second_byte)
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if self.payload_length < 126:
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pass
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elif self.payload_length < MAX_16_BIT_INT:
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# '!H' pack as 16 bit unsigned short
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# add 2 byte extended payload length
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b += struct.pack('!H', self.payload_length)
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elif self.payload_length < MAX_64_BIT_INT:
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# '!Q' = pack as 64 bit unsigned long long
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# add 8 bytes extended payload length
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b += struct.pack('!Q', self.payload_length)
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if self.masking_key is not None:
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b += self.masking_key
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return b
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@classmethod
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def from_file(klass, fp):
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"""
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read a websockets frame header
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"""
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first_byte = utils.bytes_to_int(fp.safe_read(1))
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second_byte = utils.bytes_to_int(fp.safe_read(1))
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fin = utils.getbit(first_byte, 7)
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rsv1 = utils.getbit(first_byte, 6)
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rsv2 = utils.getbit(first_byte, 5)
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rsv3 = utils.getbit(first_byte, 4)
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# grab right-most 4 bits
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opcode = first_byte & 15
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mask_bit = utils.getbit(second_byte, 7)
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# grab the next 7 bits
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length_code = second_byte & 127
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# payload_lengthy > 125 indicates you need to read more bytes
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# to get the actual payload length
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if length_code <= 125:
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payload_length = length_code
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elif length_code == 126:
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payload_length = utils.bytes_to_int(fp.safe_read(2))
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elif length_code == 127:
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payload_length = utils.bytes_to_int(fp.safe_read(8))
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# masking key only present if mask bit set
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if mask_bit == 1:
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masking_key = fp.safe_read(4)
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else:
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masking_key = None
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return klass(
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fin=fin,
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rsv1=rsv1,
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rsv2=rsv2,
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rsv3=rsv3,
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opcode=opcode,
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mask=mask_bit,
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length_code=length_code,
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payload_length=payload_length,
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masking_key=masking_key,
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)
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def __eq__(self, other):
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return self.to_bytes() == other.to_bytes()
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class Frame(object):
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"""
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Represents one websockets frame.
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Constructor takes human readable forms of the frame components
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from_bytes() is also avaliable.
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WebSockets Frame as defined in RFC6455
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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+-+-+-+-+-------+-+-------------+-------------------------------+
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|F|R|R|R| opcode|M| Payload len | Extended payload length |
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|I|S|S|S| (4) |A| (7) | (16/64) |
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|N|V|V|V| |S| | (if payload len==126/127) |
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| |1|2|3| |K| | |
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+-+-+-+-+-------+-+-------------+ - - - - - - - - - - - - - - - +
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| Extended payload length continued, if payload len == 127 |
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+ - - - - - - - - - - - - - - - +-------------------------------+
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| |Masking-key, if MASK set to 1 |
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+-------------------------------+-------------------------------+
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| Masking-key (continued) | Payload Data |
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+-------------------------------- - - - - - - - - - - - - - - - +
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: Payload Data continued ... :
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+ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - +
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| Payload Data continued ... |
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+---------------------------------------------------------------+
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"""
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def __init__(self, payload="", **kwargs):
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self.payload = payload
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kwargs["payload_length"] = kwargs.get("payload_length", len(payload))
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self.header = FrameHeader(**kwargs)
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@classmethod
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def default(cls, message, from_client=False):
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"""
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Construct a basic websocket frame from some default values.
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Creates a non-fragmented text frame.
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"""
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if from_client:
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mask_bit = 1
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masking_key = os.urandom(4)
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else:
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mask_bit = 0
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masking_key = None
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return cls(
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message,
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fin=1, # final frame
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opcode=OPCODE.TEXT, # text
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mask=mask_bit,
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masking_key=masking_key,
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)
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@classmethod
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def from_bytes(cls, bytestring):
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"""
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Construct a websocket frame from an in-memory bytestring
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to construct a frame from a stream of bytes, use from_file() directly
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"""
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return cls.from_file(tcp.Reader(io.BytesIO(bytestring)))
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def human_readable(self):
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ret = self.header.human_readable()
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if self.payload:
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ret = ret + "\nPayload:\n" + utils.cleanBin(self.payload)
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return ret
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def to_bytes(self):
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"""
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Serialize the frame to wire format. Returns a string.
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"""
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b = self.header.to_bytes()
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if self.header.masking_key:
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b += Masker(self.header.masking_key)(self.payload)
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else:
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b += self.payload
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return b
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def to_file(self, writer):
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writer.write(self.to_bytes())
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writer.flush()
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@classmethod
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def from_file(cls, fp):
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"""
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read a websockets frame sent by a server or client
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fp is a "file like" object that could be backed by a network
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stream or a disk or an in memory stream reader
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"""
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header = FrameHeader.from_file(fp)
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payload = fp.safe_read(header.payload_length)
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if header.mask == 1 and header.masking_key:
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payload = Masker(header.masking_key)(payload)
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return cls(
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payload,
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fin=header.fin,
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opcode=header.opcode,
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mask=header.mask,
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payload_length=header.payload_length,
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masking_key=header.masking_key,
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rsv1=header.rsv1,
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rsv2=header.rsv2,
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rsv3=header.rsv3,
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length_code=header.length_code
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)
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def __eq__(self, other):
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return self.to_bytes() == other.to_bytes()
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