430 lines
12 KiB
Python
430 lines
12 KiB
Python
from __future__ import annotations
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import dataclasses
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import enum
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import io
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import os
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import secrets
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import struct
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from collections.abc import Generator, Sequence
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from typing import Callable, Union
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from .exceptions import PayloadTooBig, ProtocolError
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try:
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from .speedups import apply_mask
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except ImportError:
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from .utils import apply_mask
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__all__ = [
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"Opcode",
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"OP_CONT",
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"OP_TEXT",
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"OP_BINARY",
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"OP_CLOSE",
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"OP_PING",
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"OP_PONG",
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"DATA_OPCODES",
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"CTRL_OPCODES",
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"Frame",
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"Close",
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]
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class Opcode(enum.IntEnum):
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"""Opcode values for WebSocket frames."""
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CONT, TEXT, BINARY = 0x00, 0x01, 0x02
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CLOSE, PING, PONG = 0x08, 0x09, 0x0A
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OP_CONT = Opcode.CONT
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OP_TEXT = Opcode.TEXT
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OP_BINARY = Opcode.BINARY
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OP_CLOSE = Opcode.CLOSE
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OP_PING = Opcode.PING
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OP_PONG = Opcode.PONG
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DATA_OPCODES = OP_CONT, OP_TEXT, OP_BINARY
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CTRL_OPCODES = OP_CLOSE, OP_PING, OP_PONG
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class CloseCode(enum.IntEnum):
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"""Close code values for WebSocket close frames."""
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NORMAL_CLOSURE = 1000
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GOING_AWAY = 1001
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PROTOCOL_ERROR = 1002
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UNSUPPORTED_DATA = 1003
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# 1004 is reserved
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NO_STATUS_RCVD = 1005
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ABNORMAL_CLOSURE = 1006
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INVALID_DATA = 1007
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POLICY_VIOLATION = 1008
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MESSAGE_TOO_BIG = 1009
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MANDATORY_EXTENSION = 1010
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INTERNAL_ERROR = 1011
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SERVICE_RESTART = 1012
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TRY_AGAIN_LATER = 1013
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BAD_GATEWAY = 1014
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TLS_HANDSHAKE = 1015
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# See https://www.iana.org/assignments/websocket/websocket.xhtml
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CLOSE_CODE_EXPLANATIONS: dict[int, str] = {
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CloseCode.NORMAL_CLOSURE: "OK",
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CloseCode.GOING_AWAY: "going away",
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CloseCode.PROTOCOL_ERROR: "protocol error",
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CloseCode.UNSUPPORTED_DATA: "unsupported data",
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CloseCode.NO_STATUS_RCVD: "no status received [internal]",
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CloseCode.ABNORMAL_CLOSURE: "abnormal closure [internal]",
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CloseCode.INVALID_DATA: "invalid frame payload data",
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CloseCode.POLICY_VIOLATION: "policy violation",
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CloseCode.MESSAGE_TOO_BIG: "message too big",
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CloseCode.MANDATORY_EXTENSION: "mandatory extension",
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CloseCode.INTERNAL_ERROR: "internal error",
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CloseCode.SERVICE_RESTART: "service restart",
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CloseCode.TRY_AGAIN_LATER: "try again later",
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CloseCode.BAD_GATEWAY: "bad gateway",
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CloseCode.TLS_HANDSHAKE: "TLS handshake failure [internal]",
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}
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# Close code that are allowed in a close frame.
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# Using a set optimizes `code in EXTERNAL_CLOSE_CODES`.
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EXTERNAL_CLOSE_CODES = {
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CloseCode.NORMAL_CLOSURE,
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CloseCode.GOING_AWAY,
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CloseCode.PROTOCOL_ERROR,
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CloseCode.UNSUPPORTED_DATA,
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CloseCode.INVALID_DATA,
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CloseCode.POLICY_VIOLATION,
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CloseCode.MESSAGE_TOO_BIG,
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CloseCode.MANDATORY_EXTENSION,
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CloseCode.INTERNAL_ERROR,
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CloseCode.SERVICE_RESTART,
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CloseCode.TRY_AGAIN_LATER,
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CloseCode.BAD_GATEWAY,
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}
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OK_CLOSE_CODES = {
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CloseCode.NORMAL_CLOSURE,
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CloseCode.GOING_AWAY,
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CloseCode.NO_STATUS_RCVD,
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}
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BytesLike = bytes, bytearray, memoryview
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@dataclasses.dataclass
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class Frame:
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"""
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WebSocket frame.
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Attributes:
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opcode: Opcode.
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data: Payload data.
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fin: FIN bit.
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rsv1: RSV1 bit.
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rsv2: RSV2 bit.
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rsv3: RSV3 bit.
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Only these fields are needed. The MASK bit, payload length and masking-key
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are handled on the fly when parsing and serializing frames.
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"""
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opcode: Opcode
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data: Union[bytes, bytearray, memoryview]
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fin: bool = True
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rsv1: bool = False
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rsv2: bool = False
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rsv3: bool = False
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# Configure if you want to see more in logs. Should be a multiple of 3.
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MAX_LOG_SIZE = int(os.environ.get("WEBSOCKETS_MAX_LOG_SIZE", "75"))
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def __str__(self) -> str:
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"""
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Return a human-readable representation of a frame.
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"""
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coding = None
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length = f"{len(self.data)} byte{'' if len(self.data) == 1 else 's'}"
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non_final = "" if self.fin else "continued"
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if self.opcode is OP_TEXT:
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# Decoding only the beginning and the end is needlessly hard.
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# Decode the entire payload then elide later if necessary.
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data = repr(bytes(self.data).decode())
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elif self.opcode is OP_BINARY:
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# We'll show at most the first 16 bytes and the last 8 bytes.
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# Encode just what we need, plus two dummy bytes to elide later.
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binary = self.data
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if len(binary) > self.MAX_LOG_SIZE // 3:
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cut = (self.MAX_LOG_SIZE // 3 - 1) // 3 # by default cut = 8
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binary = b"".join([binary[: 2 * cut], b"\x00\x00", binary[-cut:]])
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data = " ".join(f"{byte:02x}" for byte in binary)
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elif self.opcode is OP_CLOSE:
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data = str(Close.parse(self.data))
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elif self.data:
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# We don't know if a Continuation frame contains text or binary.
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# Ping and Pong frames could contain UTF-8.
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# Attempt to decode as UTF-8 and display it as text; fallback to
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# binary. If self.data is a memoryview, it has no decode() method,
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# which raises AttributeError.
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try:
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data = repr(bytes(self.data).decode())
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coding = "text"
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except (UnicodeDecodeError, AttributeError):
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binary = self.data
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if len(binary) > self.MAX_LOG_SIZE // 3:
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cut = (self.MAX_LOG_SIZE // 3 - 1) // 3 # by default cut = 8
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binary = b"".join([binary[: 2 * cut], b"\x00\x00", binary[-cut:]])
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data = " ".join(f"{byte:02x}" for byte in binary)
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coding = "binary"
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else:
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data = "''"
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if len(data) > self.MAX_LOG_SIZE:
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cut = self.MAX_LOG_SIZE // 3 - 1 # by default cut = 24
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data = data[: 2 * cut] + "..." + data[-cut:]
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metadata = ", ".join(filter(None, [coding, length, non_final]))
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return f"{self.opcode.name} {data} [{metadata}]"
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@classmethod
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def parse(
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cls,
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read_exact: Callable[[int], Generator[None, None, bytes]],
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*,
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mask: bool,
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max_size: int | None = None,
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extensions: Sequence[extensions.Extension] | None = None,
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) -> Generator[None, None, Frame]:
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"""
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Parse a WebSocket frame.
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This is a generator-based coroutine.
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Args:
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read_exact: Generator-based coroutine that reads the requested
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bytes or raises an exception if there isn't enough data.
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mask: Whether the frame should be masked i.e. whether the read
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happens on the server side.
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max_size: Maximum payload size in bytes.
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extensions: List of extensions, applied in reverse order.
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Raises:
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EOFError: If the connection is closed without a full WebSocket frame.
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PayloadTooBig: If the frame's payload size exceeds ``max_size``.
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ProtocolError: If the frame contains incorrect values.
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"""
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# Read the header.
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data = yield from read_exact(2)
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head1, head2 = struct.unpack("!BB", data)
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# While not Pythonic, this is marginally faster than calling bool().
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fin = True if head1 & 0b10000000 else False
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rsv1 = True if head1 & 0b01000000 else False
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rsv2 = True if head1 & 0b00100000 else False
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rsv3 = True if head1 & 0b00010000 else False
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try:
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opcode = Opcode(head1 & 0b00001111)
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except ValueError as exc:
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raise ProtocolError("invalid opcode") from exc
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if (True if head2 & 0b10000000 else False) != mask:
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raise ProtocolError("incorrect masking")
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length = head2 & 0b01111111
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if length == 126:
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data = yield from read_exact(2)
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(length,) = struct.unpack("!H", data)
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elif length == 127:
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data = yield from read_exact(8)
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(length,) = struct.unpack("!Q", data)
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if max_size is not None and length > max_size:
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raise PayloadTooBig(length, max_size)
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if mask:
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mask_bytes = yield from read_exact(4)
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# Read the data.
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data = yield from read_exact(length)
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if mask:
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data = apply_mask(data, mask_bytes)
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frame = cls(opcode, data, fin, rsv1, rsv2, rsv3)
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if extensions is None:
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extensions = []
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for extension in reversed(extensions):
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frame = extension.decode(frame, max_size=max_size)
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frame.check()
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return frame
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def serialize(
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self,
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*,
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mask: bool,
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extensions: Sequence[extensions.Extension] | None = None,
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) -> bytes:
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"""
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Serialize a WebSocket frame.
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Args:
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mask: Whether the frame should be masked i.e. whether the write
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happens on the client side.
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extensions: List of extensions, applied in order.
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Raises:
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ProtocolError: If the frame contains incorrect values.
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"""
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self.check()
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if extensions is None:
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extensions = []
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for extension in extensions:
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self = extension.encode(self)
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output = io.BytesIO()
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# Prepare the header.
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head1 = (
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(0b10000000 if self.fin else 0)
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| (0b01000000 if self.rsv1 else 0)
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| (0b00100000 if self.rsv2 else 0)
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| (0b00010000 if self.rsv3 else 0)
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| self.opcode
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)
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head2 = 0b10000000 if mask else 0
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length = len(self.data)
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if length < 126:
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output.write(struct.pack("!BB", head1, head2 | length))
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elif length < 65536:
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output.write(struct.pack("!BBH", head1, head2 | 126, length))
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else:
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output.write(struct.pack("!BBQ", head1, head2 | 127, length))
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if mask:
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mask_bytes = secrets.token_bytes(4)
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output.write(mask_bytes)
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# Prepare the data.
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if mask:
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data = apply_mask(self.data, mask_bytes)
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else:
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data = self.data
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output.write(data)
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return output.getvalue()
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def check(self) -> None:
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"""
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Check that reserved bits and opcode have acceptable values.
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Raises:
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ProtocolError: If a reserved bit or the opcode is invalid.
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"""
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if self.rsv1 or self.rsv2 or self.rsv3:
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raise ProtocolError("reserved bits must be 0")
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if self.opcode in CTRL_OPCODES:
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if len(self.data) > 125:
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raise ProtocolError("control frame too long")
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if not self.fin:
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raise ProtocolError("fragmented control frame")
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@dataclasses.dataclass
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class Close:
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"""
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Code and reason for WebSocket close frames.
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Attributes:
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code: Close code.
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reason: Close reason.
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"""
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code: int
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reason: str
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def __str__(self) -> str:
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"""
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Return a human-readable representation of a close code and reason.
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"""
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if 3000 <= self.code < 4000:
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explanation = "registered"
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elif 4000 <= self.code < 5000:
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explanation = "private use"
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else:
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explanation = CLOSE_CODE_EXPLANATIONS.get(self.code, "unknown")
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result = f"{self.code} ({explanation})"
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if self.reason:
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result = f"{result} {self.reason}"
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return result
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@classmethod
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def parse(cls, data: bytes) -> Close:
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"""
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Parse the payload of a close frame.
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Args:
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data: Payload of the close frame.
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Raises:
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ProtocolError: If data is ill-formed.
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UnicodeDecodeError: If the reason isn't valid UTF-8.
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"""
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if len(data) >= 2:
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(code,) = struct.unpack("!H", data[:2])
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reason = data[2:].decode()
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close = cls(code, reason)
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close.check()
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return close
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elif len(data) == 0:
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return cls(CloseCode.NO_STATUS_RCVD, "")
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else:
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raise ProtocolError("close frame too short")
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def serialize(self) -> bytes:
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"""
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Serialize the payload of a close frame.
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"""
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self.check()
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return struct.pack("!H", self.code) + self.reason.encode()
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def check(self) -> None:
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"""
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Check that the close code has a valid value for a close frame.
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Raises:
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ProtocolError: If the close code is invalid.
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"""
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if not (self.code in EXTERNAL_CLOSE_CODES or 3000 <= self.code < 5000):
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raise ProtocolError("invalid status code")
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# At the bottom to break import cycles created by type annotations.
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from . import extensions # noqa: E402
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