698 lines
25 KiB
Python
698 lines
25 KiB
Python
from __future__ import annotations
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import zlib
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from collections.abc import Sequence
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from typing import Any, Literal
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from .. import frames
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from ..exceptions import (
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DuplicateParameter,
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InvalidParameterName,
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InvalidParameterValue,
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NegotiationError,
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PayloadTooBig,
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ProtocolError,
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)
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from ..typing import ExtensionName, ExtensionParameter
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from .base import ClientExtensionFactory, Extension, ServerExtensionFactory
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__all__ = [
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"PerMessageDeflate",
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"ClientPerMessageDeflateFactory",
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"enable_client_permessage_deflate",
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"ServerPerMessageDeflateFactory",
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"enable_server_permessage_deflate",
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]
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_EMPTY_UNCOMPRESSED_BLOCK = b"\x00\x00\xff\xff"
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_MAX_WINDOW_BITS_VALUES = [str(bits) for bits in range(8, 16)]
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class PerMessageDeflate(Extension):
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"""
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Per-Message Deflate extension.
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"""
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name = ExtensionName("permessage-deflate")
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def __init__(
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self,
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remote_no_context_takeover: bool,
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local_no_context_takeover: bool,
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remote_max_window_bits: int,
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local_max_window_bits: int,
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compress_settings: dict[Any, Any] | None = None,
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) -> None:
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"""
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Configure the Per-Message Deflate extension.
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"""
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if compress_settings is None:
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compress_settings = {}
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assert remote_no_context_takeover in [False, True]
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assert local_no_context_takeover in [False, True]
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assert 8 <= remote_max_window_bits <= 15
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assert 8 <= local_max_window_bits <= 15
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assert "wbits" not in compress_settings
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self.remote_no_context_takeover = remote_no_context_takeover
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self.local_no_context_takeover = local_no_context_takeover
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self.remote_max_window_bits = remote_max_window_bits
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self.local_max_window_bits = local_max_window_bits
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self.compress_settings = compress_settings
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if not self.remote_no_context_takeover:
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self.decoder = zlib.decompressobj(wbits=-self.remote_max_window_bits)
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if not self.local_no_context_takeover:
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self.encoder = zlib.compressobj(
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wbits=-self.local_max_window_bits,
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**self.compress_settings,
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)
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# To handle continuation frames properly, we must keep track of
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# whether that initial frame was encoded.
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self.decode_cont_data = False
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# There's no need for self.encode_cont_data because we always encode
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# outgoing frames, so it would always be True.
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def __repr__(self) -> str:
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return (
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f"PerMessageDeflate("
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f"remote_no_context_takeover={self.remote_no_context_takeover}, "
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f"local_no_context_takeover={self.local_no_context_takeover}, "
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f"remote_max_window_bits={self.remote_max_window_bits}, "
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f"local_max_window_bits={self.local_max_window_bits})"
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)
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def decode(
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self,
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frame: frames.Frame,
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*,
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max_size: int | None = None,
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) -> frames.Frame:
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"""
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Decode an incoming frame.
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"""
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# Skip control frames.
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if frame.opcode in frames.CTRL_OPCODES:
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return frame
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# Handle continuation data frames:
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# - skip if the message isn't encoded
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# - reset "decode continuation data" flag if it's a final frame
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if frame.opcode is frames.OP_CONT:
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if not self.decode_cont_data:
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return frame
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if frame.fin:
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self.decode_cont_data = False
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# Handle text and binary data frames:
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# - skip if the message isn't encoded
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# - unset the rsv1 flag on the first frame of a compressed message
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# - set "decode continuation data" flag if it's a non-final frame
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else:
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if not frame.rsv1:
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return frame
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if not frame.fin:
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self.decode_cont_data = True
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# Re-initialize per-message decoder.
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if self.remote_no_context_takeover:
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self.decoder = zlib.decompressobj(wbits=-self.remote_max_window_bits)
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# Uncompress data. Protect against zip bombs by preventing zlib from
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# decompressing more than max_length bytes (except when the limit is
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# disabled with max_size = None).
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if frame.fin and len(frame.data) < 2044:
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# Profiling shows that appending four bytes, which makes a copy, is
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# faster than calling decompress() again when data is less than 2kB.
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data = bytes(frame.data) + _EMPTY_UNCOMPRESSED_BLOCK
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else:
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data = frame.data
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max_length = 0 if max_size is None else max_size
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try:
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data = self.decoder.decompress(data, max_length)
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if self.decoder.unconsumed_tail:
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assert max_size is not None # help mypy
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raise PayloadTooBig(None, max_size)
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if frame.fin and len(frame.data) >= 2044:
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# This cannot generate additional data.
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self.decoder.decompress(_EMPTY_UNCOMPRESSED_BLOCK)
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except zlib.error as exc:
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raise ProtocolError("decompression failed") from exc
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# Allow garbage collection of the decoder if it won't be reused.
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if frame.fin and self.remote_no_context_takeover:
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del self.decoder
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return frames.Frame(
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frame.opcode,
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data,
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frame.fin,
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# Unset the rsv1 flag on the first frame of a compressed message.
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False,
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frame.rsv2,
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frame.rsv3,
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)
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def encode(self, frame: frames.Frame) -> frames.Frame:
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"""
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Encode an outgoing frame.
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"""
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# Skip control frames.
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if frame.opcode in frames.CTRL_OPCODES:
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return frame
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# Since we always encode messages, there's no "encode continuation
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# data" flag similar to "decode continuation data" at this time.
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if frame.opcode is not frames.OP_CONT:
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# Re-initialize per-message decoder.
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if self.local_no_context_takeover:
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self.encoder = zlib.compressobj(
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wbits=-self.local_max_window_bits,
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**self.compress_settings,
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)
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# Compress data.
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data = self.encoder.compress(frame.data) + self.encoder.flush(zlib.Z_SYNC_FLUSH)
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if frame.fin:
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# Sync flush generates between 5 or 6 bytes, ending with the bytes
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# 0x00 0x00 0xff 0xff, which must be removed.
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assert data[-4:] == _EMPTY_UNCOMPRESSED_BLOCK
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# Making a copy is faster than memoryview(a)[:-4] until 2kB.
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if len(data) < 2048:
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data = data[:-4]
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else:
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data = memoryview(data)[:-4]
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# Allow garbage collection of the encoder if it won't be reused.
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if frame.fin and self.local_no_context_takeover:
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del self.encoder
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return frames.Frame(
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frame.opcode,
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data,
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frame.fin,
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# Set the rsv1 flag on the first frame of a compressed message.
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frame.opcode is not frames.OP_CONT,
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frame.rsv2,
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frame.rsv3,
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)
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def _build_parameters(
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server_no_context_takeover: bool,
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client_no_context_takeover: bool,
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server_max_window_bits: int | None,
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client_max_window_bits: int | Literal[True] | None,
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) -> list[ExtensionParameter]:
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"""
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Build a list of ``(name, value)`` pairs for some compression parameters.
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"""
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params: list[ExtensionParameter] = []
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if server_no_context_takeover:
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params.append(("server_no_context_takeover", None))
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if client_no_context_takeover:
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params.append(("client_no_context_takeover", None))
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if server_max_window_bits:
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params.append(("server_max_window_bits", str(server_max_window_bits)))
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if client_max_window_bits is True: # only in handshake requests
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params.append(("client_max_window_bits", None))
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elif client_max_window_bits:
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params.append(("client_max_window_bits", str(client_max_window_bits)))
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return params
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def _extract_parameters(
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params: Sequence[ExtensionParameter], *, is_server: bool
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) -> tuple[bool, bool, int | None, int | Literal[True] | None]:
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"""
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Extract compression parameters from a list of ``(name, value)`` pairs.
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If ``is_server`` is :obj:`True`, ``client_max_window_bits`` may be
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provided without a value. This is only allowed in handshake requests.
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"""
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server_no_context_takeover: bool = False
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client_no_context_takeover: bool = False
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server_max_window_bits: int | None = None
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client_max_window_bits: int | Literal[True] | None = None
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for name, value in params:
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if name == "server_no_context_takeover":
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if server_no_context_takeover:
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raise DuplicateParameter(name)
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if value is None:
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server_no_context_takeover = True
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else:
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raise InvalidParameterValue(name, value)
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elif name == "client_no_context_takeover":
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if client_no_context_takeover:
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raise DuplicateParameter(name)
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if value is None:
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client_no_context_takeover = True
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else:
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raise InvalidParameterValue(name, value)
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elif name == "server_max_window_bits":
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if server_max_window_bits is not None:
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raise DuplicateParameter(name)
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if value in _MAX_WINDOW_BITS_VALUES:
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server_max_window_bits = int(value)
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else:
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raise InvalidParameterValue(name, value)
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elif name == "client_max_window_bits":
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if client_max_window_bits is not None:
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raise DuplicateParameter(name)
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if is_server and value is None: # only in handshake requests
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client_max_window_bits = True
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elif value in _MAX_WINDOW_BITS_VALUES:
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client_max_window_bits = int(value)
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else:
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raise InvalidParameterValue(name, value)
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else:
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raise InvalidParameterName(name)
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return (
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server_no_context_takeover,
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client_no_context_takeover,
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server_max_window_bits,
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client_max_window_bits,
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)
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class ClientPerMessageDeflateFactory(ClientExtensionFactory):
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"""
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Client-side extension factory for the Per-Message Deflate extension.
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Parameters behave as described in `section 7.1 of RFC 7692`_.
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.. _section 7.1 of RFC 7692: https://datatracker.ietf.org/doc/html/rfc7692#section-7.1
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Set them to :obj:`True` to include them in the negotiation offer without a
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value or to an integer value to include them with this value.
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Args:
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server_no_context_takeover: Prevent server from using context takeover.
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client_no_context_takeover: Prevent client from using context takeover.
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server_max_window_bits: Maximum size of the server's LZ77 sliding window
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in bits, between 8 and 15.
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client_max_window_bits: Maximum size of the client's LZ77 sliding window
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in bits, between 8 and 15, or :obj:`True` to indicate support without
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setting a limit.
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compress_settings: Additional keyword arguments for :func:`zlib.compressobj`,
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excluding ``wbits``.
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"""
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name = ExtensionName("permessage-deflate")
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def __init__(
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self,
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server_no_context_takeover: bool = False,
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client_no_context_takeover: bool = False,
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server_max_window_bits: int | None = None,
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client_max_window_bits: int | Literal[True] | None = True,
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compress_settings: dict[str, Any] | None = None,
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) -> None:
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"""
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Configure the Per-Message Deflate extension factory.
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"""
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if not (server_max_window_bits is None or 8 <= server_max_window_bits <= 15):
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raise ValueError("server_max_window_bits must be between 8 and 15")
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if not (
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client_max_window_bits is None
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or client_max_window_bits is True
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or 8 <= client_max_window_bits <= 15
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):
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raise ValueError("client_max_window_bits must be between 8 and 15")
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if compress_settings is not None and "wbits" in compress_settings:
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raise ValueError(
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"compress_settings must not include wbits, "
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"set client_max_window_bits instead"
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)
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self.server_no_context_takeover = server_no_context_takeover
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self.client_no_context_takeover = client_no_context_takeover
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self.server_max_window_bits = server_max_window_bits
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self.client_max_window_bits = client_max_window_bits
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self.compress_settings = compress_settings
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def get_request_params(self) -> Sequence[ExtensionParameter]:
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"""
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Build request parameters.
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"""
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return _build_parameters(
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self.server_no_context_takeover,
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self.client_no_context_takeover,
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self.server_max_window_bits,
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self.client_max_window_bits,
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)
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def process_response_params(
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self,
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params: Sequence[ExtensionParameter],
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accepted_extensions: Sequence[Extension],
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) -> PerMessageDeflate:
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"""
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Process response parameters.
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Return an extension instance.
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"""
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if any(other.name == self.name for other in accepted_extensions):
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raise NegotiationError(f"received duplicate {self.name}")
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# Request parameters are available in instance variables.
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# Load response parameters in local variables.
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(
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server_no_context_takeover,
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client_no_context_takeover,
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server_max_window_bits,
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client_max_window_bits,
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) = _extract_parameters(params, is_server=False)
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# After comparing the request and the response, the final
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# configuration must be available in the local variables.
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# server_no_context_takeover
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#
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# Req. Resp. Result
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# ------ ------ --------------------------------------------------
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# False False False
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# False True True
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# True False Error!
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# True True True
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if self.server_no_context_takeover:
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if not server_no_context_takeover:
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raise NegotiationError("expected server_no_context_takeover")
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# client_no_context_takeover
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#
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# Req. Resp. Result
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# ------ ------ --------------------------------------------------
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# False False False
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# False True True
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# True False True - must change value
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# True True True
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if self.client_no_context_takeover:
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if not client_no_context_takeover:
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client_no_context_takeover = True
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# server_max_window_bits
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# Req. Resp. Result
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# ------ ------ --------------------------------------------------
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# None None None
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# None 8≤M≤15 M
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# 8≤N≤15 None Error!
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# 8≤N≤15 8≤M≤N M
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# 8≤N≤15 N<M≤15 Error!
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if self.server_max_window_bits is None:
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pass
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else:
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if server_max_window_bits is None:
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raise NegotiationError("expected server_max_window_bits")
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elif server_max_window_bits > self.server_max_window_bits:
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raise NegotiationError("unsupported server_max_window_bits")
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# client_max_window_bits
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# Req. Resp. Result
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# ------ ------ --------------------------------------------------
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# None None None
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# None 8≤M≤15 Error!
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# True None None
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# True 8≤M≤15 M
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# 8≤N≤15 None N - must change value
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# 8≤N≤15 8≤M≤N M
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# 8≤N≤15 N<M≤15 Error!
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if self.client_max_window_bits is None:
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if client_max_window_bits is not None:
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raise NegotiationError("unexpected client_max_window_bits")
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elif self.client_max_window_bits is True:
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pass
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else:
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if client_max_window_bits is None:
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client_max_window_bits = self.client_max_window_bits
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elif client_max_window_bits > self.client_max_window_bits:
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raise NegotiationError("unsupported client_max_window_bits")
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return PerMessageDeflate(
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server_no_context_takeover, # remote_no_context_takeover
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client_no_context_takeover, # local_no_context_takeover
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server_max_window_bits or 15, # remote_max_window_bits
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client_max_window_bits or 15, # local_max_window_bits
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self.compress_settings,
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)
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def enable_client_permessage_deflate(
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extensions: Sequence[ClientExtensionFactory] | None,
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) -> Sequence[ClientExtensionFactory]:
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"""
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Enable Per-Message Deflate with default settings in client extensions.
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If the extension is already present, perhaps with non-default settings,
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the configuration isn't changed.
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"""
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if extensions is None:
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extensions = []
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if not any(
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extension_factory.name == ClientPerMessageDeflateFactory.name
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for extension_factory in extensions
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):
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extensions = list(extensions) + [
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ClientPerMessageDeflateFactory(
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compress_settings={"memLevel": 5},
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)
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]
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return extensions
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|
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class ServerPerMessageDeflateFactory(ServerExtensionFactory):
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"""
|
|
Server-side extension factory for the Per-Message Deflate extension.
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Parameters behave as described in `section 7.1 of RFC 7692`_.
|
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.. _section 7.1 of RFC 7692: https://datatracker.ietf.org/doc/html/rfc7692#section-7.1
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Set them to :obj:`True` to include them in the negotiation offer without a
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value or to an integer value to include them with this value.
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Args:
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server_no_context_takeover: Prevent server from using context takeover.
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client_no_context_takeover: Prevent client from using context takeover.
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server_max_window_bits: Maximum size of the server's LZ77 sliding window
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in bits, between 8 and 15.
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client_max_window_bits: Maximum size of the client's LZ77 sliding window
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in bits, between 8 and 15.
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compress_settings: Additional keyword arguments for :func:`zlib.compressobj`,
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excluding ``wbits``.
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require_client_max_window_bits: Do not enable compression at all if
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client doesn't advertise support for ``client_max_window_bits``;
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the default behavior is to enable compression without enforcing
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``client_max_window_bits``.
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"""
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|
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name = ExtensionName("permessage-deflate")
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|
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def __init__(
|
|
self,
|
|
server_no_context_takeover: bool = False,
|
|
client_no_context_takeover: bool = False,
|
|
server_max_window_bits: int | None = None,
|
|
client_max_window_bits: int | None = None,
|
|
compress_settings: dict[str, Any] | None = None,
|
|
require_client_max_window_bits: bool = False,
|
|
) -> None:
|
|
"""
|
|
Configure the Per-Message Deflate extension factory.
|
|
|
|
"""
|
|
if not (server_max_window_bits is None or 8 <= server_max_window_bits <= 15):
|
|
raise ValueError("server_max_window_bits must be between 8 and 15")
|
|
if not (client_max_window_bits is None or 8 <= client_max_window_bits <= 15):
|
|
raise ValueError("client_max_window_bits must be between 8 and 15")
|
|
if compress_settings is not None and "wbits" in compress_settings:
|
|
raise ValueError(
|
|
"compress_settings must not include wbits, "
|
|
"set server_max_window_bits instead"
|
|
)
|
|
if client_max_window_bits is None and require_client_max_window_bits:
|
|
raise ValueError(
|
|
"require_client_max_window_bits is enabled, "
|
|
"but client_max_window_bits isn't configured"
|
|
)
|
|
|
|
self.server_no_context_takeover = server_no_context_takeover
|
|
self.client_no_context_takeover = client_no_context_takeover
|
|
self.server_max_window_bits = server_max_window_bits
|
|
self.client_max_window_bits = client_max_window_bits
|
|
self.compress_settings = compress_settings
|
|
self.require_client_max_window_bits = require_client_max_window_bits
|
|
|
|
def process_request_params(
|
|
self,
|
|
params: Sequence[ExtensionParameter],
|
|
accepted_extensions: Sequence[Extension],
|
|
) -> tuple[list[ExtensionParameter], PerMessageDeflate]:
|
|
"""
|
|
Process request parameters.
|
|
|
|
Return response params and an extension instance.
|
|
|
|
"""
|
|
if any(other.name == self.name for other in accepted_extensions):
|
|
raise NegotiationError(f"skipped duplicate {self.name}")
|
|
|
|
# Load request parameters in local variables.
|
|
(
|
|
server_no_context_takeover,
|
|
client_no_context_takeover,
|
|
server_max_window_bits,
|
|
client_max_window_bits,
|
|
) = _extract_parameters(params, is_server=True)
|
|
|
|
# Configuration parameters are available in instance variables.
|
|
|
|
# After comparing the request and the configuration, the response must
|
|
# be available in the local variables.
|
|
|
|
# server_no_context_takeover
|
|
#
|
|
# Config Req. Resp.
|
|
# ------ ------ --------------------------------------------------
|
|
# False False False
|
|
# False True True
|
|
# True False True - must change value to True
|
|
# True True True
|
|
|
|
if self.server_no_context_takeover:
|
|
if not server_no_context_takeover:
|
|
server_no_context_takeover = True
|
|
|
|
# client_no_context_takeover
|
|
#
|
|
# Config Req. Resp.
|
|
# ------ ------ --------------------------------------------------
|
|
# False False False
|
|
# False True True (or False)
|
|
# True False True - must change value to True
|
|
# True True True (or False)
|
|
|
|
if self.client_no_context_takeover:
|
|
if not client_no_context_takeover:
|
|
client_no_context_takeover = True
|
|
|
|
# server_max_window_bits
|
|
|
|
# Config Req. Resp.
|
|
# ------ ------ --------------------------------------------------
|
|
# None None None
|
|
# None 8≤M≤15 M
|
|
# 8≤N≤15 None N - must change value
|
|
# 8≤N≤15 8≤M≤N M
|
|
# 8≤N≤15 N<M≤15 N - must change value
|
|
|
|
if self.server_max_window_bits is None:
|
|
pass
|
|
|
|
else:
|
|
if server_max_window_bits is None:
|
|
server_max_window_bits = self.server_max_window_bits
|
|
elif server_max_window_bits > self.server_max_window_bits:
|
|
server_max_window_bits = self.server_max_window_bits
|
|
|
|
# client_max_window_bits
|
|
|
|
# Config Req. Resp.
|
|
# ------ ------ --------------------------------------------------
|
|
# None None None
|
|
# None True None - must change value
|
|
# None 8≤M≤15 M (or None)
|
|
# 8≤N≤15 None None or Error!
|
|
# 8≤N≤15 True N - must change value
|
|
# 8≤N≤15 8≤M≤N M (or None)
|
|
# 8≤N≤15 N<M≤15 N
|
|
|
|
if self.client_max_window_bits is None:
|
|
if client_max_window_bits is True:
|
|
client_max_window_bits = self.client_max_window_bits
|
|
|
|
else:
|
|
if client_max_window_bits is None:
|
|
if self.require_client_max_window_bits:
|
|
raise NegotiationError("required client_max_window_bits")
|
|
elif client_max_window_bits is True:
|
|
client_max_window_bits = self.client_max_window_bits
|
|
elif self.client_max_window_bits < client_max_window_bits:
|
|
client_max_window_bits = self.client_max_window_bits
|
|
|
|
return (
|
|
_build_parameters(
|
|
server_no_context_takeover,
|
|
client_no_context_takeover,
|
|
server_max_window_bits,
|
|
client_max_window_bits,
|
|
),
|
|
PerMessageDeflate(
|
|
client_no_context_takeover, # remote_no_context_takeover
|
|
server_no_context_takeover, # local_no_context_takeover
|
|
client_max_window_bits or 15, # remote_max_window_bits
|
|
server_max_window_bits or 15, # local_max_window_bits
|
|
self.compress_settings,
|
|
),
|
|
)
|
|
|
|
|
|
def enable_server_permessage_deflate(
|
|
extensions: Sequence[ServerExtensionFactory] | None,
|
|
) -> Sequence[ServerExtensionFactory]:
|
|
"""
|
|
Enable Per-Message Deflate with default settings in server extensions.
|
|
|
|
If the extension is already present, perhaps with non-default settings,
|
|
the configuration isn't changed.
|
|
|
|
"""
|
|
if extensions is None:
|
|
extensions = []
|
|
if not any(
|
|
ext_factory.name == ServerPerMessageDeflateFactory.name
|
|
for ext_factory in extensions
|
|
):
|
|
extensions = list(extensions) + [
|
|
ServerPerMessageDeflateFactory(
|
|
server_max_window_bits=12,
|
|
client_max_window_bits=12,
|
|
compress_settings={"memLevel": 5},
|
|
)
|
|
]
|
|
return extensions
|