428 lines
15 KiB
Python
428 lines
15 KiB
Python
from __future__ import annotations
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import dataclasses
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import os
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import re
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import sys
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import warnings
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from collections.abc import Generator
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from typing import Callable
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from .datastructures import Headers
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from .exceptions import SecurityError
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from .version import version as websockets_version
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__all__ = [
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"SERVER",
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"USER_AGENT",
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"Request",
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"Response",
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]
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PYTHON_VERSION = "{}.{}".format(*sys.version_info)
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# User-Agent header for HTTP requests.
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USER_AGENT = os.environ.get(
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"WEBSOCKETS_USER_AGENT",
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f"Python/{PYTHON_VERSION} websockets/{websockets_version}",
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)
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# Server header for HTTP responses.
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SERVER = os.environ.get(
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"WEBSOCKETS_SERVER",
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f"Python/{PYTHON_VERSION} websockets/{websockets_version}",
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)
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# Maximum total size of headers is around 128 * 8 KiB = 1 MiB.
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MAX_NUM_HEADERS = int(os.environ.get("WEBSOCKETS_MAX_NUM_HEADERS", "128"))
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# Limit request line and header lines. 8KiB is the most common default
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# configuration of popular HTTP servers.
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MAX_LINE_LENGTH = int(os.environ.get("WEBSOCKETS_MAX_LINE_LENGTH", "8192"))
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# Support for HTTP response bodies is intended to read an error message
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# returned by a server. It isn't designed to perform large file transfers.
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MAX_BODY_SIZE = int(os.environ.get("WEBSOCKETS_MAX_BODY_SIZE", "1_048_576")) # 1 MiB
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def d(value: bytes) -> str:
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"""
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Decode a bytestring for interpolating into an error message.
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"""
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return value.decode(errors="backslashreplace")
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# See https://datatracker.ietf.org/doc/html/rfc7230#appendix-B.
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# Regex for validating header names.
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_token_re = re.compile(rb"[-!#$%&\'*+.^_`|~0-9a-zA-Z]+")
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# Regex for validating header values.
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# We don't attempt to support obsolete line folding.
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# Include HTAB (\x09), SP (\x20), VCHAR (\x21-\x7e), obs-text (\x80-\xff).
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# The ABNF is complicated because it attempts to express that optional
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# whitespace is ignored. We strip whitespace and don't revalidate that.
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# See also https://www.rfc-editor.org/errata_search.php?rfc=7230&eid=4189
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_value_re = re.compile(rb"[\x09\x20-\x7e\x80-\xff]*")
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@dataclasses.dataclass
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class Request:
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"""
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WebSocket handshake request.
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Attributes:
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path: Request path, including optional query.
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headers: Request headers.
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"""
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path: str
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headers: Headers
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# body isn't useful is the context of this library.
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_exception: Exception | None = None
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@property
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def exception(self) -> Exception | None: # pragma: no cover
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warnings.warn( # deprecated in 10.3 - 2022-04-17
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"Request.exception is deprecated; use ServerProtocol.handshake_exc instead",
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DeprecationWarning,
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)
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return self._exception
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@classmethod
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def parse(
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cls,
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read_line: Callable[[int], Generator[None, None, bytes]],
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) -> Generator[None, None, Request]:
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"""
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Parse a WebSocket handshake request.
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This is a generator-based coroutine.
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The request path isn't URL-decoded or validated in any way.
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The request path and headers are expected to contain only ASCII
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characters. Other characters are represented with surrogate escapes.
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:meth:`parse` doesn't attempt to read the request body because
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WebSocket handshake requests don't have one. If the request contains a
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body, it may be read from the data stream after :meth:`parse` returns.
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Args:
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read_line: Generator-based coroutine that reads a LF-terminated
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line or raises an exception if there isn't enough data
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Raises:
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EOFError: If the connection is closed without a full HTTP request.
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SecurityError: If the request exceeds a security limit.
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ValueError: If the request isn't well formatted.
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"""
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# https://datatracker.ietf.org/doc/html/rfc7230#section-3.1.1
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# Parsing is simple because fixed values are expected for method and
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# version and because path isn't checked. Since WebSocket software tends
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# to implement HTTP/1.1 strictly, there's little need for lenient parsing.
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try:
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request_line = yield from parse_line(read_line)
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except EOFError as exc:
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raise EOFError("connection closed while reading HTTP request line") from exc
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try:
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method, raw_path, protocol = request_line.split(b" ", 2)
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except ValueError: # not enough values to unpack (expected 3, got 1-2)
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raise ValueError(f"invalid HTTP request line: {d(request_line)}") from None
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if protocol != b"HTTP/1.1":
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raise ValueError(
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f"unsupported protocol; expected HTTP/1.1: {d(request_line)}"
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)
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if method != b"GET":
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raise ValueError(f"unsupported HTTP method; expected GET; got {d(method)}")
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path = raw_path.decode("ascii", "surrogateescape")
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headers = yield from parse_headers(read_line)
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# https://datatracker.ietf.org/doc/html/rfc7230#section-3.3.3
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if "Transfer-Encoding" in headers:
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raise NotImplementedError("transfer codings aren't supported")
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if "Content-Length" in headers:
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raise ValueError("unsupported request body")
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return cls(path, headers)
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def serialize(self) -> bytes:
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"""
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Serialize a WebSocket handshake request.
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"""
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# Since the request line and headers only contain ASCII characters,
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# we can keep this simple.
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request = f"GET {self.path} HTTP/1.1\r\n".encode()
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request += self.headers.serialize()
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return request
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@dataclasses.dataclass
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class Response:
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"""
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WebSocket handshake response.
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Attributes:
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status_code: Response code.
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reason_phrase: Response reason.
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headers: Response headers.
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body: Response body.
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"""
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status_code: int
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reason_phrase: str
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headers: Headers
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body: bytes = b""
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_exception: Exception | None = None
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@property
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def exception(self) -> Exception | None: # pragma: no cover
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warnings.warn( # deprecated in 10.3 - 2022-04-17
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"Response.exception is deprecated; "
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"use ClientProtocol.handshake_exc instead",
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DeprecationWarning,
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)
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return self._exception
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@classmethod
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def parse(
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cls,
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read_line: Callable[[int], Generator[None, None, bytes]],
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read_exact: Callable[[int], Generator[None, None, bytes]],
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read_to_eof: Callable[[int], Generator[None, None, bytes]],
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include_body: bool = True,
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) -> Generator[None, None, Response]:
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"""
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Parse a WebSocket handshake response.
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This is a generator-based coroutine.
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The reason phrase and headers are expected to contain only ASCII
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characters. Other characters are represented with surrogate escapes.
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Args:
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read_line: Generator-based coroutine that reads a LF-terminated
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line or raises an exception if there isn't enough data.
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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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read_to_eof: Generator-based coroutine that reads until the end
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of the stream.
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Raises:
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EOFError: If the connection is closed without a full HTTP response.
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SecurityError: If the response exceeds a security limit.
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LookupError: If the response isn't well formatted.
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ValueError: If the response isn't well formatted.
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"""
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# https://datatracker.ietf.org/doc/html/rfc7230#section-3.1.2
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try:
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status_line = yield from parse_line(read_line)
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except EOFError as exc:
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raise EOFError("connection closed while reading HTTP status line") from exc
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try:
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protocol, raw_status_code, raw_reason = status_line.split(b" ", 2)
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except ValueError: # not enough values to unpack (expected 3, got 1-2)
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raise ValueError(f"invalid HTTP status line: {d(status_line)}") from None
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if protocol != b"HTTP/1.1":
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raise ValueError(
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f"unsupported protocol; expected HTTP/1.1: {d(status_line)}"
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)
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try:
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status_code = int(raw_status_code)
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except ValueError: # invalid literal for int() with base 10
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raise ValueError(
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f"invalid status code; expected integer; got {d(raw_status_code)}"
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) from None
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if not 100 <= status_code < 600:
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raise ValueError(
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f"invalid status code; expected 100–599; got {d(raw_status_code)}"
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)
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if not _value_re.fullmatch(raw_reason):
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raise ValueError(f"invalid HTTP reason phrase: {d(raw_reason)}")
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reason = raw_reason.decode("ascii", "surrogateescape")
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headers = yield from parse_headers(read_line)
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if include_body:
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body = yield from read_body(
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status_code, headers, read_line, read_exact, read_to_eof
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)
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else:
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body = b""
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return cls(status_code, reason, headers, body)
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def serialize(self) -> bytes:
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"""
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Serialize a WebSocket handshake response.
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"""
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# Since the status line and headers only contain ASCII characters,
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# we can keep this simple.
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response = f"HTTP/1.1 {self.status_code} {self.reason_phrase}\r\n".encode()
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response += self.headers.serialize()
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response += self.body
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return response
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def parse_line(
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read_line: Callable[[int], Generator[None, None, bytes]],
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) -> Generator[None, None, bytes]:
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"""
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Parse a single line.
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CRLF is stripped from the return value.
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Args:
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read_line: Generator-based coroutine that reads a LF-terminated line
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or raises an exception if there isn't enough data.
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Raises:
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EOFError: If the connection is closed without a CRLF.
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SecurityError: If the response exceeds a security limit.
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"""
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try:
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line = yield from read_line(MAX_LINE_LENGTH)
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except RuntimeError:
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raise SecurityError("line too long")
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# Not mandatory but safe - https://datatracker.ietf.org/doc/html/rfc7230#section-3.5
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if not line.endswith(b"\r\n"):
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raise EOFError("line without CRLF")
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return line[:-2]
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def parse_headers(
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read_line: Callable[[int], Generator[None, None, bytes]],
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) -> Generator[None, None, Headers]:
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"""
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Parse HTTP headers.
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Non-ASCII characters are represented with surrogate escapes.
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Args:
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read_line: Generator-based coroutine that reads a LF-terminated line
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or raises an exception if there isn't enough data.
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Raises:
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EOFError: If the connection is closed without complete headers.
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SecurityError: If the request exceeds a security limit.
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ValueError: If the request isn't well formatted.
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"""
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# https://datatracker.ietf.org/doc/html/rfc7230#section-3.2
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# We don't attempt to support obsolete line folding.
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headers = Headers()
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for _ in range(MAX_NUM_HEADERS + 1):
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try:
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line = yield from parse_line(read_line)
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except EOFError as exc:
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raise EOFError("connection closed while reading HTTP headers") from exc
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if line == b"":
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break
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try:
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raw_name, raw_value = line.split(b":", 1)
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except ValueError: # not enough values to unpack (expected 2, got 1)
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raise ValueError(f"invalid HTTP header line: {d(line)}") from None
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if not _token_re.fullmatch(raw_name):
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raise ValueError(f"invalid HTTP header name: {d(raw_name)}")
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raw_value = raw_value.strip(b" \t")
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if not _value_re.fullmatch(raw_value):
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raise ValueError(f"invalid HTTP header value: {d(raw_value)}")
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name = raw_name.decode("ascii") # guaranteed to be ASCII at this point
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value = raw_value.decode("ascii", "surrogateescape")
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headers[name] = value
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else:
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raise SecurityError("too many HTTP headers")
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return headers
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def read_body(
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status_code: int,
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headers: Headers,
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read_line: Callable[[int], Generator[None, None, bytes]],
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read_exact: Callable[[int], Generator[None, None, bytes]],
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read_to_eof: Callable[[int], Generator[None, None, bytes]],
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) -> Generator[None, None, bytes]:
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# https://datatracker.ietf.org/doc/html/rfc7230#section-3.3.3
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# Since websockets only does GET requests (no HEAD, no CONNECT), all
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# responses except 1xx, 204, and 304 include a message body.
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if 100 <= status_code < 200 or status_code == 204 or status_code == 304:
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return b""
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# MultipleValuesError is sufficiently unlikely that we don't attempt to
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# handle it when accessing headers. Instead we document that its parent
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# class, LookupError, may be raised.
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# Conversions from str to int are protected by sys.set_int_max_str_digits..
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elif (coding := headers.get("Transfer-Encoding")) is not None:
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if coding != "chunked":
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raise NotImplementedError(f"transfer coding {coding} isn't supported")
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body = b""
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while True:
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chunk_size_line = yield from parse_line(read_line)
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raw_chunk_size = chunk_size_line.split(b";", 1)[0]
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# Set a lower limit than default_max_str_digits; 1 EB is plenty.
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if len(raw_chunk_size) > 15:
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str_chunk_size = raw_chunk_size.decode(errors="backslashreplace")
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raise SecurityError(f"chunk too large: 0x{str_chunk_size} bytes")
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chunk_size = int(raw_chunk_size, 16)
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if chunk_size == 0:
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break
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if len(body) + chunk_size > MAX_BODY_SIZE:
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raise SecurityError(
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f"chunk too large: {chunk_size} bytes after {len(body)} bytes"
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)
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body += yield from read_exact(chunk_size)
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if (yield from read_exact(2)) != b"\r\n":
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raise ValueError("chunk without CRLF")
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# Read the trailer.
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yield from parse_headers(read_line)
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return body
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elif (raw_content_length := headers.get("Content-Length")) is not None:
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# Set a lower limit than default_max_str_digits; 1 EiB is plenty.
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if len(raw_content_length) > 18:
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raise SecurityError(f"body too large: {raw_content_length} bytes")
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content_length = int(raw_content_length)
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if content_length > MAX_BODY_SIZE:
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raise SecurityError(f"body too large: {content_length} bytes")
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return (yield from read_exact(content_length))
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else:
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try:
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return (yield from read_to_eof(MAX_BODY_SIZE))
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except RuntimeError:
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raise SecurityError(f"body too large: over {MAX_BODY_SIZE} bytes")
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