421 lines
14 KiB
Python
421 lines
14 KiB
Python
"""
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WSGI Protocol Linter
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====================
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This module provides a middleware that performs sanity checks on the
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behavior of the WSGI server and application. It checks that the
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:pep:`3333` WSGI spec is properly implemented. It also warns on some
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common HTTP errors such as non-empty responses for 304 status codes.
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.. autoclass:: LintMiddleware
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:copyright: 2007 Pallets
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:license: BSD-3-Clause
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"""
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import typing as t
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from types import TracebackType
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from urllib.parse import urlparse
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from warnings import warn
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from ..datastructures import Headers
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from ..http import is_entity_header
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from ..wsgi import FileWrapper
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if t.TYPE_CHECKING:
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from _typeshed.wsgi import StartResponse
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from _typeshed.wsgi import WSGIApplication
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from _typeshed.wsgi import WSGIEnvironment
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class WSGIWarning(Warning):
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"""Warning class for WSGI warnings."""
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class HTTPWarning(Warning):
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"""Warning class for HTTP warnings."""
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def check_type(context: str, obj: object, need: t.Type = str) -> None:
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if type(obj) is not need:
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warn(
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f"{context!r} requires {need.__name__!r}, got {type(obj).__name__!r}.",
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WSGIWarning,
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stacklevel=3,
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)
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class InputStream:
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def __init__(self, stream: t.IO[bytes]) -> None:
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self._stream = stream
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def read(self, *args: t.Any) -> bytes:
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if len(args) == 0:
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warn(
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"WSGI does not guarantee an EOF marker on the input stream, thus making"
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" calls to 'wsgi.input.read()' unsafe. Conforming servers may never"
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" return from this call.",
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WSGIWarning,
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stacklevel=2,
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)
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elif len(args) != 1:
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warn(
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"Too many parameters passed to 'wsgi.input.read()'.",
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WSGIWarning,
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stacklevel=2,
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)
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return self._stream.read(*args)
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def readline(self, *args: t.Any) -> bytes:
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if len(args) == 0:
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warn(
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"Calls to 'wsgi.input.readline()' without arguments are unsafe. Use"
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" 'wsgi.input.read()' instead.",
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WSGIWarning,
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stacklevel=2,
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)
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elif len(args) == 1:
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warn(
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"'wsgi.input.readline()' was called with a size hint. WSGI does not"
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" support this, although it's available on all major servers.",
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WSGIWarning,
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stacklevel=2,
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)
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else:
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raise TypeError("Too many arguments passed to 'wsgi.input.readline()'.")
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return self._stream.readline(*args)
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def __iter__(self) -> t.Iterator[bytes]:
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try:
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return iter(self._stream)
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except TypeError:
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warn("'wsgi.input' is not iterable.", WSGIWarning, stacklevel=2)
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return iter(())
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def close(self) -> None:
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warn("The application closed the input stream!", WSGIWarning, stacklevel=2)
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self._stream.close()
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class ErrorStream:
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def __init__(self, stream: t.IO[str]) -> None:
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self._stream = stream
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def write(self, s: str) -> None:
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check_type("wsgi.error.write()", s, str)
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self._stream.write(s)
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def flush(self) -> None:
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self._stream.flush()
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def writelines(self, seq: t.Iterable[str]) -> None:
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for line in seq:
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self.write(line)
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def close(self) -> None:
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warn("The application closed the error stream!", WSGIWarning, stacklevel=2)
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self._stream.close()
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class GuardedWrite:
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def __init__(self, write: t.Callable[[bytes], object], chunks: t.List[int]) -> None:
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self._write = write
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self._chunks = chunks
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def __call__(self, s: bytes) -> None:
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check_type("write()", s, bytes)
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self._write(s)
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self._chunks.append(len(s))
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class GuardedIterator:
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def __init__(
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self,
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iterator: t.Iterable[bytes],
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headers_set: t.Tuple[int, Headers],
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chunks: t.List[int],
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) -> None:
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self._iterator = iterator
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self._next = iter(iterator).__next__
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self.closed = False
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self.headers_set = headers_set
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self.chunks = chunks
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def __iter__(self) -> "GuardedIterator":
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return self
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def __next__(self) -> bytes:
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if self.closed:
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warn("Iterated over closed 'app_iter'.", WSGIWarning, stacklevel=2)
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rv = self._next()
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if not self.headers_set:
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warn(
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"The application returned before it started the response.",
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WSGIWarning,
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stacklevel=2,
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)
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check_type("application iterator items", rv, bytes)
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self.chunks.append(len(rv))
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return rv
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def close(self) -> None:
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self.closed = True
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if hasattr(self._iterator, "close"):
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self._iterator.close() # type: ignore
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if self.headers_set:
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status_code, headers = self.headers_set
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bytes_sent = sum(self.chunks)
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content_length = headers.get("content-length", type=int)
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if status_code == 304:
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for key, _value in headers:
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key = key.lower()
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if key not in ("expires", "content-location") and is_entity_header(
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key
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):
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warn(
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f"Entity header {key!r} found in 304 response.", HTTPWarning
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)
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if bytes_sent:
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warn("304 responses must not have a body.", HTTPWarning)
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elif 100 <= status_code < 200 or status_code == 204:
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if content_length != 0:
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warn(
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f"{status_code} responses must have an empty content length.",
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HTTPWarning,
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)
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if bytes_sent:
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warn(f"{status_code} responses must not have a body.", HTTPWarning)
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elif content_length is not None and content_length != bytes_sent:
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warn(
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"Content-Length and the number of bytes sent to the"
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" client do not match.",
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WSGIWarning,
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)
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def __del__(self) -> None:
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if not self.closed:
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try:
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warn(
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"Iterator was garbage collected before it was closed.", WSGIWarning
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)
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except Exception:
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pass
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class LintMiddleware:
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"""Warns about common errors in the WSGI and HTTP behavior of the
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server and wrapped application. Some of the issues it checks are:
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- invalid status codes
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- non-bytes sent to the WSGI server
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- strings returned from the WSGI application
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- non-empty conditional responses
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- unquoted etags
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- relative URLs in the Location header
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- unsafe calls to wsgi.input
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- unclosed iterators
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Error information is emitted using the :mod:`warnings` module.
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:param app: The WSGI application to wrap.
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.. code-block:: python
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from werkzeug.middleware.lint import LintMiddleware
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app = LintMiddleware(app)
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"""
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def __init__(self, app: "WSGIApplication") -> None:
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self.app = app
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def check_environ(self, environ: "WSGIEnvironment") -> None:
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if type(environ) is not dict:
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warn(
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"WSGI environment is not a standard Python dict.",
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WSGIWarning,
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stacklevel=4,
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)
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for key in (
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"REQUEST_METHOD",
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"SERVER_NAME",
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"SERVER_PORT",
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"wsgi.version",
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"wsgi.input",
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"wsgi.errors",
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"wsgi.multithread",
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"wsgi.multiprocess",
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"wsgi.run_once",
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):
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if key not in environ:
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warn(
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f"Required environment key {key!r} not found",
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WSGIWarning,
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stacklevel=3,
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)
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if environ["wsgi.version"] != (1, 0):
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warn("Environ is not a WSGI 1.0 environ.", WSGIWarning, stacklevel=3)
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script_name = environ.get("SCRIPT_NAME", "")
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path_info = environ.get("PATH_INFO", "")
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if script_name and script_name[0] != "/":
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warn(
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f"'SCRIPT_NAME' does not start with a slash: {script_name!r}",
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WSGIWarning,
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stacklevel=3,
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)
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if path_info and path_info[0] != "/":
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warn(
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f"'PATH_INFO' does not start with a slash: {path_info!r}",
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WSGIWarning,
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stacklevel=3,
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)
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def check_start_response(
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self,
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status: str,
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headers: t.List[t.Tuple[str, str]],
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exc_info: t.Optional[
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t.Tuple[t.Type[BaseException], BaseException, TracebackType]
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],
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) -> t.Tuple[int, Headers]:
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check_type("status", status, str)
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status_code_str = status.split(None, 1)[0]
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if len(status_code_str) != 3 or not status_code_str.isdecimal():
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warn("Status code must be three digits.", WSGIWarning, stacklevel=3)
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if len(status) < 4 or status[3] != " ":
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warn(
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f"Invalid value for status {status!r}. Valid status strings are three"
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" digits, a space and a status explanation.",
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WSGIWarning,
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stacklevel=3,
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)
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status_code = int(status_code_str)
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if status_code < 100:
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warn("Status code < 100 detected.", WSGIWarning, stacklevel=3)
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if type(headers) is not list:
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warn("Header list is not a list.", WSGIWarning, stacklevel=3)
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for item in headers:
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if type(item) is not tuple or len(item) != 2:
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warn("Header items must be 2-item tuples.", WSGIWarning, stacklevel=3)
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name, value = item
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if type(name) is not str or type(value) is not str:
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warn(
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"Header keys and values must be strings.", WSGIWarning, stacklevel=3
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)
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if name.lower() == "status":
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warn(
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"The status header is not supported due to"
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" conflicts with the CGI spec.",
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WSGIWarning,
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stacklevel=3,
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)
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if exc_info is not None and not isinstance(exc_info, tuple):
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warn("Invalid value for exc_info.", WSGIWarning, stacklevel=3)
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headers = Headers(headers)
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self.check_headers(headers)
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return status_code, headers
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def check_headers(self, headers: Headers) -> None:
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etag = headers.get("etag")
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if etag is not None:
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if etag.startswith(("W/", "w/")):
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if etag.startswith("w/"):
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warn(
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"Weak etag indicator should be upper case.",
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HTTPWarning,
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stacklevel=4,
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)
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etag = etag[2:]
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if not (etag[:1] == etag[-1:] == '"'):
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warn("Unquoted etag emitted.", HTTPWarning, stacklevel=4)
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location = headers.get("location")
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if location is not None:
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if not urlparse(location).netloc:
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warn(
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"Absolute URLs required for location header.",
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HTTPWarning,
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stacklevel=4,
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)
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def check_iterator(self, app_iter: t.Iterable[bytes]) -> None:
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if isinstance(app_iter, bytes):
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warn(
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"The application returned a bytestring. The response will send one"
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" character at a time to the client, which will kill performance."
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" Return a list or iterable instead.",
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WSGIWarning,
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stacklevel=3,
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)
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def __call__(self, *args: t.Any, **kwargs: t.Any) -> t.Iterable[bytes]:
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if len(args) != 2:
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warn("A WSGI app takes two arguments.", WSGIWarning, stacklevel=2)
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if kwargs:
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warn(
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"A WSGI app does not take keyword arguments.", WSGIWarning, stacklevel=2
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)
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environ: "WSGIEnvironment" = args[0]
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start_response: "StartResponse" = args[1]
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self.check_environ(environ)
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environ["wsgi.input"] = InputStream(environ["wsgi.input"])
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environ["wsgi.errors"] = ErrorStream(environ["wsgi.errors"])
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# Hook our own file wrapper in so that applications will always
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# iterate to the end and we can check the content length.
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environ["wsgi.file_wrapper"] = FileWrapper
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headers_set: t.List[t.Any] = []
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chunks: t.List[int] = []
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def checking_start_response(
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*args: t.Any, **kwargs: t.Any
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) -> t.Callable[[bytes], None]:
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if len(args) not in {2, 3}:
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warn(
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f"Invalid number of arguments: {len(args)}, expected 2 or 3.",
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WSGIWarning,
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stacklevel=2,
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)
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if kwargs:
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warn("'start_response' does not take keyword arguments.", WSGIWarning)
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status: str = args[0]
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headers: t.List[t.Tuple[str, str]] = args[1]
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exc_info: t.Optional[
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t.Tuple[t.Type[BaseException], BaseException, TracebackType]
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] = (args[2] if len(args) == 3 else None)
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headers_set[:] = self.check_start_response(status, headers, exc_info)
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return GuardedWrite(start_response(status, headers, exc_info), chunks)
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app_iter = self.app(environ, t.cast("StartResponse", checking_start_response))
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self.check_iterator(app_iter)
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return GuardedIterator(
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app_iter, t.cast(t.Tuple[int, Headers], headers_set), chunks
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)
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