236 lines
7.6 KiB
Python
236 lines
7.6 KiB
Python
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"""
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Basic HTTP Proxy
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================
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.. autoclass:: ProxyMiddleware
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:copyright: 2007 Pallets
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:license: BSD-3-Clause
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"""
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from __future__ import annotations
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import typing as t
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from http import client
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from urllib.parse import quote
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from urllib.parse import urlsplit
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from ..datastructures import EnvironHeaders
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from ..http import is_hop_by_hop_header
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from ..wsgi import get_input_stream
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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 ProxyMiddleware:
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"""Proxy requests under a path to an external server, routing other
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requests to the app.
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This middleware can only proxy HTTP requests, as HTTP is the only
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protocol handled by the WSGI server. Other protocols, such as
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WebSocket requests, cannot be proxied at this layer. This should
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only be used for development, in production a real proxy server
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should be used.
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The middleware takes a dict mapping a path prefix to a dict
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describing the host to be proxied to::
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app = ProxyMiddleware(app, {
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"/static/": {
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"target": "http://127.0.0.1:5001/",
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}
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})
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Each host has the following options:
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``target``:
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The target URL to dispatch to. This is required.
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``remove_prefix``:
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Whether to remove the prefix from the URL before dispatching it
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to the target. The default is ``False``.
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``host``:
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``"<auto>"`` (default):
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The host header is automatically rewritten to the URL of the
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target.
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``None``:
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The host header is unmodified from the client request.
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Any other value:
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The host header is overwritten with the value.
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``headers``:
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A dictionary of headers to be sent with the request to the
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target. The default is ``{}``.
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``ssl_context``:
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A :class:`ssl.SSLContext` defining how to verify requests if the
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target is HTTPS. The default is ``None``.
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In the example above, everything under ``"/static/"`` is proxied to
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the server on port 5001. The host header is rewritten to the target,
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and the ``"/static/"`` prefix is removed from the URLs.
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:param app: The WSGI application to wrap.
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:param targets: Proxy target configurations. See description above.
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:param chunk_size: Size of chunks to read from input stream and
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write to target.
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:param timeout: Seconds before an operation to a target fails.
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.. versionadded:: 0.14
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"""
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def __init__(
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self,
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app: WSGIApplication,
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targets: t.Mapping[str, dict[str, t.Any]],
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chunk_size: int = 2 << 13,
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timeout: int = 10,
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) -> None:
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def _set_defaults(opts: dict[str, t.Any]) -> dict[str, t.Any]:
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opts.setdefault("remove_prefix", False)
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opts.setdefault("host", "<auto>")
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opts.setdefault("headers", {})
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opts.setdefault("ssl_context", None)
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return opts
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self.app = app
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self.targets = {
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f"/{k.strip('/')}/": _set_defaults(v) for k, v in targets.items()
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}
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self.chunk_size = chunk_size
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self.timeout = timeout
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def proxy_to(
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self, opts: dict[str, t.Any], path: str, prefix: str
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) -> WSGIApplication:
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target = urlsplit(opts["target"])
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# socket can handle unicode host, but header must be ascii
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host = target.hostname.encode("idna").decode("ascii")
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def application(
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environ: WSGIEnvironment, start_response: StartResponse
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) -> t.Iterable[bytes]:
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headers = list(EnvironHeaders(environ).items())
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headers[:] = [
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(k, v)
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for k, v in headers
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if not is_hop_by_hop_header(k)
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and k.lower() not in ("content-length", "host")
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]
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headers.append(("Connection", "close"))
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if opts["host"] == "<auto>":
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headers.append(("Host", host))
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elif opts["host"] is None:
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headers.append(("Host", environ["HTTP_HOST"]))
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else:
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headers.append(("Host", opts["host"]))
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headers.extend(opts["headers"].items())
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remote_path = path
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if opts["remove_prefix"]:
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remote_path = remote_path[len(prefix) :].lstrip("/")
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remote_path = f"{target.path.rstrip('/')}/{remote_path}"
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content_length = environ.get("CONTENT_LENGTH")
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chunked = False
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if content_length not in ("", None):
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headers.append(("Content-Length", content_length)) # type: ignore
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elif content_length is not None:
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headers.append(("Transfer-Encoding", "chunked"))
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chunked = True
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try:
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if target.scheme == "http":
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con = client.HTTPConnection(
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host, target.port or 80, timeout=self.timeout
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)
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elif target.scheme == "https":
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con = client.HTTPSConnection(
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host,
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target.port or 443,
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timeout=self.timeout,
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context=opts["ssl_context"],
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)
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else:
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raise RuntimeError(
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"Target scheme must be 'http' or 'https', got"
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f" {target.scheme!r}."
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)
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con.connect()
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# safe = https://url.spec.whatwg.org/#url-path-segment-string
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# as well as percent for things that are already quoted
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remote_url = quote(remote_path, safe="!$&'()*+,/:;=@%")
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querystring = environ["QUERY_STRING"]
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if querystring:
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remote_url = f"{remote_url}?{querystring}"
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con.putrequest(environ["REQUEST_METHOD"], remote_url, skip_host=True)
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for k, v in headers:
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if k.lower() == "connection":
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v = "close"
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con.putheader(k, v)
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con.endheaders()
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stream = get_input_stream(environ)
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while True:
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data = stream.read(self.chunk_size)
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if not data:
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break
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if chunked:
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con.send(b"%x\r\n%s\r\n" % (len(data), data))
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else:
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con.send(data)
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resp = con.getresponse()
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except OSError:
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from ..exceptions import BadGateway
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return BadGateway()(environ, start_response)
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start_response(
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f"{resp.status} {resp.reason}",
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[
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(k.title(), v)
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for k, v in resp.getheaders()
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if not is_hop_by_hop_header(k)
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],
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)
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def read() -> t.Iterator[bytes]:
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while True:
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try:
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data = resp.read(self.chunk_size)
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except OSError:
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break
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if not data:
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break
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yield data
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return read()
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return application
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def __call__(
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self, environ: WSGIEnvironment, start_response: StartResponse
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) -> t.Iterable[bytes]:
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path = environ["PATH_INFO"]
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app = self.app
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for prefix, opts in self.targets.items():
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if path.startswith(prefix):
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app = self.proxy_to(opts, path, prefix)
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break
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return app(environ, start_response)
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