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