proxy_fix.py
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"""
X-Forwarded-For Proxy Fix
=========================
This module provides a middleware that adjusts the WSGI environ based on
``X-Forwarded-`` headers that proxies in front of an application may
set.
When an application is running behind a proxy server, WSGI may see the
request as coming from that server rather than the real client. Proxies
set various headers to track where the request actually came from.
This middleware should only be applied if the application is actually
behind such a proxy, and should be configured with the number of proxies
that are chained in front of it. Not all proxies set all the headers.
Since incoming headers can be faked, you must set how many proxies are
setting each header so the middleware knows what to trust.
.. autoclass:: ProxyFix
:copyright: 2007 Pallets
:license: BSD-3-Clause
"""
from werkzeug.http import parse_list_header
class ProxyFix(object):
"""Adjust the WSGI environ based on ``X-Forwarded-`` that proxies in
front of the application may set.
- ``X-Forwarded-For`` sets ``REMOTE_ADDR``.
- ``X-Forwarded-Proto`` sets ``wsgi.url_scheme``.
- ``X-Forwarded-Host`` sets ``HTTP_HOST``, ``SERVER_NAME``, and
``SERVER_PORT``.
- ``X-Forwarded-Port`` sets ``HTTP_HOST`` and ``SERVER_PORT``.
- ``X-Forwarded-Prefix`` sets ``SCRIPT_NAME``.
You must tell the middleware how many proxies set each header so it
knows what values to trust. It is a security issue to trust values
that came from the client rather than a proxy.
The original values of the headers are stored in the WSGI
environ as ``werkzeug.proxy_fix.orig``, a dict.
:param app: The WSGI application to wrap.
:param x_for: Number of values to trust for ``X-Forwarded-For``.
:param x_proto: Number of values to trust for ``X-Forwarded-Proto``.
:param x_host: Number of values to trust for ``X-Forwarded-Host``.
:param x_port: Number of values to trust for ``X-Forwarded-Port``.
:param x_prefix: Number of values to trust for
``X-Forwarded-Prefix``.
.. code-block:: python
from werkzeug.middleware.proxy_fix import ProxyFix
# App is behind one proxy that sets the -For and -Host headers.
app = ProxyFix(app, x_for=1, x_host=1)
.. versionchanged:: 1.0
Deprecated code has been removed:
* The ``num_proxies`` argument and attribute.
* The ``get_remote_addr`` method.
* The environ keys ``orig_remote_addr``,
``orig_wsgi_url_scheme``, and ``orig_http_host``.
.. versionchanged:: 0.15
All headers support multiple values. The ``num_proxies``
argument is deprecated. Each header is configured with a
separate number of trusted proxies.
.. versionchanged:: 0.15
Original WSGI environ values are stored in the
``werkzeug.proxy_fix.orig`` dict. ``orig_remote_addr``,
``orig_wsgi_url_scheme``, and ``orig_http_host`` are deprecated
and will be removed in 1.0.
.. versionchanged:: 0.15
Support ``X-Forwarded-Port`` and ``X-Forwarded-Prefix``.
.. versionchanged:: 0.15
``X-Forwarded-Host`` and ``X-Forwarded-Port`` modify
``SERVER_NAME`` and ``SERVER_PORT``.
"""
def __init__(self, app, x_for=1, x_proto=1, x_host=0, x_port=0, x_prefix=0):
self.app = app
self.x_for = x_for
self.x_proto = x_proto
self.x_host = x_host
self.x_port = x_port
self.x_prefix = x_prefix
def _get_real_value(self, trusted, value):
"""Get the real value from a list header based on the configured
number of trusted proxies.
:param trusted: Number of values to trust in the header.
:param value: Comma separated list header value to parse.
:return: The real value, or ``None`` if there are fewer values
than the number of trusted proxies.
.. versionchanged:: 1.0
Renamed from ``_get_trusted_comma``.
.. versionadded:: 0.15
"""
if not (trusted and value):
return
values = parse_list_header(value)
if len(values) >= trusted:
return values[-trusted]
def __call__(self, environ, start_response):
"""Modify the WSGI environ based on the various ``Forwarded``
headers before calling the wrapped application. Store the
original environ values in ``werkzeug.proxy_fix.orig_{key}``.
"""
environ_get = environ.get
orig_remote_addr = environ_get("REMOTE_ADDR")
orig_wsgi_url_scheme = environ_get("wsgi.url_scheme")
orig_http_host = environ_get("HTTP_HOST")
environ.update(
{
"werkzeug.proxy_fix.orig": {
"REMOTE_ADDR": orig_remote_addr,
"wsgi.url_scheme": orig_wsgi_url_scheme,
"HTTP_HOST": orig_http_host,
"SERVER_NAME": environ_get("SERVER_NAME"),
"SERVER_PORT": environ_get("SERVER_PORT"),
"SCRIPT_NAME": environ_get("SCRIPT_NAME"),
}
}
)
x_for = self._get_real_value(self.x_for, environ_get("HTTP_X_FORWARDED_FOR"))
if x_for:
environ["REMOTE_ADDR"] = x_for
x_proto = self._get_real_value(
self.x_proto, environ_get("HTTP_X_FORWARDED_PROTO")
)
if x_proto:
environ["wsgi.url_scheme"] = x_proto
x_host = self._get_real_value(self.x_host, environ_get("HTTP_X_FORWARDED_HOST"))
if x_host:
environ["HTTP_HOST"] = x_host
parts = x_host.split(":", 1)
environ["SERVER_NAME"] = parts[0]
if len(parts) == 2:
environ["SERVER_PORT"] = parts[1]
x_port = self._get_real_value(self.x_port, environ_get("HTTP_X_FORWARDED_PORT"))
if x_port:
host = environ.get("HTTP_HOST")
if host:
parts = host.split(":", 1)
host = parts[0] if len(parts) == 2 else host
environ["HTTP_HOST"] = "%s:%s" % (host, x_port)
environ["SERVER_PORT"] = x_port
x_prefix = self._get_real_value(
self.x_prefix, environ_get("HTTP_X_FORWARDED_PREFIX")
)
if x_prefix:
environ["SCRIPT_NAME"] = x_prefix
return self.app(environ, start_response)