django/middleware/common.py
import re
from urllib.parse import urlparse
from django.conf import settings
from django.core.exceptions import PermissionDenied
from django.core.mail import mail_managers
from django.http import HttpResponsePermanentRedirect
from django.urls import is_valid_path
from django.utils.deprecation import MiddlewareMixin
from django.utils.http import escape_leading_slashes
class CommonMiddleware(MiddlewareMixin):
"""
"Common" middleware for taking care of some basic operations:
- Forbid access to User-Agents in settings.DISALLOWED_USER_AGENTS
- URL rewriting: Based on the APPEND_SLASH and PREPEND_WWW settings,
append missing slashes and/or prepends missing "www."s.
- If APPEND_SLASH is set and the initial URL doesn't end with a
slash, and it is not found in urlpatterns, form a new URL by
appending a slash at the end. If this new URL is found in
urlpatterns, return an HTTP redirect to this new URL; otherwise
process the initial URL as usual.
This behavior can be customized by subclassing CommonMiddleware and
overriding the response_redirect_class attribute.
"""
response_redirect_class = HttpResponsePermanentRedirect
def process_request(self, request):
"""
Check for denied User-Agents and rewrite the URL based on
settings.APPEND_SLASH and settings.PREPEND_WWW
"""
# Check for denied User-Agents
user_agent = request.META.get("HTTP_USER_AGENT")
if user_agent is not None:
for user_agent_regex in settings.DISALLOWED_USER_AGENTS:
if user_agent_regex.search(user_agent):
raise PermissionDenied("Forbidden user agent")
# Check for a redirect based on settings.PREPEND_WWW
host = request.get_host()
if settings.PREPEND_WWW and host and not host.startswith("www."):
# Check if we also need to append a slash so we can do it all
# with a single redirect. (This check may be somewhat expensive,
# so we only do it if we already know we're sending a redirect,
# or in process_response if we get a 404.)
if self.should_redirect_with_slash(request):
path = self.get_full_path_with_slash(request)
else:
path = request.get_full_path()
return self.response_redirect_class(f"{request.scheme}://www.{host}{path}")
def should_redirect_with_slash(self, request):
"""
Return True if settings.APPEND_SLASH is True and appending a slash to
the request path turns an invalid path into a valid one.
"""
if settings.APPEND_SLASH and not request.path_info.endswith("/"):
urlconf = getattr(request, "urlconf", None)
if not is_valid_path(request.path_info, urlconf):
match = is_valid_path("%s/" % request.path_info, urlconf)
if match:
view = match.func
return getattr(view, "should_append_slash", True)
return False
def get_full_path_with_slash(self, request):
"""
Return the full path of the request with a trailing slash appended.
Raise a RuntimeError if settings.DEBUG is True and request.method is
DELETE, POST, PUT, or PATCH.
"""
new_path = request.get_full_path(force_append_slash=True)
# Prevent construction of scheme relative urls.
new_path = escape_leading_slashes(new_path)
if settings.DEBUG and request.method in ("DELETE", "POST", "PUT", "PATCH"):
raise RuntimeError(
"You called this URL via %(method)s, but the URL doesn't end "
"in a slash and you have APPEND_SLASH set. Django can't "
"redirect to the slash URL while maintaining %(method)s data. "
"Change your form to point to %(url)s (note the trailing "
"slash), or set APPEND_SLASH=False in your Django settings."
% {
"method": request.method,
"url": request.get_host() + new_path,
}
)
return new_path
def process_response(self, request, response):
"""
When the status code of the response is 404, it may redirect to a path
with an appended slash if should_redirect_with_slash() returns True.
"""
# If the given URL is "Not Found", then check if we should redirect to
# a path with a slash appended.
if response.status_code == 404 and self.should_redirect_with_slash(request):
return self.response_redirect_class(self.get_full_path_with_slash(request))
# Add the Content-Length header to non-streaming responses if not
# already set.
if not response.streaming and not response.has_header("Content-Length"):
response.headers["Content-Length"] = str(len(response.content))
return response
class BrokenLinkEmailsMiddleware(MiddlewareMixin):
def process_response(self, request, response):
"""Send broken link emails for relevant 404 NOT FOUND responses."""
if response.status_code == 404 and not settings.DEBUG:
domain = request.get_host()
path = request.get_full_path()
referer = request.META.get("HTTP_REFERER", "")
if not self.is_ignorable_request(request, path, domain, referer):
ua = request.META.get("HTTP_USER_AGENT", "<none>")
ip = request.META.get("REMOTE_ADDR", "<none>")
mail_managers(
"Broken %slink on %s"
% (
(
"INTERNAL "
if self.is_internal_request(domain, referer)
else ""
),
domain,
),
"Referrer: %s\nRequested URL: %s\nUser agent: %s\n"
"IP address: %s\n" % (referer, path, ua, ip),
fail_silently=True,
)
return response
def is_internal_request(self, domain, referer):
"""
Return True if the referring URL is the same domain as the current
request.
"""
# Different subdomains are treated as different domains.
return bool(re.match("^https?://%s/" % re.escape(domain), referer))
def is_ignorable_request(self, request, uri, domain, referer):
"""
Return True if the given request *shouldn't* notify the site managers
according to project settings or in situations outlined by the inline
comments.
"""
# The referer is empty.
if not referer:
return True
# APPEND_SLASH is enabled and the referer is equal to the current URL
# without a trailing slash indicating an internal redirect.
if settings.APPEND_SLASH and uri.endswith("/") and referer == uri[:-1]:
return True
# A '?' in referer is identified as a search engine source.
if not self.is_internal_request(domain, referer) and "?" in referer:
return True
# The referer is equal to the current URL, ignoring the scheme (assumed
# to be a poorly implemented bot).
parsed_referer = urlparse(referer)
if parsed_referer.netloc in ["", domain] and parsed_referer.path == uri:
return True
return any(pattern.search(uri) for pattern in settings.IGNORABLE_404_URLS)