import re
from django.conf import settings
from django import http
from django.core.mail import mail_managers
from django.utils.http import urlquote
from django.core import urlresolvers
from django.utils.hashcompat import md5_constructor
class CommonMiddleware(object):
"""
"Common" middleware for taking care of some basic operations:
- Forbids access to User-Agents in settings.DISALLOWED_USER_AGENTS
- URL rewriting: Based on the APPEND_SLASH and PREPEND_WWW settings,
this middleware appends 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, a new URL is formed by
appending a slash at the end. If this new URL is found in
urlpatterns, then an HTTP-redirect is returned to this new URL;
otherwise the initial URL is processed as usual.
- ETags: If the USE_ETAGS setting is set, ETags will be calculated from
the entire page content and Not Modified responses will be returned
appropriately.
"""
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
if 'HTTP_USER_AGENT' in request.META:
for user_agent_regex in settings.DISALLOWED_USER_AGENTS:
if user_agent_regex.search(request.META['HTTP_USER_AGENT']):
return http.HttpResponseForbidden('<h1>Forbidden</h1>')
# Check for a redirect based on settings.APPEND_SLASH
# and settings.PREPEND_WWW
host = request.get_host()
old_url = [host, request.path]
new_url = old_url[:]
if (settings.PREPEND_WWW and old_url[0] and
not old_url[0].startswith('www.')):
new_url[0] = 'www.' + old_url[0]
# Append a slash if APPEND_SLASH is set and the URL doesn't have a
# trailing slash and there is no pattern for the current path
if settings.APPEND_SLASH and (not old_url[1].endswith('/')):
urlconf = getattr(request, 'urlconf', None)
if (not _is_valid_path(request.path_info, urlconf) and
_is_valid_path("%s/" % request.path_info, urlconf)):
new_url[1] = new_url[1] + '/'
if settings.DEBUG and request.method == 'POST':
raise RuntimeError, (""
"You called this URL via POST, 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 POST data. "
"Change your form to point to %s%s (note the trailing "
"slash), or set APPEND_SLASH=False in your Django "
"settings.") % (new_url[0], new_url[1])
if new_url == old_url:
# No redirects required.
return
if new_url[0]:
newurl = "%s://%s%s" % (
request.is_secure() and 'https' or 'http',
new_url[0], urlquote(new_url[1]))
else:
newurl = urlquote(new_url[1])
if request.GET:
newurl += '?' + request.META['QUERY_STRING']
return http.HttpResponsePermanentRedirect(newurl)
def process_response(self, request, response):
"Check for a flat page (for 404s) and calculate the Etag, if needed."
if response.status_code == 404:
if settings.SEND_BROKEN_LINK_EMAILS:
# If the referrer was from an internal link or a non-search-engine site,
# send a note to the managers.
domain = request.get_host()
referer = request.META.get('HTTP_REFERER', None)
is_internal = _is_internal_request(domain, referer)
path = request.get_full_path()
if referer and not _is_ignorable_404(path) and (is_internal or '?' not in referer):
ua = request.META.get('HTTP_USER_AGENT', '<none>')
ip = request.META.get('REMOTE_ADDR', '<none>')
mail_managers("Broken %slink on %s" % ((is_internal and 'INTERNAL ' or ''), domain),
"Referrer: %s\nRequested URL: %s\nUser agent: %s\nIP address: %s\n" \
% (referer, request.get_full_path(), ua, ip))
return response
# Use ETags, if requested.
if settings.USE_ETAGS:
if response.has_header('ETag'):
etag = response['ETag']
else:
etag = '"%s"' % md5_constructor(response.content).hexdigest()
if response.status_code >= 200 and response.status_code < 300 and request.META.get('HTTP_IF_NONE_MATCH') == etag:
cookies = response.cookies
response = http.HttpResponseNotModified()
response.cookies = cookies
else:
response['ETag'] = etag
return response
def _is_ignorable_404(uri):
"""
Returns True if a 404 at the given URL *shouldn't* notify the site managers.
"""
for start in settings.IGNORABLE_404_STARTS:
if uri.startswith(start):
return True
for end in settings.IGNORABLE_404_ENDS:
if uri.endswith(end):
return True
return False
def _is_internal_request(domain, referer):
"""
Returns true if the referring URL is the same domain as the current request.
"""
# Different subdomains are treated as different domains.
return referer is not None and re.match("^https?://%s/" % re.escape(domain), referer)
def _is_valid_path(path, urlconf=None):
"""
Returns True if the given path resolves against the default URL resolver,
False otherwise.
This is a convenience method to make working with "is this a match?" cases
easier, avoiding unnecessarily indented try...except blocks.
"""
try:
urlresolvers.resolve(path, urlconf)
return True
except urlresolvers.Resolver404:
return False
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