Origin: backport, commit:27cd872e6e36a81d0bb6f5b8765a1705fecfc253
Description: Added ALLOWED_HOSTS setting for HTTP host header validation.
Bug-Debian: http://bugs.debian.org/701186

--- a/django/conf/global_settings.py
+++ b/django/conf/global_settings.py
@@ -29,6 +29,10 @@ ADMINS = ()
 #   * Receive x-headers
 INTERNAL_IPS = ()
 
+# Hosts/domain names that are valid for this site.
+# "*" matches anything, ".example.com" matches example.com and all subdomains
+ALLOWED_HOSTS = ['*']
+
 # Local time zone for this installation. All choices can be found here:
 # http://en.wikipedia.org/wiki/List_of_tz_zones_by_name (although not all
 # systems may support all possibilities).
--- a/django/conf/project_template/settings.py
+++ b/django/conf/project_template/settings.py
@@ -20,6 +20,10 @@ DATABASES = {
     }
 }
 
+# Hosts/domain names that are valid for this site; required if DEBUG is False
+# See https://docs.djangoproject.com/en/{{ docs_version }}/ref/settings/#allowed-hosts
+ALLOWED_HOSTS = []
+
 # Local time zone for this installation. Choices can be found here:
 # http://en.wikipedia.org/wiki/List_of_tz_zones_by_name
 # although not all choices may be available on all operating systems.
--- a/django/http/__init__.py
+++ b/django/http/__init__.py
@@ -60,11 +60,15 @@ class HttpRequest(object):
             if server_port != (self.is_secure() and '443' or '80'):
                 host = '%s:%s' % (host, server_port)
 
-        # Disallow potentially poisoned hostnames.
-        if not host_validation_re.match(host.lower()):
-            raise SuspiciousOperation('Invalid HTTP_HOST header: %s' % host)
-
-        return host
+        if settings.DEBUG:
+            allowed_hosts = ['*']
+        else:
+            allowed_hosts = settings.ALLOWED_HOSTS
+        if validate_host(host, allowed_hosts):
+            return host
+        else:
+            raise SuspiciousOperation(
+                "Invalid HTTP_HOST header (you may need to set ALLOWED_HOSTS): %s" % host)
 
     def get_full_path(self):
         return ''
@@ -505,3 +509,43 @@ def str_to_unicode(s, encoding):
     else:
         return s
 
+def validate_host(host, allowed_hosts):
+    """
+    Validate the given host header value for this site.
+
+    Check that the host looks valid and matches a host or host pattern in the
+    given list of ``allowed_hosts``. Any pattern beginning with a period
+    matches a domain and all its subdomains (e.g. ``.example.com`` matches
+    ``example.com`` and any subdomain), ``*`` matches anything, and anything
+    else must match exactly.
+
+    Return ``True`` for a valid host, ``False`` otherwise.
+
+    """
+    # All validation is case-insensitive
+    host = host.lower()
+
+    # Basic sanity check
+    if not host_validation_re.match(host):
+        return False
+
+    # Validate only the domain part.
+    if host[-1] == ']':
+        # It's an IPv6 address without a port.
+        domain = host
+    else:
+        domain = host.rsplit(':', 1)[0]
+
+    for pattern in allowed_hosts:
+        pattern = pattern.lower()
+        match = (
+            pattern == '*' or
+            pattern.startswith('.') and (
+                domain.endswith(pattern) or domain == pattern[1:]
+                ) or
+            pattern == domain
+            )
+        if match:
+            return True
+
+    return False
--- a/django/test/utils.py
+++ b/django/test/utils.py
@@ -62,6 +62,9 @@ def setup_test_environment():
     mail.original_email_backend = settings.EMAIL_BACKEND
     settings.EMAIL_BACKEND = 'django.core.mail.backends.locmem.EmailBackend'
 
+    settings._original_allowed_hosts = settings.ALLOWED_HOSTS
+    settings.ALLOWED_HOSTS = ['*']
+
     mail.outbox = []
 
     deactivate()
@@ -82,6 +85,9 @@ def teardown_test_environment():
     settings.EMAIL_BACKEND = mail.original_email_backend
     del mail.original_email_backend
 
+    settings.ALLOWED_HOSTS = settings._original_allowed_hosts
+    del settings._original_allowed_hosts
+
     del mail.outbox
 
 def get_runner(settings):
--- a/docs/ref/settings.txt
+++ b/docs/ref/settings.txt
@@ -74,6 +74,42 @@ of (Full name, e-mail address). Example:
 Note that Django will e-mail *all* of these people whenever an error happens.
 See :doc:`/howto/error-reporting` for more information.
 
+.. setting:: ALLOWED_HOSTS
+
+ALLOWED_HOSTS
+-------------
+
+Default: ``['*']``
+
+A list of strings representing the host/domain names that this Django site can
+serve. This is a security measure to prevent an attacker from poisoning caches
+and password reset emails with links to malicious hosts by submitting requests
+with a fake HTTP ``Host`` header, which is possible even under many
+seemingly-safe webserver configurations.
+
+Values in this list can be fully qualified names (e.g. ``'www.example.com'``),
+in which case they will be matched against the request's ``Host`` header
+exactly (case-insensitive, not including port). A value beginning with a period
+can be used as a subdomain wildcard: ``'.example.com'`` will match
+``example.com``, ``www.example.com``, and any other subdomain of
+``example.com``. A value of ``'*'`` will match anything; in this case you are
+responsible to provide your own validation of the ``Host`` header (perhaps in a
+middleware; if so this middleware must be listed first in
+:setting:`MIDDLEWARE_CLASSES`).
+
+If the ``Host`` header (or ``X-Forwarded-Host`` if
+:setting:`USE_X_FORWARDED_HOST` is enabled) does not match any value in this
+list, the :meth:`django.http.HttpRequest.get_host()` method will raise
+:exc:`~django.core.exceptions.SuspiciousOperation`.
+
+When :setting:`DEBUG` is ``True`` or when running tests, host validation is
+disabled; any host will be accepted. Thus it's usually only necessary to set it
+in production.
+
+This validation only applies via :meth:`~django.http.HttpRequest.get_host()`;
+if your code accesses the ``Host`` header directly from ``request.META`` you
+are bypassing this security protection.
+
 .. setting:: ALLOWED_INCLUDE_ROOTS
 
 ALLOWED_INCLUDE_ROOTS