A Django App that adds CORS (Cross-Origin Resource Sharing) headers to responses.
Although JSON-P is useful, it is strictly limited to GET requests. CORS
builds on top of XmlHttpRequest to allow developers to make cross-domain
requests, similar to same-domain requests. Read more about it here:
http://www.html5rocks.com/en/tutorials/cors/
Tested with all combinations of:
- Python: 2.7, 3.6
- Django: 1.11, 2.0, 2.1
Install from pip:
pip install django-cors-headersand then add it to your installed apps:
INSTALLED_APPS = (
...
'corsheaders',
...
)You will also need to add a middleware class to listen in on responses:
MIDDLEWARE = [ # Or MIDDLEWARE_CLASSES on Django < 1.10
...
'corsheaders.middleware.CorsMiddleware',
'django.middleware.common.CommonMiddleware',
...
]CorsMiddleware should be placed as high as possible, especially before any
middleware that can generate responses such as Django's CommonMiddleware or
Whitenoise's WhiteNoiseMiddleware. If it is not before, it will not be able
to add the CORS headers to these responses.
Also if you are using CORS_REPLACE_HTTPS_REFERER it should be placed before
Django's CsrfViewMiddleware (see more below).
Configure the middleware's behaviour in your Django settings. You must add the
hosts that are allowed to do cross-site requests to
CORS_ORIGIN_WHITELIST, or set CORS_ORIGIN_ALLOW_ALL to True
to allow all hosts.
If True, the whitelist will not be used and all origins will be accepted.
Defaults to False.
A list of origin hostnames that are authorized to make cross-site HTTP
requests. The value 'null' can also appear in this list, and will match the
Origin: null header that is used in "privacy-sensitive contexts", such as when the client is
running from a file:// domain. Defaults to [].
Example:
CORS_ORIGIN_WHITELIST = (
'google.com',
'hostname.example.com',
'localhost:8000',
'127.0.0.1:9000'
)A list of regexes that match origin regex list of origin hostnames that are
authorized to make cross-site HTTP requests. Defaults to []. Useful when
CORS_ORIGIN_WHITELIST is impractical, such as when you have a large
number of subdomains.
Example:
CORS_ORIGIN_REGEX_WHITELIST = (r'^(https?://)?(\w+\.)?google\.com$', )The following are optional settings, for which the defaults probably suffice.
A regex which restricts the URL's for which the CORS headers will be sent.
Defaults to r'^.*$', i.e. match all URL's. Useful when you only need CORS
on a part of your site, e.g. an API at /api/.
Example:
CORS_URLS_REGEX = r'^/api/.*$'A list of HTTP verbs that are allowed for the actual request. Defaults to:
CORS_ALLOW_METHODS = (
'DELETE',
'GET',
'OPTIONS',
'PATCH',
'POST',
'PUT',
)The default can be imported as corsheaders.defaults.default_methods so you
can just extend it with your custom methods. This allows you to keep up to date
with any future changes. For example:
from corsheaders.defaults import default_methods
CORS_ALLOW_METHODS = default_methods + (
'POKE',
)The list of non-standard HTTP headers that can be used when making the actual request. Defaults to:
CORS_ALLOW_HEADERS = (
'accept',
'accept-encoding',
'authorization',
'content-type',
'dnt',
'origin',
'user-agent',
'x-csrftoken',
'x-requested-with',
)The default can be imported as corsheaders.defaults.default_headers so you
can extend it with your custom headers. This allows you to keep up to date with
any future changes. For example:
from corsheaders.defaults import default_headers
CORS_ALLOW_HEADERS = default_headers + (
'my-custom-header',
)The list of HTTP headers that are to be exposed to the browser. Defaults to
[].
The number of seconds a client/browser can cache the preflight response. If
this is 0 (or any falsey value), no max age header will be sent. Defaults to
86400 (one day).
Note: A preflight request is an extra request that is made when making a
"not-so-simple" request (e.g. Content-Type is not
application/x-www-form-urlencoded) to determine what requests the server
actually accepts. Read more about it in the HTML 5 Rocks CORS tutorial.
If True, cookies will be allowed to be included in cross-site HTTP
requests. Defaults to False.
If set, this should be the path to a model to look up allowed origins, in the
form app.modelname. Defaults to None.
The model should inherit from corsheaders.models.AbstractCorsModel and specify
the allowed origin in the CharField called cors.
Most sites will need to take advantage of the Cross-Site Request Forgery
protection that Django
offers. CORS and CSRF are separate, and Django has no way of using your CORS
configuration to exempt sites from the Referer checking that it does on
secure requests. The way to do that is with its CSRF_TRUSTED_ORIGINS setting.
For example:
CORS_ORIGIN_WHITELIST = (
'read.only.com',
'change.allowed.com',
)
CSRF_TRUSTED_ORIGINS = (
'change.allowed.com',
)CSRF_TRUSTED_ORIGINS was introduced in Django 1.9, so users of earlier
versions will need an alternate solution. If CORS_REPLACE_HTTPS_REFERER is
True, CorsMiddleware will change the Referer header to something
that will pass Django's CSRF checks whenever the CORS checks pass. Defaults to
False.
Note that unlike CSRF_TRUSTED_ORIGINS, this setting does not allow you to
distinguish between domains that are trusted to read resources by CORS and
domains that are trusted to change resources by avoiding CSRF protection.
With this feature enabled you should also add
corsheaders.middleware.CorsPostCsrfMiddleware after
django.middleware.csrf.CsrfViewMiddleware in your MIDDLEWARE_CLASSES to
undo the Referer replacement:
MIDDLEWARE_CLASSES = [
...
'corsheaders.middleware.CorsMiddleware',
...
'django.middleware.csrf.CsrfViewMiddleware',
'corsheaders.middleware.CorsPostCsrfMiddleware',
...
]If you have a use case that requires more than just the above configuration,
you can attach code to check if a given request should be allowed. For example,
this can be used to read the list of origins you allow from a model. Attach any
number of handlers to the check_request_enabled
Django signal, which
provides the request argument (use **kwargs in your handler to protect
against any future arguments being added). If any handler attached to the
signal returns a truthy value, the request will be allowed.
For example you might define a handler like this:
# myapp/handlers.py
from corsheaders.signals import check_request_enabled
from .models import MySite
def cors_allow_mysites(sender, request, **kwargs):
return MySite.objects.filter(host=request.host).exists()
check_request_enabled.connect(cors_allow_mysites)Then connect it at app ready time using a Django AppConfig:
# myapp/__init__.py
default_app_config = 'myapp.apps.MyAppConfig'# myapp/apps.py
from django.apps import AppConfig
class MyAppConfig(AppConfig):
name = 'myapp'
def ready(self):
# Makes sure all signal handlers are connected
from . import handlers # noqaA common use case for the signal is to allow all origins to access a subset of URL's, whilst allowing a normal set of origins to access all URL's. This isn't possible using just the normal configuration, but it can be achieved with a signal handler.
First set CORS_ORIGIN_WHITELIST to the list of trusted origins that are
allowed to access every URL, and then add a handler to
check_request_enabled to allow CORS regardless of the origin for the
unrestricted URL's. For example:
# myapp/handlers.py
from corsheaders.signals import check_request_enabled
def cors_allow_api_to_everyone(sender, request, **kwargs):
return request.path.startswith('/api/')
check_request_enabled.connect(cors_allow_api_to_everyone)django-cors-headers was created by Otto Yiu (@ottoyiu) and has been worked on by 25+ contributors.
Thanks to every contributor, and if you want to get involved please don't
hesitate to make a pull request.