Flask-CORS

A Flask extension for handling Cross Origin Resource Sharing (CORS), making cross-origin AJAX possible.

This package has a simple philosophy: when you want to enable CORS, you wish to enable it for all use cases on a domain. This means no mucking around with different allowed headers, methods, etc.

By default, submission of cookies across domains is disabled due to the security implications. Please see the documentation for how to enable credential'ed requests, and please make sure you add some sort of CSRF protection before doing so!

Installation

Install the extension with using pip, or easy_install.

``` {.sourceCode .bash} $ pip install -U flask-cors

Usage
-----

This package exposes a Flask extension which by default enables CORS
support on all routes, for all origins and methods. It allows
parameterization of all CORS headers on a per-resource level. The
package also contains a decorator, for those who prefer this approach.

### Simple Usage

In the simplest case, initialize the Flask-Cors extension with default
arguments in order to allow CORS for all domains on all routes. See the
full list of options in the
[documentation](https://flask-cors.corydolphin.com/en/latest/api.html#extension).


``` {.sourceCode .python}
from flask import Flask
from flask_cors import CORS

app = Flask(__name__)
CORS(app)

@app.route("/")
def helloWorld():
  return "Hello, cross-origin-world!"

Resource specific CORS

Alternatively, you can specify CORS options on a resource and origin level of granularity by passing a dictionary as the [resources]{.title-ref} option, mapping paths to a set of options. See the full list of options in the documentation.

``` {.sourceCode .python} app = Flask(name) cors = CORS(app, resources={r”/api/”: {“origins”: “”}})

@app.route(“/api/v1/users”) def list_users(): return “user example”

#### Route specific CORS via decorator

This extension also exposes a simple decorator to decorate flask routes
with. Simply add `@cross_origin()` below a call to Flask\'s
`@app.route(..)` to allow CORS on a given route. See the full list of
options in the [decorator
documentation](https://flask-cors.corydolphin.com/en/latest/api.html#decorator).


``` {.sourceCode .python}
@app.route("/")
@cross_origin()
def helloWorld():
  return "Hello, cross-origin-world!"

Documentation

For a full list of options, please see the full documentation

Troubleshooting

If things aren't working as you expect, enable logging to help understand what is going on under the hood, and why.

``` {.sourceCode .python} logging.getLogger(‘flask_cors’).level = logging.DEBUG

```

Tests

A simple set of tests is included in test/. To run, install nose, and simply invoke nosetests or python setup.py test to exercise the tests.

If nosetests does not work for you, due to it no longer working with newer python versions. You can use pytest to run the tests instead.

Contributing

Questions, comments or improvements? Please create an issue on Github, tweet at \@corydolphin or send me an email. I do my best to include every contribution proposed in any way that I can.

Credits

This Flask extension is based upon the Decorator for the HTTP Access Control written by Armin Ronacher.

Change Log

3.1.01

• Include examples to specify that schema and port must be included in … by @YPCrumble in https://github.com/corydolphin/flask-cors/pull/294
• two small changes to the documentation, based on issue #290 by @bbbart in https://github.com/corydolphin/flask-cors/pull/291
• Fix typo by @sunarch in https://github.com/corydolphin/flask-cors/pull/304
• FIX: typo in CSRF by @sattamjh in https://github.com/corydolphin/flask-cors/pull/315
• Test against recent Python versions by @pylipp in https://github.com/corydolphin/flask-cors/pull/314
• Correct spelling mistakes by @EdwardBetts in https://github.com/corydolphin/flask-cors/pull/311
• ‘Access-Control-Allow-Private-Network = true’ header for http response by @chelo-kjml in https://github.com/corydolphin/flask-cors/pull/318
• docs: Fix a few typos by @timgates42 in https://github.com/corydolphin/flask-cors/pull/323
• [Docs] Fix typo in configuration documentation by @sachit-shroff in https://github.com/corydolphin/flask-cors/pull/316

3.0.10

Adds support for PPC64 and ARM64 builds for distribution. Thanks @sreekanth370

3.0.9

Security

• Escape path before evaluating resource rules (thanks to Colby Morgan). Prior to this, flask-cors incorrectly evaluated CORS resource matching before path expansion. E.g. “/api/../foo.txt” would incorrectly match resources for “/api/*” whereas the path actually expands simply to “/foo.txt”

3.0.8

Fixes : DeprecationWarning: Using or importing the ABCs from ‘collections’ in Python 3.7. Thank you @juanmaneo and @jdevera for the contribution.

3.0.7

Updated logging.warn to logging.warning (#234) Thanks Vaibhav

3.0.6

Manual error in release process. Identical contents at 3.0.5.

3.0.5

Fixes incorrect handling of regexes containing [, and a few other special characters. Fixes Issue #212

3.0.4

Handle response.headers being None. (Fixes issue #217)

3.0.3

Ensure that an Origin of ‘*’ is never sent if supports_credentials is True (fixes Issue #202)

• If always_send=True, and '*' is in the allowed origins, and a request is made without an Origin header, no Access-Control-Allow-Origins header will now be returned. This is breaking if you depended on it, but was a bug as it goes against the spec.

3.0.2

Fixes Issue #187: regression whereby header (and domain) matching was incorrectly case sensitive. Now it is not, making the behavior identical to 2.X and 1.X.

3.0.1

Fixes Issue #183: regression whereby regular expressions for origins with an “?” are not properly matched.

3.0.0

This release is largely a number of small bug fixes and improvements, along with a default change in behavior, which is technically a breaking change.

Breaking Change We added an always_send option, enabled by default, which makes Flask-CORS inject headers even if the request did not have an ‘Origin’ header. Because this makes debugging far easier, and has very little downside, it has also been set as the default, making it technically a breaking change. If this actually broke something for you, please let me know, and I’ll help you work around it. (#156) c7a1ecdad375a796155da6aca6a1f750337175f3

Other improvements:

• Adds building of universal wheels (#175) 4674c3d54260f8897bd18e5502509363dcd0d0da
• Makes Flask-CORS compatible with OAuthLib’s custom header class … (#172) aaaf904845997a3b684bc6677bdfc91656a85a04
• Fixes incorrect substring matches when strings are used as origins or headers (#165) 9cd3f295bd6b0ba87cc5f2afaca01b91ff43e72c
• Fixes logging when unknown options are supplied (#152) bddb13ca6636c5d559ec67a95309c9607a3fcaba

2.1.3

Fixes Vary:Origin header sending behavior when regex origins are used.

2.1.2

Fixes package installation. Requirements.txt was not included in Manifest.

2.1.1

Stop dynamically referecing logger.

Disable internal logging by default and reduce logging verbosity

2.1.0

Adds support for Flask Blueprints.

2.0.1

Fixes Issue #124 where only the first of multiple headers with the same name would be passed through.

2.0.0

New Defaults

1. New defaults allow all origins, all headers.

Breaking Changes

1. Removed always_send option.
2. Removed ‘headers’ option as a backwards-compatible alias for ‘allowed_headers’ to reduce confusion.

2.0.0rc1

Would love to get some feedback to make sure there are no unexpected regressions. This should be backwards compatible for most people.

Update default options and parameters in a backwards incompatible way.

By default, all headers are now allowed, and only requests with an Origin header have CORS headers returned. If an Origin header is not present, no CORS headers are returned.

Removed the following options: always_send, headers.

Extension and decorator are now in separate modules sharing a core module. Test have been moved into the respective tests.extension and tests.decorator modules. More work to decompose these tests is needed.

1.10.3

Release Version 1.10.3

• Adds logging to Flask-Cors so it is easy to see what is going on and why
• Adds support for compiled regexes as origins

Big thanks to @michalbachowski and @digitizdat!

1.10.2

This release fixes the behavior of Access-Control-Allow-Headers and Access-Control-Expose-Headers, which was previously swapped since 1.9.0.

To further fix the confusion, the headers parameter was renamed to more explicitly be allow_headers.

Thanks @maximium for the bug report and implementation!

1.10.1

This is a bug fix release, fixing: Incorrect handling of resources and intercept_exceptions App Config options https://github.com/wcdolphin/flask-cors/issues/84 Issue with functools.partial in 1.10.0 using Python 2.7.9 https://github.com/wcdolphin/flask-cors/issues/83

Shoutout to @diiq and @joonathan for reporting these issues!

1.10.0

• Adds support for returning CORS headers with uncaught exceptions in production so 500s will have expected CORS headers set. This will allow clients to better surface the errors, rather than failing due to security. Reported and tested by @robertfw – thanks!
• Improved conformance of preflight request handling to W3C spec.
• Code simplification and 100% test coverage :sunglasses:

1.9.0

• Improves API consistency, allowing a CORS resource of ‘*’
• Improves documentation of the CORS app extension
• Fixes test import errors on Python 3.4.1 (Thanks @wking )

1.8.1

Thanks to @wking’s work in PR https://github.com/wcdolphin/flask-cors/pull/71 python setup.py test will now work.

v1.8.0

Adds support for regular expressions in the list of origins.

This allows subdomain wildcarding and should be fully backwards compatible.

Credit to @marcoqu for opening https://github.com/wcdolphin/flask-cors/issues/54 which inspired this work

Earlier

Prior version numbers were not kept track of in this system.