Flask Azure AD OAuth Provider

Python Flask extension for using Azure Active Directory with OAuth to protect applications

Purpose

This provider defines an AuthLib Resource Protector to authenticate and authorise users and other applications to access features or resources within a Flask application using the OAuth functionality provided by Azure Active Directory as part of the Microsoft identity platform.

This provider depends on Azure Active Directory, acting as a identity provider, to issue OAuth access tokens which contain the identity of a user or application and any permissions they have been assigned through the Azure Portal and management APIs. These permissions are declared in Azure Active Directory application registrations.

This provider enables Flask applications, acting as service providers, to validate access tokens to check the identity of the user or application (authentication), and the permissions required to access the Flask route being accessed.

Specifically this provider supports these scenarios:

application to application
- supports authentication and authorisation
- used to allow a client application access to some functionality or resources in another application
- can be used to allow background tasks between applications where a user is not routinely involved (e.g. a nightly data synchronisation)
- uses the identity of the application acting as a client for authentication
- uses the permissions assigned to the application acting as a client for authorisation
- based on the Client Credentials OAuth2 grant type
- Azure documentation

Other scenarios may be added in future versions of this provider.

Installation

This package can be installed using Pip from PyPi:

$ pip install flask-azure-oauth

Usage

This provider provides an AuthLib Resource Protector which can be used as a decorator on Flask routes.

A minimal application would look like this:

from flask import Flask

from flask_azure_oauth import FlaskAzureOauth

app = Flask(__name__)

app.config['AZURE_OAUTH_TENANCY'] = 'xxx'
app.config['AZURE_OAUTH_APPLICATION_ID'] = 'xxx'
app.config['AZURE_OAUTH_CLIENT_APPLICATION_IDS'] = ['xxx']

auth = FlaskAzureOauth()
auth.init_app(app=app)

@app.route('/unprotected')
def unprotected():
    return 'hello world'

@app.route('/protected')
@auth()
def protected():
    return 'hello authenticated entity'

@app.route('/protected-with-single-scope')
@auth('required-scope')
def protected_with_scope():
    return 'hello authenticated and authorised entity'

@app.route('/protected-with-multiple-scopes')
@auth('required-scope1 required-scope2')
def protected_with_multiple_scopes():
    return 'hello authenticated and authorised entity'

When the decorator (auth in this example) is used by itself any authenticated user or application will be able to access the decorated route. See the /protected route above for an example.

To require one or more Scopes, add them to the decorator call. Only users or applications with all of the scopes specified will be able to access the decorated route. See the /protected-with-single-scope and /protected-with-multiple-scopes routes above for examples.

Configuration options

The resource protector requires some configuration options to validate tokens correctly. These are read from the config object of a Flask application using the init_app() method.

Before these options can be set you will need to:

register the application to be protected
define the permissions this application supports
register the application(s) that will granted these permissions
assign permissions to this/these application(s)

Configuration Option	Data Type	Required	Description
`AZURE_OAUTH_TENANCY`	Str	Yes	ID of the Azure AD tenancy all applications and users are registered within
`AZURE_OAUTH_APPLICATION_ID`	Str	Yes	ID of the Azure AD application registration for the application being protected
`AZURE_OAUTH_CLIENT_APPLICATION_IDS`	List[Str]	Yes	ID(s) of the Azure AD application registration(s) for the application(s) granted access to the application being protected

Testing support

When a Flask application is in testing mode (i.e. app.config['TESTING']=True), this provider will generate a local JSON Web Key Set, containing a single key, which can be used to sign tokens with arbitrary scopes.

This can be used to test routes that require a scope or scopes, by allowing tokens to be generated with or without required scopes to test both authorised and unauthorised responses.

Typically the instance of this provider will be defined outside of an application, and therefore persist between application instances and tests. To prevent issues where signing keys generated in one application instance 'leak' into another, this provider should be reset after each test using the reset_app() method.

For example:

import unittest

from http import HTTPStatus
from flask_azure_oauth.tokens import TestJwt


class AppTestCase(unittest.TestCase):
    def setUp(self):
        # 'create_app()' should return a Flask application where `app.config['TESTING'] = True` has been set
        self.app = create_app('testing')
        self.app_context = self.app.app_context()
        self.app_context.push()
        self.client = self.app.test_client()

    def tearDown(self):
        # 'auth ' should refer to the instance of this provider
        auth.reset_app()

    def test_protected_route_with_multiple_scopes_authorised(self):
        # Generate token with required scopes
        token = TestJwt(app=self.app, scopes=['required-scope1', 'required-scope2'])
        
        # Make request to protected route with token
        response = self.client.get(
            '/protected-with-multiple-scopes',
            headers={'authorization': f"bearer { token }"}
        )
        self.assertEqual(HTTPStatus.OK, response.status_code)
        self.app_context.pop()
    
    def test_protected_route_with_multiple_scopes_unauthorised(self):
        # Generate token with no scopes
        token = TestJwt(app=self.app)
        
        # Make request to protected route with token
        response = self.client.get(
            '/protected-with-multiple-scopes',
            headers={'authorization': f"bearer { token }"}
        )
        self.assertEqual(HTTPStatus.FORBIDDEN, response.status_code)
        self.app_context.pop()

Permissions, roles and scopes

Permissions, roles and scopes can all be considered things Applications, users or groups can do within an application - such as using a feature or acting on a resource. In the context of this provider, they define which routes and resources can be used within a Flask application.

Note: This provider currently does not support or discuss assigning permissions to users or groups. This is planned for a future release.

Permissions are defined in the application manifest of each application being protected. These can then be assigned to either other applications and/or users (or groups of users) as roles. Roles are expressed within access tokens issued by Azure in the non-standard roles claim, which is otherwise equivalent to standard OAuth scopes.

Defining permissions within an application registration

Note: You need to have already Registered the application to be protected within Azure before following these instructions.

Follow these instructions.

Note: This provider currently does not support or discuss assigning permissions to users or groups, therefore, ensure all roles use Application for the allowedMemberTypes property.

For example:

"appRoles": [
  {
    "allowedMemberTypes": [
      "Application"
    ],
    "displayName": "List all Foo resources",
    "id": "112b3a76-2dd0-4d09-9976-9f94b2ed965d",
    "isEnabled": true,
    "description": "Allows access to basic information for all Foo resources",
    "value": "Foo.List.All"
  }
],

Assigning permissions for one application to use another

Note: You need to have already Registered both the application to be protected and the application that will be granted permissions within Azure. You also need to define the permissions in the protected application you wish to assign to the other application.

Follow these instructions.

Note: This provider currently does not support or discuss assigning permissions to users or groups, therefore, do not follow the instructions to sign users into an application or use other user related functionality.

Applications, users, groups and tenancies

Applications, users and groups of users can all be considered things that Permissions can be assigned to and will be generically referred to as entities. All of these entities reside in a single Azure tenancy.

Note: This provider currently does not support or discuss using users or groups of users as entities. This is planned for a future release.

Applications include services being protected by this provider, and those that will be granted access to use such applications as a client. Within Azure, all applications are represented by application registrations.

Registering an application in Azure

Follow these instructions.

Note: These instructions apply both to applications that will be protected by this provider, and those that will be granted access to use such applications as a client.

Developing

A docker container ran through Docker Compose is used as a development environment for this project. It includes development only dependencies listed in requirements.txt, a local Flask application in app.py and Integration tests.

Ensure classes and methods are defined within the flask_azure_oauth package.

Ensure Integration tests are written for any new feature, or changes to existing features.

If you have access to the BAS GitLab instance, pull the Docker image from the BAS Docker Registry:

$ docker login docker-registry.data.bas.ac.uk
$ docker-compose pull

# To run the local Flask application using the Flask development server
$ docker-compose up

# To start a shell
$ docker-compose run app ash

Code Style

PEP-8 style and formatting guidelines must be used for this project, with the exception of the 80 character line limit.

Flake8 is used to ensure compliance, and is ran on each commit through Continuous Integration.

To check compliance locally:

$ docker-compose run app flake8 . --ignore=E501

Dependencies

Development Python dependencies should be declared in requirements.txt to be included in the development environment.

Runtime Python dependencies should be declared in requirements.txt and setup.py to also be installed as dependencies of this package in other applications.

All dependencies should be periodically reviewed and update as new versions are released.

$ docker-compose run app ash
$ pip install [dependency]==
# this will display a list of available versions, add the latest to `requirements.txt` and or `setup.py`
$ exit
$ docker-compose down
$ docker-compose build

If you have access to the BAS GitLab instance, push the Docker image to the BAS Docker Registry:

$ docker login docker-registry.data.bas.ac.uk
$ docker-compose push

Dependency vulnerability scanning

To ensure the security of this API, all dependencies are checked against Snyk for vulnerabilities.

Warning: Snyk relies on known vulnerabilities and can't check for issues that are not in it's database. As with all security tools, Snyk is an aid for spotting common mistakes, not a guarantee of secure code.

Some vulnerabilities have been ignored in this project, see .snyk for definitions and the Dependency exceptions section for more information.

Through Continuous Integration, on each commit current dependencies are tested and a snapshot uploaded to Snyk. This snapshot is then monitored for vulnerabilities.

Dependency vulnerability exceptions

This project contains known vulnerabilities that have been ignored for a specific reason.

Py-Yaml yaml.load() function allows Arbitrary Code Execution
- currently no known or planned resolution
- indirect dependency, required through the bandit package
- severity is rated high
- risk judged to be low as we don't use the Yaml module in this application
- ignored for 1 year for re-review

Static security scanning

To ensure the security of this API, source code is checked against Bandit for issues such as not sanitising user inputs or using weak cryptography.

Warning: Bandit is a static analysis tool and can't check for issues that are only be detectable when running the application. As with all security tools, Bandit is an aid for spotting common mistakes, not a guarantee of secure code.

Through Continuous Integration, each commit is tested.

To check locally:

$ docker-compose run app bandit -r .

Testing

Integration tests

This project uses integration tests to ensure features work as expected and to guard against regressions and vulnerabilities.

The Python UnitTest library is used for running tests using Flask's test framework. Test cases are defined in files within tests/ and are automatically loaded when using the test Flask CLI command included in the local Flask application in the development environment.

Tests are automatically ran on each commit through Continuous Integration.

To run tests manually:

$ docker-compose run -e FLASK_ENV=testing app flask test

To run tests using PyCharm:

Run -> Edit Configurations
Add New Configuration -> Python Tests -> Unittests

In Configuration tab:

Script path: [absolute path to project]/tests
Python interpreter: Project interpreter (app service in project Docker Compose)
Working directory: [absolute path to project]
Path mappings: [absolute path to project]=/usr/src/app

Note: This configuration can be also be used to debug tests (by choosing debug instead of run).

Continuous Integration

All commits will trigger a Continuous Integration process using GitLab's CI/CD platform, configured in .gitlab-ci.yml.

This process will run the application Integration tests.

Pip dependencies are also checked and monitored for vulnerabilities.

Distribution

Both source and binary versions of the package are build using SetupTools, which can then be published to the Python package index for use in other applications. Package settings are defined in setup.py.

This project is built and published to PyPi automatically through Continuous Deployment.

To build the source and binary artefacts for this project manually:

$ docker-compose run app ash
# build package to /build, /dist and /flask_azure_oauth.egg-info
$ python setup.py sdist bdist_wheel
$ exit
$ docker-compose down

To publish built artefacts for this project manually to PyPi testing:

$ docker-compose run app ash
$ python -m twine upload --repository-url https://test.pypi.org/legacy/ dist/*
# project then available at: https://test.pypi.org/project/flask-azure-oauth/
$ exit
$ docker-compose down

To publish manually to PyPi:

$ docker-compose run app ash
$ python -m twine upload --repository-url https://pypi.org/legacy/ dist/*
# project then available at: https://pypi.org/project/flask-azure-oauth/
$ exit
$ docker-compose down

Continuous Deployment

A Continuous Deployment process using GitLab's CI/CD platform is configured in .gitlab-ci.yml. This will:

build the source and binary artefacts for this project
publish built artefacts for this project to the relevant PyPi repository

This process will deploy changes to PyPi testing on all commits to the master branch.

This process will deploy changes to PyPi on all tagged commits.

Release procedure

At release

create a release branch
bump version in setup.py as per SemVer
close release in CHANGELOG.md
push changes, merge the release branch into master and tag with version

The project will be built and published to PyPi automatically through Continuous Deployment.

Feedback

The maintainer of this project is the BAS Web & Applications Team, they can be contacted at: servicedesk@bas.ac.uk.

Issue tracking

This project uses issue tracking, see the Issue tracker for more information.

Note: Read & write access to this issue tracker is restricted. Contact the project maintainer to request access.

License

You may use and re-use this software and associated documentation files free of charge in any format or medium, under the terms of the Open Government Licence v3.0.

You may obtain a copy of the Open Government Licence at http://www.nationalarchives.gov.uk/doc/open-government-licence/

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README.md

README.md

Flask Azure AD OAuth Provider

Purpose

Installation

Usage

Configuration options

Testing support

Permissions, roles and scopes

Defining permissions within an application registration

Assigning permissions for one application to use another

Applications, users, groups and tenancies

Registering an application in Azure

Developing

Code Style

Dependencies

Dependency vulnerability scanning

Dependency vulnerability exceptions

Static security scanning

Testing

Integration tests

Continuous Integration

Distribution

Continuous Deployment

Release procedure

At release

Feedback

Issue tracking

License

Files

README.md

Latest commit

History

README.md

File metadata and controls

Flask Azure AD OAuth Provider

Purpose

Installation

Usage

Configuration options

Testing support

Permissions, roles and scopes

Defining permissions within an application registration

Assigning permissions for one application to use another

Applications, users, groups and tenancies

Registering an application in Azure

Developing

Code Style

Dependencies

Dependency vulnerability scanning

Dependency vulnerability exceptions

Static security scanning

Testing

Integration tests

Continuous Integration

Distribution

Continuous Deployment

Release procedure

At release

Feedback

Issue tracking

License