django_hmac_authentication

Django hmac authentication with multiple encrypted hmac secrets per user

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Features

#	Feature	Description
1	Multiple hmac secrets per user	Each secret is protected with a separate key
2	Django Model and Authentication	Django ApiHMACKey and Authentication classes HMACAuthentication for Django Rest Framework
3	Obtain credentials	Django management command or a configured url to get credentials
4	Reject stale requests	Reject requests earlier than configured timeout and also with future timestamps
5	Supported HMAC hash functions	HMAC-SHA512, HMAC-SHA384, HMAC-SHA256
6	Clients	Javascript and Python clients for programmatic access. See example_django_project and Postman collections
7	Auto-Revoke	Optional configuration to auto revoke keys after N failed attempts to authenticate
8	Auto-Expire	Optional HMAC_EXPIRES_IN configuration. If set HMAC keys will expire after interval
9	Performance (Caching)	* Option to speedup using a cache in Django's CACHES settings. * A lru_cache is enabled locally to save compute time to decode hmac key
10	Kill switch	An out-of-band capability to reject requests
11	Throttling	Throttling requests on hmac key used
12	Supported encryption ciphers	AES-256, CAMELLIA-256 to encrypt user's hmac secrets

What's new

Camellia 256 cipher is used along with aes. Package now picks one of AES-256 or Camellia-256 to secure users' HMAC secrets at runtime. Encryption now has two algorithms instead of just one. Client side changes not required. To use new feature just update package and run migrations.

1. Install

pip install django_hmac_authentication

2. Configuration

2.1 settings.py

See example configurations below.

1. In Django INSTALLED_APPS

Add django_hmac_authentication to INSTALLED_APPS

2. In REST_FRAMEWORK

Add HMAC authentication class to REST_FRAMEWORK settings dict.

3. Package specific settings in HMAC_AUTHENTICATION_SETTINGS

• MAX_HMACS_PER_USER Default: 10. Maximum hmac secrets per user
• HMAC_AUTH_REQUEST_TIMEOUT Requests earlier than this are rejected. Default: 5 in seconds
• Optional settings
  • HMAC_AUTH_FAILED_ATTEMPTS_THRESHOLDMax attempts to authenticate after which key is auto-revoked
  • HMAC_EXPIRES_IN HMAC keys will auto-expire after this period in hours, minutes or seconds. Example'1h', '5m', '3600s'
  • HMAC_CACHE_ALIAS Alias of a cache backend in Django's CACHES settings. When set, the cache specified by the alias is used to cache hmac keys. Example: hmac_cache. Default: None (i.e caching disabled)
  • HMAC_KILL_SWITCH If set, enables checking cache to force-reject requests for certain keys. HMAC_CACHE_ALIAS must be set.

    Note: The hmac keys in this package can be disabled and enabled using the admin interface. This switch helps when that option is not feasible and out of band intervention is needed. See example_django_project/scripts/out_of_band_hmac_kill_switch.py for a sample program that demonstrates switching keys on/off. Depending on cache backend used and CACHES configuration in settings.py, the cache key needs to be formatted. See Django cache key formatting based on configuration

  • Throttling Add throttling class in REST_FRAMEWORK > DEFAULT_THROTTLE_CLASSES as
    django_hmac_authentication.throttling.HMACApiKeyRateThrottle. Throttling uses cache and HMAC_CACHE_ALIAS must be set. By default all hmac keys are created with rate 200/min. Rate can be changed on admin interface.

Example

HMAC_AUTHENTICATION_SETTINGS = {
    'MAX_HMACS_PER_USER':10,
    'HMAC_AUTH_REQUEST_TIMEOUT': 4,
    # Optional configurations
    'HMAC_AUTH_FAILED_ATTEMPTS_THRESHOLD': 10,
    'HMAC_EXPIRES_IN': '5m',
    # This cache alias must be defined in Django's CACHES. 
    # See https://docs.djangoproject.com/en/4.2/ref/settings/#caches
    'HMAC_CACHE_ALIAS': 'hmac_cache',
    'HMAC_KILL_SWITCH': True
}

INSTALLED_APPS = [
    ...,
    'rest_framework',
    'django_hmac_authentication',
    ...
]

REST_FRAMEWORK = {
    'DEFAULT_PERMISSION_CLASSES': [
        'rest_framework.permissions.IsAuthenticated',
    ],
    'DEFAULT_AUTHENTICATION_CLASSES': [
        'rest_framework.authentication.SessionAuthentication',
        # Add authentication class
        'django_hmac_authentication.authentication.HMACAuthentication',
    ],
    # Throttling
    'DEFAULT_THROTTLE_CLASSES': [
        'django_hmac_authentication.throttling.HMACApiKeyRateThrottle'
    ],
}

2.2 urls.py

Add url to obtain HMAC key and secret

...
from django_hmac_authentication.views import CreateApiHMACKey

urlpatterns = [
    ...,
    # django_hmac_authentication
    path('obtain-hmac-api-key/', 
         CreateApiHMACKey.as_view(), 
         name='api_hmac_key'),
    ...
]

2.3 Run migrations

python manage.py migrate django_hmac_authentication

3. Usage

3.1 Obtain HMAC key and secret

3.1.1 Using management command

Use management command to create a HMAC API key with secret for a user

python manage.py create_hmac_for_user bob
{"api_key": "f4c3801c-a277-4fcb-92bb-44cb814026f6", "api_secret": "vEOQRdvaK4jyeLKGNP9oqpYTUvt/GZWbGG6iNmnDh8c=", "message": "These credentials will be lost forever if not stored now"}

3.1.2 Using curl

# Use the url from configuration
curl -X POST -H "Content-Type: application/json" -d '{"username":"bob", "password":"bobspassword"}' http://127.0.0.1:8000/obtain-hmac-api-key/ 
{"api_key":"7ebc25d7-d237-4f90-b4ad-98f0c228fc1e","api_secret":"EDQppq0B3rIxvaA7PyPUHPF6kiXTnnbvnMiZDzYFSRA=","message":"These credentials will be lost forever if not stored now"}

4. Sign requests client-side

4.1 Javascript client

See example_django_project/javascript_topman_collection folder

A postman collection with environment is provided which can be imported to Postman. A prerequest script for generating the signature is provided (same as included in postman collection).

4.2 Python client

See example_django_project/example_python_client.py

5. Signature

5.1 How is it calculated

Signature is calculated on hash( request body json ) + utc 8601

request data
    │
    ▼
  json
    │
    ▼
  hash  +   ;  +  utc 8601
 ────────────┬─────────────
             │
             ▼
         signature

• Hash function is one of supported methods in Authorization header
• UTC time now in ISO 8601 format. Example 2023-05-07T14:15:37.862560+00:00

6. Authorization header

Syntax: METHOD api_key;signature;request_utc_8601

• method: One of HMAC-SHA512, HMAC-SHA384, HMAC-SHA256
• api_key: Key used to identify the hmac secret used to generate signature
• signature: base64 signature
• request_utc: time in ISO 8601 set in signed string

Example

'HMAC-SHA512 aa733037-e4c0-4f75-a864-df6c1966481b;6k3XaUREI6dDw6thyQWASJjzjsx1M7GOZAglguv0OElpRue1+gb7CK2n3JpzJGz9VcREw2y3rIW5zoZYEUY+0w==;2023-05-07T14:15:37.862560+00:00'

7. Protecting user's hmac secret

Django settings.SECRET_KEY                 salt per user
           │                               │   │
           │                               │   │
           └───────────►   pbkdf2_hmac  ◄──┘   │
                                │              │
                                │              │
                                ▼              │
                              256 bit key      │
                                │              │
                                │              │
                                ▼              │
   encrypt user secret  ◄───── aes/camellia    │
                                ▲              │
                                │              │
                               iv ◄────────────┘

8. License

Apache2 License

9. Github

https://github.com/harisankar-krishna-swamy/django_hmac_authentication

10. See also

https://www.okta.com/au/identity-101/hmac/

https://docs.python.org/3/library/hashlib.html

https://learn.microsoft.com/en-us/azure/communication-services/tutorials/hmac-header-tutorial?pivots=programming-language-python