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Provides easy integration of the HMAC signatures for your REST Flask Applications.

Project description

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This module provides an authentication to Flask routes. The intended use case is for use with REST APIs. It’s simply designed to check that a client is entitled to access a particular route in a Flask application, based on the fact that it must possess a copy of the secret key.



app = Flask(__name__)
app.config['HMAC_KEY'] = 's3cr3tk3y'  # define the secret key in an app config

def no_auth_view():
    return "no_auth_view"

@hmac.auth()  # decorate view
def hmac_auth_view():
    return "hmac_auth_view"

@hmac.auth(only=["foo"])  # decorate view, only allows foo client access
def hmac_auth_view():
    return "hmac_auth_view"


Call without payload

sig = hmac.make_hmac()  # generate signature
response = requests.get(
    headers={hmac.header: sig}

You can also use multiple keys between different applications. Secret keys are stored in HMAC_KEYS in the app settings as a dictionary:

app.config['HMAC_KEYS'] = {
    'aservice': 'akey',
    'bservice': 'bkey'

Then the secret key has to generated with make_hmac_for method.

hmac.make_hmac_for('aservice', request_data)  # data is optional

# signature validation for multiple keys


Call with payload

Request payload has to be used as a data for HMAC generation.

data = json.dumps({'foo': 'boo'})

sig = hmac.make_hmac(data)  # generate signature
response =
    headers={hmac.header: sig}

You can define custom errors overwriting abort method:

class MyHmac(Hmac):

    def abort(self):
        message = {'status': '403', 'message': 'not authorized'}
        response = jsonify(message)
        response.status_code = 403
        return response

For HMAC auth of all views you can use Flask’s before_request:

def before_request():
    except HmacException:
        return abort(400)

Generate signature for/from another application:

sig = make_hmac(self, data, key=another_app_key)

Change Log


  • New HMAC_ERROR_CODE configuration option to allow different HTTP Status code responses on failure


  • BREAKING CHANGE: @hmac.auth decorator now needs to be called as @hmac.auth()

  • New only argument for @hmac.auth() to only allow specific clients access


  • Swaps urlsafe_b64encode for b64encode


  • Support multiple keys


  • Able to change secret key in make_hmac method

  • Method validate_signature created which can be used outside of Hmac class

  • Custom exceptions


  • Initial release including the core feature set

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