Hawk authentication strategy for the requests python library.
Python

README.rst

Requests-Hawk

https://travis-ci.org/mozilla-services/requests-hawk.png

This project allows you to use the python requests library with the hawk authentication mechanism.

Hawk itself does not provide any mechanism for obtaining or transmitting the set of shared credentials required, but this project proposes a scheme we use across mozilla services projects.

Great, how can I use it?

First, you'll need to install it:

pip install requests-hawk

Then, in your project, if you know the id and key, you can use:

import requests
from requests_hawk import HawkAuth

hawk_auth = HawkAuth(id='my-hawk-id', key='my-hawk-secret-key')
requests.post("https://example.com/url", auth=hawk_auth)

Or if you need to derive them from the hawk session token, instead use:

import requests
from requests_hawk import HawkAuth

hawk_auth = HawkAuth(
    hawk_session=resp.headers['hawk-session-token'],
    server_url=self.server_url
)
requests.post("/url", auth=hawk_auth)

In the second example, the server_url parameter to HawkAuth was used to provide a default host name, to avoid having to repeat it for each request.

If you wish to override the default algorithm of sha256, pass the desired algorithm name using the optional algorithm parameter.

Note: The credentials parameter has been removed. Instead pass id and key separately (as above), or pass the existing dict as **credentials.

Integration with httpie

Httpie is a tool which lets you do requests to a distant server in a nice and easy way. Under the hood, httpie uses the requests library. We've made it simple for you to plug hawk with it.

If you know the id and key, use it like that:

http POST localhost:5000/registration\
--auth-type=hawk --auth='id:key'

Or, if you want to use the hawk session token, you can do as follows:

http POST localhost:5000/registration\
--auth-type=hawk --auth='c0d8cd2ec579a3599bef60f060412f01f5dc46f90465f42b5c47467481315f51:'

Take care, don't forget to add the extra : at the end of the hawk session token for it to be considered like so.

How are the shared credentials shared?

Okay, on to the actual details.

The server gives you a session token, that you'll need to derive to get the hawk credentials.

Do an HKDF derivation on the given session token. You'll need to use the following parameters:

key_material = HKDF(hawk_session, '', 'identity.mozilla.com/picl/v1/sessionToken', 32*2)

The key material you'll get out of the HKDF needs to be separated into two parts, the first 32 hex characters are the hawk id, and the next 32 ones are the hawk key:

credentials = {
    'id': keyMaterial[0:32]
    'key': keyMaterial[32:64]
    'algorithm': 'sha256'
}

Run tests

To run test, you can use tox:

tox