Restful authentication between two GAE apps.

Question

Hello everyone, i am trying to write a restful google app engine application (python) that accepts requests only from another GAE that i wrote. I dont like any of the ways that i thought of to get this done, please advice if you know of something better than:

• Get SSL setup, and simply add the credentials on the request that my consuming app will send. I dont like it cause SSL will slow things down.

• Security by obsecurity. Add a random number in my request that is in Xmod0, where X is a secret number that both applications know. I just,,,, dont like this.

• Check the HTTP header to see where is the request coming from. This option is the one that i hate the least, not alot of processing, and spoofing an HTTP request is not really worth it, for my application's data.

Is there any other clean solution for this?

Answer 1

Use an HMAC. Embed the same secret in each app, and sign requests and responses using the HMAC. Don't forget to include nonces and timestamps to prevent replay attacks!