watcha-synapse/docs/jwt.md

JWT Login Type

Synapse comes with a non-standard login type to support JSON Web Tokens. In general the documentation for the login endpoint is still valid (and the mechanism works similarly to the token based login).

To log in using a JSON Web Token, clients should submit a /login request as follows:

{
  "type": "org.matrix.login.jwt",
  "token": "<jwt>"
}

Note that the login type of m.login.jwt is supported, but is deprecated. This will be removed in a future version of Synapse.

The token field should include the JSON web token with the following claims:

• The sub (subject) claim is required and should encode the local part of the user ID.
• The expiration time (exp), not before time (nbf), and issued at (iat) claims are optional, but validated if present.
• The issuer (iss) claim is optional, but required and validated if configured.
• The audience (aud) claim is optional, but required and validated if configured. Providing the audience claim when not configured will cause validation to fail.

In the case that the token is not valid, the homeserver must respond with 403 Forbidden and an error code of M_FORBIDDEN.

As with other login types, there are additional fields (e.g. device_id and initial_device_display_name) which can be included in the above request.

Preparing Synapse

The JSON Web Token integration in Synapse uses the PyJWT library, which must be installed as follows:

• The relevant libraries are included in the Docker images and Debian packages provided by matrix.org so no further action is needed.

• If you installed Synapse into a virtualenv, run /path/to/env/bin/pip install synapse[pyjwt] to install the necessary dependencies.

• For other installation mechanisms, see the documentation provided by the maintainer.

To enable the JSON web token integration, you should then add an jwt_config section to your configuration file (or uncomment the enabled: true line in the existing section). See sample_config.yaml for some sample settings.

How to test JWT as a developer

Although JSON Web Tokens are typically generated from an external server, the examples below use PyJWT directly.

1. Configure Synapse with JWT logins, note that this example uses a pre-shared secret and an algorithm of HS256:

   jwt_config:
       enabled: true
       secret: "my-secret-token"
       algorithm: "HS256"
   

2. Generate a JSON web token:

   $ pyjwt --key=my-secret-token --alg=HS256 encode sub=test-user
   eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJ0ZXN0LXVzZXIifQ.Ag71GT8v01UO3w80aqRPTeuVPBIBZkYhNTJJ-_-zQIc
   

3. Query for the login types and ensure org.matrix.login.jwt is there:

   curl http://localhost:8080/_matrix/client/r0/login
   

4. Login used the generated JSON web token from above:

   $ curl http://localhost:8082/_matrix/client/r0/login -X POST \
       --data '{"type":"org.matrix.login.jwt","token":"eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJ0ZXN0LXVzZXIifQ.Ag71GT8v01UO3w80aqRPTeuVPBIBZkYhNTJJ-_-zQIc"}'
   {
       "access_token": "<access token>",
       "device_id": "ACBDEFGHI",
       "home_server": "localhost:8080",
       "user_id": "@test-user:localhost:8480"
   }
   

You should now be able to use the returned access token to query the client API.