mod_auth_oauth_external

This module provides external authentication via an external OAuth 2 authorization server and supports the SASL OAUTHBEARER authentication mechanism as well as PLAIN for legacy clients (this is all of them).

How it works

Using OAuth 2.0 in XMPP is explained in XEP-0493: OAuth Client Login. Clients pass tokens from the Authorization Server to Prosody, which attempts to validate the tokens using the configured validation endpoint.

Legacy clients have to use SASL PLAIN, where Prosody receives the users username and password and attempts to validate this using the OAuth 2 resource owner password grant.

Configuration

Example

-- authentication = "oauth_external"

oauth_external_discovery_url = "https//auth.example.com/auth/realms/TheRealm/.well-known/openid-configuration"
oauth_external_token_endpoint = "https//auth.example.com/auth/realms/TheRealm/protocol/openid-connect/token"
oauth_external_validation_endpoint = "https//auth.example.com/auth/realms/TheRealm/protocol/openid-connect/userinfo"
oauth_external_username_field = "xmpp_username"

Common

oauth_external_issuer

Optional URL string representing the Authorization server identity.

oauth_external_discovery_url

Optional URL string pointing to OAuth 2.0 Authorization Server Metadata. Lets clients discover where they should retrieve access tokens from if they don’t have one yet. Default based on oauth_external_issuer is set, otherwise empty.

oauth_external_validation_endpoint

URL string. The token validation endpoint, should validate the token and return a JSON structure containing the username of the user logging in the field specified by oauth_external_username_field. Commonly the OpenID UserInfo endpoint If left unset, only SASL PLAIN is supported and the username provided there is assumed correct.

oauth_external_username_field

String. Default is "preferred_username". Field in the JSON structure returned by the validation endpoint that contains the XMPP localpart.

For SASL PLAIN

oauth_external_resource_owner_password

Boolean. Defaults to true. Whether to allow the insecure resource owner password grant and SASL PLAIN.

oauth_external_token_endpoint

URL string. OAuth 2 Token Endpoint used to retrieve token in order to then retrieve the username.

oauth_external_client_id

String. Client ID used to identify Prosody during the resource owner password grant.

oauth_external_client_secret

String. Client secret used to identify Prosody during the resource owner password grant.

oauth_external_scope

String. Defaults to "openid". Included in request for resource owner password grant.

Compatibility

Prosody

Identity Provider

Tested with

• KeyCloak
• Mastodon

Future work

• Automatically discover endpoints from Discovery URL
• Configurable input username mapping (e.g. user → user@host).
• SCRAM over HTTP?!

sudo prosodyctl install --server=https://modules.prosody.im/rocks/ mod_auth_oauth_external