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Keycloak Token Exchange SPI Examples

The purpose of the examples in this repo is to demonstrate the use of the upcoming Token Exchange SPI in Keycloak.

Setup

Building and installing

  1. Check out and build the token-exchange-spi Keycloak branch;
  2. Build the project and deploy the JAR with the examples to Keycloak.

Importing realm data

Go to Keycloak admin console, then import alice-realm.json and bob-realm.json.

Running the examples

Run Keycloak:

bin/standalone.sh -Dkeycloak.profile=preview

Run Postman, open the Token Exchange SPI Examples collection and run it. Alternatively, use Newman:

newman run "Token Exchange SPI Examples.postman_collection.json"

Examples

Cross-realm impersonation

In Keycloak, the impersonation feature only works withing a realm (i.e. the impersonator and the user to be impersonated must belong to the same realm). Cross-realm token exchange could be emulated to some extent using brokering, but this solution has a lot of limitations.

In this example, simple brokerless trust is established between the realms:

  • both impersonator's and target user's realms must belong to the same Keycloak instance;
  • impersonator's and target user's realms must be different;
  • the call must be made to the target realm's token endpoint;
  • the impersonator must possess the x-impersonation-{REALM} realm role, where {REALM} is the name of the target realm;
  • the target user must belong to the X-Impersonation group.

⚠️ In other words, any RealmA user possessing the x-impersonation-RealmB role will be able to impersonate any RealmB user, provided that the latter belongs to the X-Impersonation group. This pseudo ACL is obviously too weak for production use, and has been added for demo purposes only.

If all conditions are met, then the following direct exchange becomes possible:

curl -X POST \
    -d "client_id=starting-client" \
    -d "client_secret=geheim" \
    --data-urlencode "grant_type=urn:ietf:params:oauth:grant-type:token-exchange" \
    -d "subject_token=...." \
    --data-urlencode "requested_token_type=urn:ietf:params:oauth:token-type:access_token" \
    -d "audience=target-client" \
    -d "scope=foobar" \
    -d "requested_subject=wburke" \
    http://localhost:8080/auth/realms/myrealm/protocol/openid-connect/token

The result of the exchange is the following access token:

{
  "exp": 1620249595,
  "iat": 1620249295,
  "jti": "8d7a25c9-9201-4949-9e74-848947e71f35",
  "iss": "http://localhost:8080/auth/realms/myrealm",
  "aud": "target-client",
  "sub": "a2482293-2712-4730-90b9-3027f1370727",
  "typ": "Bearer",
  "azp": "starting-client",
  "session_state": "d9911a93-f8b7-4a3a-973e-f7534f08b61f",
  "acr": "1",
  "realm_access": {
    "roles": [
      "offline_access",
      "uma_authorization"
    ]
  },
  "resource_access": {
    "account": {
      "roles": [
        "manage-account",
        "manage-account-links",
        "view-profile"
      ]
    }
  },
  "scope": "email profile foobar x-impersonation",
  "email_verified": false,
  "act": {
    "iss": "http://localhost:8080/auth/realms/alice",
    "sub": "7705a5cc-099a-452d-9c97-32e47acb8bac",
    "preferred_username": "alice"
  },
  "preferred_username": "wburke"
}

Please note the presence of the x-impersonation scope automatically added by the token exchange provider, as well as the act claim containing impersonator info.