Demonstrate impersonation

This page demonstrates token exchange with impersonation. The example exchanges an access token for an access token with reduced scopes. You can also exchange ID tokens with impersonation.

Prepare the demonstration

Start by preparing the demonstration:

Create a may act script.
Create the OAuth 2.0 client the subject uses.
Create the OAuth 2.0 client for impersonation.
Create a resource owner account.

May act script

The script adds a may_act claim to the subject token.

In the Advanced Identity Cloud admin UI, select Scripts > Auth Scripts > + New Script.
In the New Script window, select OAuth2 May Act and continue.

In the new script window, name the script May act and save the following JavaScript:

(function () {
    var frJava = JavaImporter(
        org.forgerock.json.JsonValue
    );

    var mayAct = frJava.JsonValue.json(frJava.JsonValue.object())
    mayAct.put('client_id', 'impersonationClient')
    token.setMayAct(mayAct)
}());

This script generates a may_act claim to permit the impersonating actor client to exchange the subject token.

Subject client

The OAuth 2.0 client profile in this example overrides the OAuth 2.0 provider settings. This lets you test the script without affecting access tokens issued to other clients.

Create a confidential OAuth 2.0 client account to get an original token for the subject.

In the Advanced Identity Cloud admin UI, select Applications > + Add Application, and create a new Web client with the following settings:

Client ID

myClient

Client Secret

mySecret
Add the following settings under Sign On > General Settings and save your work:

Sign-in URLs

https://www.example.com:443/callback

Scopes

change_data
create_accounts
read_accounts
transfer
Override OAuth 2.0 provider settings for this client.

Under Native Consoles > Access Management, select Realms > alpha > Applications > OAuth 2.0 > Clients > myClient. Switch to the OAuth2 Provider Overrides tab, update the following settings and save your work:

Enable OAuth2 Provider Overrides

Enabled

OAuth2 Access Token May Act Script

May act

OIDC ID Token May Act Script

May act

Actor client

Create a confidential OAuth 2.0 client account for the service that acts on behalf of the user.

In the Advanced Identity Cloud admin UI, select Applications > + Add Application, and create a new Service client with the following settings:

Client ID

impersonationClient

Client Secret

mySecret
Add the following settings under Sign On > General Settings and save your work:

Sign-in URLs

https://www.example.com:443/callback

Grant Types

Refresh Token
Token Exchange

Scopes

transfer

Resource owner

An OAuth 2.0 client requests the access token on behalf of a resource owner.

Create a user profile.
Record the username and password.

Test the demonstration

After preparing the demonstration, test your work using HTTP calls to REST endpoints.

The demonstration uses the Authorization code grant flow followed by token exchange:

The resource owner authenticates to obtain an SSO token.
The subject client relies on Implied Consent being enabled (default) in the Advanced Identity Cloud admin UI under Applications > Client ID > Sign On > Advanced settings > Authentication. It assumes the resource owner grants the client access.
The subject client requests the authorization code and exchanges it for an access token. Your script sets the may_act claim in the access token.
The actor client exchanges the subject token for an access token.

Follow these steps:

Authenticate as the resource owner:

curl \
--request POST \
--header 'Content-Type: application/json' \
--header 'X-OpenAM-Username: <resource-owner-username>' \
--header 'X-OpenAM-Password: <resource-owner-password>' \
--header 'Accept-API-Version: resource=2.0, protocol=1.0' \
'https://<tenant-env-fqdn>/am/json/realms/root/realms/alpha/authenticate'
{"tokenId":"<resource-owner-tokenId>","successUrl":"/enduser/?realm=/alpha","realm":"/alpha"}

Request the authorization code as the subject client:

curl \
--dump-header - \
--request POST \
--cookie '<session-cookie-name>=<resource-owner-tokenId>' \
--data 'scope=change_data create_accounts read_accounts transfer' \
--data 'response_type=code' \
--data 'client_id=myClient' \
--data 'csrf=<resource-owner-tokenId>' \
--data 'redirect_uri=https://www.example.com:443/callback' \
--data 'state=abc123' \
--data 'decision=allow' \
'https://<tenant-env-fqdn>/am/oauth2/realms/root/realms/alpha/authorize'
...
location: https://www.example.com:443/callback?code=<authorization-code>&iss=https%3A%2F%2F...
...

If you’re exchanging an ID token instead of an access token, set scope=openid profile here to return the ID token in the next command.

Exchange the authorization code for an access token or ID token as the subject client:

curl \
--request POST \
--user 'myClient:mySecret' \
--data 'grant_type=authorization_code' \
--data 'code=<authorization-code>' \
--data 'redirect_uri=https://www.example.com:443/callback' \
'https://<tenant-env-fqdn>/am/oauth2/realms/root/realms/alpha/access_token'
{
  "access_token": "<access-token>",
  "refresh_token": "<refresh-token>",
  "scope": "change_data transfer create_accounts read_accounts",
  "token_type": "Bearer",
  "expires_in": 3599
}

Your script has set the may_act claim, which is not directly visible. To see the may_act claim, you must introspect the access token.

Request an exchanged token as the actor client:

curl \
--request POST \
--user 'impersonationClient:mySecret' \
--data 'grant_type=urn:ietf:params:oauth:grant-type:token-exchange' \
--data 'scope=transfer' \
--data 'subject_token=<access-token>' \
--data 'subject_token_type=urn:ietf:params:oauth:token-type:access_token' \
'https://<tenant-env-fqdn>/am/oauth2/realms/root/realms/alpha/access_token'
{
  "access_token": "<exchanged-token>",
  "refresh_token": "<new-refresh-token>",
  "issued_token_type": "urn:ietf:params:oauth:token-type:access_token",
  "scope": "transfer",
  "token_type": "Bearer",
  "expires_in": 3599
}

The issued_token_type shows this is an exchanged token.

If your subject token is an ID token rather than an access token, set subject_token_type=urn:ietf:params:oauth:token-type:id_token and provide the ID token as the value of subject_token.

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