How does ForgeRock AM implement OAuth 2.0 and what grant types does it support?

ForgeRock AM acts as a fully compliant OAuth 2.0 Authorization Server. It issues access tokens, refresh tokens, and (when OIDC is enabled) ID tokens. The OAuth2 provider is configured per-realm, which means different business units can have different token lifetimes, signing keys, PKCE requirements, and scope policies within the same AM deployment.

AM supports all five major OAuth 2.0 grant types defined in RFC 6749 plus several extensions:

• Authorization Code — Standard redirect-based flow; supports PKCE (RFC 7636) to prevent authorization code interception attacks.
• Implicit — Deprecated in OAuth 2.1; still available but not recommended for new applications.
• Resource Owner Password Credentials (ROPC) — Direct username/password exchange; only appropriate for trusted first-party clients.
• Client Credentials — Machine-to-machine authentication where no user is involved; the client authenticates using its own credentials.
• Refresh Token — Exchange a refresh token for a new access token without re-authentication.
• Device Authorization Grant (RFC 8628) — For input-constrained devices (smart TVs, CLI tools) that cannot host a browser redirect.
• Token Exchange (RFC 8693) — Allows trusted services to exchange one token for another, enabling delegation and impersonation patterns.

Token format is configurable: AM can issue opaque bearer tokens (random strings stored in CTS) or stateless JWT access tokens. JWT tokens are self-contained — resource servers can validate them locally using AM's published JWKS without a round-trip to AM's introspection endpoint, improving performance at scale. Scopes in AM are validated against a configurable scope implementation — either a built-in provider or a custom scripted scope handler written in JavaScript or Groovy.

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