OAuth / OIDC Endpoints

Modgud implements the OpenID Connect protocol via OpenIddict 7. Every endpoint is realm-scoped via the host header — each realm has its own issuer, discovery document, JWKS, and token surface.

Cryptographic constraints

Setting	Value
Access-token signing algorithm	RS256
ID-token signing algorithm	RS256
PKCE method	S256 (plain is rejected)
Realm signing keys	RSA, one keypair per realm

The signing keys live in RealmSigningKey Marten documents, rotated on demand from admin. The JWKS endpoint exposes the public set.

Discovery

Endpoint	Description
`GET /.well-known/openid-configuration`	OIDC discovery document for the current realm
`GET /.well-known/jwks`	JSON Web Key Set (for JWT validation)

Example discovery for realm acme.example.com:

https://acme.example.com/.well-known/openid-configuration

→ Returns issuer: "https://acme.example.com" plus the realm's endpoint URLs. Tokens from this discovery are valid only in this realm.

Implemented via RealmIssuerHandler (see OAuth implementation).

The discovery document advertises only enabled scopes that are public-listed (OAuthScope.ShowInDiscoveryDocument = true). The implicit-scope-per-API entries default to false (private), so they don't leak the realm's resource-server inventory. See Concepts: OAuth for the RealmScopesSupportedHandler rationale.

Endpoint map

All under /connect/..., all realm-scoped via the domain:

Endpoint	Method	Purpose
`/connect/authorize`	`GET`/`POST`	Authorization endpoint (Code + PKCE)
`/connect/token`	`POST`	Token endpoint (code exchange, client credentials, refresh, device)
`/connect/userinfo`	`GET`/`POST`	UserInfo endpoint (claims + per-Audience `resource_access`)
`/connect/introspect`	`POST`	Token introspection
`/connect/revoke`	`POST`	Token revocation
`/connect/logout`	`GET`/`POST`	End-session endpoint (RP-initiated logout)
`/connect/device`	`POST`	Device-authorization endpoint (CLI / TV / set-top boxes)
`/connect/verify`	`GET`	User-verification endpoint for the device flow
`/connect/register`	`POST`	Dynamic Client Registration (RFC 7591). Registration only — there is no RFC 7592 management surface.
`/connect/consent`	`GET`/`POST`	Consent ticket resolve + decision (the SPA calls these after `/connect/authorize` redirects it to `/consent?ticket=…`)

Supported flows

The discovery doc lists grant_types_supported:

Grant type	Use case
`authorization_code`	Standard interactive login (web, SPA, mobile). PKCE required (S256).
`refresh_token`	Token rotation. Single-use — each refresh issues a new refresh-token and invalidates the old one.
`client_credentials`	Server-to-server. Must be linked to a `ServiceAccount` (the SA-managed mutation guard rejects free-standing CC clients).
`urn:ietf:params:oauth:grant-type:device_code`	Device flow for input-constrained clients.

response_modes_supported: query, form_post, fragment. response_types_supported: code (no implicit, no hybrid).

Authorization Code + PKCE

Request

GET /connect/authorize?
    client_id=acme-web&
    redirect_uri=https://acme.example.com/callback&
    response_type=code&
    scope=openid+profile+email+roles+permissions&
    state=<csrf>&
    code_challenge=<base64url(sha256(verifier))>&
    code_challenge_method=S256

If not logged in → 302 to the realm's /login (the cookie auth handler returns 401 outside the OAuth flow; /connect/authorize is the exception that drives the login UX). After successful login and consent → 302 to the redirect_uri with ?code=…&state=….

Token exchange

POST /connect/token
Content-Type: application/x-www-form-urlencoded

grant_type=authorization_code
code=…
redirect_uri=https://acme.example.com/callback
code_verifier=…
client_id=acme-web
client_secret=…           # for confidential clients

Response:

{
  "access_token": "…",      // reference id or JWT (per client choice)
  "token_type": "Bearer",
  "expires_in": 3600,
  "refresh_token": "…",     // if offline_access requested
  "id_token": "…"           // if openid requested
}

Client Credentials

POST /connect/token
Content-Type: application/x-www-form-urlencoded

grant_type=client_credentials
client_id=acme-cron
client_secret=…
scope=billing.read

The client must be linked to a Service Account (LinkedServiceAccountId). The sub claim in the resulting token is the Service Account's id; the SA is treated as a non-human principal that goes through the normal Group→Role→Permission resolver.

Refresh Token

POST /connect/token
Content-Type: application/x-www-form-urlencoded

grant_type=refresh_token
refresh_token=…
client_id=acme-web
client_secret=…

Single-use with rotation: every use issues a new refresh token and invalidates the old one. Replay attempts return invalid_grant.

Device flow

For CLI tools, set-top boxes, anything without a browser.

1. Device requests a code

POST /connect/device
Content-Type: application/x-www-form-urlencoded

client_id=acme-cli
scope=openid+profile

Response:

{
  "device_code": "…",
  "user_code": "ABCD-EFGH",
  "verification_uri": "https://acme.example.com/connect/verify",
  "verification_uri_complete": "https://acme.example.com/connect/verify?user_code=ABCD-EFGH",
  "expires_in": 600,
  "interval": 5
}

2. User visits the verification URL

GET /connect/verify shows a form for the user_code. After login + consent the device-code is approved.

3. Device polls the token endpoint

POST /connect/token
Content-Type: application/x-www-form-urlencoded

grant_type=urn:ietf:params:oauth:grant-type:device_code
device_code=…
client_id=acme-cli

Returns authorization_pending until the user has verified; then a normal token response.

UserInfo

Accepts both GET and POST (per the OIDC spec):

GET /connect/userinfo
Authorization: Bearer <access_token>

Returns the claims for the bearer token, plus a Keycloak-style resource_access block keyed per Audience:

{
  "sub":   "abc123…",
  "email": "alice@example.com",
  "resource_access": {
    "billing": {
      "roles": ["Editor"],
      "permissions": ["invoice:read", "invoice:write"]
    }
  }
}

roles is emitted when scope=roles was granted.
permissions is emitted when scope=permissions was granted, bypass-pre-expanded and narrowed to the calling OAuthApi's PermissionIds subset.
One block per audience listed in aud; a microservice within a multi-RS App sees only its declared subset.

See Apps and resource_access for the full emission story.

Introspection

POST /connect/introspect
Authorization: Basic <base64(client_id:client_secret)>
Content-Type: application/x-www-form-urlencoded

token=<token>

Returns active: true/false plus all the token's claims. Used by resource servers that hold reference tokens (server-side opaque) to validate them against the issuer.

Revocation

POST /connect/revoke
Authorization: Basic <base64(client_id:client_secret)>
Content-Type: application/x-www-form-urlencoded

token=<token>
token_type_hint=access_token   # or refresh_token

Reference tokens become immediately invalid; JWTs can't actually be revoked server-side (they self-validate against JWKS), but their parent authorization is killed so any associated refresh tokens stop working.

Dynamic Client Registration (DCR)

RFC 7591 registration only, scoped to the realm. Disabled by default; enabled per-realm in Realm Settings → Dynamic Client Registration. There is no RFC 7592 management surface — GET/PUT/DELETE on a per-client registration URL is not implemented. The endpoint mints a client and is done; later changes go through the admin UI.

Register a new client

POST /connect/register
Content-Type: application/json

{
  "client_name": "Some MCP Server",
  "redirect_uris": ["https://mcp.example.com/callback"],
  "grant_types": ["authorization_code", "refresh_token"],
  "response_types": ["code"],
  "scope": "openid profile",
  "token_endpoint_auth_method": "none"
}

Response (201 Created — RFC 7591 §3.2.1):

{
  "client_id": "dcr_…",
  "client_id_issued_at": 1735689600,
  "token_endpoint_auth_method": "none",
  "grant_types": ["authorization_code", "refresh_token"],
  "response_types": ["code"],
  "redirect_uris": ["https://mcp.example.com/callback"],
  "client_name": "Some MCP Server",
  "scope": "openid profile"
}

The response echoes the sanitized registration plus the assigned client_id and client_id_issued_at. No client_secret is issued (public PKCE clients only), and there is no registration_access_token / registration_client_uri — RFC 7592 management is out of scope. DCR-registered clients are marked [unverified] in their display name to flag them in admin grids (the consent page renders the same marker).

DCR constraints

Only none (PKCE-only public client) and client_secret_basic auth methods accepted.
Redirect URIs must be HTTPS or localhost; deep-link schemes are rejected.
Triple opt-in: the realm must enable DCR globally; the requested scopes must be per-Scope-DCR-allowed; the resource server (if any) must be per-API-DCR-allowed.
Unverified DCR clients with no recent last_used_at activity are garbage-collected by the daily dcr-gc Quartz job (default TTL: 90 days).

Per-realm isolation

Each realm has:

Its own OAuth clients (OAuthApplicationState in the tenant store)
Its own scopes (OAuthScopeState)
Its own API resources (OAuthApiState)
Its own authorizations + tokens
Its own issuer (realm domain via RealmIssuerHandler)
Its own discovery document and JWKS

Tokens from realm A are invalid in realm B — issuer mismatch alone suffices for rejection. Identical client_id strings in two realms are different clients.

Per-client token format

Per client you can choose between Reference Token (default) and JWT:

Format	Storage	Validation	Revocation
Reference	Server-side `OpenIddictTokenDocument`	API calls `/connect/introspect`	Immediate
JWT	Self-contained	API verifies locally with JWKS	Effective only on refresh expiry

Switched per request via AccessTokenTypeHandler. Reference tokens are the right default for first-party apps (cheap revocation, no extra trust in the JWT lib version on the RS side); JWTs are the right pick for high-throughput RS scenarios where the introspection call would dominate latency.

OAuth admin endpoints

For managing the OAuth entities (clients, scopes, APIs) see Admin API → OAuth Clients/Scopes/APIs.

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OAuth / OIDC Endpoints

Cryptographic constraints

Discovery

Endpoint map

Supported flows

Authorization Code + PKCE

Request

Token exchange

Client Credentials

Refresh Token

Device flow

1. Device requests a code

2. User visits the verification URL

3. Device polls the token endpoint

UserInfo

Introspection

Revocation

Dynamic Client Registration (DCR)

Register a new client

DCR constraints

Per-realm isolation

Per-client token format

OAuth admin endpoints

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OAuth / OIDC Endpoints

Cryptographic constraints

Discovery

Endpoint map

Supported flows

Authorization Code + PKCE

Request

Token exchange

Client Credentials

Refresh Token

Device flow

1. Device requests a code

2. User visits the verification URL

3. Device polls the token endpoint

UserInfo

Introspection

Revocation

Dynamic Client Registration (DCR)

Register a new client

DCR constraints

Per-realm isolation

Per-client token format

OAuth admin endpoints