MCP clients were being kicked back to an interactive login on a short cycle, reporting "requires re-authorization (token expired)". Cause: /.well-known/oauth-protected-resource advertised only openid/profile/email plus the audience scope. A client requests exactly the scopes it finds there, and Authentik issues a refresh token only when offline_access is among them — so the client received an access token with nothing to renew it with. Once that token aged out, re-authenticating by hand was the only path forward. This is the same trap the audience scope already documents one comment further up: a scope missing from this document is a scope the client will never ask for, however the IdP is configured. Adds OIDC_OFFLINE_ACCESS (default false). Enabling it appends offline_access to the advertised scopes. Left opt-in rather than always-on because it is only half the fix — the IdP also needs an offline_access scope mapping on the provider, and advertising a scope the IdP doesn't offer risks an invalid_scope rejection that would break authentication outright. A deployment turns this on after configuring its IdP; README documents both halves and how to verify each. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
46 lines
1.9 KiB
TypeScript
46 lines
1.9 KiB
TypeScript
import { NextResponse } from "next/server";
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import { env } from "@/lib/env";
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import { mcpIssuer } from "@/lib/auth/jwt";
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export const runtime = "nodejs";
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export const dynamic = "force-dynamic";
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/**
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* RFC 9728 — OAuth 2.0 Protected Resource Metadata.
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*
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* MCP clients discover the authorization server (Authentik) via this
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* endpoint after receiving a 401 with `WWW-Authenticate: resource_metadata=...`.
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*/
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export function GET() {
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const resource = env().PUBLIC_URL.replace(/\/$/, "");
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// The audience scope MUST be advertised. Authentik only evaluates a scope
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// mapping when the client requests that scope by name, and the client only
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// learns scope names from this document. Omit it and every access token
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// arrives without `aud`, which jwt.ts rejects as "claim invalid: aud".
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const audienceScope =
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env().OIDC_AUDIENCE_SCOPE ?? `aud-${env().OIDC_AUDIENCE}`;
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// Same mechanism as the audience scope, different consequence: a client
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// only requests `offline_access` if it sees the name here, and without
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// that request the IdP returns no refresh token — so the client cannot
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// renew and the user gets kicked back to an interactive login whenever
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// the access token expires.
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//
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// Opt-in, because the IdP needs a matching scope mapping; advertising one
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// it doesn't offer can fail the whole authorization request.
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const scopes = ["openid", "profile", "email", audienceScope];
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if (env().OIDC_OFFLINE_ACCESS) scopes.push("offline_access");
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return NextResponse.json({
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resource,
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// The MCP application's issuer, which is not necessarily the Web UI's —
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// see mcpIssuer(). Advertising the wrong one sends clients to a discovery
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// document whose tokens this endpoint will then reject on `iss`.
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authorization_servers: [mcpIssuer()], // as configured, slash and all
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scopes_supported: scopes,
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bearer_methods_supported: ["header"],
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resource_documentation: `${resource}/`,
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});
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}
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