Authorization Server: DPoP Support (SEP-1932)

src/scenarios/authorization-server/auth/spec-references.ts

@@ -8,5 +8,26 @@ export const SpecReferences: { [key: string]: SpecReference } = {
   OAUTH_2_1_AUTHORIZATION_CODE_GRANT: {
     id: 'OAUTH-2.1-authorization-code-grant',
     url: 'https://www.ietf.org/archive/id/draft-ietf-oauth-v2-1-13.html#section-4.1'
+  },
+  // DPoP (SEP-1932 / RFC 9449) — authorization-server concerns.
+  SEP_1932_DPOP: {
+    id: 'SEP-1932-DPoP',
+    url: 'https://github.com/modelcontextprotocol/modelcontextprotocol/pull/1932'
+  },
+  DPOP_EXTENSION: {
+    id: 'MCP-DPoP-Extension',
+    url: 'https://github.com/modelcontextprotocol/ext-auth/blob/pieterkas-dpop-extension/specification/draft/dpop-extension.mdx'
+  },
+  RFC_9449_AS_METADATA: {
+    id: 'RFC-9449-authorization-server-metadata',
+    url: 'https://www.rfc-editor.org/rfc/rfc9449.html#section-5.1'
+  },
+  RFC_9449_PUBLIC_KEY_CONFIRMATION: {
+    id: 'RFC-9449-public-key-confirmation',
+    url: 'https://www.rfc-editor.org/rfc/rfc9449.html#section-6'
+  },
+  RFC_9449_ALGORITHMS: {
+    id: 'RFC-9449-dpop-proof-jwt-syntax',
+    url: 'https://www.rfc-editor.org/rfc/rfc9449.html#section-11.6'
   }
 };

src/scenarios/authorization-server/dpop.test.ts

@@ -0,0 +1,171 @@
+import { describe, it, expect } from 'vitest';
+import {
+  createAuthServer,
+  type AuthServerOptions
+} from '../client/auth/helpers/createAuthServer';
+import { ServerLifecycle } from '../client/auth/helpers/serverLifecycle';
+import { testScenarioContext } from '../../mock-server/testing';
+import type { CheckStatus, ConformanceCheck } from '../../types';
+import { DPoPAuthorizationServerScenario, negotiateProofAlg } from './dpop';
+
+const ALL_IDS = [
+  'sep-1932-as-metadata-alg-values',
+  'sep-1932-as-no-none-alg',
+  'sep-1932-as-token-binding'
+] as const;
+
+const statusOf = (
+  checks: ConformanceCheck[],
+  id: string
+): CheckStatus | undefined => checks.find((c) => c.id === id)?.status;
+
+/**
+ * Start an in-process test AS (real Express app, no mocks) with the given DPoP
+ * options, run the scenario against its live URL, and return the emitted checks.
+ * The AS 302s straight to the redirect_uri, so the scenario auto-follows headless.
+ */
+async function runAgainst(
+  dpopOptions: Partial<AuthServerOptions>,
+  // `false` means "send no client_id" — a plain `undefined` would re-trigger the
+  // default via JS default-parameter semantics.
+  clientId: string | false = 'test-client-id'
+): Promise<ConformanceCheck[]> {
+  const lifecycle = new ServerLifecycle();
+  const app = createAuthServer(testScenarioContext(), [], lifecycle.getUrl, {
+    loggingEnabled: false,
+    grantTypesSupported: ['authorization_code', 'refresh_token'],
+    ...dpopOptions
+  });
+  await lifecycle.start(app);
+  try {
+    return await new DPoPAuthorizationServerScenario().run(
+      { url: lifecycle.getUrl(), port: 45678, clientId: clientId || undefined },
+      {}
+    );
+  } finally {
+    await lifecycle.stop();
+  }
+}
+
+// A DPoP-capable AS: advertises an asymmetric alg and issues bound tokens.
+// (`dpop_bound_access_tokens` is per-client registration metadata, RFC 9449
+// §5.2 — not an AS option — so it is deliberately not set here.)
+const COMPLIANT: Partial<AuthServerOptions> = {
+  dpopSigningAlgValuesSupported: ['ES256']
+};
+
+describe('DPoPAuthorizationServerScenario — compliant AS', () => {
+  it('emits all three sep-1932-as-* checks as SUCCESS', async () => {
+    const checks = await runAgainst(COMPLIANT);
+    for (const id of ALL_IDS) {
+      expect(statusOf(checks, id)).toBe('SUCCESS');
+    }
+    expect(checks.filter((c) => c.status === 'FAILURE')).toHaveLength(0);
+  });
+
+  it('binds the issued token to the presented proof key (cnf.jkt matches)', async () => {
+    const checks = await runAgainst(COMPLIANT);
+    const binding = checks.find((c) => c.id === 'sep-1932-as-token-binding');
+    expect(binding?.status).toBe('SUCCESS');
+    const details = binding?.details as {
+      tokenType: string;
+      cnfJkt: string;
+      expectedJkt: string;
+    };
+    expect(details.tokenType).toBe('DPoP');
+    expect(details.cnfJkt).toBe(details.expectedJkt);
+  });
+});
+
+// Isolation matrix: each defect fails EXACTLY its target check, the rest stay
+// SUCCESS. (`omit-alg-values` is not here — dropping the field means "not a DPoP
+// AS", which SKIPs the whole scenario; see the support-gate tests below.)
+describe('DPoPAuthorizationServerScenario — one-defect isolation', () => {
+  const CASES = [
+    {
+      misbehavior: 'empty-alg-values',
+      target: 'sep-1932-as-metadata-alg-values'
+    },
+    { misbehavior: 'include-none', target: 'sep-1932-as-no-none-alg' },
+    { misbehavior: 'unbound-token', target: 'sep-1932-as-token-binding' }
+  ] as const;
+
+  for (const { misbehavior, target } of CASES) {
+    it(`misbehaving AS (${misbehavior}) fails only ${target}`, async () => {
+      const checks = await runAgainst({
+        ...COMPLIANT,
+        dpopMisbehavior: misbehavior
+      });
+      expect(statusOf(checks, target)).toBe('FAILURE');
+      for (const id of ALL_IDS.filter((c) => c !== target)) {
+        expect(statusOf(checks, id)).toBe('SUCCESS');
+      }
+    });
+  }
+
+  it('fails the no-none-alg check when a symmetric algorithm is advertised', async () => {
+    const checks = await runAgainst({
+      dpopSigningAlgValuesSupported: ['ES256', 'HS256']
+    });
+    expect(statusOf(checks, 'sep-1932-as-metadata-alg-values')).toBe('SUCCESS');
+    expect(statusOf(checks, 'sep-1932-as-no-none-alg')).toBe('FAILURE');
+  });
+});
+
+describe('DPoPAuthorizationServerScenario — skip conditions', () => {
+  it('skips the token-binding check when no client_id is supplied', async () => {
+    const checks = await runAgainst(COMPLIANT, false);
+    expect(statusOf(checks, 'sep-1932-as-metadata-alg-values')).toBe('SUCCESS');
+    expect(statusOf(checks, 'sep-1932-as-no-none-alg')).toBe('SUCCESS');
+    expect(statusOf(checks, 'sep-1932-as-token-binding')).toBe('SKIPPED');
+  });
+
+  it('skips token binding when no advertised proof alg is supported (no ES256 fallback)', async () => {
+    // ES256K is asymmetric (passes no-none-alg) but not one the harness can
+    // produce; the scenario must SKIP rather than send an unadvertised ES256
+    // proof the AS would reject and mis-score as a binding failure.
+    const checks = await runAgainst({
+      dpopSigningAlgValuesSupported: ['ES256K']
+    });
+    expect(statusOf(checks, 'sep-1932-as-metadata-alg-values')).toBe('SUCCESS');
+    expect(statusOf(checks, 'sep-1932-as-no-none-alg')).toBe('SUCCESS');
+    expect(statusOf(checks, 'sep-1932-as-token-binding')).toBe('SKIPPED');
+  });
+
+  it('skips the whole scenario when the AS does not advertise DPoP support', async () => {
+    // No dpop_signing_alg_values_supported → not a DPoP AS (RFC 9449 §5.1), so
+    // the DPoP requirements do not apply: every check SKIPs rather than fails.
+    const checks = await runAgainst({ dpopMisbehavior: 'omit-alg-values' });
+    for (const id of ALL_IDS) {
+      expect(statusOf(checks, id)).toBe('SKIPPED');
+    }
+    expect(checks.filter((c) => c.status === 'FAILURE')).toHaveLength(0);
+  });
+});
+
+describe('negotiateProofAlg (dpop_signing_alg_values_supported shapes)', () => {
+  it('picks the first supported alg from a non-empty array', () => {
+    expect(negotiateProofAlg(['ES256'])).toBe('ES256');
+    expect(negotiateProofAlg(['RS256', 'ES256'])).toBe('RS256');
+  });
+
+  it('returns null for a non-empty array with no supported alg (→ SKIP)', () => {
+    expect(negotiateProofAlg(['ES256K'])).toBeNull();
+  });
+
+  it('falls back to ES256 only for an empty array or an absent field', () => {
+    expect(negotiateProofAlg([])).toBe('ES256');
+    // Absent never reaches here in the scenario (the support gate SKIPs upstream),
+    // but the contract still treats undefined as the empty/best-effort case.
+    expect(negotiateProofAlg(undefined)).toBe('ES256');
+  });
+
+  it('returns null for a present-but-non-array (malformed) value (→ SKIP)', () => {
+    // Regression guard: a string or JSON null must NOT fall through to the
+    // ES256 fallback, which would mis-score token binding.
+    expect(negotiateProofAlg('RS256')).toBeNull();
+    expect(negotiateProofAlg(null)).toBeNull();
+    expect(negotiateProofAlg(42)).toBeNull();
+    expect(negotiateProofAlg({ 0: 'ES256' })).toBeNull();
+  });
+});