fix: ensure that OIDC correlation cookies are present in callback

server/routes/auth.test.ts

@@ -768,5 +768,63 @@ describe('OpenID Connect', () => {
       assert.strictEqual(response.status, 403);
       assert.strictEqual(response.body.error, ApiErrorCode.Unauthorized);
     });
+
+    it('rejects callback when correlation cookies are missing', async function () {
+      await setupFetchMock();
+
+      const callbackUrl = new URL(OIDC_REDIRECT_URL);
+      callbackUrl.searchParams.set('code', '123456');
+      callbackUrl.searchParams.set('state', 'somestate');
+
+      // Send callback with no signed cookies at all
+      const response = await request(app)
+        .post('/auth/oidc/callback/test')
+        .set('Accept', 'application/json')
+        .send({ callbackUrl: callbackUrl.toString() });
+
+      assert.strictEqual(response.status, 400);
+      assert.strictEqual(
+        response.body.error,
+        ApiErrorCode.OidcAuthorizationFailed
+      );
+    });
+
+    it('rejects callback when only one correlation cookie is present', async function () {
+      await setupFetchMock();
+
+      // Perform login to get only the state cookie
+      const loginResponse = await request(app)
+        .get('/auth/oidc/login/test')
+        .set('Accept', 'application/json');
+
+      assert.strictEqual(loginResponse.status, 200);
+
+      const redirectUrl = new URL(loginResponse.body.redirectUrl);
+      const state = redirectUrl.searchParams.get('state');
+
+      // Extract only the state cookie, dropping the PKCE verifier cookie
+      const cookies = loginResponse.get('Set-Cookie');
+      assert.notStrictEqual(cookies, undefined);
+      const stateCookieOnly = cookies!
+        .filter((c) => c.includes('oidc-state'))
+        .map((c) => c.split(';')[0])
+        .join('; ');
+
+      const callbackUrl = new URL(OIDC_REDIRECT_URL);
+      callbackUrl.searchParams.set('code', '123456');
+      if (state) callbackUrl.searchParams.set('state', state);
+
+      const response = await request(app)
+        .post('/auth/oidc/callback/test')
+        .set('Accept', 'application/json')
+        .set('Cookie', stateCookieOnly)
+        .send({ callbackUrl: callbackUrl.toString() });
+
+      assert.strictEqual(response.status, 400);
+      assert.strictEqual(
+        response.body.error,
+        ApiErrorCode.OidcAuthorizationFailed
+      );
+    });
   });
 });

server/routes/auth.ts

@@ -798,6 +798,19 @@ authRoutes.post(
     const pkceCodeVerifier: string | undefined =
       req.signedCookies[OIDC_CODE_VERIFIER_KEY];
     const expectedState: string | undefined = req.signedCookies[OIDC_STATE_KEY];
+
+    if (!pkceCodeVerifier || !expectedState) {
+      logger.warn('Rejected OIDC callback without correlation cookies', {
+        label: 'Auth',
+        provider: provider.slug,
+        ip: req.ip,
+      });
+      return next({
+        status: 400,
+        error: ApiErrorCode.OidcAuthorizationFailed,
+      });
+    }
+
     res.clearCookie(OIDC_CODE_VERIFIER_KEY);
     res.clearCookie(OIDC_STATE_KEY);