backend-common: extract NoopTokenManager from ServerTokenManager

Signed-off-by: MT Lewis <mtlewis@users.noreply.github.com>

packages/backend-common/src/tokens/ServerTokenManager.test.ts

@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 import { ConfigReader } from '@backstage/config';
+import { TokenManager } from './types';
 import { ServerTokenManager } from './ServerTokenManager';
 
 const emptyConfig = new ConfigReader({});
@@ -122,8 +123,40 @@ describe('ServerTokenManager', () => {
     });
   });
 
+  describe('ServerTokenManager.fromConfig', () => {
+    it('should throw if backend auth configuration is missing', () => {
+      expect(() =>
+        ServerTokenManager.fromConfig(new ConfigReader({})),
+      ).toThrow();
+    });
+
+    it('should throw if no keys are included in the configuration', () => {
+      expect(() =>
+        ServerTokenManager.fromConfig(
+          new ConfigReader({
+            backend: { auth: { keys: [] } },
+          }),
+        ),
+      ).toThrow();
+    });
+
+    it('should throw if any key is missing a secret property', () => {
+      expect(() =>
+        ServerTokenManager.fromConfig(
+          new ConfigReader({
+            backend: {
+              auth: {
+                keys: [{ secret: '123' }, {}, { secret: '789' }],
+              },
+            },
+          }),
+        ),
+      ).toThrow();
+    });
+  });
+
   describe('ServerTokenManager.noop', () => {
-    let noopTokenManager: ServerTokenManager;
+    let noopTokenManager: TokenManager;
 
     beforeEach(() => {
       noopTokenManager = ServerTokenManager.noop();
@@ -146,11 +179,11 @@ describe('ServerTokenManager', () => {
       ).resolves.not.toThrow();
     });
 
-    it('should not accept signed tokens', async () => {
+    it('should accept signed tokens', async () => {
       const tokenManager = ServerTokenManager.fromConfig(configWithSecret);
       await expect(
         noopTokenManager.authenticate((await tokenManager.getToken()).token),
-      ).rejects.toThrowError(/invalid server token/i);
+      ).resolves.not.toThrow();
     });
   });
 });

packages/backend-common/src/tokens/ServerTokenManager.ts

@@ -19,6 +19,14 @@ import { Config } from '@backstage/config';
 import { AuthenticationError } from '@backstage/errors';
 import { TokenManager } from './types';
 
+class NoopTokenManager implements TokenManager {
+  async getToken() {
+    return { token: '' };
+  }
+
+  async authenticate() {}
+}
+
 /**
  * Creates and validates tokens for use during backend-to-backend
  * authentication.
@@ -26,12 +34,11 @@ import { TokenManager } from './types';
  * @public
  */
 export class ServerTokenManager implements TokenManager {
-  private readonly verificationKeys: JWKS.KeyStore | JWK.NoneKey;
-  private readonly signingKey: JWK.Key | JWK.NoneKey;
-  private readonly signingAlgorithm: string | undefined;
+  private readonly verificationKeys: JWKS.KeyStore;
+  private readonly signingKey: JWK.Key;
 
   static noop() {
-    return new ServerTokenManager();
+    return new NoopTokenManager();
   }
 
   static fromConfig(config: Config) {
@@ -43,20 +50,21 @@ export class ServerTokenManager implements TokenManager {
   }
 
   private constructor(secrets?: string[]) {
-    if (secrets?.length) {
-      this.verificationKeys = new JWKS.KeyStore(
-        secrets.map(k => JWK.asKey({ kty: 'oct', k })),
+    if (!secrets?.length) {
+      throw new Error(
+        'No secrets provided when constructing ServerTokenManager',
       );
-      this.signingKey = this.verificationKeys.all()[0];
-      this.signingAlgorithm = 'HS256';
-    } else {
-      this.verificationKeys = this.signingKey = JWK.None;
     }
+
+    this.verificationKeys = new JWKS.KeyStore(
+      secrets.map(k => JWK.asKey({ kty: 'oct', k })),
+    );
+    this.signingKey = this.verificationKeys.all()[0];
   }
 
   async getToken(): Promise<{ token: string }> {
     const jwt = JWT.sign({ sub: 'backstage-server' }, this.signingKey, {
-      algorithm: this.signingAlgorithm,
+      algorithm: 'HS256',
     });
 
     return { token: jwt };