backend-{plugin,app}-api: added addAuthPolicy to HttpRouterService + implementation

Co-authored-by: Fredrik Adelöw <freben@gmail.com>
Co-authored-by: Carl-Erik Bergström <cbergstrom@spotify.com>
Co-authored-by: blam <ben@blam.sh>
Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

packages/backend-app-api/package.json

@@ -73,6 +73,7 @@
     "minimist": "^1.2.5",
     "morgan": "^1.10.0",
     "node-forge": "^1.3.1",
+    "path-to-regexp": "^6.2.1",
     "selfsigned": "^2.0.0",
     "stoppable": "^1.1.0",
     "winston": "^3.2.1",

packages/backend-app-api/src/services/implementations/httpRouter/createCredentialsBarrier.ts

@@ -0,0 +1,89 @@
+/*
+ * Copyright 2024 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import {
+  HttpAuthService,
+  HttpRouterServiceAuthPolicy,
+} from '@backstage/backend-plugin-api';
+import { RequestHandler } from 'express';
+import { pathToRegexp } from 'path-to-regexp';
+
+export function createPathPolicyPredicate(policyPath: string) {
+  if (policyPath === '/' || policyPath === '*') {
+    return () => true;
+  }
+
+  const pathRegex = pathToRegexp(policyPath, undefined, {
+    end: false,
+  });
+
+  return (path: string): boolean => {
+    return pathRegex.test(path);
+  };
+}
+
+export function createCredentialsBarrier(options: {
+  httpAuth: HttpAuthService;
+}): {
+  middleware: RequestHandler;
+  addAuthPolicy: (policy: HttpRouterServiceAuthPolicy) => void;
+} {
+  const { httpAuth } = options;
+
+  const unauthenticatedPredicates = new Array<(path: string) => boolean>();
+  const cookiePredicates = new Array<(path: string) => boolean>();
+
+  const middleware: RequestHandler = async (req, _, next) => {
+    const allowsUnauthenticated = unauthenticatedPredicates.some(predicate =>
+      predicate(req.path),
+    );
+
+    if (allowsUnauthenticated) {
+      next();
+      return;
+    }
+
+    const allowsCookie = cookiePredicates.some(predicate =>
+      predicate(req.path),
+    );
+
+    if (allowsCookie) {
+      // don't we need a user-cookie allow type here?
+      await httpAuth.credentials(req, {
+        allow: ['user-cookie', 'user', 'service'],
+      });
+      next();
+      return;
+    }
+
+    await httpAuth.credentials(req, {
+      allow: ['user', 'service'],
+    });
+    next();
+  };
+
+  const addAuthPolicy = (policy: HttpRouterServiceAuthPolicy) => {
+    if (policy.allow === 'unauthenticated') {
+      unauthenticatedPredicates.push(createPathPolicyPredicate(policy.path));
+    } else if (policy.allow === 'user-cookie') {
+      cookiePredicates.push(createPathPolicyPredicate(policy.path));
+    }
+
+    throw new Error('Invalid auth policy');
+  };
+
+  return { middleware, addAuthPolicy };
+}

packages/backend-plugin-api/api-report.md

@@ -299,10 +299,20 @@ export interface HttpAuthService {
 
 // @public (undocumented)
 export interface HttpRouterService {
+  // (undocumented)
+  addAuthPolicy(policy: HttpRouterServiceAuthPolicy): void;
   // (undocumented)
   use(handler: Handler): void;
 }
 
+// @public (undocumented)
+export interface HttpRouterServiceAuthPolicy {
+  // (undocumented)
+  allow: 'unauthenticated' | 'user-cookie';
+  // (undocumented)
+  path: string;
+}
+
 // @public (undocumented)
 export interface IdentityService extends IdentityApi {}
 

packages/backend-plugin-api/src/services/definitions/HttpRouterService.ts

@@ -16,9 +16,17 @@
 
 import { Handler } from 'express';
 
+/** @public */
+export interface HttpRouterServiceAuthPolicy {
+  path: string;
+  allow: 'unauthenticated' | 'user-cookie';
+}
+
 /**
  * @public
  */
 export interface HttpRouterService {
   use(handler: Handler): void;
+
+  addAuthPolicy(policy: HttpRouterServiceAuthPolicy): void;
 }

packages/backend-plugin-api/src/services/definitions/index.ts

@@ -29,7 +29,10 @@ export type {
 export type { RootConfigService } from './RootConfigService';
 export type { DatabaseService } from './DatabaseService';
 export type { DiscoveryService } from './DiscoveryService';
-export type { HttpRouterService } from './HttpRouterService';
+export type {
+  HttpRouterService,
+  HttpRouterServiceAuthPolicy,
+} from './HttpRouterService';
 export type {
   HttpAuthService,
   BackstageCredentialTypes,

packages/backend-test-utils/src/next/services/mockServices.ts

@@ -182,6 +182,7 @@ export namespace mockServices {
     export const factory = httpRouterServiceFactory;
     export const mock = simpleMock(coreServices.httpRouter, () => ({
       use: jest.fn(),
+      addAuthPolicy: jest.fn(),
     }));
   }
   export namespace rootHttpRouter {

yarn.lock

@@ -3258,6 +3258,7 @@ __metadata:
     minimist: ^1.2.5
     morgan: ^1.10.0
     node-forge: ^1.3.1
+    path-to-regexp: ^6.2.1
     selfsigned: ^2.0.0
     stoppable: ^1.1.0
     supertest: ^6.1.3
@@ -37508,10 +37509,10 @@ __metadata:
   languageName: node
   linkType: hard
 
-"path-to-regexp@npm:^6.2.0":
-  version: 6.2.0
-  resolution: "path-to-regexp@npm:6.2.0"
-  checksum: a6aca74d2d6e2e7594d812f653cf85e9cb5054d3a8d80f099722a44ef6ad22639b02078e5ea83d11db16321c3e4359e3f1ab0274fa78dad0754a6e53f630b0fc
+"path-to-regexp@npm:^6.2.0, path-to-regexp@npm:^6.2.1":
+  version: 6.2.1
+  resolution: "path-to-regexp@npm:6.2.1"
+  checksum: f0227af8284ea13300f4293ba111e3635142f976d4197f14d5ad1f124aebd9118783dd2e5f1fe16f7273743cc3dbeddfb7493f237bb27c10fdae07020cc9b698
   languageName: node
   linkType: hard