Merge pull request #7463 from Sarabadu/feat/accept-glob-pattern

[WIP]Add Glob pattern to Cors config

.changeset/rich-deers-run.md

@@ -0,0 +1,14 @@
+---
+'@backstage/backend-common': patch
+---
+
+Add glob patterns support to config CORS options. It's possible to send patterns like:
+
+```yaml
+backend:
+  cors:
+    origin:
+      - https://*.my-domain.com
+      - http://localhost:700[0-9]
+      - https://sub-domain-+([0-9]).my-domain.com
+```

packages/backend-common/src/service/lib/config.test.ts

@@ -15,7 +15,7 @@
  */
 
 import { ConfigReader } from '@backstage/config';
-import { readCspOptions } from './config';
+import { readCorsOptions, readCspOptions } from './config';
 
 describe('config', () => {
   describe('readCspOptions', () => {
@@ -42,4 +42,67 @@ describe('config', () => {
       expect(() => readCspOptions(config)).toThrow(/wanted string-array/);
     });
   });
+
+  describe('readCorsOptions', () => {
+    it('reads single string', () => {
+      const mockCallback = jest.fn();
+      const config = new ConfigReader({ cors: { origin: 'https://*.value*' } });
+      const cors = readCorsOptions(config);
+      expect(cors).toEqual(
+        expect.objectContaining({
+          origin: expect.any(Function),
+        }),
+      );
+      const origin = cors?.origin as Function;
+      origin('https://a.value', mockCallback); // valid origin
+      origin('http://a.value', mockCallback); // invalid origin
+      origin(undefined, mockCallback); // when not origin needs to reject the call
+
+      expect(mockCallback.mock.calls[0][0]).toBe(null);
+      expect(mockCallback.mock.calls[1][0]).toBe(null);
+
+      expect(mockCallback.mock.calls[0][1]).toBe(true);
+      expect(mockCallback.mock.calls[1][1]).toBe(false);
+      expect(mockCallback.mock.calls[2][1]).toBe(false);
+    });
+
+    it('reads string array', () => {
+      const mockCallback = jest.fn();
+      const config = new ConfigReader({
+        cors: {
+          origin: ['http?(s)://*.value?(-+([0-9])).com', 'http://*.value'],
+        },
+      });
+      const cors = readCorsOptions(config);
+      expect(cors).toEqual(
+        expect.objectContaining({
+          origin: expect.any(Function),
+        }),
+      );
+      const origin = cors?.origin as Function;
+      origin('https://a.b.c.value-9.com', mockCallback);
+      origin('http://a.value-999.com', mockCallback);
+      origin('http://a.value', mockCallback);
+      origin('http://a.valuex', mockCallback);
+
+      expect(mockCallback.mock.calls[0][0]).toBe(null);
+      expect(mockCallback.mock.calls[1][0]).toBe(null);
+      expect(mockCallback.mock.calls[2][0]).toBe(null);
+      expect(mockCallback.mock.calls[3][0]).toBe(null);
+
+      expect(mockCallback.mock.calls[0][1]).toBe(true);
+      expect(mockCallback.mock.calls[1][1]).toBe(true);
+      expect(mockCallback.mock.calls[2][1]).toBe(true);
+      expect(mockCallback.mock.calls[3][1]).toBe(false);
+    });
+
+    it('reads undefined origin', () => {
+      const config = new ConfigReader({
+        cors: {},
+      });
+      const cors = readCorsOptions(config);
+      expect(cors).toEqual(expect.objectContaining({}));
+      expect(cors?.origin).toBeUndefined();
+    });
+  });
 });

packages/backend-common/src/service/lib/config.ts

@@ -16,6 +16,7 @@
 
 import { Config } from '@backstage/config';
 import { CorsOptions } from 'cors';
+import { Minimatch } from 'minimatch';
 
 export type BaseOptions = {
   listenPort?: string | number;
@@ -46,6 +47,13 @@ export type CertificateAttributes = {
  */
 export type CspOptions = Record<string, string[]>;
 
+type StaticOrigin = boolean | string | RegExp | (boolean | string | RegExp)[];
+
+type CustomOrigin = (
+  requestOrigin: string | undefined,
+  callback: (err: Error | null, origin?: StaticOrigin) => void,
+) => void;
+
 /**
  * Reads some base options out of a config object.
  *
@@ -112,7 +120,7 @@ export function readCorsOptions(config: Config): CorsOptions | undefined {
   }
 
   return removeUnknown({
-    origin: getOptionalStringOrStrings(cc, 'origin'),
+    origin: createCorsOriginMatcher(getOptionalStringOrStrings(cc, 'origin')),
     methods: getOptionalStringOrStrings(cc, 'methods'),
     allowedHeaders: getOptionalStringOrStrings(cc, 'allowedHeaders'),
     exposedHeaders: getOptionalStringOrStrings(cc, 'exposedHeaders'),
@@ -207,16 +215,45 @@ function getOptionalStringOrStrings(
   key: string,
 ): string | string[] | undefined {
   const value = config.getOptional(key);
-  if (
-    value === undefined ||
-    typeof value === 'string' ||
-    isStringArray(value)
-  ) {
+  if (value === undefined || isStringOrStrings(value)) {
     return value;
   }
   throw new Error(`Expected string or array of strings, got ${typeof value}`);
 }
 
+function createCorsOriginMatcher(
+  originValue: string | string[] | undefined,
+): CustomOrigin | undefined {
+  if (originValue === undefined) {
+    return originValue;
+  }
+
+  if (!isStringOrStrings(originValue)) {
+    throw new Error(
+      `Expected string or array of strings, got ${typeof originValue}`,
+    );
+  }
+
+  const allowedOrigin =
+    typeof originValue === 'string' ? [originValue] : originValue;
+
+  const allowedOriginPatterns =
+    allowedOrigin?.map(
+      pattern => new Minimatch(pattern, { nocase: true, noglobstar: true }),
+    ) ?? [];
+
+  return (origin, callback) => {
+    return callback(
+      null,
+      allowedOriginPatterns.some(pattern => pattern.match(origin ?? '')),
+    );
+  };
+}
+
+function isStringOrStrings(value: any): value is string | string[] {
+  return typeof value === 'string' || isStringArray(value);
+}
+
 function isStringArray(value: any): value is string[] {
   if (!Array.isArray(value)) {
     return false;