allow any type for customResponseHeaders config (elastic#66689)

* allow any type of value for customResponseHeaders and convert them

* fix test config creation

* add `?? {}` to avoid breaking all tests...

src/core/server/http/cookie_session_storage.test.ts

@@ -62,6 +62,7 @@ configService.atPath.mockReturnValue(
       disableProtection: true,
       whitelist: [],
     },
+    customResponseHeaders: {},
   } as any)
 );
 

src/core/server/http/http_config.test.ts

@@ -18,7 +18,8 @@
  */
 
 import uuid from 'uuid';
-import { config } from '.';
+import { config, HttpConfig } from './http_config';
+import { CspConfig } from '../csp';
 
 const validHostnames = ['www.example.com', '8.8.8.8', '::1', 'localhost'];
 const invalidHostname = 'asdf$%^';
@@ -107,6 +108,23 @@ test('throws if xsrf.whitelist element does not start with a slash', () => {
   );
 });
 
+test('accepts any type of objects for custom headers', () => {
+  const httpSchema = config.schema;
+  const obj = {
+    customResponseHeaders: {
+      string: 'string',
+      bool: true,
+      number: 12,
+      array: [1, 2, 3],
+      nested: {
+        foo: 1,
+        bar: 'dolly',
+      },
+    },
+  };
+  expect(() => httpSchema.validate(obj)).not.toThrow();
+});
+
 describe('with TLS', () => {
   test('throws if TLS is enabled but `redirectHttpFromPort` is equal to `port`', () => {
     const httpSchema = config.schema;
@@ -173,3 +191,30 @@ describe('with compression', () => {
     expect(() => httpSchema.validate(obj)).toThrowErrorMatchingSnapshot();
   });
 });
+
+describe('HttpConfig', () => {
+  it('converts customResponseHeaders to strings or arrays of strings', () => {
+    const httpSchema = config.schema;
+    const rawConfig = httpSchema.validate({
+      customResponseHeaders: {
+        string: 'string',
+        bool: true,
+        number: 12,
+        array: [1, 2, 3],
+        nested: {
+          foo: 1,
+          bar: 'dolly',
+        },
+      },
+    });
+    const httpConfig = new HttpConfig(rawConfig, CspConfig.DEFAULT);
+
+    expect(httpConfig.customResponseHeaders).toEqual({
+      string: 'string',
+      bool: 'true',
+      number: '12',
+      array: ['1', '2', '3'],
+      nested: '{"foo":1,"bar":"dolly"}',
+    });
+  });
+});

src/core/server/http/http_config.ts

@@ -57,7 +57,7 @@ export const config = {
         ),
         schema.boolean({ defaultValue: false })
       ),
-      customResponseHeaders: schema.recordOf(schema.string(), schema.string(), {
+      customResponseHeaders: schema.recordOf(schema.string(), schema.any(), {
         defaultValue: {},
       }),
       host: schema.string({
@@ -136,7 +136,7 @@ export class HttpConfig {
   public socketTimeout: number;
   public port: number;
   public cors: boolean | { origin: string[] };
-  public customResponseHeaders: Record<string, string>;
+  public customResponseHeaders: Record<string, string | string[]>;
   public maxPayload: ByteSizeValue;
   public basePath?: string;
   public rewriteBasePath: boolean;
@@ -153,7 +153,15 @@ export class HttpConfig {
     this.host = rawHttpConfig.host;
     this.port = rawHttpConfig.port;
     this.cors = rawHttpConfig.cors;
-    this.customResponseHeaders = rawHttpConfig.customResponseHeaders;
+    this.customResponseHeaders = Object.entries(rawHttpConfig.customResponseHeaders ?? {}).reduce(
+      (headers, [key, value]) => {
+        return {
+          ...headers,
+          [key]: Array.isArray(value) ? value.map(e => convertHeader(e)) : convertHeader(value),
+        };
+      },
+      {}
+    );
     this.maxPayload = rawHttpConfig.maxPayload;
     this.name = rawHttpConfig.name;
     this.basePath = rawHttpConfig.basePath;
@@ -166,3 +174,7 @@ export class HttpConfig {
     this.xsrf = rawHttpConfig.xsrf;
   }
 }
+
+const convertHeader = (entry: any): string => {
+  return typeof entry === 'object' ? JSON.stringify(entry) : String(entry);
+};

src/core/server/http/test_utils.ts

@@ -45,6 +45,7 @@ configService.atPath.mockReturnValue(
       disableProtection: true,
       whitelist: [],
     },
+    customResponseHeaders: {},
   } as any)
 );