[Reporting] Update some runtime validations

docs/settings/reporting-settings.asciidoc

@@ -54,6 +54,14 @@ The protocol for accessing Kibana, typically `http` or `https`.
 `xpack.reporting.kibanaServer.hostname`::
 The hostname for accessing {kib}, if different from the `server.host` value.
 
+[NOTE]
+============
+Reporting authenticates requests on the Kibana page only when the hostname matches the
+`xpack.reporting.kibanaServer.hostname` setting. Therefore Reporting would fail if the
+set value redirects to another server. For that reason, `"0"` is an invalid setting
+because, in the Reporting browser, it becomes an automatic redirect to `"0.0.0.0"`.
+============
+
 
 [float]
 [[reporting-job-queue-settings]]

x-pack/legacy/plugins/reporting/config.ts

@@ -14,7 +14,7 @@ export async function config(Joi: any) {
     enabled: Joi.boolean().default(true),
     kibanaServer: Joi.object({
       protocol: Joi.string().valid(['http', 'https']),
-      hostname: Joi.string(),
+      hostname: Joi.string().invalid('0'),
       port: Joi.number().integer(),
     }).default(),
     queue: Joi.object({

x-pack/legacy/plugins/reporting/server/lib/validate/__tests__/validate_config.js → x-pack/legacy/plugins/reporting/server/lib/validate/__tests__/validate_encryption_key.js

@@ -6,10 +6,9 @@
 
 import expect from '@kbn/expect';
 import sinon from 'sinon';
-import { validateConfig } from '../validate_config';
+import { validateEncryptionKey } from '../validate_encryption_key';
 
-// FAILING: https://github.com/elastic/kibana/issues/51373
-describe.skip('Reporting: Validate config', () => {
+describe('Reporting: Validate config', () => {
   const logger = {
     warning: sinon.spy(),
   };
@@ -25,7 +24,7 @@ describe.skip('Reporting: Validate config', () => {
         set: sinon.stub(),
       };
 
-      expect(() => validateConfig(config, logger)).not.to.throwError();
+      expect(() => validateEncryptionKey({ config: () => config }, logger)).not.to.throwError();
 
       sinon.assert.calledWith(config.set, 'xpack.reporting.encryptionKey');
       sinon.assert.calledWithMatch(logger.warning, /Generating a random key/);

x-pack/legacy/plugins/reporting/server/lib/validate/__tests__/validate_server_host.ts

@@ -0,0 +1,30 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+import expect from '@kbn/expect';
+import sinon from 'sinon';
+import { ServerFacade } from '../../../../types';
+import { validateServerHost } from '../validate_server_host';
+
+const configKey = 'xpack.reporting.kibanaServer.hostname';
+
+describe('Reporting: Validate server host setting', () => {
+  it(`should log a warning and set ${configKey} if server.host is "0"`, () => {
+    const getStub = sinon.stub();
+    getStub.withArgs('server.host').returns('0');
+    getStub.withArgs(configKey).returns(undefined);
+    const config = {
+      get: getStub,
+      set: sinon.stub(),
+    };
+
+    expect(() =>
+      validateServerHost(({ config: () => config } as unknown) as ServerFacade)
+    ).to.throwError();
+
+    sinon.assert.calledWith(config.set, configKey);
+  });
+});

x-pack/legacy/plugins/reporting/server/lib/validate/index.ts

@@ -7,8 +7,9 @@
 import { ServerFacade, Logger } from '../../../types';
 import { HeadlessChromiumDriverFactory } from '../../browsers/chromium/driver_factory';
 import { validateBrowser } from './validate_browser';
-import { validateConfig } from './validate_config';
+import { validateEncryptionKey } from './validate_encryption_key';
 import { validateMaxContentLength } from './validate_max_content_length';
+import { validateServerHost } from './validate_server_host';
 
 export async function runValidations(
   server: ServerFacade,
@@ -18,13 +19,12 @@ export async function runValidations(
   try {
     await Promise.all([
       validateBrowser(server, browserFactory, logger),
-      validateConfig(server, logger),
+      validateEncryptionKey(server, logger),
       validateMaxContentLength(server, logger),
+      validateServerHost(server),
     ]);
     logger.debug(`Reporting plugin self-check ok!`);
   } catch (err) {
-    logger.warning(
-      `Reporting plugin self-check failed. Please check the Kibana Reporting settings. ${err}`
-    );
+    logger.warning(`Reporting plugin self-check generated a warning: ${err}`);
   }
 }

x-pack/legacy/plugins/reporting/server/lib/validate/validate_config.ts → x-pack/legacy/plugins/reporting/server/lib/validate/validate_encryption_key.ts

@@ -7,11 +7,12 @@
 import crypto from 'crypto';
 import { ServerFacade, Logger } from '../../../types';
 
-export function validateConfig(serverFacade: ServerFacade, logger: Logger) {
+export function validateEncryptionKey(serverFacade: ServerFacade, logger: Logger) {
   const config = serverFacade.config();
 
   const encryptionKey = config.get('xpack.reporting.encryptionKey');
   if (encryptionKey == null) {
+    // TODO this should simply throw an error and let the handler conver it to a warning mesasge. See validateServerHost.
     logger.warning(
       `Generating a random key for xpack.reporting.encryptionKey. To prevent pending reports from failing on restart, please set ` +
         `xpack.reporting.encryptionKey in kibana.yml`

x-pack/legacy/plugins/reporting/server/lib/validate/validate_max_content_length.ts

@@ -25,6 +25,7 @@ export async function validateMaxContentLength(server: ServerFacade, logger: Log
   const kibanaMaxContentBytes: number = config.get(KIBANA_MAX_SIZE_BYTES_PATH);
 
   if (kibanaMaxContentBytes > elasticSearchMaxContentBytes) {
+    // TODO this should simply throw an error and let the handler conver it to a warning mesasge. See validateServerHost.
     logger.warning(
       `${KIBANA_MAX_SIZE_BYTES_PATH} (${kibanaMaxContentBytes}) is higher than ElasticSearch's ${ES_MAX_SIZE_BYTES_PATH} (${elasticSearchMaxContentBytes}). ` +
         `Please set ${ES_MAX_SIZE_BYTES_PATH} in ElasticSearch to match, or lower your ${KIBANA_MAX_SIZE_BYTES_PATH} in Kibana to avoid this warning.`

x-pack/legacy/plugins/reporting/server/lib/validate/validate_server_host.ts

@@ -0,0 +1,27 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+import { ServerFacade } from '../../../types';
+
+const configKey = 'xpack.reporting.kibanaServer.hostname';
+
+export function validateServerHost(serverFacade: ServerFacade) {
+  const config = serverFacade.config();
+
+  const serverHost = config.get('server.host');
+  const reportingKibanaHostName = config.get(configKey);
+
+  if (!reportingKibanaHostName && serverHost === '0') {
+    // @ts-ignore: No set() method on KibanaConfig, just get() and has()
+    config.set(configKey, '0.0.0.0'); // update config in memory to allow Reporting to work
+
+    throw new Error(
+      `Found 'server.host: "0"' in settings. This is incompatible with Reporting. ` +
+        `To enable Reporting to work, '${configKey}: 0.0.0.0' is being automatically to the configuration. ` +
+        `You can change to 'server.host: 0.0.0.0' or add '${configKey}: 0.0.0.0' in kibana.yml to prevent this message.`
+    );
+  }
+}