Update /os/v1/config endpoint for config.json migration

See: https://balena.fibery.io/Work/Improvement/os-config-improving-the-interface-for-config.json-modification-901
Change-type: minor
Signed-off-by: Christina Ying Wang <[email protected]>

src/features/os-config/index.ts

@@ -1,27 +1,45 @@
-import type { Application, RequestHandler } from 'express';
+import type { Application } from 'express';
 
 import {
 	DEVICE_CONFIG_OPENVPN_CA,
 	DEVICE_CONFIG_OPENVPN_CONFIG,
 	DEVICE_CONFIG_SSH_AUTHORIZED_KEYS,
+	LOGS_HOST,
 } from '../../lib/config';
 import { b64decode } from '../../lib/utils';
 
-const getOsConfiguration: RequestHandler = (_req, res) => {
-	res.json({
-		services: {
-			openvpn: {
-				config: DEVICE_CONFIG_OPENVPN_CONFIG,
-				ca: b64decode(DEVICE_CONFIG_OPENVPN_CA),
-			},
-			ssh: {
-				authorized_keys: DEVICE_CONFIG_SSH_AUTHORIZED_KEYS,
-			},
-		},
-		schema_version: '1.0.0',
-	});
+// OS service configurations
+const services = {
+	openvpn: {
+		config: DEVICE_CONFIG_OPENVPN_CONFIG,
+		ca: b64decode(DEVICE_CONFIG_OPENVPN_CA),
+	},
+	ssh: {
+		authorized_keys: DEVICE_CONFIG_SSH_AUTHORIZED_KEYS,
+	},
+};
+
+// Config.json migrations: Changes should be evaluated for security risks before applying.
+//
+// - A field may not be deleted from config.json.
+// - A field with a value of non-null tells os-config that the value will be updated
+//   to the new value if it's different.
+// - A field not found in the whitelist of the os-config schema will be ignored.
+const config = {
+	overrides: {
+		...(LOGS_HOST != null && { logsEndpoint: `https://${LOGS_HOST}` }),
+	},
 };
 
 export const setup = (app: Application) => {
-	app.get('/os/v1/config/', getOsConfiguration);
+	app.get('/os/v1/config/', (_req, res) => {
+		res.json({
+			services,
+			// Older os-configs don't know how to handle the config field, but
+			// luckily serde-rs ignores unknown fields by default.
+			config,
+			/** @deprecated schema_version is an outdated field kept for compatibility with legacy os-configs */
+			schema_version: '1.0.0',
+		});
+	});
 };

test/22_os-config.ts

@@ -0,0 +1,35 @@
+import { expect } from 'chai';
+
+import { supertest } from './test-lib/supertest';
+import { LOGS_HOST } from '../src/lib/config';
+
+describe('OS configuration endpoints', () => {
+	describe('/os/v1/config', () => {
+		it('should return a valid JSON response', async () => {
+			const { body } = await supertest().get('/os/v1/config').expect(200);
+
+			// Service configurations should be valid for their respective services
+			expect(body)
+				.to.have.property('services')
+				.that.has.all.keys('openvpn', 'ssh');
+			expect(body.services.openvpn).to.have.all.keys('config', 'ca');
+			expect(body.services.openvpn.config).to.be.a('string');
+			expect(body.services.openvpn.ca).to.be.a('string');
+			expect(body.services.ssh)
+				.to.have.property('authorized_keys')
+				.that.is.a('string');
+
+			// schema_version is kept for backwards compatibility
+			expect(body).to.have.property('schema_version').that.equals('1.0.0');
+
+			// Config should contain config.json overrides
+			expect(body)
+				.to.have.property('config')
+				.that.deep.equals({
+					overrides: {
+						...(LOGS_HOST != null && { logsEndpoint: `https://${LOGS_HOST}` }),
+					},
+				});
+		});
+	});
+});