fix(core): Log warning where file values contain white space at the start or end (e.g. new lines) (#24442)

packages/@n8n/config/src/decorators.ts

@@ -21,7 +21,15 @@ const readEnv = (envName: string) => {
 
 	// Read the value from a file, if "_FILE" environment variable is defined
 	const filePath = process.env[`${envName}_FILE`];
-	if (filePath) return readFileSync(filePath, 'utf8');
+	if (filePath) {
+		const value = readFileSync(filePath, 'utf8');
+		if (value !== value.trim()) {
+			console.warn(
+				`[n8n] Warning: The file specified by ${envName}_FILE contains leading or trailing whitespace, which may cause authentication failures.`,
+			);
+		}
+		return value;
+	}
 
 	return undefined;
 };

packages/@n8n/config/test/config.test.ts

@@ -516,6 +516,24 @@ describe('GlobalConfig', () => {
 		expect(mockFs.readFileSync).toHaveBeenCalled();
 	});
 
+	it('should warn when _FILE env variable value contains whitespace', () => {
+		const passwordFile = '/path/to/postgres/password';
+		process.env = {
+			DB_POSTGRESDB_PASSWORD_FILE: passwordFile,
+		};
+		mockFs.readFileSync
+			.calledWith(passwordFile, 'utf8')
+			.mockReturnValueOnce('password-from-file\n');
+
+		const config = Container.get(GlobalConfig);
+		expect(config.database.postgresdb.password).toBe('password-from-file');
+		expect(consoleWarnMock).toHaveBeenCalledWith(
+			expect.stringContaining(
+				'DB_POSTGRESDB_PASSWORD_FILE contains leading or trailing whitespace',
+			),
+		);
+	});
+
 	it('should handle invalid numbers', () => {
 		process.env = {
 			DB_LOGGING_MAX_EXECUTION_TIME: 'abcd',

packages/@n8n/config/test/decorators.test.ts

@@ -1,10 +1,22 @@
 import { Container } from '@n8n/di';
+import fs from 'fs';
 
 import { Config, Env } from '../src/decorators';
 
+jest.mock('fs');
+const mockFs = jest.mocked(fs);
+
 describe('decorators', () => {
+	const originalEnv = process.env;
+
 	beforeEach(() => {
 		Container.reset();
+		process.env = {};
+		jest.clearAllMocks();
+	});
+
+	afterEach(() => {
+		process.env = originalEnv;
 	});
 
 	it('should throw when explicit typing is missing', () => {
@@ -19,4 +31,56 @@ describe('decorators', () => {
 			'Invalid decorator metadata on key "value" on InvalidConfig\n Please use explicit typing on all config fields',
 		);
 	});
+
+	it('should read value from _FILE env variable', () => {
+		const filePath = '/path/to/secret';
+		process.env.TEST_VALUE_FILE = filePath;
+		mockFs.readFileSync.mockReturnValueOnce('secret-value');
+
+		@Config
+		class TestConfig {
+			@Env('TEST_VALUE')
+			value: string = 'default';
+		}
+
+		const config = Container.get(TestConfig);
+		expect(config.value).toBe('secret-value');
+		expect(mockFs.readFileSync).toHaveBeenCalledWith(filePath, 'utf8');
+	});
+
+	it('should warn when _FILE env variable value contains whitespace', () => {
+		const filePath = '/path/to/secret';
+		process.env.TEST_VALUE_FILE = filePath;
+		mockFs.readFileSync.mockReturnValueOnce('secret-value\n');
+		const consoleWarnSpy = jest.spyOn(console, 'warn').mockImplementation();
+
+		@Config
+		class TestConfig {
+			@Env('TEST_VALUE')
+			value: string = 'default';
+		}
+
+		const config = Container.get(TestConfig);
+		expect(config.value).toBe('secret-value');
+		expect(consoleWarnSpy).toHaveBeenCalledWith(
+			expect.stringContaining('TEST_VALUE_FILE contains leading or trailing whitespace'),
+		);
+		consoleWarnSpy.mockRestore();
+	});
+
+	it('should prefer direct env variable over _FILE variant', () => {
+		const filePath = '/path/to/secret';
+		process.env.TEST_VALUE = 'direct-value';
+		process.env.TEST_VALUE_FILE = filePath;
+
+		@Config
+		class TestConfig {
+			@Env('TEST_VALUE')
+			value: string = 'default';
+		}
+
+		const config = Container.get(TestConfig);
+		expect(config.value).toBe('direct-value');
+		expect(mockFs.readFileSync).not.toHaveBeenCalled();
+	});
 });

packages/cli/src/config/index.ts

@@ -49,6 +49,11 @@ if (!inE2ETests && !inTest) {
 					}
 					throw error;
 				}
+				if (value !== value.trim()) {
+					console.warn(
+						`[n8n] Warning: The file specified by ${envName} contains leading or trailing whitespace, which may cause authentication failures.`,
+					);
+				}
 				config.set(key, value);
 			}
 		}