Add RedsocksConf.stringify method

`stringify` takes a RedsocksConfig, an internal object
representation of the redsocks.conf file, and transforms
it into a valid string that can be written to redsocks.conf.

Signed-off-by: Christina Ying Wang <christina@balena.io>

src/host-config/index.ts

@@ -4,6 +4,7 @@ import * as config from '../config';
 import { pathOnRoot } from '../lib/host-utils';
 
 export * from './proxy';
+export * from './types';
 
 const hostnamePath = pathOnRoot('/etc/hostname');
 

src/host-config/proxy.ts

@@ -24,10 +24,31 @@ const isAuthField = (field: string): boolean =>
 const blockRegexFor = (blockLabel: string) =>
 	new RegExp(`${blockLabel}\\s?{([\\s\\S]+?)}(?=\\s|$)`);
 
+const baseBlock = {
+	log_debug: 'off',
+	log_info: 'on',
+	log: 'stderr',
+	daemon: 'off',
+	redirector: 'iptables',
+};
+
 export class RedsocksConf {
-	// public static stringify(_config: RedsocksConfig): string {
-	// 	return 'TODO';
-	// }
+	public static stringify(config: RedsocksConfig): string {
+		const blocks: string[] = [];
+
+		if (config.redsocks && Object.keys(config.redsocks).length > 0) {
+			blocks.push(RedsocksConf.stringifyBlock('base', baseBlock));
+			blocks.push(
+				RedsocksConf.stringifyBlock('redsocks', {
+					...config.redsocks,
+					local_ip: '127.0.0.1',
+					local_port: 12345,
+				}),
+			);
+		}
+
+		return blocks.length ? blocks.join('\n') : '';
+	}
 
 	public static parse(rawConf: string): RedsocksConfig {
 		const conf: RedsocksConfig = {};
@@ -63,6 +84,20 @@ export class RedsocksConf {
 		}
 	}
 
+	private static stringifyBlock(
+		label: string,
+		block: Record<string, any>,
+	): string {
+		const lines = Object.entries(block).map(([key, value]) => {
+			if (isAuthField(key)) {
+				// Add double quotes around login and password fields
+				value = `${value.startsWith('"') ? '' : '"'}${value}${value.endsWith('"') ? '' : '"'}`;
+			}
+			return `\t${key} = ${value};`;
+		});
+		return `${label} {\n${lines.join('\n')}\n}\n`;
+	}
+
 	/**
 	 * Given the raw contents of a block redsocks.conf file,
 	 * extract to a key-value object.

test/unit/host-config.spec.ts

@@ -6,6 +6,124 @@ import * as hostConfig from '~/src/host-config/index';
 import log from '~/lib/supervisor-console';
 
 describe('RedsocksConf', () => {
+	describe('stringify', () => {
+		it('stringifies RedsocksConfig into config string', () => {
+			const conf: hostConfig.RedsocksConfig = {
+				redsocks: {
+					type: 'socks5',
+					ip: 'example.org',
+					port: 1080,
+					login: '"foo"',
+					password: '"bar"',
+				},
+			};
+			const confStr = hostConfig.RedsocksConf.stringify(conf);
+			expect(confStr).to.equal(
+				stripIndent`
+				base {
+					log_debug = off;
+					log_info = on;
+					log = stderr;
+					daemon = off;
+					redirector = iptables;
+				}
+
+				redsocks {
+					type = socks5;
+					ip = example.org;
+					port = 1080;
+					login = "foo";
+					password = "bar";
+					local_ip = 127.0.0.1;
+					local_port = 12345;
+				}
+			` + '\n',
+			);
+		});
+
+		it('adds double quotes to auth fields if not exists', () => {
+			const conf: hostConfig.RedsocksConfig = {
+				redsocks: {
+					type: 'socks5',
+					ip: 'example.org',
+					port: 1080,
+					login: 'foo',
+					password: 'bar',
+				},
+			};
+			const confStr = hostConfig.RedsocksConf.stringify(conf);
+			expect(confStr).to.equal(
+				stripIndent`
+				base {
+					log_debug = off;
+					log_info = on;
+					log = stderr;
+					daemon = off;
+					redirector = iptables;
+				}
+
+				redsocks {
+					type = socks5;
+					ip = example.org;
+					port = 1080;
+					login = "foo";
+					password = "bar";
+					local_ip = 127.0.0.1;
+					local_port = 12345;
+				}
+			` + '\n',
+			);
+		});
+
+		it('accepts port field of type string', () => {
+			const conf = {
+				redsocks: {
+					type: 'socks5',
+					ip: 'example.org',
+					port: '1080',
+					login: 'foo',
+					password: 'bar',
+				},
+			} as unknown as hostConfig.RedsocksConfig;
+			const confStr = hostConfig.RedsocksConf.stringify(conf);
+			expect(confStr).to.equal(
+				stripIndent`
+				base {
+					log_debug = off;
+					log_info = on;
+					log = stderr;
+					daemon = off;
+					redirector = iptables;
+				}
+
+				redsocks {
+					type = socks5;
+					ip = example.org;
+					port = 1080;
+					login = "foo";
+					password = "bar";
+					local_ip = 127.0.0.1;
+					local_port = 12345;
+				}
+			` + '\n',
+			);
+		});
+
+		it('stringifies to empty string when provided empty RedsocksConfig', () => {
+			const conf: hostConfig.RedsocksConfig = {};
+			const confStr = hostConfig.RedsocksConf.stringify(conf);
+			expect(confStr).to.equal('');
+		});
+
+		it('stringifies to empty string when provided empty redsocks block', () => {
+			const conf: hostConfig.RedsocksConfig = {
+				redsocks: {} as hostConfig.ProxyConfig,
+			};
+			const confStr = hostConfig.RedsocksConf.stringify(conf);
+			expect(confStr).to.equal('');
+		});
+	});
+
 	describe('parse', () => {
 		it('parses config string into RedsocksConfig', () => {
 			const redsocksConfStr = stripIndent`