Allow users decide what HTTP status to use for redirecting

src/client.js

@@ -1,12 +1,13 @@
 import { client } from "./sni.js";
 import { findTxtRecord, isHostBlacklisted, combineURLs } from "./util.js";
-const record_prefix = 'forward-domain=';
+
 /**
  * @typedef {Object} Cache
  * @property {string} url
  * @property {boolean} expand
  * @property {boolean} blacklisted
  * @property {number} expire
+ * @property {number} httpStatus
  */
 /**
  * @type {Object<string, Cache>}
@@ -18,7 +19,11 @@ const resolveCache = {};
  */
 async function buildCache(host) {
     let expand = false;
-    let url = await findTxtRecord(host, record_prefix);
+    let recordData = await findTxtRecord(host);
+    if (!recordData) {
+        throw new Error(`The record data for "${host}" is missing`);
+    }
+    let {url, httpStatus = '301'} = recordData;
     if (url.indexOf('http://') !== 0 && url.indexOf('https://') !== 0) {
         throw new Error(url + ' in TXT record is not an absolute URL');
     }
@@ -26,11 +31,16 @@ async function buildCache(host) {
         url = url.slice(0, -1);
         expand = true;
     }
+    if(!['301', '302'].includes(httpStatus)) {
+        httpStatus = '301';
+        console.warn(`The record "${url}" wants to use the http status code ${httpStatus} which is not allowed (only 301 and 302). Using 301 instead.`);
+    }
     return {
         url,
         expand,
         blacklisted: isHostBlacklisted(host),
         expire: Date.now() + 86400 * 1000,
+        httpStatus: parseInt(httpStatus),
     };
 }
 const acme_prefix = '/.well-known/acme-challenge/';
@@ -65,12 +75,12 @@ const listener = async function (req, res) {
             resolveCache[host] = cache;
         }
         if (cache.blacklisted) {
-            res.writeHead(301, {
+            res.writeHead(cache.httpStatus, {
                 'Location': (process.env.BLACKLIST_REDIRECT || 'https://forwarddomain.net/blacklisted') + "?d=" + req.headers.host,
             });
             return;
         }
-        res.writeHead(301, {
+        res.writeHead(cache.httpStatus, {
             'Location': cache.expand ? combineURLs(cache.url, url) : cache.url,
         });
         return;

src/util.js

@@ -2,6 +2,8 @@ import { default as axios } from "axios";
 import crypto from "crypto";
 import fs from "fs";
 
+const recordParamDestUrl = 'forward-domain';
+const recordParamHttpStatus = 'http-status';
 const blacklistURL = (process.env.BLACKLIST_HOSTS || "").split(',').reduce((acc, host) => {
     acc[host] = true;
     return acc;
@@ -39,21 +41,36 @@ export async function ensureDir(dir) {
 }
 
 /**
- * @param {string} host
- * @param {string} prefix
+ * @param {string} value
  */
-export async function findTxtRecord(host, prefix, required = true) {
+const parseTxtRecordData = (value) => {
+    const result = {};
+    for (const part of value.split(';')) {
+        const [key, value] = part.split('=');
+        if (key && value) {
+            result[key] = value;
+        }
+    }
+    return result;
+}
+
+/**
+ * @param {string} host
+ * @return {Promise<{url: string, httpStatus?: string} | null>}
+ */
+export async function findTxtRecord(host) {
     const resolve = await axios(`https://dns.google/resolve?name=_.${encodeURIComponent(host)}&type=TXT`);
     if (resolve.data.Answer) {
         for (const head of resolve.data.Answer) {
-            if (!head.data.startsWith(prefix))
+            if (!head.data.includes(recordParamDestUrl))
                 continue;
-            return head.data.slice(prefix.length);
+            const txtData = parseTxtRecordData(head.data);
+            return {
+                url: txtData[recordParamDestUrl], 
+                httpStatus: txtData[recordParamHttpStatus],
+            };
         }
     }
-    if (required) {
-        throw new Error(prefix + ' TXT is missing');
-    }
     return null;
 }