Add subdomain support

src/app.ts

@@ -89,7 +89,6 @@ if (config.ARNS_ROOT_HOST !== undefined) {
 
   app.use(
     createSandboxMiddleware({
-      rootHost: config.ARNS_ROOT_HOST,
       sandboxProtocol: config.SANDBOX_PROTOCOL,
     }),
   );

src/config.ts

@@ -70,6 +70,8 @@ export const ANS104_INDEX_FILTER = createFilter(
   JSON.parse(ANS104_INDEX_FILTER_STRING),
 );
 export const ARNS_ROOT_HOST = env.varOrUndefined('ARNS_ROOT_HOST');
+export const ROOT_HOST_SUBDOMAIN_LENGTH =
+  ARNS_ROOT_HOST !== undefined ? ARNS_ROOT_HOST.split('.').length - 2 : 0;
 export const SANDBOX_PROTOCOL = env.varOrUndefined('SANDBOX_PROTOCOL');
 export const START_WRITERS =
   env.varOrDefault('START_WRITERS', 'true') === 'true';

src/middleware/arns.ts

@@ -18,6 +18,7 @@
 import { Handler } from 'express';
 import { asyncMiddleware } from 'middleware-async';
 
+import * as config from '../config.js';
 import { sendNotFound } from '../routes/data.js';
 import { NameResolver } from '../types.js';
 
@@ -32,26 +33,32 @@ export const createArnsMiddleware = ({
 }): Handler =>
   asyncMiddleware(async (req, res, next) => {
     if (
-      Array.isArray(req.subdomains) &&
-      req.subdomains.length === 1 &&
-      !EXCLUDED_SUBDOMAINS.has(req.subdomains[0]) &&
+      // Ignore subdomains that are part of the ArNS root hostname.
+      !Array.isArray(req.subdomains) ||
+      req.subdomains.length === config.ROOT_HOST_SUBDOMAIN_LENGTH
+    ) {
+      next();
+      return;
+    }
+    const arnsSubdomain = req.subdomains[config.ROOT_HOST_SUBDOMAIN_LENGTH - 1];
+    if (
+      EXCLUDED_SUBDOMAINS.has(arnsSubdomain) ||
       // Avoid collisions with sandbox URLs by ensuring the subdomain length
       // is below the mininimum length of a sandbox subdomain. Undernames are
       // are an exception because they can be longer and '_' cannot appear in
       // base32.
-      (req.subdomains[0].length <= 48 || req.subdomains[0].match(/_/))
+      (arnsSubdomain.length > 48 && !arnsSubdomain.match(/_/))
     ) {
-      const { resolvedId, ttl } = await nameResolver.resolve(req.subdomains[0]);
-      if (resolvedId !== undefined) {
-        res.header('X-ArNS-Resolved-Id', resolvedId);
-        res.header('X-ArNS-TTL-Seconds', ttl.toString());
-        res.header('Cache-Control', `public, max-age=${ttl}`);
-        dataHandler(req, res, next);
-        return;
-      } else {
-        sendNotFound(res);
-        return;
-      }
+      next();
+      return;
+    }
+    const { resolvedId, ttl } = await nameResolver.resolve(arnsSubdomain);
+    if (resolvedId === undefined) {
+      sendNotFound(res);
+      return;
     }
-    next();
+    res.header('X-ArNS-Resolved-Id', resolvedId);
+    res.header('X-ArNS-TTL-Seconds', ttl.toString());
+    res.header('Cache-Control', `public, max-age=${ttl}`);
+    dataHandler(req, res, next);
   });

src/middleware/sandbox.ts

@@ -19,11 +19,12 @@ import { Handler, Request } from 'express';
 import url from 'node:url';
 import { base32 } from 'rfc4648';
 
+import * as config from '../config.js';
 import { fromB64Url } from '../lib/encoding.js';
 
 function getRequestSandbox(req: Request): string | undefined {
-  if (req.subdomains.length === 1) {
-    return req.subdomains[0];
+  if (req.subdomains.length > config.ROOT_HOST_SUBDOMAIN_LENGTH) {
+    return req.subdomains[req.subdomains.length - 1];
   }
   return undefined;
 }
@@ -37,14 +38,12 @@ function sandboxFromId(id: string): string {
 }
 
 export function createSandboxMiddleware({
-  rootHost,
   sandboxProtocol,
 }: {
-  rootHost?: string;
   sandboxProtocol?: string;
 }): Handler {
   return (req, res, next) => {
-    if (rootHost === undefined) {
+    if (config.ARNS_ROOT_HOST === undefined) {
       next();
       return;
     }
@@ -63,7 +62,7 @@ export function createSandboxMiddleware({
       const protocol = sandboxProtocol ?? (req.secure ? 'https' : 'http');
       return res.redirect(
         302,
-        `${protocol}://${idSandbox}.${rootHost}${path}?${queryString}`,
+        `${protocol}://${idSandbox}.${config.ARNS_ROOT_HOST}${path}?${queryString}`,
       );
     }