fix(security): CVE-HSYNC-2026-006 - Comprehensive host validation

lib/socket-listeners.js

@@ -9,6 +9,67 @@ debugError.color = 1;
 
 let net;
 
+// Localhost aliases that all refer to the same machine
+const LOCALHOST_ALIASES = new Set([
+  'localhost',
+  '127.0.0.1',
+  '::1',
+  '0.0.0.0',
+  '0:0:0:0:0:0:0:1',
+  '[::1]',
+  '[0:0:0:0:0:0:0:1]',
+]);
+
+/**
+ * Normalize a hostname for comparison
+ * - Lowercase
+ * - Remove trailing dots (DNS root)
+ * - Strip IPv6 brackets
+ * - Expand common IPv6 localhost representations
+ * @param {string} hostname
+ * @returns {string}
+ */
+function normalizeHostname(hostname) {
+  if (!hostname) return '';
+  let normalized = hostname.toLowerCase().trim();
+
+  // Remove trailing dot (DNS root indicator)
+  if (normalized.endsWith('.')) {
+    normalized = normalized.slice(0, -1);
+  }
+
+  // Strip IPv6 brackets for comparison
+  if (normalized.startsWith('[') && normalized.endsWith(']')) {
+    normalized = normalized.slice(1, -1);
+  }
+
+  return normalized;
+}
+
+/**
+ * Check if two hostnames refer to the same host
+ * Handles localhost aliases, IPv6, and normalization
+ * @param {string} host1
+ * @param {string} host2
+ * @returns {boolean}
+ */
+export function isSameHost(host1, host2) {
+  const norm1 = normalizeHostname(host1);
+  const norm2 = normalizeHostname(host2);
+
+  // Direct match after normalization
+  if (norm1 === norm2) {
+    return true;
+  }
+
+  // Check if both are localhost aliases
+  if (LOCALHOST_ALIASES.has(norm1) && LOCALHOST_ALIASES.has(norm2)) {
+    return true;
+  }
+
+  return false;
+}
+
 export function setNet(netImpl) {
   net = netImpl;
 }
@@ -40,7 +101,10 @@ export function initListeners(hsyncClient) {
       cleanHost = cleanHost.substring(0, cleanHost.length - 1);
     }
     const url = new URL(cleanHost);
-    if (url.hostname.toLowerCase() === hsyncClient.myHostName.toLowerCase()) {
+    // Security: Use comprehensive hostname comparison to prevent bypass attacks
+    // CVE-HSYNC-2026-006: Simple string comparison could be bypassed via
+    // localhost aliases, IPv6, trailing dots, etc.
+    if (isSameHost(url.hostname, hsyncClient.myHostName)) {
       throw new Error('targetHost must be a different host');
     }
     debug('creating handler', port, cleanHost);

test/unit/socket-listeners.test.js

@@ -1,5 +1,49 @@
 import { describe, it, expect, vi, beforeEach } from 'vitest';
-import { initListeners, setNet } from '../../lib/socket-listeners.js';
+import { initListeners, setNet, isSameHost } from '../../lib/socket-listeners.js';
+
+describe('isSameHost', () => {
+  it('should match identical hostnames', () => {
+    expect(isSameHost('example.com', 'example.com')).toBe(true);
+  });
+
+  it('should be case insensitive', () => {
+    expect(isSameHost('Example.COM', 'example.com')).toBe(true);
+    expect(isSameHost('LOCALHOST', 'localhost')).toBe(true);
+  });
+
+  it('should handle trailing dots (DNS root)', () => {
+    expect(isSameHost('example.com.', 'example.com')).toBe(true);
+    expect(isSameHost('example.com', 'example.com.')).toBe(true);
+  });
+
+  it('should match localhost aliases', () => {
+    expect(isSameHost('localhost', '127.0.0.1')).toBe(true);
+    expect(isSameHost('localhost', '::1')).toBe(true);
+    expect(isSameHost('127.0.0.1', '::1')).toBe(true);
+    expect(isSameHost('localhost', '0.0.0.0')).toBe(true);
+  });
+
+  it('should handle IPv6 brackets', () => {
+    expect(isSameHost('[::1]', '::1')).toBe(true);
+    expect(isSameHost('[::1]', 'localhost')).toBe(true);
+  });
+
+  it('should handle expanded IPv6 localhost', () => {
+    expect(isSameHost('0:0:0:0:0:0:0:1', '::1')).toBe(true);
+    expect(isSameHost('0:0:0:0:0:0:0:1', 'localhost')).toBe(true);
+  });
+
+  it('should not match different hosts', () => {
+    expect(isSameHost('example.com', 'other.com')).toBe(false);
+    expect(isSameHost('localhost', 'example.com')).toBe(false);
+  });
+
+  it('should handle empty/null inputs', () => {
+    expect(isSameHost('', '')).toBe(true);
+    expect(isSameHost('example.com', '')).toBe(false);
+    expect(isSameHost('', 'example.com')).toBe(false);
+  });
+});
 
 describe('socket-listeners', () => {
   let mockNet;
@@ -100,6 +144,60 @@ describe('socket-listeners', () => {
       ).toThrow('targetHost must be a different host');
     });
 
+    it('should throw if targetHost matches client with different case', () => {
+      expect(() =>
+        listeners.addSocketListener({
+          port: 3000,
+          targetHost: 'https://LOCAL.EXAMPLE.COM',
+        })
+      ).toThrow('targetHost must be a different host');
+    });
+
+    it('should throw if targetHost matches client with trailing dot', () => {
+      expect(() =>
+        listeners.addSocketListener({
+          port: 3000,
+          targetHost: 'https://local.example.com.',
+        })
+      ).toThrow('targetHost must be a different host');
+    });
+
+    it('should block localhost bypass via 127.0.0.1', () => {
+      mockHsyncClient.myHostName = 'localhost';
+      listeners = initListeners(mockHsyncClient);
+
+      expect(() =>
+        listeners.addSocketListener({
+          port: 3000,
+          targetHost: 'https://127.0.0.1',
+        })
+      ).toThrow('targetHost must be a different host');
+    });
+
+    it('should block localhost bypass via IPv6 ::1', () => {
+      mockHsyncClient.myHostName = 'localhost';
+      listeners = initListeners(mockHsyncClient);
+
+      expect(() =>
+        listeners.addSocketListener({
+          port: 3000,
+          targetHost: 'https://[::1]',
+        })
+      ).toThrow('targetHost must be a different host');
+    });
+
+    it('should block localhost bypass via 0.0.0.0', () => {
+      mockHsyncClient.myHostName = '127.0.0.1';
+      listeners = initListeners(mockHsyncClient);
+
+      expect(() =>
+        listeners.addSocketListener({
+          port: 3000,
+          targetHost: 'https://0.0.0.0',
+        })
+      ).toThrow('targetHost must be a different host');
+    });
+
     it('should clean trailing slash from targetHost', () => {
       const listener = listeners.addSocketListener({
         port: 3000,