From f862e2f7dfa6da5312fae3d74fe49d2669c1aa4b Mon Sep 17 00:00:00 2001
From: Chris Tate <chris@ctate.dev>
Date: Mon, 26 Jan 2026 00:42:00 -0600
Subject: [PATCH] Security: Reject cross-origin connections to daemon and
 stream server (#274)

---
 src/daemon.test.ts   | 36 ++++++++++++++++++++++++++++++++++++
 src/daemon.ts        | 13 +++++++++++++
 src/stream-server.ts | 20 +++++++++++++++++++-
 3 files changed, 68 insertions(+), 1 deletion(-)

diff --git a/src/daemon.test.ts b/src/daemon.test.ts
index 8825b65..62ef417 100644
--- a/src/daemon.test.ts
+++ b/src/daemon.test.ts
@@ -3,6 +3,42 @@ import * as os from 'os';
 import * as path from 'path';
 import { getSocketDir } from './daemon.js';
 
+/**
+ * HTTP request detection pattern used in daemon.ts to prevent cross-origin attacks.
+ * This pattern detects HTTP method prefixes that browsers must send when using fetch().
+ */
+const HTTP_REQUEST_PATTERN = /^(GET|POST|PUT|DELETE|HEAD|OPTIONS|PATCH|CONNECT|TRACE)\s/i;
+
+describe('HTTP request detection (security)', () => {
+  it('should detect POST requests from fetch()', () => {
+    const httpRequest = 'POST / HTTP/1.1\r\nHost: 127.0.0.1:51234\r\n';
+    expect(HTTP_REQUEST_PATTERN.test(httpRequest.trimStart())).toBe(true);
+  });
+
+  it('should detect GET requests', () => {
+    expect(HTTP_REQUEST_PATTERN.test('GET / HTTP/1.1')).toBe(true);
+  });
+
+  it('should detect OPTIONS preflight requests', () => {
+    expect(HTTP_REQUEST_PATTERN.test('OPTIONS / HTTP/1.1')).toBe(true);
+  });
+
+  it('should NOT detect valid JSON commands', () => {
+    const jsonCommand = '{"id":"1","action":"navigate","url":"https://example.com"}';
+    expect(HTTP_REQUEST_PATTERN.test(jsonCommand.trimStart())).toBe(false);
+  });
+
+  it('should NOT detect JSON with leading whitespace', () => {
+    const jsonCommand = '  {"id":"1","action":"click","selector":"button"}';
+    expect(HTTP_REQUEST_PATTERN.test(jsonCommand.trimStart())).toBe(false);
+  });
+
+  it('should be case insensitive for HTTP methods', () => {
+    expect(HTTP_REQUEST_PATTERN.test('post / HTTP/1.1')).toBe(true);
+    expect(HTTP_REQUEST_PATTERN.test('Post / HTTP/1.1')).toBe(true);
+  });
+});
+
 describe('getSocketDir', () => {
   const originalEnv = { ...process.env };
 
diff --git a/src/daemon.ts b/src/daemon.ts
index 7447261..3a3b1a4 100644
--- a/src/daemon.ts
+++ b/src/daemon.ts
@@ -196,10 +196,23 @@ export async function startDaemon(options?: { streamPort?: number }): Promise<vo
 
   const server = net.createServer((socket) => {
     let buffer = '';
+    let httpChecked = false;
 
     socket.on('data', async (data) => {
       buffer += data.toString();
 
+      // Security: Detect and reject HTTP requests to prevent cross-origin attacks.
+      // Browsers using fetch() must send HTTP headers (e.g., "POST / HTTP/1.1"),
+      // while legitimate clients send raw JSON starting with "{".
+      if (!httpChecked) {
+        httpChecked = true;
+        const trimmed = buffer.trimStart();
+        if (/^(GET|POST|PUT|DELETE|HEAD|OPTIONS|PATCH|CONNECT|TRACE)\s/i.test(trimmed)) {
+          socket.destroy();
+          return;
+        }
+      }
+
       // Process complete lines
       while (buffer.includes('\n')) {
         const newlineIdx = buffer.indexOf('\n');
diff --git a/src/stream-server.ts b/src/stream-server.ts
index 002d3cc..83136d6 100644
--- a/src/stream-server.ts
+++ b/src/stream-server.ts
@@ -87,7 +87,25 @@ export class StreamServer {
   start(): Promise<void> {
     return new Promise((resolve, reject) => {
       try {
-        this.wss = new WebSocketServer({ port: this.port });
+        this.wss = new WebSocketServer({
+          port: this.port,
+          // Security: Reject cross-origin WebSocket connections from browsers.
+          // This prevents malicious web pages from connecting and injecting input events.
+          verifyClient: (info: {
+            origin: string;
+            secure: boolean;
+            req: import('http').IncomingMessage;
+          }) => {
+            const origin = info.origin;
+            // Allow connections with no origin (non-browser clients like CLI tools)
+            // Reject connections from web pages (which always have an origin)
+            if (origin && !origin.startsWith('file://')) {
+              console.log(`[StreamServer] Rejected connection from origin: ${origin}`);
+              return false;
+            }
+            return true;
+          },
+        });
 
         this.wss.on('connection', (ws) => {
           this.handleConnection(ws);