fix(security): harden sandbox novnc observer flow

src/agents/sandbox/browser.create.test.ts

@@ -162,7 +162,7 @@ describe("ensureSandboxBrowser create args", () => {
     const passwordEntry = envEntries.find((entry) =>
       entry.startsWith("OPENCLAW_BROWSER_NOVNC_PASSWORD="),
     );
-    expect(passwordEntry).toMatch(/^OPENCLAW_BROWSER_NOVNC_PASSWORD=[a-f0-9]{8}$/);
+    expect(passwordEntry).toMatch(/^OPENCLAW_BROWSER_NOVNC_PASSWORD=[A-Za-z0-9]{8}$/);
     expect(result?.noVncUrl).toMatch(/^http:\/\/127\.0\.0\.1:19000\/sandbox\/novnc\?token=/);
     expect(result?.noVncUrl).not.toContain("password=");
   });

src/agents/sandbox/browser.novnc-url.test.ts

@@ -2,45 +2,55 @@ import { describe, expect, it } from "vitest";
 import {
   buildNoVncDirectUrl,
   buildNoVncObserverTokenUrl,
+  buildNoVncObserverTargetUrl,
   consumeNoVncObserverToken,
+  generateNoVncPassword,
   issueNoVncObserverToken,
   resetNoVncObserverTokensForTests,
 } from "./novnc-auth.js";
 
 describe("noVNC auth helpers", () => {
   it("builds the default observer URL without password", () => {
-    expect(buildNoVncDirectUrl(45678)).toBe(
-      "http://127.0.0.1:45678/vnc.html?autoconnect=1&resize=remote",
-    );
+    expect(buildNoVncDirectUrl(45678)).toBe("http://127.0.0.1:45678/vnc.html");
   });
 
-  it("adds an encoded password query parameter when provided", () => {
-    expect(buildNoVncDirectUrl(45678, "a+b c&d")).toBe(
-      "http://127.0.0.1:45678/vnc.html?autoconnect=1&resize=remote&password=a%2Bb+c%26d",
+  it("builds a fragment-based observer target URL with password", () => {
+    expect(buildNoVncObserverTargetUrl({ port: 45678, password: "a+b c&d" })).toBe(
+      "http://127.0.0.1:45678/vnc.html#autoconnect=1&resize=remote&password=a%2Bb+c%26d",
     );
   });
 
   it("issues one-time short-lived observer tokens", () => {
     resetNoVncObserverTokensForTests();
     const token = issueNoVncObserverToken({
-      url: "http://127.0.0.1:50123/vnc.html?autoconnect=1&resize=remote&password=abcd1234",
+      noVncPort: 50123,
+      password: "abcd1234",
       nowMs: 1000,
       ttlMs: 100,
     });
     expect(buildNoVncObserverTokenUrl("http://127.0.0.1:19999", token)).toBe(
       `http://127.0.0.1:19999/sandbox/novnc?token=${token}`,
     );
-    expect(consumeNoVncObserverToken(token, 1050)).toContain("/vnc.html?");
+    expect(consumeNoVncObserverToken(token, 1050)).toEqual({
+      noVncPort: 50123,
+      password: "abcd1234",
+    });
     expect(consumeNoVncObserverToken(token, 1050)).toBeNull();
   });
 
   it("expires observer tokens", () => {
     resetNoVncObserverTokensForTests();
     const token = issueNoVncObserverToken({
-      url: "http://127.0.0.1:50123/vnc.html?autoconnect=1&resize=remote&password=abcd1234",
+      noVncPort: 50123,
+      password: "abcd1234",
       nowMs: 1000,
       ttlMs: 100,
     });
     expect(consumeNoVncObserverToken(token, 1200)).toBeNull();
   });
+
+  it("generates 8-char alphanumeric passwords", () => {
+    const password = generateNoVncPassword();
+    expect(password).toMatch(/^[a-zA-Z0-9]{8}$/);
+  });
 });

src/agents/sandbox/browser.ts

@@ -24,7 +24,6 @@ import {
   readDockerPort,
 } from "./docker.js";
 import {
-  buildNoVncDirectUrl,
   buildNoVncObserverTokenUrl,
   consumeNoVncObserverToken,
   generateNoVncPassword,
@@ -390,8 +389,10 @@ export async function ensureSandboxBrowser(params: {
   const noVncUrl =
     mappedNoVnc && noVncEnabled
       ? (() => {
-          const directUrl = buildNoVncDirectUrl(mappedNoVnc, noVncPassword);
-          const token = issueNoVncObserverToken({ url: directUrl });
+          const token = issueNoVncObserverToken({
+            noVncPort: mappedNoVnc,
+            password: noVncPassword,
+          });
           return buildNoVncObserverTokenUrl(resolvedBridge.baseUrl, token);
         })()
       : undefined;

src/agents/sandbox/novnc-auth.ts

@@ -1,13 +1,21 @@
 import crypto from "node:crypto";
 
 export const NOVNC_PASSWORD_ENV_KEY = "OPENCLAW_BROWSER_NOVNC_PASSWORD";
-const NOVNC_TOKEN_TTL_MS = 5 * 60 * 1000;
+const NOVNC_TOKEN_TTL_MS = 60 * 1000;
+const NOVNC_PASSWORD_LENGTH = 8;
+const NOVNC_PASSWORD_ALPHABET = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
 
 type NoVncObserverTokenEntry = {
-  url: string;
+  noVncPort: number;
+  password?: string;
   expiresAt: number;
 };
 
+export type NoVncObserverTokenPayload = {
+  noVncPort: number;
+  password?: string;
+};
+
 const NO_VNC_OBSERVER_TOKENS = new Map<string, NoVncObserverTokenEntry>();
 
 function pruneExpiredNoVncObserverTokens(now: number) {
@@ -24,22 +32,31 @@ export function isNoVncEnabled(params: { enableNoVnc: boolean; headless: boolean
 
 export function generateNoVncPassword() {
   // VNC auth uses an 8-char password max.
-  return crypto.randomBytes(4).toString("hex");
+  let out = "";
+  for (let i = 0; i < NOVNC_PASSWORD_LENGTH; i += 1) {
+    out += NOVNC_PASSWORD_ALPHABET[crypto.randomInt(0, NOVNC_PASSWORD_ALPHABET.length)];
+  }
+  return out;
 }
 
-export function buildNoVncDirectUrl(port: number, password?: string) {
+export function buildNoVncDirectUrl(port: number) {
+  return `http://127.0.0.1:${port}/vnc.html`;
+}
+
+export function buildNoVncObserverTargetUrl(params: { port: number; password?: string }) {
   const query = new URLSearchParams({
     autoconnect: "1",
     resize: "remote",
   });
-  if (password?.trim()) {
-    query.set("password", password);
+  if (params.password?.trim()) {
+    query.set("password", params.password);
   }
-  return `http://127.0.0.1:${port}/vnc.html?${query.toString()}`;
+  return `${buildNoVncDirectUrl(params.port)}#${query.toString()}`;
 }
 
 export function issueNoVncObserverToken(params: {
-  url: string;
+  noVncPort: number;
+  password?: string;
   ttlMs?: number;
   nowMs?: number;
 }): string {
@@ -47,13 +64,17 @@ export function issueNoVncObserverToken(params: {
   pruneExpiredNoVncObserverTokens(now);
   const token = crypto.randomBytes(24).toString("hex");
   NO_VNC_OBSERVER_TOKENS.set(token, {
-    url: params.url,
+    noVncPort: params.noVncPort,
+    password: params.password?.trim() || undefined,
     expiresAt: now + Math.max(1, params.ttlMs ?? NOVNC_TOKEN_TTL_MS),
   });
   return token;
 }
 
-export function consumeNoVncObserverToken(token: string, nowMs?: number): string | null {
+export function consumeNoVncObserverToken(
+  token: string,
+  nowMs?: number,
+): NoVncObserverTokenPayload | null {
   const now = nowMs ?? Date.now();
   pruneExpiredNoVncObserverTokens(now);
   const normalized = token.trim();
@@ -68,7 +89,7 @@ export function consumeNoVncObserverToken(token: string, nowMs?: number): string
   if (entry.expiresAt <= now) {
     return null;
   }
-  return entry.url;
+  return { noVncPort: entry.noVncPort, password: entry.password };
 }
 
 export function buildNoVncObserverTokenUrl(baseUrl: string, token: string) {