From 10d759fade0a97ad7623ab46f6b4e49ffcbfa642 Mon Sep 17 00:00:00 2001
From: MK <fengmk2@gmail.com>
Date: Wed, 10 Jun 2026 23:05:46 +0800
Subject: [PATCH] fix(security): use CSPRNG for CSP nonce generation

The CSP nonce was generated with `nanoid/non-secure`, which derives
every character from `Math.random()`. A predictable nonce weakens
nonce-based CSP as a defense against XSS. Switch to the crypto-backed
`nanoid` entry point so the nonce stays unpredictable.
---
 plugins/security/src/app/extend/context.ts |  2 +-
 plugins/security/test/csp.test.ts          | 20 ++++++++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/plugins/security/src/app/extend/context.ts b/plugins/security/src/app/extend/context.ts
index 3d9c413576..dd8fe3bc14 100644
--- a/plugins/security/src/app/extend/context.ts
+++ b/plugins/security/src/app/extend/context.ts
@@ -2,7 +2,7 @@ import { debuglog } from 'node:util';
 
 import Tokens from 'csrf';
 import { Context } from 'egg';
-import { nanoid } from 'nanoid/non-secure';
+import { nanoid } from 'nanoid';
 
 import type { SecurityConfig } from '../../config/config.default.ts';
 import type { HttpClientRequestURL, HttpClientOptions, HttpClientResponse } from '../../lib/extend/safe_curl.ts';
diff --git a/plugins/security/test/csp.test.ts b/plugins/security/test/csp.test.ts
index 380a2a3f60..f0d7efc28a 100644
--- a/plugins/security/test/csp.test.ts
+++ b/plugins/security/test/csp.test.ts
@@ -94,6 +94,26 @@ describe.skipIf(process.platform === 'win32')('test/csp.test.ts', () => {
       const nonce = res.text;
       expect(res.headers['x-csp-nonce']).toBe(nonce);
     });
+
+    it('should generate unpredictable nonce even when Math.random is fixed', async () => {
+      // The CSP nonce must come from a cryptographically secure RNG.
+      // `nanoid/non-secure` derives every char from `Math.random()`, so pinning
+      // `Math.random` to a constant would make the nonce fully predictable.
+      // A CSPRNG-backed nonce stays random regardless of `Math.random`.
+      mm(Math, 'random', () => 0);
+      try {
+        const res1 = await app.httpRequest().get('/testcsp').expect(200);
+        const res2 = await app.httpRequest().get('/testcsp').expect(200);
+        expect(res1.text.length).toBe(16);
+        expect(res2.text.length).toBe(16);
+        // not constant across requests
+        expect(res1.text).not.toBe(res2.text);
+        // not the predictable value Math.random()===0 would produce
+        expect(res1.text).not.toBe('u'.repeat(16));
+      } finally {
+        mm.restore();
+      }
+    });
   });
 
   it('should ignore path', async () => {