From 8395a4e55a87c9ffb6e89f00f79f03e9d15f7411 Mon Sep 17 00:00:00 2001
From: electron-rare <108685187+electron-rare@users.noreply.github.com>
Date: Wed, 10 Jun 2026 21:29:16 +0200
Subject: [PATCH] feat: allowlist html sanitizer

---
 src/lib/sanitize.test.ts | 21 +++++++++++++++++++++
 src/lib/sanitize.ts      | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 56 insertions(+)
 create mode 100644 src/lib/sanitize.test.ts
 create mode 100644 src/lib/sanitize.ts

diff --git a/src/lib/sanitize.test.ts b/src/lib/sanitize.test.ts
new file mode 100644
index 0000000..e895657
--- /dev/null
+++ b/src/lib/sanitize.test.ts
@@ -0,0 +1,21 @@
+import { describe, it, expect } from 'vitest';
+import { sanitizeHtml } from './sanitize';
+
+describe('sanitizeHtml', () => {
+  it('keeps structural/prose tags', () => {
+    const html = '<h1>T</h1><p>a <strong>b</strong> <em>c</em></p><ul><li>x</li></ul><pre><code>y</code></pre><table><tr><td>z</td></tr></table>';
+    expect(sanitizeHtml(html)).toBe(html);
+  });
+  it('strips script/style/iframe and event handlers', () => {
+    expect(sanitizeHtml('<p onclick="x()">a</p><script>evil()</script><iframe src="x"></iframe>')).toBe('<p>a</p>');
+  });
+  it('keeps safe links and images, strips javascript: urls', () => {
+    expect(sanitizeHtml('<a href="https://x.y">l</a><a href="javascript:e()">m</a><img src="https://x.y/i.png" alt="i">'))
+      .toBe('<a href="https://x.y">l</a><a>m</a><img src="https://x.y/i.png" alt="i">');
+  });
+  it('realistic Moodle fragment: div/span survive, class stripped', () => {
+    const input = '<div class="no-overflow"><h3>Registres ESP32</h3><p>Le registre <span class="highlight">GPIO_OUT</span> contrôle les sorties.</p><pre><code>#define GPIO_OUT 0x3FF44004</code></pre></div>';
+    const expected = '<div><h3>Registres ESP32</h3><p>Le registre <span>GPIO_OUT</span> contrôle les sorties.</p><pre><code>#define GPIO_OUT 0x3FF44004</code></pre></div>';
+    expect(sanitizeHtml(input)).toBe(expected);
+  });
+});
diff --git a/src/lib/sanitize.ts b/src/lib/sanitize.ts
new file mode 100644
index 0000000..d6fe2bd
--- /dev/null
+++ b/src/lib/sanitize.ts
@@ -0,0 +1,35 @@
+const ALLOWED: Record<string, string[]> = {
+  h1: [], h2: [], h3: [], h4: [], p: [], br: [], hr: [],
+  strong: [], b: [], em: [], i: [], u: [], s: [], mark: [], small: [], sub: [], sup: [],
+  ul: [], ol: ['start'], li: [], blockquote: [], pre: [], code: [],
+  table: [], thead: [], tbody: [], tr: [], th: ['colspan', 'rowspan'], td: ['colspan', 'rowspan'],
+  a: ['href', 'title'], img: ['src', 'alt', 'title', 'width', 'height'],
+  figure: [], figcaption: [], div: [], span: [], dl: [], dt: [], dd: [],
+};
+const DROP_WITH_CONTENT = new Set(['script', 'style', 'iframe', 'object', 'embed', 'noscript']);
+const SAFE_URL = /^(https?:|\/|#|mailto:)/i;
+
+export function sanitizeHtml(html: string): string {
+  let out = html;
+  for (const tag of DROP_WITH_CONTENT) {
+    out = out.replace(new RegExp(`<${tag}[\\s\\S]*?</${tag}>`, 'gi'), '');
+    out = out.replace(new RegExp(`<${tag}[^>]*/?>`, 'gi'), '');
+  }
+  return out.replace(/<\/?([a-zA-Z][a-zA-Z0-9]*)((?:\s+[^<>]*?)?)(\/?)>/g, (m, name, attrs, selfClose) => {
+    const tag = name.toLowerCase();
+    if (!(tag in ALLOWED)) return '';
+    if (m.startsWith('</')) return `</${tag}>`;
+    const allowed = ALLOWED[tag];
+    let kept = '';
+    const attrRe = /([a-zA-Z-]+)\s*=\s*("([^"]*)"|'([^']*)'|(\S+))/g;
+    let a: RegExpExecArray | null;
+    while ((a = attrRe.exec(attrs)) !== null) {
+      const attr = a[1].toLowerCase();
+      const val = a[3] ?? a[4] ?? a[5] ?? '';
+      if (!allowed.includes(attr)) continue;
+      if ((attr === 'href' || attr === 'src') && !SAFE_URL.test(val)) continue;
+      kept += ` ${attr}="${val.replace(/"/g, '&quot;')}"`;
+    }
+    return `<${tag}${kept}>`;
+  });
+}