From 27ab64902b55b499b40ae0a3e0de276dd1238160 Mon Sep 17 00:00:00 2001
From: undefined <i@undefined.moe>
Date: Wed, 9 Feb 2022 17:15:58 +0800
Subject: [PATCH] ui: fix xss whitelist for katex

---
 .../ui-default/backendlib/markdown-it-xss.ts  | 59 +++++++++++--------
 packages/ui-default/backendlib/template.js    |  8 +--
 packages/ui-default/package.json              |  2 +-
 3 files changed, 38 insertions(+), 31 deletions(-)

diff --git a/packages/ui-default/backendlib/markdown-it-xss.ts b/packages/ui-default/backendlib/markdown-it-xss.ts
index 2dba4cc30..f618a3ced 100644
--- a/packages/ui-default/backendlib/markdown-it-xss.ts
+++ b/packages/ui-default/backendlib/markdown-it-xss.ts
@@ -1,7 +1,35 @@
 import * as Xss from 'xss';
 
 const stack = [];
-let isFull = false;
+
+const tagCheck = new Xss.FilterXSS({
+  css: false,
+  whiteList: {},
+  onIgnoreTag(tag, html, options) {
+    if (html.endsWith('/>')) return html;
+    if (!options.isClosing) {
+      stack.push(tag);
+      return html;
+    }
+    if (stack.length === 0) {
+      return html.replace(/</g, '&lt;').replace(/>/g, '&gt;'); // 没有标签可供闭合
+    }
+    if (stack[stack.length - 1] === tag) {
+      stack.pop(); // 正常关闭
+      return html;
+    }
+    if (stack.length - 2 >= 0 && stack[stack.length - 2] === tag) {
+      // 可能丢失了一个结束标签
+      stack.pop();
+      stack.pop();
+      return html;
+    }
+    return html.replace(/</g, '&lt;').replace(/>/g, '&gt;'); // 可能多出了一个结束标签
+  },
+  onIgnoreTagAttr(tag, name, value) {
+    return value;
+  },
+});
 
 const xss = new Xss.FilterXSS({
   whiteList: {
@@ -76,34 +104,13 @@ const xss = new Xss.FilterXSS({
     if (name === 'class') return value.replace(/badge/g, 'xss-badge');
     return value;
   },
-  onTag(tag, html, options) {
-    if (!options.isWhite || !isFull) return null;
-    if (!options.isClosing) {
-      stack.push(tag);
-      return null;
-    }
-    if (stack.length === 0) return `&lt;/${tag}&gt;`; // 没有标签可供闭合
-    if (stack[stack.length - 1] === tag) {
-      stack.pop(); // 正常关闭
-      return null;
-    }
-    if (stack.length - 2 >= 0 && stack[stack.length - 2] === tag) {
-      // 可能丢失了一个结束标签
-      stack.pop();
-      stack.pop();
-      return null;
-    }
-    return `&lt;/${tag}&gt;`; // 可能多出了一个结束标签
-  },
 });
 
-xss.process = ((original) => (html: string, full: boolean = false) => {
+function ensureTag(html: string) {
   stack.length = 0;
-  isFull = full;
-  const res = original(html);
-  if (!full) return res;
+  const res = tagCheck.process(html);
   return res + stack.map((i) => `</${i}>`).join('');
-})(xss.process.bind(xss));
+}
 
 function xssProtector(md) {
   function protector(state) {
@@ -126,4 +133,4 @@ function xssProtector(md) {
   md.core.ruler.after('linkify', 'xss', protector);
 }
 
-module.exports = { xss, xssProtector };
+module.exports = { xss, ensureTag, xssProtector };
diff --git a/packages/ui-default/backendlib/template.js b/packages/ui-default/backendlib/template.js
index 9b127f17e..c19f7d370 100644
--- a/packages/ui-default/backendlib/template.js
+++ b/packages/ui-default/backendlib/template.js
@@ -9,7 +9,7 @@ const argv = require('cac')().parse();
 const { findFileSync } = require('@hydrooj/utils/lib/utils');
 const status = require('@hydrooj/utils/lib/status');
 const markdown = require('./markdown');
-const { xss } = require('./markdown-it-xss');
+const { xss, ensureTag } = require('./markdown-it-xss');
 
 const { misc, buildContent, avatar } = global.Hydro.lib;
 
@@ -63,8 +63,8 @@ class Nunjucks extends nunjucks.Environment {
     this.addFilter('dumpYaml', (self) => yaml.dump(self));
     this.addFilter('serialize', (self, ignoreFunction = true) => serialize(self, { ignoreFunction }));
     this.addFilter('assign', (self, data) => Object.assign(self, data));
-    this.addFilter('markdown', (self, html = false) => xss.process(markdown.render(self, html), true));
-    this.addFilter('markdownInline', (self, html = false) => xss.process(markdown.renderInline(self, html), true));
+    this.addFilter('markdown', (self, html = false) => ensureTag(markdown.render(self, html), true));
+    this.addFilter('markdownInline', (self, html = false) => ensureTag(markdown.renderInline(self, html), true));
     this.addFilter('ansi', (self) => misc.ansiToHtml(self));
     this.addFilter('base64_encode', (s) => Buffer.from(s).toString('base64'));
     this.addFilter('base64_decode', (s) => Buffer.from(s, 'base64').toString());
@@ -87,7 +87,7 @@ class Nunjucks extends nunjucks.Environment {
         else s = s[langs[0]];
       }
       if (s instanceof Array) s = buildContent(s, html ? 'html' : 'markdown', (str) => str.translate(language));
-      return xss.process(html ? s : markdown.render(s), true);
+      return ensureTag(html ? xss.process(s) : markdown.render(s), true);
     });
     this.addFilter('log', (self) => {
       console.log(self);
diff --git a/packages/ui-default/package.json b/packages/ui-default/package.json
index 203ccacb1..5c0340353 100644
--- a/packages/ui-default/package.json
+++ b/packages/ui-default/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@hydrooj/ui-default",
-  "version": "4.31.10",
+  "version": "4.31.11",
   "author": "undefined <i@undefined.moe>",
   "license": "AGPL-3.0",
   "main": "hydro.js",