Potential fix for code scanning alert no. 3: DOM text reinterpreted as HTML - #153
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セキュリティ修正のレビュー結果
このPRは、DOM text reinterpretation脆弱性（Code Scanning Alert #3）に対する重要なセキュリティ修正を実装しています。
主な改善点
sanitizeUrl関数の追加により、iframe srcでの危険なプロトコル（javascript:など）の実行を防止- URL検証により、HTTPSとHTTPのみを許可する適切な制限を実装
修正が必要な問題
- サーバーサイドレンダリング対応:
window.location.originへの依存を削除し、絶対URLのみを受け入れるように修正 - プロトコル検証の強化: より厳密な否定的検証ロジックの実装
- 入力検証の一貫性: URL入力フィールドでも同様の検証を適用することを推奨
セキュリティ修正の方向性は正しいですが、上記の改善により、より堅牢な実装になります。
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| const sanitizeUrl = (value: string | undefined | null): string | undefined => { | ||
| if (!value) return undefined; | ||
| try { | ||
| const url = new URL(value, typeof window !== 'undefined' ? window.location.origin : undefined); |
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🛑 セキュリティ脆弱性: sanitizeUrl関数でサーバーサイドレンダリング時にベースURLが未定義になる可能性があります。window.location.originが利用できない場合、相対URLが予期しない動作を引き起こす可能性があります1。
Suggested change
| const url = new URL(value, typeof window !== 'undefined' ? window.location.origin : undefined); | |
| const url = new URL(value); |
Footnotes
-
CWE-20: Improper Input Validation - https://cwe.mitre.org/data/definitions/20.html ↩
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| if (url.protocol === 'http:' || url.protocol === 'https:') { | ||
| return url.toString(); | ||
| } |
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プロトコル検証が不完全です。`
Suggested change
| if (url.protocol === 'http:' || url.protocol === 'https:') { | |
| return url.toString(); | |
| } | |
| if (url.protocol !== 'http:' && url.protocol !== 'https:') { | |
| return undefined; | |
| } |
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Potential fix for https://github.com/poad/llm-ts-example/security/code-scanning/3
In general terms, the problem should be fixed by validating and constraining the user-provided string before using it as the
srcof the<iframe>. The validation should ensure that only well-formed URLs with allowed schemes (e.g.,http:andhttps:) are accepted, and anything else is rejected or results in no navigation. This avoids interpreting arbitrary DOM text as a URL/HTML-like context and blocks vectors such asjavascript:alert(1)or malformed URLs.For this specific code, the least invasive fix is:
URLobject and confirms that the protocol is one of an allowlist, likehttp:orhttps:. If parsing fails or the protocol is not allowed, returnundefined.src: instead of(src ?? url) || undefined, compute asafeSrcas either the sanitizedsrcprop or the sanitized contexturl, and pass that tosrc. If both are invalid, the iframe will havesrc={undefined}, effectively loading nothing.These changes all live in
chat-app/components/ai-elements/web-preview.tsx. We will:sanitizeUrlhelper function near the top of the file (where it’s easy to see and reuse).WebPreviewBody, computeconst safeSrc = sanitizeUrl(src ?? url);and usesafeSrc || undefinedfor the iframesrc.No external libraries are strictly required; we can safely use the built-in
URLclass in modern browsers/Next.js.Suggested fixes powered by Copilot Autofix. Review carefully before merging.