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Brave Browserの脆弱性を見つけた話(iOS編)

Brave Browserの脆弱性を見つけた話(iOS編)

Shibuya.XSS techtalk #12の発表資料です。

MUNEAKI NISHIMURA

July 25, 2023
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  1. CSPのnonceはどのように埋め込まれるのか︖ HTMLテンプレート内に埋め込まれた特殊⽂字列をNative側(Swift)で置換する 12 https://github.com/brave/brave-ios/pull/4209/files#diff-eaeef15a290e9e5e9bcaae784f18d874f8c932dfa3de416a5820eccd6b2d8cfbR54 <h1 id="reader-title"></h1> <div>%READER-CREDITS%</div> <script nonce="%READER-TITLE-NONCE%"> document.getElementById("reader-title").textContent

    = "%READER-TITLE%"; </script> <div> %READER-CONTENT% </div> HTMLテンプレート .replacingOccurrences(of: "%READER-TITLE%", with: readabilityResult.title) .replacingOccurrences(of: "%READER-CREDITS%", with: readabilityResult.credits) .replacingOccurrences(of: "%READER-CONTENT%", with: readabilityResult.content) .replacingOccurrences(of: "%READER-TITLE-NONCE%", with: titleNonce) テンプレート内の特殊⽂字列を置換するSwiftコード
  2. HTMLテンプレート置換処理の実際の動き 1/8 はじめに元のページのタイトルが埋め込まれる 13 .replacingOccurrences(of: "%READER-TITLE%", with: readabilityResult.title) .replacingOccurrences(of: "%READER-CREDITS%",

    with: readabilityResult.credits) .replacingOccurrences(of: "%READER-CONTENT%", with: readabilityResult.content) .replacingOccurrences(of: "%READER-TITLE-NONCE%", with: titleNonce) テンプレート内の特殊⽂字列を置換するSwiftコード <h1 id="reader-title"></h1> <div>%READER-CREDITS%</div> <script nonce="%READER-TITLE-NONCE%"> document.getElementById("reader-title").textContent = "%READER-TITLE%"; </script> <div> %READER-CONTENT% </div> HTMLテンプレート
  3. HTMLテンプレート置換処理の実際の動き 2/8 はじめに元のページのタイトルが埋め込まれる 14 <h1 id="reader-title"></h1> <div>%READER-CREDITS%</div> <script nonce="%READER-TITLE-NONCE%"> document.getElementById(“reader-title”).textContent

    = "Title"; </script> <div> %READER-CONTENT% </div> HTMLテンプレート .replacingOccurrences(of: "%READER-TITLE%", with: readabilityResult.title) .replacingOccurrences(of: "%READER-CREDITS%", with: readabilityResult.credits) .replacingOccurrences(of: "%READER-CONTENT%", with: readabilityResult.content) .replacingOccurrences(of: "%READER-TITLE-NONCE%", with: titleNonce) テンプレート内の特殊⽂字列を置換するSwiftコード
  4. HTMLテンプレート置換処理の実際の動き 3/8 次に元のページのクレジットが埋め込まれる 15 テンプレート内の特殊⽂字列を置換するSwiftコード .replacingOccurrences(of: "%READER-TITLE%", with: readabilityResult.title) .replacingOccurrences(of:

    "%READER-CREDITS%", with: readabilityResult.credits) .replacingOccurrences(of: "%READER-CONTENT%", with: readabilityResult.content) .replacingOccurrences(of: "%READER-TITLE-NONCE%", with: titleNonce) <h1 id="reader-title"></h1> <div>%READER-CREDITS%</div> <script nonce="%READER-TITLE-NONCE%"> document.getElementById(“reader-title”).textContent = "Title"; </script> <div> %READER-CONTENT% </div> HTMLテンプレート
  5. HTMLテンプレート置換処理の実際の動き 4/8 次に元のページのクレジットが埋め込まれる 16 テンプレート内の特殊⽂字列を置換するSwiftコード .replacingOccurrences(of: "%READER-TITLE%", with: readabilityResult.title) .replacingOccurrences(of:

    "%READER-CREDITS%", with: readabilityResult.credits) .replacingOccurrences(of: "%READER-CONTENT%", with: readabilityResult.content) .replacingOccurrences(of: "%READER-TITLE-NONCE%", with: titleNonce) <h1 id="reader-title"></h1> <div>Credit</div> <script nonce="%READER-TITLE-NONCE%"> document.getElementById(“reader-title”).textContent = "Title"; </script> <div> %READER-CONTENT% </div> HTMLテンプレート
  6. HTMLテンプレート置換処理の実際の動き 5/8 続いて元のページの本⽂が埋め込まれて… 17 テンプレート内の特殊⽂字列を置換するSwiftコード .replacingOccurrences(of: "%READER-TITLE%", with: readabilityResult.title) .replacingOccurrences(of:

    "%READER-CREDITS%", with: readabilityResult.credits) .replacingOccurrences(of: "%READER-CONTENT%", with: readabilityResult.content) .replacingOccurrences(of: "%READER-TITLE-NONCE%", with: titleNonce) <h1 id="reader-title"></h1> <div>Credit</div> <script nonce="%READER-TITLE-NONCE%"> document.getElementById(“reader-title”).textContent = "Title"; </script> <div> %READER-CONTENT% </div> HTMLテンプレート
  7. HTMLテンプレート置換処理の実際の動き 6/8 続いて元のページの本⽂が埋め込まれて… 18 テンプレート内の特殊⽂字列を置換するSwiftコード .replacingOccurrences(of: "%READER-TITLE%", with: readabilityResult.title) .replacingOccurrences(of:

    "%READER-CREDITS%", with: readabilityResult.credits) .replacingOccurrences(of: "%READER-CONTENT%", with: readabilityResult.content) .replacingOccurrences(of: "%READER-TITLE-NONCE%", with: titleNonce) <h1 id="reader-title"></h1> <div>Credit</div> <script nonce="%READER-TITLE-NONCE%"> document.getElementById(“reader-title”).textContent = "Title"; </script> <div> Contents </div> HTMLテンプレート
  8. HTMLテンプレート置換処理の実際の動き 7/8 最後にランダムなnonceの値が埋め込まれる 19 テンプレート内の特殊⽂字列を置換するSwiftコード .replacingOccurrences(of: "%READER-TITLE%", with: readabilityResult.title) .replacingOccurrences(of:

    "%READER-CREDITS%", with: readabilityResult.credits) .replacingOccurrences(of: "%READER-CONTENT%", with: readabilityResult.content) .replacingOccurrences(of: "%READER-TITLE-NONCE%", with: titleNonce) <h1 id="reader-title"></h1> <div>Credit</div> <script nonce="%READER-TITLE-NONCE%"> document.getElementById(“reader-title”).textContent = "Title"; </script> <div> Contents </div> HTMLテンプレート
  9. HTMLテンプレート置換処理の実際の動き 8/8 最後にランダムなnonceの値が埋め込まれる 20 テンプレート内の特殊⽂字列を置換するSwiftコード .replacingOccurrences(of: "%READER-TITLE%", with: readabilityResult.title) .replacingOccurrences(of:

    "%READER-CREDITS%", with: readabilityResult.credits) .replacingOccurrences(of: "%READER-CONTENT%", with: readabilityResult.content) .replacingOccurrences(of: "%READER-TITLE-NONCE%", with: titleNonce) <h1 id="reader-title"></h1> <div>Credit</div> <script nonce="80841642004944135718143322189292"> document.getElementById(“reader-title”).textContent = "Title"; </script> <div> Contents </div> HTMLテンプレート
  10. HTMLテンプレート置換処理の実際の動き(再掲) 1/8 はじめに元のページのタイトルが埋め込まれる 22 .replacingOccurrences(of: "%READER-TITLE%", with: readabilityResult.title) .replacingOccurrences(of: "%READER-CREDITS%",

    with: readabilityResult.credits) .replacingOccurrences(of: "%READER-CONTENT%", with: readabilityResult.content) .replacingOccurrences(of: "%READER-TITLE-NONCE%", with: titleNonce) テンプレート内の特殊⽂字列を置換するSwiftコード <h1 id="reader-title"></h1> <div>%READER-CREDITS%</div> <script nonce="%READER-TITLE-NONCE%"> document.getElementById("reader-title").textContent = "%READER-TITLE%"; </script> <div> %READER-CONTENT% </div> HTMLテンプレート
  11. HTMLテンプレート置換処理の実際の動き(再掲) 2/8 はじめに元のページのタイトルが埋め込まれる 23 <h1 id="reader-title"></h1> <div>%READER-CREDITS%</div> <script nonce="%READER-TITLE-NONCE%"> document.getElementById(“reader-title”).textContent

    = "Title"; </script> <div> %READER-CONTENT% </div> HTMLテンプレート .replacingOccurrences(of: "%READER-TITLE%", with: readabilityResult.title) .replacingOccurrences(of: "%READER-CREDITS%", with: readabilityResult.credits) .replacingOccurrences(of: "%READER-CONTENT%", with: readabilityResult.content) .replacingOccurrences(of: "%READER-TITLE-NONCE%", with: titleNonce) テンプレート内の特殊⽂字列を置換するSwiftコード
  12. HTMLテンプレート置換処理の実際の動き(再掲) 3/8 次に元のページのクレジットが埋め込まれる 24 テンプレート内の特殊⽂字列を置換するSwiftコード .replacingOccurrences(of: "%READER-TITLE%", with: readabilityResult.title) .replacingOccurrences(of:

    "%READER-CREDITS%", with: readabilityResult.credits) .replacingOccurrences(of: "%READER-CONTENT%", with: readabilityResult.content) .replacingOccurrences(of: "%READER-TITLE-NONCE%", with: titleNonce) <h1 id="reader-title"></h1> <div>%READER-CREDITS%</div> <script nonce="%READER-TITLE-NONCE%"> document.getElementById(“reader-title”).textContent = "Title"; </script> <div> %READER-CONTENT% </div> HTMLテンプレート
  13. HTMLテンプレート置換処理の実際の動き(再掲) 4/8 次に元のページのクレジットが埋め込まれる 25 テンプレート内の特殊⽂字列を置換するSwiftコード .replacingOccurrences(of: "%READER-TITLE%", with: readabilityResult.title) .replacingOccurrences(of:

    "%READER-CREDITS%", with: readabilityResult.credits) .replacingOccurrences(of: "%READER-CONTENT%", with: readabilityResult.content) .replacingOccurrences(of: "%READER-TITLE-NONCE%", with: titleNonce) <h1 id="reader-title"></h1> <div> </div> <script nonce="%READER-TITLE-NONCE%"> document.getElementById(“reader-title”).textContent = "Title"; </script> <div> %READER-CONTENT% </div> HTMLテンプレート
  14. HTMLテンプレート置換処理の実際の動き(再掲) 5/8 続いて元のページの本⽂が埋め込まれて… 26 テンプレート内の特殊⽂字列を置換するSwiftコード .replacingOccurrences(of: "%READER-TITLE%", with: readabilityResult.title) .replacingOccurrences(of:

    "%READER-CREDITS%", with: readabilityResult.credits) .replacingOccurrences(of: "%READER-CONTENT%", with: readabilityResult.content) .replacingOccurrences(of: "%READER-TITLE-NONCE%", with: titleNonce) <h1 id="reader-title"></h1> <div> </div> <script nonce="%READER-TITLE-NONCE%"> document.getElementById(“reader-title”).textContent = "Title"; </script> <div> %READER-CONTENT% </div> HTMLテンプレート
  15. HTMLテンプレート置換処理の実際の動き(再掲) 6/8 続いて元のページの本⽂が埋め込まれて… 27 テンプレート内の特殊⽂字列を置換するSwiftコード .replacingOccurrences(of: "%READER-TITLE%", with: readabilityResult.title) .replacingOccurrences(of:

    "%READER-CREDITS%", with: readabilityResult.credits) .replacingOccurrences(of: "%READER-CONTENT%", with: readabilityResult.content) .replacingOccurrences(of: "%READER-TITLE-NONCE%", with: titleNonce) <h1 id="reader-title"></h1> <div> </div> <script nonce="%READER-TITLE-NONCE%"> document.getElementById(“reader-title”).textContent = "Title"; </script> <div> Contents </div> HTMLテンプレート
  16. HTMLテンプレート置換処理の実際の動き(再掲) 7/8 最後にランダムなnonceの値が埋め込まれる 28 テンプレート内の特殊⽂字列を置換するSwiftコード .replacingOccurrences(of: "%READER-TITLE%", with: readabilityResult.title) .replacingOccurrences(of:

    "%READER-CREDITS%", with: readabilityResult.credits) .replacingOccurrences(of: "%READER-CONTENT%", with: readabilityResult.content) .replacingOccurrences(of: "%READER-TITLE-NONCE%", with: titleNonce) <h1 id="reader-title"></h1> <div> %READER-TITLE-NONCE% </div> <script nonce="%READER-TITLE-NONCE%"> document.getElementById(“reader-title”).textContent = "Title"; </script> <div> Contents </div> HTMLテンプレート
  17. HTMLテンプレート置換処理の実際の動き(再掲) 8/8 最後にランダムなnonceの値が埋め込まれる 29 テンプレート内の特殊⽂字列を置換するSwiftコード .replacingOccurrences(of: "%READER-TITLE%", with: readabilityResult.title) .replacingOccurrences(of:

    "%READER-CREDITS%", with: readabilityResult.credits) .replacingOccurrences(of: "%READER-CONTENT%", with: readabilityResult.content) .replacingOccurrences(of: "%READER-TITLE-NONCE%", with: titleNonce) <h1 id="reader-title"></h1> <div> 80841642004944135718143322189292 </div> <script nonce="80841642004944135718143322189292"> document.getElementById(“reader-title”).textContent = "Title"; </script> <div> Contents </div> HTMLテンプレート
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