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πŸ›‘οΈ Sentinel: [MEDIUM] CSP λ³΄μ•ˆ κ°•ν™” (Nonce λ„μž… 및 인라인 μŠ€νƒ€μΌ 제거) #111

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πŸ›‘οΈ Sentinel: [MEDIUM] CSP λ³΄μ•ˆ κ°•ν™” (Nonce λ„μž… 및 인라인 μŠ€νƒ€μΌ 제거) #111

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1 change: 1 addition & 0 deletions .jules/sentinel.md
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Expand Up @@ -22,3 +22,4 @@
**Vulnerability:** Defense in Depth (CSP Missing)
**Learning:** Even when inputs are properly escaped, statically generated HTML that displays file/directory structures should implement a Content Security Policy (CSP) to provide an extra layer of defense against potential XSS bypasses.
**Prevention:** Include a strict CSP meta tag (e.g., `default-src 'none'; style-src 'unsafe-inline';`) in auto-generated HTML headers when external scripts or resources are not required.
## 2024-06-29 - [html4tree] Strict CSP Nonce Implementation\n**Vulnerability:** Weak Content Security Policy (CSP)\n**Learning:** The previous CSP allowed `style-src 'unsafe-inline'`, which is generally discouraged as it can weaken defense-in-depth against XSS attacks. The html4tree output relied on `style="..."` attributes.\n**Prevention:** A secure random `nonce` is now generated per execution using `java.security.SecureRandom` and applied to the `<style>` block. Inline styles were refactored into CSS classes (`.item-link`, `.empty-msg`) to eliminate the need for `unsafe-inline`.
26 changes: 21 additions & 5 deletions src/main/kotlin/html4tree/main.kt
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@@ -1,6 +1,9 @@

package html4tree

import java.io.File
import java.security.SecureRandom
import java.util.Base64
import java.nio.file.Files
import java.nio.file.LinkOption
import java.nio.file.StandardCopyOption
Expand Down Expand Up @@ -132,8 +135,12 @@ fun process_dir(curr_dir: File){

val exclude: Set<String> = process_ignore_file(curr_dir)

val nonceBytes = ByteArray(16)
SecureRandom().nextBytes(nonceBytes)
val nonce = Base64.getEncoder().encodeToString(nonceBytes)

val css = """
<style>
<style nonce="${nonce}">
ul {
list-style-type: none;
padding-left: 0;
Expand All @@ -150,6 +157,15 @@ fun process_dir(curr_dir: File){
outline: 2px solid #0366d6;
outline-offset: -2px;
}
.item-link {
display: block;
width: 100%;
}
.empty-msg {
padding: 0.5rem;
color: #666;
font-style: italic;
}
</style>
"""

Expand All @@ -159,7 +175,7 @@ fun process_dir(curr_dir: File){
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<!-- λ³΄μ•ˆ ν–₯상: 인라인 슀크립트 μ‹€ν–‰ 방지 -->
<meta http-equiv="Content-Security-Policy" content="default-src 'none'; style-src 'unsafe-inline';">
<meta http-equiv="Content-Security-Policy" content="default-src 'none'; style-src 'nonce-${nonce}';">
<title>${curr_dir.getName().escapeHtml()}</title>
${css}
</head>
Expand All @@ -168,7 +184,7 @@ fun process_dir(curr_dir: File){
<h1>${curr_dir.getName().escapeHtml()}</h1>
<nav aria-label="Directory listing">
<ul>
<li><a style="display:block; width:100%" href="./.." aria-label="μƒμœ„ λ””λ ‰ν† λ¦¬λ‘œ 이동"><span aria-hidden="true">&#x21B0;</span> ..</a></li>
<li><a class="item-link" href="./.." aria-label="μƒμœ„ λ””λ ‰ν† λ¦¬λ‘œ 이동"><span aria-hidden="true">&#x21B0;</span> ..</a></li>
"""

val index_middle = fun():String{
Expand All @@ -183,13 +199,13 @@ fun process_dir(curr_dir: File){
val encodedHref = if (isLinkedDirectory) { "./${fileName.urlEncodePath()}/" } else { "./${fileName.urlEncodePath()}" }
val ariaLabel = "${fileName} ${if (isLinkedDirectory) { "디렉토리" } else { "파일" }}".escapeHtml()
val icon = if (isLinkedDirectory) { "&#128193;" } else { "&rtrif;" }
l.append(""" <li><a style="display:block; width:100%" href="${encodedHref}" aria-label="${ariaLabel}"><span aria-hidden="true">${icon}</span> ${fileName.escapeHtml()}</a></li>""")
l.append(""" <li><a class="item-link" href="${encodedHref}" aria-label="${ariaLabel}"><span aria-hidden="true">${icon}</span> ${fileName.escapeHtml()}</a></li>""")
l.append('\n')
}
}

if(l.isEmpty()){
l.append(""" <li><div style="padding: 0.5rem; color: #666; font-style: italic;">이 λ””λ ‰ν† λ¦¬λŠ” λΉ„μ–΄ μžˆμŠ΅λ‹ˆλ‹€.</div></li>""")
l.append(""" <li><div class="empty-msg">이 λ””λ ‰ν† λ¦¬λŠ” λΉ„μ–΄ μžˆμŠ΅λ‹ˆλ‹€.</div></li>""")
l.append('\n')
}

Expand Down
3 changes: 2 additions & 1 deletion src/test/kotlin/html4tree/MainTest.kt
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Expand Up @@ -159,7 +159,8 @@ class MainTest {
assertTrue(htmlContent.contains("&#128193;"))
assertFalse(htmlContent.contains("test.ignore"))
assertTrue(htmlContent.contains("Content-Security-Policy"))
assertTrue(htmlContent.contains("default-src 'none'; style-src 'unsafe-inline';"))
assertTrue(htmlContent.contains("default-src 'none'; style-src 'nonce-"))
assertTrue(htmlContent.contains("class=\"item-link\""))
}

@Test
Expand Down
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