🛡️ Sentinel: [HIGH] 심볼릭 링크를 통한 경로 탐색(Path Traversal) 취약점 수정

.jules/sentinel.md

@@ -22,3 +22,8 @@
 **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.
+
+## 2024-07-24 - File Path Resolution leading to Path Traversal bypassing NOFOLLOW_LINKS
+**Vulnerability:** Symlink path traversal via `File.canonicalFile` bypassing subsequent `NOFOLLOW_LINKS` checks.
+**Learning:** In Java/Kotlin, resolving a `File` path using `.canonicalFile` inherently follows symlinks to return the final target location. When this resolved target is then passed to a function that supposedly restricts symlinks (like `Files.isDirectory(..., LinkOption.NOFOLLOW_LINKS)`), the check evaluates the target, not the original symlink. This entirely bypasses the intended security control.
+**Prevention:** When intending to prevent following symlinks or strictly operate on the actual path provided without resolving targets, avoid using `File.canonicalFile`. Instead, normalize the path string logically using `.absoluteFile.toPath().normalize().toFile()`. This resolves `.` and `..` without implicitly following any symbolic links in the path.

CHANGELOG.md

@@ -0,0 +1,4 @@
+# Changelog
+
+## Unreleased
+- 🛡️ Sentinel: [HIGH] `File.canonicalFile` 대신 `.absoluteFile.toPath().normalize().toFile()`을 사용하여 심볼릭 링크를 통해 의도하지 않은 디렉토리로 이동하는 경로 탐색(Path Traversal) 취약점을 수정했습니다.

src/main/kotlin/html4tree/main.kt

@@ -23,7 +23,7 @@ fun main(args: Array<String>)  = Html4tree().main(args)
 
 fun go(topDir: String, maxLevel: Int)  {
     require(topDir.isNotBlank())
-    val top_dir = File(topDir).canonicalFile
+    val top_dir = File(topDir).absoluteFile.toPath().normalize().toFile()
     require(Files.isDirectory(top_dir.toPath(), LinkOption.NOFOLLOW_LINKS)) { "Top directory must be an existing non-symlink directory" }
 
     val ll = LinkedList()