vuln-fix: Partial Path Traversal Vulnerability

This fixes a partial path traversal vulnerability.

Replaces `dir.getCanonicalPath().startsWith(parent.getCanonicalPath())`, which is vulnerable to partial path traversal attacks, with the more secure `dir.getCanonicalFile().toPath().startsWith(parent.getCanonicalFile().toPath())`.

To demonstrate this vulnerability, consider `"/usr/outnot".startsWith("/usr/out")`.
The check is bypassed although `/outnot` is not under the `/out` directory.
It's important to understand that the terminating slash may be removed when using various `String` representations of the `File` object.
For example, on Linux, `println(new File("/var"))` will print `/var`, but `println(new File("/var", "/")` will print `/var/`;
however, `println(new File("/var", "/").getCanonicalPath())` will print `/var`.

Weakness: CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Severity: Medium
CVSSS: 6.1
Detection: CodeQL & OpenRewrite (https://public.moderne.io/recipes/org.openrewrite.java.security.PartialPathTraversalVulnerability)

Reported-by: Jonathan Leitschuh <[email protected]>
Signed-off-by: Jonathan Leitschuh <[email protected]>

Bug-tracker: JLLeitschuh/security-research#13

Co-authored-by: Moderne <[email protected]>

src/main/java/org/zeroturnaround/zip/commons/FileUtilsV2_2.java

@@ -576,7 +576,7 @@ public static void copyDirectory(File srcDir, File destDir,
 
     // Cater for destination being directory within the source directory (see IO-141)
     List<String> exclusionList = null;
-    if (destDir.getCanonicalPath().startsWith(srcDir.getCanonicalPath())) {
+    if (destDir.getCanonicalFile().toPath().startsWith(srcDir.getCanonicalFile().toPath())) {
       File[] srcFiles = filter == null ? srcDir.listFiles() : srcDir.listFiles(filter);
       if (srcFiles != null && srcFiles.length > 0) {
         exclusionList = new ArrayList<String>(srcFiles.length);
@@ -997,7 +997,7 @@ public static void moveDirectory(File srcDir, File destDir) throws IOException {
     }
     boolean rename = srcDir.renameTo(destDir);
     if (!rename) {
-      if (destDir.getCanonicalPath().startsWith(srcDir.getCanonicalPath())) {
+      if (destDir.getCanonicalFile().toPath().startsWith(srcDir.getCanonicalFile().toPath())) {
         throw new IOException("Cannot move directory: "+srcDir+" to a subdirectory of itself: "+destDir);
       }
       copyDirectory( srcDir, destDir );