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 <Jonathan.Leitschuh@gmail.com>
Signed-off-by: Jonathan Leitschuh <Jonathan.Leitschuh@gmail.com>

Bug-tracker: https://github.com/JLLeitschuh/security-research/issues/13

Co-authored-by: Moderne <team@moderne.io>

1 files changed, 1 insertions, 1 deletions

diff --git a/testing/src/test/java/org/aspectj/testing/util/FileUtil.java b/testing/src/test/java/org/aspectj/testing/util/FileUtil.java
index 03b29a85a..103eba59b 100644
--- a/testing/src/test/java/org/aspectj/testing/util/FileUtil.java
+++ b/testing/src/test/java/org/aspectj/testing/util/FileUtil.java
@@ -477,7 +477,7 @@ public class FileUtil {
         throws IOException {
         String path = in.getCanonicalPath();
         String parentPath = parent.getCanonicalPath();
-        if (!path.startsWith(parentPath)) {
+        if (!in.getCanonicalFile().toPath().startsWith(parentPath)) {
             throw new Error("not parent: " + parentPath + " of " + path);
         } else {
             path = path.substring(1+parentPath.length());