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]>

legacy/src/main/java/thredds/cataloggen/config/LocalDatasetSource.java

@@ -108,7 +108,7 @@ private void checkAccessPoint() throws IOException {
 
       // Check that accessPoint file starts with accessPointHeader.
       if (!apFile.getPath().startsWith(aphFile.getPath())
-          && !apFile.getCanonicalPath().startsWith(aphFile.getCanonicalPath())) {
+          && !apFile.getCanonicalFile().toPath().startsWith(aphFile.getCanonicalFile().toPath())) {
         String tmpMsg = "The accessPoint <" + apFile.getPath() + " or " + apFile.getCanonicalPath()
             + "> must start with the accessPointHeader <" + aphFile.getPath() + " or " + aphFile.getCanonicalPath()
             + ">.";