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]>

core/src/main/java/apoc/log/Neo4jLogStream.java

@@ -56,8 +56,7 @@ public Stream<FileEntry> stream(
         File f = new File(logDir, logName);
 
         try {
-            String canonicalPath = f.getCanonicalPath();
-            if (!canonicalPath.startsWith(logDir.getAbsolutePath())) {
+            if (!f.getCanonicalFile().toPath().startsWith(logDir.getAbsolutePath())) {
                 throw new RuntimeException("The path you are trying to access has a canonical path outside of the logs " +
                         "directory, and this procedure is only permitted to access files in the log directory.  This may " +
                         "occur if the path in question is a symlink or other link.");