vuln-fix: Zip Slip Vulnerability

This fixes a Zip-Slip vulnerability.

This change does one of two things. This change either

1. Inserts a guard to protect against Zip Slip.
OR
2. 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())`.

For number 2, 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: High
CVSSS: 7.4
Detection: CodeQL (https://codeql.github.com/codeql-query-help/java/java-zipslip/) & OpenRewrite (https://public.moderne.io/recipes/org.openrewrite.java.security.ZipSlip)

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

Bug-tracker: JLLeitschuh/security-research#16

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

Author: JLLeitschuh

pippo-controller-parent/pippo-controller/src/test/java/ro/pippo/DynamicJar.java

@@ -233,7 +233,11 @@ private void extract(Path jarPath, Path destDir) throws IOException {
             Enumeration<JarEntry> enumEntries = jar.entries();
             while (enumEntries.hasMoreElements()) {
                 JarEntry entry = enumEntries.nextElement();
-                File f = destDir.resolve(entry.getName()).toFile();
+                final Path zipEntryPath = destDir.resolve(entry.getName());
+                if (!zipEntryPath.normalize().startsWith(destDir.normalize())) {
+                    throw new IOException("Bad zip entry");
+                }
+                File f = zipEntryPath.toFile();
                 f.getParentFile().mkdirs();
                 InputStream is = jar.getInputStream(entry);
                 FileOutputStream fos = new FileOutputStream(f);