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]>

src/main/java/com/ninjaflip/androidrevenge/core/apktool/apkinfo/manifestextractor/Extract.java

@@ -87,7 +87,7 @@ public void unZip(String apkFile) throws Exception {
             // Create Zip Entry Folder
             File zeFile = extractFolder;
             if (zeFolder != null) {
-                zeFile = new File(extractFolder.getPath() + File.separator + zeFolder);
+                zeFile = new File(extractFolder.getPath(), zeFolder);
                 if (!zeFile.exists())
                     zeFile.mkdirs();
             }
@@ -112,7 +112,13 @@ public void unZip(String apkFile) throws Exception {
             int count;
             byte data[] = new byte[BUFFER];
 
-            FileOutputStream fos = new FileOutputStream(zeFile.getPath() + File.separator + zeName);
+            final File zipEntryFile = new File(zeFile.getPath(), zeName);
+
+            if (!zipEntryFile.toPath().normalize().startsWith(zeFile.getPath())) {
+                throw new RuntimeException("Bad zip entry");
+            }
+
+            FileOutputStream fos = new FileOutputStream(zipEntryFile);
             dest = new BufferedOutputStream(fos, BUFFER);
 
             while ((count = zin.read(data, 0, BUFFER)) != -1) {