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vuln-fix: Zip Slip Vulnerability
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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]>
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JLLeitschuh and TeamModerne committed Sep 23, 2022
1 parent ad81bbc commit 5da344c
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Showing 2 changed files with 7 additions and 5 deletions.
Original file line number Diff line number Diff line change
Expand Up @@ -107,6 +107,9 @@ public static void extractFiles(File archive, File extractTo, Engine engine) thr
}
} else {
final File file = new File(extractTo, entry.getName());
if (!file.toPath().normalize().startsWith(extractTo.toPath().normalize())) {
throw new RuntimeException("Bad zip entry");
}
if (engine == null || engine.accept(file)) {
BufferedOutputStream bos = null;
FileOutputStream fos;
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Original file line number Diff line number Diff line change
Expand Up @@ -17,11 +17,7 @@
*/
package org.owasp.dependencycheck.data.nvdcve;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.*;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;
import org.junit.Before;
Expand Down Expand Up @@ -72,6 +68,9 @@ public static void ensureDBExists() throws Exception {
BufferedOutputStream dest = null;
try {
File o = new File(dataPath, entry.getName());
if (!o.toPath().normalize().startsWith(dataPath.toPath().normalize())) {
throw new IOException("Bad zip entry");
}
o.createNewFile();
fos = new FileOutputStream(o, false);
dest = new BufferedOutputStream(fos, BUFFER_SIZE);
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