Arbitrary File Write via Archive Extraction (Zip Slip) Affecting zip-local package, versions <0.3.5

zip-local is a to zip and unzip local directories

Affected versions of this package are vulnerable to Arbitrary File Write via Archive Extraction (Zip Slip) which can lead to an extraction of a crafted file outside the intended extraction directory.

var zipper = require('zip-local');

zipper.unzip("zipslip.zip", function(error, unzipped) {

if(!error) {
// extract to the current working directory
unzipped.save(null, function() { });

var unzippedfs = unzipped.memory();

}
});

Execute the following commands

1. npm install zip-local # Install affected module
2. zipslip example file can be found at - https://github.com/snyk/zip-slip-vulnerability/blob/master/archives/zip-slip.zip
3. node poc.js # Run the PoC

It is exploited using a specially crafted zip archive, that holds path traversal filenames. When exploited, a filename in a malicious archive is concatenated to the target extraction directory, which results in the final path ending up outside of the target folder. For instance, a zip may hold a file with a "../../file.exe" location and thus break out of the target folder. If an executable or a configuration file is overwritten with a file containing malicious code, the problem can turn into an arbitrary code execution issue quite easily.

The following is an example of a zip archive with one benign file and one malicious file. Extracting the malicous file will result in traversing out of the target folder, ending up in /root/.ssh/ overwriting the authorized_keys file:

+2018-04-15 22:04:29 ..... 19 19 good.txt

+2018-04-15 22:04:42 ..... 20 20 ../../../../../../root/.ssh/authorized_keys

• Github Commit
• Vulnerable Code