Arbitrary File Write via Archive Extraction (Zip Slip) Affecting github.com/u-root/u-root/pkg/uzip package, versions <0.9.0

github.com/u-root/u-root/pkg/uzip is a package that provides Go versions of standard Linux tools and bootloaders. It also provides tools for compiling Go programs in a single binary and creating initramfs images.

Affected versions of this package are vulnerable to Arbitrary File Write via Archive Extraction (Zip Slip). It is vulnerable to both leading and non-leading relative path traversal attacks in zip file extraction.

PoC

package main

import (
    "fmt"
    uzip "github.com/u-root/u-root/pkg/uzip"
)
func main() {
    file := "relative.zip"
err := uzip.FromZip(file, ".")
if err != nil {
fmt.Println(err)
}

}

with "relative.zip" being a zip archive that includes a file with filepath that uses leading or non-leading "../" .

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

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