Arbitrary File Write via Archive Extraction (Zip Slip) Affecting github.com/u-root/u-root/pkg/tarutil package, versions <0.9.0
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Test your applications- Snyk ID SNYK-GOLANG-GITHUBCOMUROOTUROOTPKGTARUTIL-570428
- published 1 Sep 2020
- disclosed 1 Sep 2020
- credit Georgios Gkitsas of Snyk Security Team
Introduced: 1 Sep 2020
CVE-2020-7669 Open this link in a new tabHow to fix?
Upgrade github.com/u-root/u-root/pkg/tarutil
to version 0.9.0 or higher.
Overview
github.com/u-root/u-root/pkg/tarutil 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 tar file extraction.
PoC
package main
import (
"os"
"fmt"
tar "github.com/u-root/u-root/pkg/tarutil"
)
func main() {
file := "relative.tar"
f, err := os.Open(file)
if err != nil {
fmt.Println(err)
}
defer f.Close()
if err := tar.ExtractDir(f, "."); err != nil {
fmt.Println(err)
}
}
with "relative.tar" being a tar archive that includes a file with filepath that uses leading or non-leading "../" .
Details
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