An issue, found in the Go programming language with the cgo tool, may lead to the generation of unexpected code at build time. This vulnerability has been assigned the identifier CVE-2023-29402. The issue arises due to the go command generating unexpected code when using cgo, resulting in unpredictable behavior when running a Go program that uses cgo. The vulnerability is triggered when an untrusted module contains directories with newline characters in their names.

This vulnerability is particularly concerning for those who use modules retrieved using GOPATH-mode (i.e., with GO111MODULE=off). Modules fetched using the go get command are not affected.

In this post, we will discuss the vulnerability in detail, including how the vulnerability can be exploited, how to reproduce it, and how it can be mitigated. We will also provide code snippets and links to help you understand and resolve the issue.

Exploit Details

The problem arises when cgo is used to generate code during the Go build process. Cgo is responsible for assisting with the integration of C libraries into Go programs. The unexpected code generation may lead to security vulnerabilities or crashes when executing Go applications.

The exploit is triggered when an untrusted module containing directory names with newline characters is loaded. This can lead to cgo generating the unexpected code, causing issues during execution. It is important to note that modules using the go get command will not be affected by this vulnerability.

Let's consider a simple example of cgo usage

package main

/*
#include <stdio.h>

void helloWorld() {
    printf("Hello, World!\n");
}
*/
import "C"

func main() {
    C.helloWorld()
}

The code above contains an embedded C function helloWorld(), which is called using the C pseudo-package in the Go code. The issue lies in the way cgo handles newline characters when generating the build code.

To demonstrate the vulnerability, we can create a directory with a newline character in its name and place the Go file with cgo usage inside of it.

$ mkdir "exploit\ndir" && cp main.go "exploit\ndir"
$ cd "exploit\ndir"
$ GO111MODULE=off go build

When executed, the Go application might exhibit unexpected behavior or even crash due to the generated code issues.

Original References

The issue was initially reported by the Go security team, and you can find more information about it in the Go vulnerability database.

Mitigation Measures

To mitigate this vulnerability, ensure that the affected modules are either migrated to use the go get command or eliminate newline characters in directory names of untrusted modules to which cgo is applied. Additionally, it is recommended to always keep your Go installation up-to-date as the Go team is continuously working to address potential vulnerabilities and improve the language's security.

To ensure you stay up-to-date with this and other Go vulnerabilities, refer to the official Go vulnerability database, which contains comprehensive information and remediation tactics for known vulnerabilities.

In conclusion, while CVE-2023-29402 is a relatively rare issue, it is still important to be aware of it and take the necessary precautions when using cgo with Go projects. Always keep your Go installation updated, and ensure that you follow best practices in Go programming to minimize your security threats.

Timeline

Published on: 06/08/2023 21:15:00 UTC
Last modified on: 06/16/2023 14:12:00 UTC