CVE-2023-29403: Understanding the Unix Privilege Escalation Vulnerability in Go Runtime

A recently discovered security vulnerability (CVE-2023-29403) within the Go runtime for Unix platforms has caught the attention of developers and security professionals alike. This vulnerability enables privilege escalation when running binaries with setuid or setgid bits. In this in-depth post, we'll dive into the details of this vulnerability, discussing its origins, the threat it poses, and the steps you can take to mitigate it.

Background

For those unfamiliar with Unix permissions, setuid (set user ID upon execution) and setgid (set group ID upon execution) are special bits that allow a program to run with elevated privileges. These bits are necessary for some programs to function correctly, but can also be a potential security risk when misused.

The issue at hand lies in the Go runtime's handling of these special bits for Unix platforms. The runtime does not differentiate between regular and setuid/setgid binaries, resulting in potentially dangerous behavior. This can occur in instances such as:

Dumping memory state

2. Assuming the status of standard input/output (I/O) file descriptors

Go Runtime Vulnerability Exploitation

To better understand the scope of this vulnerability, let's take a look at how it can be exploited.

A threat actor could use this vulnerability to execute a setuid/setgid binary with the standard I/O file descriptors closed. Consequently, any files opened by the binary could be read or written with elevated privileges, potentially giving unauthorized access to sensitive information or allowing malicious modifications to the filesystem. Here's a code snippet to illustrate this exploit:

package main

import (
	"fmt"
	"os"
)

func main() {
	file, err := os.OpenFile("sensitive_file", os.O_RDWR, 0644)
	if err != nil {
		fmt.Fprintln(os.Stderr, "Error opening file:", err)
		return
	}

	// Do something with the file
}

In this example, the sensitive_file could be inadvertently opened with elevated privileges, resulting in unintended consequences.

Another exploit scenario is when a setuid/setgid program is terminated unexpectedly, either via panic or signal. In this case, the program may leak the contents of its registers, making it a security risk.

Mitigating the Vulnerability

Given the seriousness of this issue, it is crucial to implement a proper fix. To protect your Go programs, the following steps are recommended:

1. Avoid using setuid/setgid permissions for Go binaries when possible.
2. Ensure that standard I/O file descriptors are not closed when executing a setuid/setgid binary.

For more information on this vulnerability, check the following resources

1. CVE-2023-29403 Details - Official details regarding the vulnerability.
2. Go Runtime Documentation - Official guidelines on using setuid/setgid in Go programs.
3. Unix Permissions Explained - A comprehensive guide to Unix permissions, including setuid and setgid.

Conclusion

The CVE-2023-29403 vulnerability in the Go runtime for Unix platforms poses a significant threat to developers and users alike. By understanding its origins and adopting appropriate mitigation strategies, you can protect your Go-based applications from this dangerous vulnerability. Stay informed and vigilant to ensure the security of your projects.

Timeline

Published on: 06/08/2023 21:15:00 UTC
Last modified on: 07/21/2023 04:15:00 UTC