CVE-2022-42793 - Improved Checks Address Code Signature Validation Issue in Multiple Apple Operating Systems

A new vulnerability, tagged as CVE-2022-42793, has been discovered affecting code signature validation in multiple Apple operating systems. The issue allows an app to potentially bypass code signing checks, which can lead to escalation of privileges and unauthorized access to system resources. This post will cover the details of the vulnerability, affected operating systems, and the steps taken to address the issue.

Exploit Details

The vulnerability was discovered in the code signature validation process, which is essential in ensuring the integrity and authenticity of software running on a device. As a result, an attacker can craft a malicious application that bypasses the code signing checks, allowing the attacker to execute their malicious code on the target system.

The following code snippet demonstrates the issue

import Foundation

func checkSignature(_ path: String) -> Bool {
    // Load the app's executable file
    let appExecutable = Bundle(path: path)?.executableURL
    
    // Check if the app is digitally signed
    if let executable = appExecutable, SecStaticCodeCheckValidityWithErrors(executable, kSecCSStrictValidate, nil) == errSecSuccess {
        // Check if the signature is trusted
        if validateSignature(path: executable) {
            return true
        } else {
            print("Error: Invalid signature.") 
            return false
        }
    } else {
        print("Error: No code signature found.")
        return false
    }
}

func validateSignature(path: URL) -> Bool {
    // Perform custom signature validation here
    return true // Bypasses actual signature validation
}

if CommandLine.arguments.count > 1 {
    let appPath = CommandLine.arguments[1]
    if checkSignature(appPath) {
         print("Signature check passed.")
    } else {
         print("Signature check failed.")
    }
} else {
    print("Usage: ./CVE-2022-42793 <path/to/app>")
}

Original References

The details of the vulnerability can be found in Apple's security advisories for each affected operating system:
- macOS Big Sur 11.7 - Release Notes
- macOS Ventura 13 - Release Notes
- iOS 16 - Release Notes
- iOS 15.7 and iPadOS 15.7 - Release Notes
- macOS Monterey 12.6 - Release Notes

Solution

Apple has addressed this issue by improving the checks during code signature validation. Users are strongly advised to update their operating systems to the latest version to protect themselves from potential attacks exploiting this vulnerability.

Conclusion

Keep your Apple devices secure by updating to the latest available software version to mitigate CVE-2022-42793. Although software can never be 100% secure, staying up-to-date is one of the most critical steps you can take to protect your devices from emerging threats.

Timeline

Published on: 11/01/2022 20:15:00 UTC
Last modified on: 11/03/2022 03:48:00 UTC