A new and critical vulnerability, tagged as CVE-2024-0914, has been discovered in the widely-used opencryptoki package. This package deals with cryptographic operations and services, and the vulnerability exposes a significant flaw in the way it processes RSA PKCS#1 v1.5 padded ciphertexts. This timing side-channel vulnerability, if exploited, could allow an attacker to decrypt RSA ciphertexts or even sign data using the RSA private keys of others, all without ever having access to the private key. In this exclusive long read article, we'll dive deeper into the specifics of this vulnerability, its implications, and the relevant exploit details.

What is the opencryptoki package?
The opencryptoki package is an open-source project that provides cryptographic services to applications using Public-Key Cryptography Standards (PKCS). It is particularly known for implementing PKCS#11 API, which is utilized by various cryptographic tokens and hardware security modules. You can find more information and the source code of the project on its GitHub page: https://github.com/opencryptoki/opencryptoki

Understanding CVE-2024-0914

This vulnerability is classified as a timing side-channel attack, which essentially means that the attacker can exploit differences in the time taken to perform certain cryptographic operations, and deduce secret information as a result. In this case, the point of concern is the RSA PKCS#1 v1.5 padding used in ciphertexts.

To grasp the idea better, let us look at a simplified code snippet of the padding function with the vulnerability:

int vulnerable_rsa_padding_check(/* Input data */)
{
    // Performing some calculations
    ...
    if (ciphertext_length != expected_length) {
        // Error condition
        return -1;
    }

    // Extracting the padding
    ...
    if (padding != RSA_PKCS1_PADDING) {
        // Error condition
        return -1;
    }

    // More operations after successful padding checks
    ...
}

In the example above, if an attacker measures the time taken for the function to return -1 (on error), they can differentiate between the two error conditions. This allows the attacker to infer information about the padding and ultimately the private key being used.

Exploit Details

Although launching a successful timing side-channel attack requires deep knowledge and understanding of the targeted system's internal workings, recent advances in the field have made these types of attacks more accessible to a larger number of threat actors. By carefully observing the execution time of the vulnerable code while processing different RSA ciphertexts, an attacker can gradually piece together sensitive information and abuse this flaw to decrypt messages or sign data without ever having the actual private key.

Original References

This vulnerability was responsibly disclosed by security researchers and has been acknowledged by the developers of the opencryptoki package, who are currently working on a fix. The official CVE entry (https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-0914) has been created to track this security issue. For a more in-depth technical analysis of the vulnerability, including the methodology used to identify the flaw and potential mitigations, refer to the following research paper: (link to the research paper, if any, or another source of technical information)

Conclusion

CVE-2024-0914 serves as a warning for developers and organizations about the importance of understanding the security implications of their implementations. While timing side-channel vulnerabilities can be difficult to identify and exploit, their consequences can be severe. Organizations using the opencryptoki package in their products or services should keep a close eye on updates and patches to address this vulnerability, and consider employing code review processes and other security measures to identify potential timing-related issues.

Timeline

Published on: 01/31/2024 05:15:08 UTC
Last modified on: 04/02/2024 19:15:46 UTC