"VCEK Does Not Sign The Attestation Report" Error When Using VLEK Signatures
Problem Description
When executing make attest_verity_vm, you may encounter the error "VCEK does not sign the attestation report". This issue arises when your attestation report is signed using VLEK (Versioned Loaded Endorsement Key) rather than VCEK. In this article, we will delve into the root cause of this problem and explore suggested improvements to resolve it.
Root Cause
The attestation report JSON file (attestation_report.json) contains a field called sig_algo that identifies the signing algorithm used. The possible values for sig_algo are:
sig_algo: 0 = VCEK signingsig_algo: 1 = VLEK signing
With the introduction of newer SEV-SNP firmware (v1.55+), AMD has transitioned from VCEK to VLEK for signing attestation reports. However, the verification code in this repository appears to only support VCEK verification, leading to the error.
Suggested Improvements
To address this issue, we recommend the following improvements:
1. Documentation Update
Add a note explaining the VCEK vs. VLEK distinction and how to identify which is being used. This will help users understand the difference between the two signing algorithms and how to troubleshoot the issue.
2. Error Message Enhancement
Include specific guidance about VLEK in error messages. This will provide users with more accurate information about the issue and help them resolve it more efficiently.
3. Code Improvement (optional)
Consider adding VLEK support or a fallback mechanism to the verification code. This will ensure that the tool can handle both VCEK and VLEK signed attestation reports.
Current Limitations
The current error messages only suggest double-checking the vm-config.toml parameters, which can be misleading when the actual issue is related to the signature verification method. This highlights the need for improved documentation and error handling.
Environment Details
The following environment details are relevant to this issue:
- SEV-SNP Firmware: 1.55, build 8
- Linux kernel: 6.9.0-rc7-snp-host
- Signature algorithm in report: 1 (VLEK)
Contributing to the Solution
If you are interested in contributing to the solution, you can start by updating the documentation to include information about VCEK vs. VLEK. You can also consider submitting a pull request with a code fix to add VLEK support or a fallback mechanism.
Conclusion
The "VCEK does not sign the attestation report" error when using VLEK signatures is a common issue with newer SEV-SNP firmware versions. By understanding the root cause and implementing the suggested improvements, we can resolve this issue and provide a more robust and user-friendly tool for attestation report verification.
Future Development
In the future, we plan to:
- Update the verification code to support VLEK signing
- Enhance error messages to provide more accurate information
- Improve documentation to include information about VCEK vs. VLEK
Contributing to the Repository
If you are interested in contributing to the repository, please feel free to submit a pull request with your proposed changes. We appreciate any contributions that can help improve the tool and make it more user-friendly.
Related Issues
If you encounter any related issues or have questions about this problem, please don't hesitate to reach out. We are here to help and provide support.
References
For more information about SEV-SNP firmware and attestation report verification, please refer to the following resources:
Acknowledgments
Frequently Asked Questions
We have compiled a list of frequently asked questions related to the "VCEK does not sign the attestation report" error when using VLEK signatures. Please find the answers to these questions below.
Q: What is the difference between VCEK and VLEK?
A: VCEK (Versioned Code Endorsement Key) and VLEK (Versioned Loaded Endorsement Key) are two different signing algorithms used for attestation reports. VCEK is used in older SEV-SNP firmware versions, while VLEK is used in newer versions (v1.55+).
Q: Why am I getting the "VCEK does not sign the attestation report" error when using VLEK signatures?
A: The error occurs because the verification code in this repository only supports VCEK verification, and not VLEK. This is due to the transition from VCEK to VLEK in newer SEV-SNP firmware versions.
Q: How can I identify which signing algorithm is being used in my attestation report?
A: You can check the sig_algo field in the attestation report JSON file (attestation_report.json). If the value is 0, it means VCEK is being used, and if the value is 1, it means VLEK is being used.
Q: What are the implications of using VLEK signatures with older verification code?
A: Using VLEK signatures with older verification code can lead to errors and inconsistencies in the attestation report verification process. It is recommended to update the verification code to support VLEK signing.
Q: How can I update the verification code to support VLEK signing?
A: You can update the verification code by adding support for VLEK signing or implementing a fallback mechanism to handle both VCEK and VLEK signed attestation reports.
Q: What are the benefits of updating the verification code to support VLEK signing?
A: Updating the verification code to support VLEK signing will ensure that the tool can handle both VCEK and VLEK signed attestation reports, providing a more robust and user-friendly experience.
Q: Can I contribute to the solution by updating the documentation or submitting a pull request?
A: Yes, you can contribute to the solution by updating the documentation to include information about VCEK vs. VLEK or submitting a pull request with a code fix to add VLEK support or a fallback mechanism.
Q: Where can I find more information about SEV-SNP firmware and attestation report verification?
A: You can find more information about SEV-SNP firmware and attestation report verification in the following resources:
Q: How can I get help with this issue or related questions?
A: You can reach out to us through the repository issues or by sending an email to [your email address]. We are here to help and provide support.