[Secure Boot KEK Update] Siemens PK-Signed KEK Update

[wagnerdo]

OEM Certificate Submission

OEM Name: Siemens AG
Contact Email: wagner.dominik@siemens.com

Certificate Details

• Platform Key Thumbprint: 75d67554b3f49e3e83108c6daa067873dab65984
• Expiration Date: 2042-04-19

Testing Completed

• Windows validation
• Linux validation

Security Review

• No known security issues

Additional Notes

I am responsible for this submission, thus I have supplied my personal mail as contact Email.
The official security contact is productcert@siemens.com

Testing was performed with FW version V29.01.07.
Windows: Windows 10 LTSC 2021 with BitLocker enabled using PowerShell as described in Wiki
Linux: Ubuntu 22.04.1 LTS using efi-updatevar as described in Wiki

[Flickdm]

@jgeurten @SochiOgbuanya FYI

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[Flickdm]

@wagnerdo

I added a new check to my script because I when I was manually reviewing it I suspected this was a thing.

#403

 python .\scripts\validate_kek.py KEKUpdate_Siemens_PK75d67554.bin                    
INFO:root:Validating: KEKUpdate_Siemens_PK75d67554.bin
WARNING:root:  [!] ContentInfo wrapper detected in cert_data!
INFO:root:Verifying authenticated variable: KEKUpdate_Siemens_PK75d67554.bin
INFO:root:[+] Authenticated variable signature is VALID
INFO:root:  Cryptographic Signature: VALID
INFO:root:  Expected Payload: True

INFO:root:Results saved to: KEKUpdate_Siemens_PK75d67554_validation_results.json

For the same reasons I laid out here #374 (comment) having ContentInfo in your payload while technically not incorrect on firmware that's older may cause issues.

I would recommend stripping the contentinfo off in the script I added in the PR and adding the file back and doing "git commit --amend --no-edit" and a "git push -f"

[Flickdm]

@wagnerdo https://github.com/microsoft/secureboot_objects/actions/runs/24851639418?pr=402

[wagnerdo]

For the same reasons I laid out here #374 (comment) having ContentInfo in your payload while technically not incorrect on firmware that's older may cause issues.

Thanks. I noticed that commit f475aff referenced this, but was unsure whether I should apply it here as well. I did verify that our firmware will correctly process the file on a real device.
In our case, this works because our IBV has replaced the relevant EDK2 code with their own that handles this detail correctly.
For reference, the original signature was created with openssl cms -sign -outform DER -nodetach.

I would recommend stripping the contentinfo off in the script I added in the PR and adding the file back and doing "git commit --amend --no-edit" and a "git push -f"

Done, and thanks for the script! I have no doubt that the resulting file will work, but I will double-check with a real device just to be sure. Might take until monday to complete the test though.

As for CLA, clarification with Legal is ongoing and might take a while, so I expect this PR to remain in limbo for a bit.

[Flickdm]

For the same reasons I laid out here #374 (comment) having ContentInfo in your payload while technically not incorrect on firmware that's older may cause issues.

Thanks. I noticed that commit f475aff referenced this, but was unsure whether I should apply it here as well. I did verify that our firmware will correctly process the file on a real device. In our case, this works because our IBV has replaced the relevant EDK2 code with their own that handles this detail correctly. For reference, the original signature was created with openssl cms -sign -outform DER -nodetach.

I would recommend stripping the contentinfo off in the script I added in the PR and adding the file back and doing "git commit --amend --no-edit" and a "git push -f"

Done, and thanks for the script! I have no doubt that the resulting file will work, but I will double-check with a real device just to be sure. Might take until monday to complete the test though.

As for CLA, clarification with Legal is ongoing and might take a while, so I expect this PR to remain in limbo for a bit.

Yeah I personally have no doubt that the 19 bytes being removed won't impact if these binaries are successful. Its simply that you're more likely to be more successful (at least on older machines -- that you might not have without them).

I assumed you used Openssl because Openssl natively wants to do the "normal" way.

---

As for CLA, clarification with Legal is ongoing and might take a while, so I expect this PR to remain in limbo for a bit.

Let me know when you're ready for me to merge this!

[Flickdm]

https://github.com/microsoft/secureboot_objects/actions/runs/24857590443?pr=402

Confirmed -- Everything is green ✅