Hyper-V booting with Secure Boot

[skyblaster]

Given the newly available dual-signed shim I went ahead and updated my TFTP server to test.

Physical devices network boot without issue; just as they did when the shim was only signed by the 2011 cert.
However, I have never been successful with Hyper-V. See my previous findings: #57 (comment)
Shouldn't this be possible?

Here are my secure boot settings in Hyper-V:

And here is the error I get:

[NiKiZe]

So signed shim boots signed ipxe which boots signed wimboot but fails to boot signed windows bootloader?

The certificates signing the Microsoft binaries are different from the ones used for shim and wimboot, and if I remember correctly, Hyper-V will only ever allow one of them at a time, not both? (Have they released the 2023 update yet?)

But could you run this iPXE scriptlet and we can verify exactly what is available:

show efi/SecureBoot || 
show efi/AuditMode || 
show efi/DeployedMode || 
show efi/SetupMode || 

params 
param PK ${efi/PK:base64} 
chain -a http://b800.ipxe.se/?public=1##params || echo Errorno ${errno} 
isset ${b800id} && echo PK id b800.org/${b800id} - Allowed to modify EFI || 

params 
param KEK ${efi/KEK:base64} 
chain -a http://b800.ipxe.se/?public=1##params || echo Errorno ${errno} 
isset ${b800id} && echo KEK id b800.org/${b800id} - Allowed to update db and dbx|| 

params 
param db ${efi/db:base64} 
chain -a http://b800.ipxe.se/?public=1##params || echo Errorno ${errno} 
isset ${b800id} && echo db id b800.org/${b800id} - Allowed to boot || 

params 
param dbx ${efi/dbx:base64} 
chain -a http://b800.ipxe.se/?public=1##params || echo Errorno ${errno} 
isset ${b800id} && echo dbx id b800.org/${b800id} - Not allowed to boot || 

Compare to what the windows bootmgr files are signed with.

[mcb30]

The certificates signing the Microsoft binaries are different from the ones used for shim and wimboot, and if I remember correctly, Hyper-V will only ever allow one of them at a time, not both? (Have they released the 2023 update yet?)

I believe this is correct. https://learn.microsoft.com/en-us/windows-server/virtualization/hyper-v/generation-2-virtual-machine-security-features#secure-boot documents the selection, and the fact that it's a single drop-down in the UI suggests that Hyper-V is not capable of being configured to simultaneously trust both the Windows root and the UEFI CA root.

@skyblaster Everything in iPXE and wimboot is working correctly here. The problem is in Hyper-V. As far as I can tell, you will need to either disable Secure Boot, create a custom variable store (with both certs enrolled), switch to using a different hypervisor, or hope that MS at some point updates Hyper-V to include a template that trusts both roots.

[skyblaster]

Thank you both for the excellent replies. That makes perfect sense.

Just for reference, here is what I see from a Linux VM when booted with the Microsoft UEFI Certificate Authority template and indeed it does not include the Windows UEFI CA 2023 db cert:

Variable PK, length 1862
PK: List 0, type X509
    Signature 0, size 1834, owner 77fa9abd-0359-4d32-bd60-28f4e78f784b
        Subject:
            C=US, ST=Washington, L=Redmond, O=Microsoft Corporation, CN=Microsoft Hyper-V Firmware PK
        Issuer:
            C=US, ST=Washington, L=Redmond, O=Microsoft Corporation, CN=Microsoft Corporation Third Party Marketplace PCA


Variable KEK, length 3066
KEK: List 0, type X509
    Signature 0, size 1532, owner 77fa9abd-0359-4d32-bd60-28f4e78f784b
        Subject:
            C=US, ST=Washington, L=Redmond, O=Microsoft Corporation, CN=Microsoft Corporation KEK CA 2011
        Issuer:
            C=US, ST=Washington, L=Redmond, O=Microsoft Corporation, CN=Microsoft Corporation Third Party Marketplace Root
KEK: List 1, type X509
    Signature 0, size 1478, owner 77fa9abd-0359-4d32-bd60-28f4e78f784b
        Subject:
            C=US, O=Microsoft Corporation, CN=Microsoft Corporation KEK 2K CA 2023
        Issuer:
            C=US, O=Microsoft Corporation, CN=Microsoft RSA Devices Root CA 2021


Variable db, length 4850
db: List 0, type X509
    Signature 0, size 1572, owner 77fa9abd-0359-4d32-bd60-28f4e78f784b
        Subject:
            C=US, ST=Washington, L=Redmond, O=Microsoft Corporation, CN=Microsoft Corporation UEFI CA 2011
        Issuer:
            C=US, ST=Washington, L=Redmond, O=Microsoft Corporation, CN=Microsoft Corporation Third Party Marketplace Root
db: List 1, type X509
    Signature 0, size 1464, owner 77fa9abd-0359-4d32-bd60-28f4e78f784b
        Subject:
            C=US, O=Microsoft Corporation, CN=Microsoft UEFI CA 2023
        Issuer:
            C=US, O=Microsoft Corporation, CN=Microsoft RSA Devices Root CA 2021
db: List 2, type X509
    Signature 0, size 1730, owner 77fa9abd-0359-4d32-bd60-28f4e78f784b
        Subject:
            C=US, O=Microsoft Corporation, CN=Azure Services Linux Kmod PCA
        Issuer:
            C=US, O=Microsoft Corporation, CN=Microsoft RSA Services Root CA 2021