Re: [Xen-devel] Booting signed xen.efi through shim

[Tamas K Lengyel <tamas@xxxxxxxxxxxxx>]

Hi Daniel,

On Tue, Sep 12, 2017 at 11:10 PM, Daniel Kiper <daniel.kiper@xxxxxxxxxx> wrote:
> Hi Tamas,
>
> On Tue, Sep 12, 2017 at 05:40:35PM -0600, Tamas K Lengyel wrote:
>> Hi all,
>> for the last couple weeks I've been poking around the options
>> available to get Xen booted on a Secureboot enabled box. My goal is to
>> extend the chain of trust to the dom0 kernel. According to
>> https://wiki.xenproject.org/wiki/Xen_EFI this is something that's
>> supposed to be supported out-of-the-box right now via the shim
>> protocol. However, when I try to boot a signed xen.efi (4.10 unstable
>> head) through shim I get the error "Section 6 is inside image header"
>
> Strange... Could you send more info about your environment?
> C compiler type, its version, binutils version, etc. How
> did you sign xen.efi? Which tool you used to do that?
> Have you seen any warnings or errors during sign?
>

Stock tools from Debian stretch:
gcc version 6.3.0 20170516 (Debian 6.3.0-18), binutils 2.28-5. I used
sbsign 0.6 to sign xen.efi with

# sbsign --key /home/x/keys/DB.key --cert /home/x/keys/DB.crt --output
xen-signed.efi xen/xen.efi

It does produce the following warnings:

warning: data remaining[2705088 vs 2978877]: gaps between PE/COFF sections?
warning: data remaining[2705088 vs 2978880]: gaps between PE/COFF sections?

(The same cert in DER format is used when compiling the shim.)

>> and shim refuses to load Xen. OTOH I had been able to boot a
>> custom-compiled grub2 from the shim no problem with Secureboot
>
> What do you mean by "custom-compiled grub2"?
>

The latest grub2 from git with the modules all built into the image
with grub-mkimage, then doing the same signing as above with sbsign.
When that image is signed no errors/warnings are printed by sbsign.

>> enabled. The signed xen.efi also boots fine with Secureboot enabled if
>> booted directly as an EFI application (but then no dom0 verification
>
> IIRC, shim is very picky with PE format. So, anything which is loaded
> by EFI loader may not be loaded by shim.
>
>> is done AFAIU). Does anyone have any pointers on what's going on with
>
> Right, only shim provides a such functionality.
>
>> booting through the shim?
>
> I am happy to help but in cases like that I need more info, e.g.: serial
> console logs, output from "objdump -x xen/xen.efi" command, etc.

I don't really get serial output at all here as the boot gets stuck at
the shim stage. I also have been having problem getting Xen to print
to an AMT SoL when booted as an efi (it worked before as a gz using
legacy boot) but that's a separate issue. I've attached the objdump
output for xen.efi.

> Daniel
>
> PS I am traveling, so, I am reading my emails from time to time.

Same here ;)

Thanks!
Tamas

Attachment: objdump.xen.efi.txt
Description: Text document

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel