On Wed, Oct 16, 2024 at 04:35:17PM -0500, Ryan Eatmon via 
lists.yoctoproject.org wrote:
> 
> 
> On 10/16/2024 2:51 PM, Ryan Eatmon via lists.yoctoproject.org wrote:
> >
> >
> >On 10/14/2024 3:27 PM, Sergio Prado wrote:
> >>Use weak assignment to make it possible to override the default
> >>value via classes parsed after the machine configuration file.
> >>
> >>This is the case when using the tdxref-signed class from
> >>meta-toradex-security to generated signed images for AM6X.
> >>
> >>Additionally, explicitly set FIT_SIGN_NUMBITS to 4096 to align with the
> >>default rsa4096 algorithm, preventing potential mismatches between the
> >>signing algorithm and key length.
> >>
> >>Signed-off-by: Sergio Prado <[email protected]>
> >>Signed-off-by: Rogerio Borin <[email protected]>
> >>---
> >>  meta-ti-bsp/conf/machine/include/k3.inc | 9 +++++----
> >>  1 file changed, 5 insertions(+), 4 deletions(-)
> >>
> >>diff --git a/meta-ti-bsp/conf/machine/include/k3.inc
> >>b/meta-ti-bsp/conf/machine/include/k3.inc
> >>index a296f64fa141..07f0bcb48bfc 100644
> >>--- a/meta-ti-bsp/conf/machine/include/k3.inc
> >>+++ b/meta-ti-bsp/conf/machine/include/k3.inc
> >>@@ -26,10 +26,11 @@ UBOOT_SUFFIX = "img"
> >>  UBOOT_SIGN_ENABLE = "1"
> >>  UBOOT_MKIMAGE_DTCOPTS = "-I dts -O dtb"
> >>-UBOOT_SIGN_KEYNAME ?= "custMpk"
> >>-UBOOT_SIGN_KEYDIR ?= "${TI_SECURE_DEV_PKG}/keys"
> >>-FIT_HASH_ALG ?= "sha512"
> >>-FIT_SIGN_ALG ?= "rsa4096"
> >>+UBOOT_SIGN_KEYNAME ??= "custMpk"
> >>+UBOOT_SIGN_KEYDIR ??= "${TI_SECURE_DEV_PKG}/keys"
> >>+FIT_HASH_ALG ??= "sha512"
> >>+FIT_SIGN_ALG ??= "rsa4096"
> >>+FIT_SIGN_NUMBITS ??= "4096"
> >
> >These changes appear to break the build flow.  Since the the only
> >real change is the addition of FIT_SIGN_NUMBITS, I'm going to
> >assume that is the culprit.
> >
> >Signature written to 
> >'<snip>/build/arago-tmp-default-glibc/work/am62axx_evm-oe-linux/u-boot-ti-staging/2024.04+git/build/fitImage-linux',
> >node
> >'/configurations/conf-ti_k3-v3link-imx219-0-2.dtbo/signature-1'
> >Public key written to 'u-boot.dtb', node '/signature/key-custMpk'
> >Signature check bad (error 1)
> >Verifying Hash Integrity for node 'conf-ti_k3-am62a7-sk.dtb'...
> >sha256,rsa2048:custMpk-
> >  error!
> >Verification failed for '(null)' hash node in
> >'conf-ti_k3-am62a7-sk.dtb' config node
> >Failed to verify required signature 'key-custMpk'
> 
> I think the issue is that the weak assignment happens at the very
> end of parsing if there no other value for the variable.  But the
> various classes (kernel-fitimage.bbclass, uboot-sign.bbclass,
> etc...) set the variables using the ?= so that means the values we
> want for our stuff never gets set correctly.
> 
> I can see how this works for you in your case, but doing this in
> meta-ti-bsp breaks everyone not using meta-tordex-security.
> 
> I'm not really sure the best solution for this.  Should the tordex
> layer be in final control of these variables and not allow
> overrides?  Should it not be using the ?= assignment and instead use
> the = assignment to force the issue?
> 
> Denys,
> Any ideas?

Yeah, I had my suspicions about the patch, so not surprised by your 
confirmation. I'd suggest using machine or SoC overrides in toradex 
layer to change the defaults set in meta-ti k3.inc

-- 
Denys
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