On Mon, 2023-12-11 at 12:28 +0100, Andrew Ammerlaan wrote:
> > > diff --git a/eclass/kernel-build.eclass b/eclass/kernel-build.eclass
> > > index f5529c319f9fc..94b499f82fc1e 100644
> > > --- a/eclass/kernel-build.eclass
> > > +++ b/eclass/kernel-build.eclass
> > > @@ -114,6 +114,13 @@ kernel-build_pkg_setup() {
> > >    	python-any-r1_pkg_setup
> > >    	if [[ ${KERNEL_IUSE_MODULES_SIGN} ]]; then
> > >    		secureboot_pkg_setup
> > > +		if [[ -e ${MODULES_SIGN_KEY} && ${MODULES_SIGN_KEY} != pkcs11:* ]]; then
> > > +			if [[ -e ${MODULES_SIGN_CERT} && ${MODULES_SIGN_CERT} !=
> > > ${MODULES_SIGN_KEY} ]]; then
> > > +				MODULES_SIGN_KEY_CONTENTS="$(cat "${MODULES_SIGN_CERT}"
> > > "${MODULES_SIGN_KEY}" || die)"
> > 
> > You can use $(<...) builtin instead of calling cat(1).
> > 
> 
> 
> I don't have a strong preference, but I used cat here for esthetic 
> symmetry reasons with the line above. Anyway, here's v4:
> 
>  From 3890c558ff93b9cdb608a3bbcf4c3039f456b571 Mon Sep 17 00:00:00 2001
> From: Violet Purcell <vimproved@inventati.org>
> Date: Mon, 27 Nov 2023 12:12:09 -0500
> Subject: [PATCH] kernel-build.eclass: work around permissions issue with
>   module signing
> 
> Currently, using a custom path for MODULES_SIGN_KEY requires the key to
> be readable by portage:portage. This is not ideal for security, since
> the file has to be either owned by portage:portage or readable by all
> users in this case. Instead, export the contents of MODULES_SIGN_KEY to
> a variable in pkg_setup, and then create a temporary file with it in
> src_configure to ensure that the temporary key is readable by the user
> that the kernel is being built as. The variable is then unset so it does
> not end up in the final environment file.
> 
> Co-authored-by: Andrew Ammerlaan <andrewammerlaan@gentoo.org>
> Signed-off-by: Violet Purcell <vimproved@inventati.org>
> ---
>   eclass/kernel-build.eclass | 18 ++++++++++++------
>   1 file changed, 12 insertions(+), 6 deletions(-)
> 
> diff --git a/eclass/kernel-build.eclass b/eclass/kernel-build.eclass
> index f5529c319f9fc..6b692dc4f9a08 100644
> --- a/eclass/kernel-build.eclass
> +++ b/eclass/kernel-build.eclass
> @@ -114,6 +114,13 @@ kernel-build_pkg_setup() {
>   	python-any-r1_pkg_setup
>   	if [[ ${KERNEL_IUSE_MODULES_SIGN} ]]; then
>   		secureboot_pkg_setup
> +		if [[ -e ${MODULES_SIGN_KEY} && ${MODULES_SIGN_KEY} != pkcs11:* ]]; then
> +			if [[ -e ${MODULES_SIGN_CERT} && ${MODULES_SIGN_CERT} != 
> ${MODULES_SIGN_KEY} ]]; then
> +				MODULES_SIGN_KEY_CONTENTS="$(cat "${MODULES_SIGN_CERT}" 
> "${MODULES_SIGN_KEY}" || die)"
> +			else
> +				MODULES_SIGN_KEY_CONTENTS="$(< "${MODULES_SIGN_KEY}")"
> +			fi
> +		fi
>   	fi
>   }
> 
> @@ -422,12 +429,11 @@ kernel-build_merge_configs() {
>   				CONFIG_MODULE_SIG_FORCE=y
>   				CONFIG_MODULE_SIG_${MODULES_SIGN_HASH^^}=y
>   			EOF
> -			if [[ -e ${MODULES_SIGN_KEY} && -e ${MODULES_SIGN_CERT} &&
> -				${MODULES_SIGN_KEY} != ${MODULES_SIGN_CERT} &&
> -				${MODULES_SIGN_KEY} != pkcs11:* ]]
> -			then
> -				cat "${MODULES_SIGN_CERT}" "${MODULES_SIGN_KEY}" > 
> "${T}/kernel_key.pem" || die
> -				MODULES_SIGN_KEY="${T}/kernel_key.pem"
> +			if [[ -n ${MODULES_SIGN_KEY_CONTENTS} ]]; then
> +				(umask 066 && touch "${T}/kernel_key.pem" || die)
> +				echo "${MODULES_SIGN_KEY_CONTENTS}" > "${T}/kernel_key.pem" || die
> +				unset MODULES_SIGN_KEY_CONTENTS
> +				export MODULES_SIGN_KEY="${T}/kernel_key.pem"
>   			fi
>   			if [[ ${MODULES_SIGN_KEY} == pkcs11:* || -r ${MODULES_SIGN_KEY} ]]; 
> then
>   				echo "CONFIG_MODULE_SIG_KEY=\"${MODULES_SIGN_KEY}\"" \

LGTM but I didn't test it.

-- 
Best regards,
Michał Górny