Merge pull request #24 from petronio/support_external_module_signing

Add support for automatically signing external modules

Author: sakaki-

buildkernel

@@ -31,7 +31,7 @@ shopt -s nullglob
 # ********************** variables ********************* 
 PROGNAME="$(basename "${0}")"
 CONFFILE="/etc/${PROGNAME}.conf"
-VERSION="1.0.33"
+VERSION="1.0.34"
 ETCPROFILE="/etc/profile"
 DEFAULTEFIBOOTFILE="bootx64.efi"
 EFIBOOTFILE="${DEFAULTEFIBOOTFILE}"
@@ -109,6 +109,7 @@ GPGBUILDDIR="/root/tmpgpgbuild"
 TMPGPGPATH="${GPGBUILDDIR}/usr/bin/gpg"
 declare -i USINGUSBKEYFOREFI=0
 declare -i BACKUPOLDKERNEL=1
+declare -i BUILT_EXTERNAL_MODULES=1
 
 EFIPARTNAME="EFI boot partition"
 DEFAULTKEYMAP="us"
@@ -423,6 +424,29 @@ source_etc_conf_file() {
     if [[ -v INITSYSTEM ]]; then
         INITSYSTEM="${INITSYSTEM,,}"
     fi
+    # perform checks on KERNEL_SIGNING_CERT and KERNEL_SIGNING_KEY
+    if [[ -v KERNEL_SIGNING_CERT ]]; then
+        if [[ ! -v KERNEL_SIGNING_KEY ]]; then
+            die "Cannot proceed; KERNEL_SIGNING_CERT is configured, but KERNEL_SIGNING_KEY is not."
+        fi
+        if [[ "${KERNEL_SIGNING_CERT}" == "auto" || "${KERNEL_SIGNING_KEY}" == "auto" ]]; then
+            if [[ "${KERNEL_SIGNING_CERT}" != "${KERNEL_SIGNING_KEY}" ]]; then
+                die "Cannot proceed; in automatic external module signing mode, both KERNEL_SIGNING_CERT and KERNEL_SIGNING_KEY must be set to \"auto\""
+            fi
+            KERNEL_SIGNING_CERT="${LINUXDIR}/certs/signing_key.x509"
+            KERNEL_SIGNING_KEY="${LINUXDIR}/certs/signing_key.pem"
+        else
+            if [[ ! -f "${KERNEL_SIGNING_CERT}" ]]; then
+                die "Cannot proceed; KERNEL_SIGNING_CERT is not a valid path to a file."
+            fi
+            if [[ ! -f "${KERNEL_SIGNING_KEY}" ]]; then
+                die "Cannot proceed; KERNEL_SIGNING_KEY is not a valid path to a file."
+            fi
+        fi
+    fi
+    if [[ -v KERNEL_SIGNING_KEY && ! -v KERNEL_SIGNING_CERT ]]; then
+        die "Cannot proceed; KERNEL_SIGNING_KEY is configured, but KERNEL_SIGNING_CERT is not."
+    fi
 }
 setup_final_variables() {
     # post-processing once buildkernel.conf loaded
@@ -1818,8 +1842,14 @@ rebuild_external_modules_if_necessary() {
             else
                 warning "Failed to complete emerge @module-rebuild due to error"
                 warning "Continuing..."
+                BUILT_EXTERNAL_MODULES=0
             fi
         fi
+        if [[ ${BUILT_EXTERNAL_MODULES}==1 && -v KERNEL_SIGNING_CERT ]] ; then
+            for EXTERNAL_MODULE in `find /lib/modules/${NEWVERSION#"linux-"}/* -type f -name '*.ko' -not -path '*/kernel/*'`; do
+                "${LINUXDIR}/scripts/sign-file" sha512 "${KERNEL_SIGNING_KEY}" "${KERNEL_SIGNING_CERT}" "${EXTERNAL_MODULE}"
+            done
+        fi
     fi
 }
 create_initramfs_using_genkernel() {

buildkernel.8

@@ -1,4 +1,4 @@
-.TH BUILDKERNEL 8 "Version 1.0.33: October 2018"
+.TH BUILDKERNEL 8 "Version 1.0.34: April 2019"
 .SH NAME
 buildkernel \- build secure boot kernel, save to EFI system partition
 .SH SYNOPSIS
@@ -61,7 +61,7 @@ cleans the kernel tree (if you specify \fB--clean\fR; you will be asked whether
 .IP \(bu 2
 builds the kernel, and its modules, with the specified configuration; in this first pass, an empty initramfs is used (since it must be incorporated in the kernel, to be protected by UEFI secure boot, but we don't have everything necessary to include in it, yet!);
 .IP \(bu 2
-builds any external modules (such as those required for VirtualBox), using \fBemerge @module-rebuild\fR, if you so specify (using the option \fB--rebuild-external-modules\fR);
+builds any external modules (such as those required for VirtualBox), using \fBemerge @module-rebuild\fR, if you so specify (using the option \fB--rebuild-external-modules\fR), and optionally signs them (if you have set up the variables \fBKERNEL_SIGNING_CERT\fR and \fBKERNEL_SIGNING_KEY\fR in \fI/etc/buildkernel.conf\fR);
 .IP \(bu 2
 creates a first cut of the initramfs using \fBgenkernel\fR(8) (see below for more details); this will contain \fBgenkernel\fR(8)'s \fBinit\fR(8) script, compiled modules, any necessary firmware (if you haven't deblobbed), and a minimal set of binaries; it does \fInot\fR at this point contain a static copy of \fBgpg\fR;
 .IP \(bu 2

buildkernel.conf

@@ -83,6 +83,14 @@
 # however, doing so should not be necessary.
 #CMDLINE_ROOTFSTYPE="ext4"
 
+# if you sign your kernel modules, configure the signing certificate and key
+# paths to sign external modules as well once built. Setting the variables to
+# "auto" will use the kernel's automatically generated certificate and key if
+# you have configured it to generate them. By default the variable is unset and
+# modules will not be signed.
+#KERNEL_SIGNING_CERT="auto"
+#KERNEL_SIGNING_KEY="auto"
+
 # if you need to conform the config file for some reason, uncomment this
 # hook function and fill it out to suit your requirements
 # NB you should only really need to do this to override a setting forced

buildkernel.conf.5

@@ -1,4 +1,4 @@
-.TH BUILDKERNEL 5 "Version 1.0.33: October 2018"
+.TH BUILDKERNEL 5 "Version 1.0.34: April 2019"
 .SH NAME
 buildkernel.conf \- a configuration file for \fBbuildkernel\fR(8)
 .SH SYNOPSIS
@@ -194,6 +194,26 @@ automatically detect the filesystem type of \fBCMDLINE_REAL_ROOT\fR
 (falling back to \fBext4\fR, in case of error).
 
 Most users will not need to override the default.
+.br
+.TP
+.BR KERNEL_SIGNING_CERT
+If you sign your kernel modules, set this to the path for the signing
+certificate so that your external modules are signed after being built.
+Setting to \fBauto\fR uses the kernel's automatically generated signing
+certificate if you have configured it to generate it.
+
+By default this is not set and causes external modules to not be signed.
+Requires that the \fBKERNEL_SIGNING_KEY\fR variable is set.
+.br
+.TP
+.BR KERNEL_SIGNING_KEY
+If you sign your kernel modules, set this to the path for the signing key so
+that your external modules are signed after being built. Setting to \fBauto\fR
+uses the kernel's automatically generated signing key if you have configured it
+to generate it.
+
+By default this is not set and causes external modules to not be signed.
+Requires that the \fBKERNEL_SIGNING_CERT\fR variable is set.
 
 .RE
 .SH FUNCTIONS