kernel-fitimage: generate openssl RSA keys for signing fitimage

The keys are only generated if they dont exist. The key
generation can be turned off by setting FIT_GENERATE_KEYS to "0".
The default key length for private keys is 2048 and the default
format for public key certificate is x.509.

(From OE-Core rev: 8dfaf5cd4eb5c8e352e7833ec47db1a14ea58b47)

Signed-off-by: Usama Arif <usama.arif@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 44 insertions, 0 deletions

diff --git a/meta/classes/kernel-fitimage.bbclass b/meta/classes/kernel-fitimage.bbclass
index fa4ea6feef..bb2f3c4ccc 100644
--- a/meta/classes/kernel-fitimage.bbclass
+++ b/meta/classes/kernel-fitimage.bbclass
@@ -56,6 +56,22 @@ FIT_HASH_ALG ?= "sha256"
 # fitImage Signature Algo
 FIT_SIGN_ALG ?= "rsa2048"
 
+# Generate keys for signing fitImage
+FIT_GENERATE_KEYS ?= "0"
+
+# Size of private key in number of bits
+FIT_SIGN_NUMBITS ?= "2048"
+
+# args to openssl genrsa (Default is just the public exponent)
+FIT_KEY_GENRSA_ARGS ?= "-F4"
+
+# args to openssl req (Default is -batch for non interactive mode and
+# -new for new certificate)
+FIT_KEY_REQ_ARGS ?= "-batch -new"
+
+# Standard format for public key certificate
+FIT_KEY_SIGN_PKCS ?= "-x509"
+
 #
 # Emit the fitImage ITS header
 #
@@ -522,6 +538,34 @@ do_assemble_fitimage_initramfs() {
 
 addtask assemble_fitimage_initramfs before do_deploy after do_bundle_initramfs
 
+do_generate_rsa_keys() {
+        if [ "${UBOOT_SIGN_ENABLE}" = "0" ] && [ "${FIT_GENERATE_KEYS}" = "1" ]; then
+                bbwarn "FIT_GENERATE_KEYS is set to 1 eventhough UBOOT_SIGN_ENABLE is set to 0. The keys will not be generated as they won't be used."
+        fi
+
+        if [ "${UBOOT_SIGN_ENABLE}" = "1" ] && [ "${FIT_GENERATE_KEYS}" = "1" ]; then
+
+                # Generate keys only if they don't already exist
+                if [ ! -f "${UBOOT_SIGN_KEYDIR}/${UBOOT_SIGN_KEYNAME}".key ] || \
+                        [ ! -f "${UBOOT_SIGN_KEYDIR}/${UBOOT_SIGN_KEYNAME}".crt]; then
+
+                        # make directory if it does not already exist
+                        mkdir -p "${UBOOT_SIGN_KEYDIR}"
+
+                        echo "Generating RSA private key for signing fitImage"
+                        openssl genrsa ${FIT_KEY_GENRSA_ARGS} -out \
+                                "${UBOOT_SIGN_KEYDIR}/${UBOOT_SIGN_KEYNAME}".key \
+                                "${FIT_SIGN_NUMBITS}"
+
+                        echo "Generating certificate for signing fitImage"
+                        openssl req ${FIT_KEY_REQ_ARGS} "${FIT_KEY_SIGN_PKCS}" \
+                                -key "${UBOOT_SIGN_KEYDIR}/${UBOOT_SIGN_KEYNAME}".key \
+                                -out "${UBOOT_SIGN_KEYDIR}/${UBOOT_SIGN_KEYNAME}".crt
+                fi
+        fi
+}
+
+addtask generate_rsa_keys before do_assemble_fitimage after do_compile
 
 kernel_do_deploy[vardepsexclude] = "DATETIME"
 kernel_do_deploy_append() {