flatcar-scripts/core_sign_update

#!/usr/bin/env bash

# Copyright (c) 2014 CoreOS, Inc. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

# usage: ./core_generate_update_payload  --image coreos_production_update.bin \
# 		--output update.gz \
#		--private_keys update.key.pem:update2.key.pem
#		--public_keys update.pub.pem:update2.pub.pem

SCRIPT_ROOT=$(dirname $(readlink -f "$0"))
# We have to simple-mindedly set GCLIENT_ROOT in case we're running from
# au-generator.zip because common.sh will fail while auto-detect it.
export GCLIENT_ROOT=$(readlink -f "${SCRIPT_ROOT}/../../")
. "${SCRIPT_ROOT}/common.sh" || exit 1

DEFINE_string image "" "The filesystem image of /usr"
DEFINE_string kernel "" "The kernel image"
DEFINE_string output "" "Output file"
DEFINE_string private_keys "" "Path or pkcs11 URI for private keys."
DEFINE_string public_keys "" "Path to public keys in .pem format."
DEFINE_string keys_separator ":" "Separator for the above keys"

# Parse command line
FLAGS "$@" || exit 1
eval set -- "${FLAGS_ARGV}"

set -e

cleanup() {
	rm -f padding
	rm -f padding-pkcs11
	rm -f update
	rm -f update.hash
	rm -f update.padhash
	rm -f update.pkcs11-padhash
	rm -f update.signed
	rm -f update.sig.*
}

trap cleanup INT TERM EXIT

echo "=== Creating signable update payload... ==="
delta_generator \
    -new_image "$FLAGS_image" \
    -new_kernel "$FLAGS_kernel" \
    -out_file update

# The separator is configurable for backwards compatibility with old `sign.sh` scripts.
IFS="${FLAGS_keys_separator}" read -a private_keys <<< "$FLAGS_private_keys"
IFS="${FLAGS_keys_separator}" read -a public_keys <<< "$FLAGS_public_keys"

if [ ${#private_keys[@]} -ne ${#public_keys[@]} ]; then
	echo "mismatch in count of private keys and public keys"
	exit 1
fi

i=0
signature_sizes=""
for key in "${private_keys[@]}"; do
	signature_sizes=${signature_sizes}:256
	let "i += 1"
done
signature_sizes="${signature_sizes:1:${#signature_sizes}}"

delta_generator \
	--signature_size ${signature_sizes} \
	--in_file update \
	--out_hash_file update.hash

# padding for openssl rsautl -pkcs (smartcard keys)
#
# The following is an ASN.1 header. It is prepended to the actual signature
# (32 bytes) to form a sequence of 51 bytes. OpenSSL will add additional
# PKCS#1 1.5 padding during the signing operation. The padded hash will look
# as follows:
#
#    ASN1HEADER  SHA256HASH
#   |----19----||----32----|
#
# where ASN1HEADER is the ASN.1 description of the signed data. The complete 51
# bytes of actual data (i.e. the ASN.1 header complete with the hash) are
# packed as follows:
#
#  SEQUENCE(2+49) {
#   SEQUENCE(2+13) {
#    OBJECT(2+9) id-sha256
#    NULL(2+0)
#   }
#   OCTET STRING(2+32) <actual signature bytes...>
#  }
echo "MDEwDQYJYIZIAWUDBAIBBQAEIA==" | base64 -d > padding-pkcs11
cat padding-pkcs11 update.hash > update.pkcs11-padhash

# Legacy padding for openssl -raw (non smartcard keys)
#
# The following is a standard PKCS1-v1_5 padding for SHA256 signatures, as
# defined in RFC3447. It is prepended to the actual signature (32 bytes) to
# form a sequence of 256 bytes (2048 bits) that is amenable to RSA signing. The
# padded hash will look as follows:
#
#    0x00 0x01 0xff ... 0xff 0x00  ASN1HEADER  SHA256HASH
#   |--------------205-----------||----19----||----32----|
#
# where ASN1HEADER is the ASN.1 description of the signed data. The complete 51
# bytes of actual data (i.e. the ASN.1 header complete with the hash) are
# packed as follows:
#
#  SEQUENCE(2+49) {
#   SEQUENCE(2+13) {
#    OBJECT(2+9) id-sha256
#    NULL(2+0)
#   }
#   OCTET STRING(2+32) <actual signature bytes...>
#  }
echo "AAH/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////ADAxMA0GCWCGSAFlAwQCAQUABCA=" | base64 -d > padding
cat padding update.hash > update.padhash

echo "===      Signing update payload...      ==="
i=1
signature_sizes=""
for key in "${private_keys[@]}"; do
	if [[ "${key}" == pkcs11* ]]; then
		sudo OPENSSL_CONF=/etc/ssl/pkcs11.cnf openssl pkeyutl -engine pkcs11 -sign -keyform engine -inkey "${key}" -in update.pkcs11-padhash -out "update.sig.${i}"
	else
		openssl rsautl -raw -sign -inkey ${key} -in update.padhash -out update.sig.${i}
	fi
	let "i += 1"
done

files=""
for i in update.sig.*; do
	files=${files}:${i}
done
files="${files:1:${#files}}"
echo ${files}

delta_generator --signature_file ${files} --in_file update --out_file update.signed

i=1
for key in "${public_keys[@]}"; do
	version="${i}"
	if [ ${#public_keys[@]} == 1 ]; then
		version=2
	fi

	delta_generator \
		--public_key_version "${version}" \
		--public_key "${key}" \
		--in_file update.signed

	let "i += 1"
done

mv update.signed ${FLAGS_output}
echo "=== Update payload signed successfully. ==="

trap - INT TERM EXIT
cleanup noexit

echo "Done generating full update."