sign-file

#!/bin/bash
#
# Sign a module file using the given key.
#
# Format: sign-file <key> <x509> <keyid-script> <module>
#

scripts=`dirname $0`

CONFIG_MODULE_SIG_SHA512=y
if [ -r .config ]
then
    . ./.config
fi

key="$1"
x509="$2"
keyid_script="$3"
mod="$4"

if [ ! -r "$key" ]
then
    echo "Can't read private key" >&2
    exit 2
fi

if [ ! -r "$x509" ]
then
    echo "Can't read X.509 certificate" >&2
    exit 2
fi

#
# Signature parameters
#
algo=1		# Public-key crypto algorithm: RSA
hash=		# Digest algorithm
id_type=1	# Identifier type: X.509

#
# Digest the data
#
dgst=
if [ "$CONFIG_MODULE_SIG_SHA1" = "y" ]
then
    prologue="0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2B, 0x0E, 0x03, 0x02, 0x1A, 0x05, 0x00, 0x04, 0x14"
    dgst=-sha1
    hash=2
elif [ "$CONFIG_MODULE_SIG_SHA224" = "y" ]
then
    prologue="0x30, 0x2d, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x04, 0x05, 0x00, 0x04, 0x1C"
    dgst=-sha224
    hash=7
elif [ "$CONFIG_MODULE_SIG_SHA256" = "y" ]
then
    prologue="0x30, 0x31, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01, 0x05, 0x00, 0x04, 0x20"
    dgst=-sha256
    hash=4
elif [ "$CONFIG_MODULE_SIG_SHA384" = "y" ]
then
    prologue="0x30, 0x41, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x02, 0x05, 0x00, 0x04, 0x30"
    dgst=-sha384
    hash=5
elif [ "$CONFIG_MODULE_SIG_SHA512" = "y" ]
then
    prologue="0x30, 0x51, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03, 0x05, 0x00, 0x04, 0x40"
    dgst=-sha512
    hash=6
else
    echo "$0: Can't determine hash algorithm" >&2
    exit 2
fi

(
perl -e "binmode STDOUT; print pack(\"C*\", $prologue)" || exit $?
openssl dgst $dgst -binary $mod || exit $?
) >$mod.dig || exit $?

#
# Generate the binary signature, which will be just the integer that comprises
# the signature with no metadata attached.
#
openssl rsautl -sign -inkey $key -keyform PEM -in $mod.dig -out $mod.sig || exit $?

SIGNER="`perl $keyid_script $x509 signer-name`"
KEYID="`perl $keyid_script $x509 keyid`"
keyidlen=${#KEYID}
siglen=${#SIGNER}

#
# Build the signed binary
#
(
    cat $mod || exit $?
    echo '~Module signature appended~' || exit $?
    echo -n "$SIGNER" || exit $?
    echo -n "$KEYID" || exit $?

    # Preface each signature integer with a 2-byte BE length
    perl -e "binmode STDOUT; print pack(\"n\", $siglen)" || exit $?
    cat $mod.sig || exit $?

    # Generate the information block
    perl -e "binmode STDOUT; print pack(\"CCCCCxxxN\", $algo, $hash, $id_type, $signerlen, $keyidlen, $siglen + 2)" || exit $?
) >$mod~ || exit $?

mv $mod~ $mod || exit $?