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coreos_sign_update: return 'legacy' signing support

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We currently sign with both a devel key and a prod key. The devel key is
insecure and need not be included on a smartcard, so it makes sense to
leave it be on disk.

However, the previous commit's padding changes removed this legacy
method of signing.
For simplicity, simply re-introduce the old logic conditionally based on
whether it's a smartcard or not.

Alternate options could be using `-pkcs` instead of `-raw` for both
keys, but that is a more intricate change I'd be less confident in
making.
This commit is contained in:
Euan Kemp 2017-07-06 13:46:32 -07:00
parent 32eb55b808
commit 9d58bec73b
1 changed files with 35 additions and 2 deletions
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37
core_sign_update
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@ -29,9 +29,11 @@ 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.*
}
@ -64,6 +66,8 @@ delta_generator \
--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
@ -83,13 +87,42 @@ delta_generator \
# }
# OCTET STRING(2+32) <actual signature bytes...>
# }
echo "MDEwDQYJYIZIAWUDBAIBBQAEIA==" | base64 -d > padding
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
i=1
signature_sizes=""
for key in "${private_keys[@]}"; do
openssl rsautl -engine pkcs11 -pkcs -sign -inkey ${key} -keyform engine -in update.padhash -out update.sig.${i}
if [[ "${key}" == pkcs11* ]]; then
openssl rsautl -engine pkcs11 -pkcs -sign -inkey ${key} -keyform engine -in update.pkcs11-padhash -out update.sig.${i}
else
openssl rsautl -raw -sign -inkey ${key} -in update.padhash -out update.sig.${i}
fi
let "i += 1"
done