mirror of
https://github.com/torvalds/linux.git
synced 2024-11-25 05:32:00 +00:00
58d416351e
Add a new helper print-cert-tbs-hash.sh to generate a TBSCertificate hash from a given certificate. This is useful to generate a blacklist key description used to forbid loading a specific certificate in a keyring, or to invalidate a certificate provided by a PKCS#7 file. This kind of hash formatting is required to populate the file pointed out by CONFIG_SYSTEM_BLACKLIST_HASH_LIST, but only the kernel code was available to understand how to effectively create such hash. Cc: David Howells <dhowells@redhat.com> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Eric Snowberg <eric.snowberg@oracle.com> Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Link: https://lore.kernel.org/r/20210712170313.884724-2-mic@digikod.net Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
92 lines
3.1 KiB
Bash
Executable File
92 lines
3.1 KiB
Bash
Executable File
#!/bin/bash
|
|
# SPDX-License-Identifier: GPL-2.0
|
|
#
|
|
# Copyright © 2020, Microsoft Corporation. All rights reserved.
|
|
#
|
|
# Author: Mickaël Salaün <mic@linux.microsoft.com>
|
|
#
|
|
# Compute and print the To Be Signed (TBS) hash of a certificate. This is used
|
|
# as description of keys in the blacklist keyring to identify certificates.
|
|
# This output should be redirected, without newline, in a file (hash0.txt) and
|
|
# signed to create a PKCS#7 file (hash0.p7s). Both of these files can then be
|
|
# loaded in the kernel with.
|
|
#
|
|
# Exemple on a workstation:
|
|
# ./print-cert-tbs-hash.sh certificate-to-invalidate.pem > hash0.txt
|
|
# openssl smime -sign -in hash0.txt -inkey builtin-private-key.pem \
|
|
# -signer builtin-certificate.pem -certfile certificate-chain.pem \
|
|
# -noattr -binary -outform DER -out hash0.p7s
|
|
#
|
|
# Exemple on a managed system:
|
|
# keyctl padd blacklist "$(< hash0.txt)" %:.blacklist < hash0.p7s
|
|
|
|
set -u -e -o pipefail
|
|
|
|
CERT="${1:-}"
|
|
BASENAME="$(basename -- "${BASH_SOURCE[0]}")"
|
|
|
|
if [ $# -ne 1 ] || [ ! -f "${CERT}" ]; then
|
|
echo "usage: ${BASENAME} <certificate>" >&2
|
|
exit 1
|
|
fi
|
|
|
|
# Checks that it is indeed a certificate (PEM or DER encoded) and exclude the
|
|
# optional PEM text header.
|
|
if ! PEM="$(openssl x509 -inform DER -in "${CERT}" 2>/dev/null || openssl x509 -in "${CERT}")"; then
|
|
echo "ERROR: Failed to parse certificate" >&2
|
|
exit 1
|
|
fi
|
|
|
|
# TBSCertificate starts at the second entry.
|
|
# Cf. https://tools.ietf.org/html/rfc3280#section-4.1
|
|
#
|
|
# Exemple of first lines printed by openssl asn1parse:
|
|
# 0:d=0 hl=4 l= 763 cons: SEQUENCE
|
|
# 4:d=1 hl=4 l= 483 cons: SEQUENCE
|
|
# 8:d=2 hl=2 l= 3 cons: cont [ 0 ]
|
|
# 10:d=3 hl=2 l= 1 prim: INTEGER :02
|
|
# 13:d=2 hl=2 l= 20 prim: INTEGER :3CEB2CB8818D968AC00EEFE195F0DF9665328B7B
|
|
# 35:d=2 hl=2 l= 13 cons: SEQUENCE
|
|
# 37:d=3 hl=2 l= 9 prim: OBJECT :sha256WithRSAEncryption
|
|
RANGE_AND_DIGEST_RE='
|
|
2s/^\s*\([0-9]\+\):d=\s*[0-9]\+\s\+hl=\s*[0-9]\+\s\+l=\s*\([0-9]\+\)\s\+cons:\s*SEQUENCE\s*$/\1 \2/p;
|
|
7s/^\s*[0-9]\+:d=\s*[0-9]\+\s\+hl=\s*[0-9]\+\s\+l=\s*[0-9]\+\s\+prim:\s*OBJECT\s*:\(.*\)$/\1/p;
|
|
'
|
|
|
|
RANGE_AND_DIGEST=($(echo "${PEM}" | \
|
|
openssl asn1parse -in - | \
|
|
sed -n -e "${RANGE_AND_DIGEST_RE}"))
|
|
|
|
if [ "${#RANGE_AND_DIGEST[@]}" != 3 ]; then
|
|
echo "ERROR: Failed to parse TBSCertificate." >&2
|
|
exit 1
|
|
fi
|
|
|
|
OFFSET="${RANGE_AND_DIGEST[0]}"
|
|
END="$(( OFFSET + RANGE_AND_DIGEST[1] ))"
|
|
DIGEST="${RANGE_AND_DIGEST[2]}"
|
|
|
|
# The signature hash algorithm is used by Linux to blacklist certificates.
|
|
# Cf. crypto/asymmetric_keys/x509_cert_parser.c:x509_note_pkey_algo()
|
|
DIGEST_MATCH=""
|
|
while read -r DIGEST_ITEM; do
|
|
if [ -z "${DIGEST_ITEM}" ]; then
|
|
break
|
|
fi
|
|
if echo "${DIGEST}" | grep -qiF "${DIGEST_ITEM}"; then
|
|
DIGEST_MATCH="${DIGEST_ITEM}"
|
|
break
|
|
fi
|
|
done < <(openssl list -digest-commands | tr ' ' '\n' | sort -ur)
|
|
|
|
if [ -z "${DIGEST_MATCH}" ]; then
|
|
echo "ERROR: Unknown digest algorithm: ${DIGEST}" >&2
|
|
exit 1
|
|
fi
|
|
|
|
echo "${PEM}" | \
|
|
openssl x509 -in - -outform DER | \
|
|
dd "bs=1" "skip=${OFFSET}" "count=${END}" "status=none" | \
|
|
openssl dgst "-${DIGEST_MATCH}" - | \
|
|
awk '{printf "tbs:" $2}'
|