projects / linux-block.git / blame
| Commit | Line | Data |
|---|---|---|
| 58d41635 MS |
1 | #!/bin/bash |
| 2 | # SPDX-License-Identifier: GPL-2.0 | |
| 3 | # | |
| 4 | # Copyright © 2020, Microsoft Corporation. All rights reserved. | |
| 5 | # | |
| 6 | # Author: Mickaël Salaün <mic@linux.microsoft.com> | |
| 7 | # | |
| 8 | # Compute and print the To Be Signed (TBS) hash of a certificate. This is used | |
| 9 | # as description of keys in the blacklist keyring to identify certificates. | |
| 10 | # This output should be redirected, without newline, in a file (hash0.txt) and | |
| 11 | # signed to create a PKCS#7 file (hash0.p7s). Both of these files can then be | |
| 12 | # loaded in the kernel with. | |
| 13 | # | |
| 14 | # Exemple on a workstation: | |
| 15 | # ./print-cert-tbs-hash.sh certificate-to-invalidate.pem > hash0.txt | |
| 16 | # openssl smime -sign -in hash0.txt -inkey builtin-private-key.pem \ | |
| 17 | # -signer builtin-certificate.pem -certfile certificate-chain.pem \ | |
| 18 | # -noattr -binary -outform DER -out hash0.p7s | |
| 19 | # | |
| 20 | # Exemple on a managed system: | |
| 21 | # keyctl padd blacklist "$(< hash0.txt)" %:.blacklist < hash0.p7s | |
| 22 | ||
| 23 | set -u -e -o pipefail | |
| 24 | ||
| 25 | CERT="${1:-}" | |
| 26 | BASENAME="$(basename -- "${BASH_SOURCE[0]}")" | |
| 27 | ||
| 28 | if [ $# -ne 1 ] || [ ! -f "${CERT}" ]; then | |
| 29 | echo "usage: ${BASENAME} <certificate>" >&2 | |
| 30 | exit 1 | |
| 31 | fi | |
| 32 | ||
| 33 | # Checks that it is indeed a certificate (PEM or DER encoded) and exclude the | |
| 34 | # optional PEM text header. | |
| 35 | if ! PEM="$(openssl x509 -inform DER -in "${CERT}" 2>/dev/null || openssl x509 -in "${CERT}")"; then | |
| 36 | echo "ERROR: Failed to parse certificate" >&2 | |
| 37 | exit 1 | |
| 38 | fi | |
| 39 | ||
| 40 | # TBSCertificate starts at the second entry. | |
| 41 | # Cf. https://tools.ietf.org/html/rfc3280#section-4.1 | |
| 42 | # | |
| 43 | # Exemple of first lines printed by openssl asn1parse: | |
| 44 | # 0:d=0 hl=4 l= 763 cons: SEQUENCE | |
| 45 | # 4:d=1 hl=4 l= 483 cons: SEQUENCE | |
| 46 | # 8:d=2 hl=2 l= 3 cons: cont [ 0 ] | |
| 47 | # 10:d=3 hl=2 l= 1 prim: INTEGER :02 | |
| 48 | # 13:d=2 hl=2 l= 20 prim: INTEGER :3CEB2CB8818D968AC00EEFE195F0DF9665328B7B | |
| 49 | # 35:d=2 hl=2 l= 13 cons: SEQUENCE | |
| 50 | # 37:d=3 hl=2 l= 9 prim: OBJECT :sha256WithRSAEncryption | |
| 51 | RANGE_AND_DIGEST_RE=' | |
| 52 | 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; | |
| 53 | 7s/^\s*[0-9]\+:d=\s*[0-9]\+\s\+hl=\s*[0-9]\+\s\+l=\s*[0-9]\+\s\+prim:\s*OBJECT\s*:\(.*\)$/\1/p; | |
| 54 | ' | |
| 55 | ||
| 56 | RANGE_AND_DIGEST=($(echo "${PEM}" | \ | |
| 57 | openssl asn1parse -in - | \ | |
| 58 | sed -n -e "${RANGE_AND_DIGEST_RE}")) | |
| 59 | ||
| 60 | if [ "${#RANGE_AND_DIGEST[@]}" != 3 ]; then | |
| 61 | echo "ERROR: Failed to parse TBSCertificate." >&2 | |
| 62 | exit 1 | |
| 63 | fi | |
| 64 | ||
| 65 | OFFSET="${RANGE_AND_DIGEST[0]}" | |
| 66 | END="$(( OFFSET + RANGE_AND_DIGEST[1] ))" | |
| 67 | DIGEST="${RANGE_AND_DIGEST[2]}" | |
| 68 | ||
| 69 | # The signature hash algorithm is used by Linux to blacklist certificates. | |
| 70 | # Cf. crypto/asymmetric_keys/x509_cert_parser.c:x509_note_pkey_algo() | |
| 71 | DIGEST_MATCH="" | |
| 72 | while read -r DIGEST_ITEM; do | |
| 73 | if [ -z "${DIGEST_ITEM}" ]; then | |
| 74 | break | |
| 75 | fi | |
| 76 | if echo "${DIGEST}" | grep -qiF "${DIGEST_ITEM}"; then | |
| 77 | DIGEST_MATCH="${DIGEST_ITEM}" | |
| 78 | break | |
| 79 | fi | |
| 80 | done < <(openssl list -digest-commands | tr ' ' '\n' | sort -ur) | |
| 81 | ||
| 82 | if [ -z "${DIGEST_MATCH}" ]; then | |
| 83 | echo "ERROR: Unknown digest algorithm: ${DIGEST}" >&2 | |
| 84 | exit 1 | |
| 85 | fi | |
| 86 | ||
| 87 | echo "${PEM}" | \ | |
| 88 | openssl x509 -in - -outform DER | \ | |
| 89 | dd "bs=1" "skip=${OFFSET}" "count=${END}" "status=none" | \ | |
| 90 | openssl dgst "-${DIGEST_MATCH}" - | \ | |
| 91 | awk '{printf "tbs:" $2}' |