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pcrlock: handle measurement logs where hash algs in header are announced in different order than in records

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Apparently on HyperV the measurement logs announce the hash algs in a
different order in the header than the records have them. Let's handle
this gracefully
This commit is contained in:
Lennart Poettering 2024-02-21 14:43:42 +01:00
parent 0691d0e5a1
commit e90a255e55
1 changed files with 14 additions and 7 deletions
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21
src/pcrlock/pcrlock.c
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@ -936,23 +936,30 @@ static int event_log_load_firmware(EventLog *el) {
assert(event->digests.count == n_algorithms);
for (size_t i = 0; i < n_algorithms; i++, ha = ha_next) {
ha_next = (const uint8_t*) ha + offsetof(TPMT_HA, digest) + algorithms[i].digestSize;
/* The TPMT_HA is not aligned in the record, hence read the hashAlg field via an unaligned read */
assert_cc(__builtin_types_compatible_p(uint16_t, typeof(TPMI_ALG_HASH)));
uint16_t hash_alg = unaligned_read_ne16((const uint8_t*) ha + offsetof(TPMT_HA, hashAlg));
if (hash_alg != algorithms[i].algorithmId)
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Hash algorithms in event log record don't match log.");
/* On some systems (some HyperV?) the order of hash algorithms announced in the
* header does not match the order in the records. Let's hence search for the right
* mapping */
size_t j;
for (j = 0; j < n_algorithms; j++)
if (hash_alg == algorithms[j].algorithmId)
break;
if (j >= n_algorithms)
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Hash algorithms in event log record not among those advertised by log header.");
if (!tpm2_hash_alg_to_string(algorithms[i].algorithmId))
ha_next = (const uint8_t*) ha + offsetof(TPMT_HA, digest) + algorithms[j].digestSize;
if (!tpm2_hash_alg_to_string(hash_alg))
continue;
r = event_log_record_add_bank(
record,
algorithms[i].algorithmId,
hash_alg,
(const uint8_t*) ha + offsetof(TPMT_HA, digest),
algorithms[i].digestSize,
algorithms[j].digestSize,
/* ret= */ NULL);
if (r < 0)
return log_error_errno(r, "Failed to add bank to event log record: %m");