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tpm: Abstract crypto agile event size calculations

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We need to calculate the size of crypto agile events in multiple
locations, including in the EFI boot stub. The easiest way to do this is
to put it in a header file as an inline and leave a wrapper to ensure we
don't end up with multiple copies of it embedded in the existing code.

Signed-off-by: Matthew Garrett <mjg59@google.com>
Reviewed-by: Bartosz Szczepanek <bsz@semihalf.com>
Tested-by: Bartosz Szczepanek <bsz@semihalf.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
This commit is contained in:
Matthew Garrett 2019-05-20 13:54:58 -07:00 committed by Jarkko Sakkinen
parent 782779b60f
commit 44038bc514
2 changed files with 69 additions and 46 deletions
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47
drivers/char/tpm/eventlog/tpm2.c
View File

@ -36,52 +36,7 @@
static size_t calc_tpm2_event_size(struct tcg_pcr_event2_head *event,
struct tcg_pcr_event *event_header)
{
struct tcg_efi_specid_event_head *efispecid;
struct tcg_event_field *event_field;
void *marker;
void *marker_start;
u32 halg_size;
size_t size;
u16 halg;
int i;
int j;
marker = event;
marker_start = marker;
marker = marker + sizeof(event->pcr_idx) + sizeof(event->event_type)
+ sizeof(event->count);
efispecid = (struct tcg_efi_specid_event_head *)event_header->event;
/* Check if event is malformed. */
if (event->count > efispecid->num_algs)
return 0;
for (i = 0; i < event->count; i++) {
halg_size = sizeof(event->digests[i].alg_id);
memcpy(&halg, marker, halg_size);
marker = marker + halg_size;
for (j = 0; j < efispecid->num_algs; j++) {
if (halg == efispecid->digest_sizes[j].alg_id) {
marker +=
efispecid->digest_sizes[j].digest_size;
break;
}
}
/* Algorithm without known length. Such event is unparseable. */
if (j == efispecid->num_algs)
return 0;
}
event_field = (struct tcg_event_field *)marker;
marker = marker + sizeof(event_field->event_size)
+ event_field->event_size;
size = marker - marker_start;
if ((event->event_type == 0) && (event_field->event_size == 0))
return 0;
return size;
return __calc_tpm2_event_size(event, event_header);
}
static void *tpm2_bios_measurements_start(struct seq_file *m, loff_t *pos)

68
include/linux/tpm_eventlog.h
View File

@ -112,4 +112,72 @@ struct tcg_pcr_event2_head {
struct tpm_digest digests[];
} __packed;
/**
* __calc_tpm2_event_size - calculate the size of a TPM2 event log entry
* @event: Pointer to the event whose size should be calculated
* @event_header: Pointer to the initial event containing the digest lengths
*
* The TPM2 event log format can contain multiple digests corresponding to
* separate PCR banks, and also contains a variable length of the data that
* was measured. This requires knowledge of how long each digest type is,
* and this information is contained within the first event in the log.
*
* We calculate the length by examining the number of events, and then looking
* at each event in turn to determine how much space is used for events in
* total. Once we've done this we know the offset of the data length field,
* and can calculate the total size of the event.
*
* Return: size of the event on success, <0 on failure
*/
static inline int __calc_tpm2_event_size(struct tcg_pcr_event2_head *event,
struct tcg_pcr_event *event_header)
{
struct tcg_efi_specid_event_head *efispecid;
struct tcg_event_field *event_field;
void *marker;
void *marker_start;
u32 halg_size;
size_t size;
u16 halg;
int i;
int j;
marker = event;
marker_start = marker;
marker = marker + sizeof(event->pcr_idx) + sizeof(event->event_type)
+ sizeof(event->count);
efispecid = (struct tcg_efi_specid_event_head *)event_header->event;
/* Check if event is malformed. */
if (event->count > efispecid->num_algs)
return 0;
for (i = 0; i < event->count; i++) {
halg_size = sizeof(event->digests[i].alg_id);
memcpy(&halg, marker, halg_size);
marker = marker + halg_size;
for (j = 0; j < efispecid->num_algs; j++) {
if (halg == efispecid->digest_sizes[j].alg_id) {
marker +=
efispecid->digest_sizes[j].digest_size;
break;
}
}
/* Algorithm without known length. Such event is unparseable. */
if (j == efispecid->num_algs)
return 0;
}
event_field = (struct tcg_event_field *)marker;
marker = marker + sizeof(event_field->event_size)
+ event_field->event_size;
size = marker - marker_start;
if ((event->event_type == 0) && (event_field->event_size == 0))
return 0;
return size;
}
#endif