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authorMatthew Garrett <mjg59@google.com>2019-05-20 13:54:58 -0700
committerJarkko Sakkinen <jarkko.sakkinen@linux.intel.com>2019-06-24 23:57:49 +0300
commit44038bc514a244fba9d0d6d698b15970185ac251 (patch)
treeabdd9223fe34fbfe6f5915f8f0b2d37071a68696 /include/linux/tpm_eventlog.h
parent782779b60faa2fc7ff609ac8ef938260fd792c0f (diff)
tpm: Abstract crypto agile event size calculations
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>
Diffstat (limited to 'include/linux/tpm_eventlog.h')
-rw-r--r--include/linux/tpm_eventlog.h68
1 files changed, 68 insertions, 0 deletions
diff --git a/include/linux/tpm_eventlog.h b/include/linux/tpm_eventlog.h
index 81519f163211..6a86144e13f1 100644
--- a/include/linux/tpm_eventlog.h
+++ b/include/linux/tpm_eventlog.h
@@ -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