grub2/grub-read-pcr.patch

--- a/include/grub/tpm.h
+++ b/include/grub/tpm.h
@@ -36,6 +36,12 @@
 
 #define EV_IPL 0x0d
 
+struct grub_tpm_digest {
+	const char *	algorithm;
+	unsigned int	size;
+	unsigned char	value[1];	/* variable length */
+};
+
 grub_err_t grub_tpm_measure (unsigned char *buf, grub_size_t size,
 			     grub_uint8_t pcr, const char *description);
 int grub_tpm_present (void);
@@ -45,5 +51,7 @@
 {
   return grub_env_get_bool ("tpm_fail_fatal", false);
 }
+struct grub_tpm_digest *grub_tpm_read_pcr (grub_uint8_t index, const char *algo);
+void grub_tpm_digest_free (struct grub_tpm_digest *d);
 
 #endif
--- a/grub-core/commands/efi/tpm.c
+++ b/grub-core/commands/efi/tpm.c
@@ -24,6 +24,7 @@
 #include <grub/efi/efi.h>
 #include <grub/efi/cc.h>
 #include <grub/efi/tpm.h>
+#include <grub/tpm2/tpm2.h>
 #include <grub/mm.h>
 #include <grub/tpm.h>
 #include <grub/term.h>
@@ -186,6 +187,91 @@
   return grub_efi_log_event_status (status);
 }
 
+static void
+grub_tpm2_select_pcr(TPML_PCR_SELECTION *o, unsigned int pcrIndex, unsigned int algo)
+{
+  TPMS_PCR_SELECTION *pcr;
+
+  pcr = &o->pcrSelections[o->count++];
+  pcr->hash = algo;
+  pcr->sizeOfSelect = 3;
+  pcr->pcrSelect[TPM2_PCR_TO_SELECT(pcrIndex)] |= TPM2_PCR_TO_BIT(pcrIndex);
+}
+
+struct grub_tpm_hash_info {
+  const char *name;
+  grub_size_t size;
+  int id;
+};
+
+static const struct grub_tpm_hash_info *
+grub_tpm2_get_digest_info (const char *algo)
+{
+  static struct grub_tpm_hash_info __hashes[] = {
+	  { "sha256",	32,	TPM_ALG_SHA256 },	/* first entry is the default */
+	  { "sha512",	64,	TPM_ALG_SHA512 },
+	  { "sha1",	20,	TPM_ALG_SHA1 },
+	  { NULL }
+  };
+  struct grub_tpm_hash_info *h;
+
+  if (algo == NULL)
+    return &__hashes[0];
+
+  for (h = __hashes; h->name; ++h)
+    if (!grub_strcmp(h->name, algo))
+      return h;
+
+  return NULL;
+}
+
+static grub_err_t
+grub_tpm2_read_pcr (grub_int8_t pcrIndex, const char *algo, struct grub_tpm_digest **ret)
+{
+  const struct grub_tpm_hash_info *info;
+  TPML_PCR_SELECTION inSelection, outSelection;
+  grub_uint32_t pcrUpdateCounter;
+  TPML_DIGEST digests = { 0 };
+  TPM2B_DIGEST *d;
+  struct grub_tpm_digest *result;
+  int rc;
+
+  info = grub_tpm2_get_digest_info (algo);
+  if (info == NULL)
+    return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("Unknown digest algorithm %s"), algo);
+
+  grub_memset(&inSelection, 0, sizeof(inSelection));
+  grub_memset(&outSelection, 0, sizeof(outSelection));
+  grub_tpm2_select_pcr(&inSelection, pcrIndex, info->id);
+
+  rc = TPM2_PCR_Read(
+      NULL,
+      &inSelection,
+      &pcrUpdateCounter,
+      &outSelection,
+      &digests,
+      NULL
+    );
+
+  if (rc != 0)
+    return grub_error (GRUB_ERR_BAD_DEVICE, "TPM2_PCR_Read failed, status=%d", rc);
+
+  d = &digests.digests[0];
+
+  *ret = result = grub_malloc (sizeof (*result) + d->size);
+  grub_memcpy (result->value, d->buffer, d->size);
+  result->algorithm = info->name;
+  result->size = d->size;
+
+  return GRUB_ERR_NONE;
+}
+
+void
+grub_tpm_digest_free (struct grub_tpm_digest *d)
+{
+  grub_free (d);
+}
+
 static grub_err_t
 grub_tpm2_log_event (grub_efi_handle_t tpm_handle, unsigned char *buf,
 		     grub_size_t size, grub_uint8_t pcr,
@@ -323,3 +409,26 @@
       return grub_tpm2_present (tpm);
     }
 }
+
+struct grub_tpm_digest *
+grub_tpm_read_pcr (grub_uint8_t pcr, const char *algo)
+{
+  grub_efi_handle_t tpm_handle;
+  grub_efi_uint8_t protocol_version;
+  struct grub_tpm_digest *result = NULL;
+
+
+  if (!grub_tpm_handle_find (&tpm_handle, &protocol_version))
+    return 0;
+
+  if (protocol_version != 2)
+    {
+      grub_error (GRUB_ERR_BAD_DEVICE, N_("%s: TPM version %d not implemented"), __func__, protocol_version);
+      return NULL;
+    }
+
+  if (grub_tpm2_read_pcr (pcr, algo, &result))
+    return NULL;
+
+  return result;
+}
--- a/include/grub/tpm2/tpm2.h
+++ b/include/grub/tpm2/tpm2.h
@@ -23,6 +23,10 @@
 #include <grub/tpm2/internal/structs.h>
 #include <grub/tpm2/internal/functions.h>
 
+/* Defined in: TCG TPM Specification, v1.59, Part 2, Section 10.6.1. */
+#define TPM2_PCR_TO_SELECT(x)  ((x) / 8)
+#define TPM2_PCR_TO_BIT(x)     (1 << ((x) % 8))
+
 /* Well-Known Windows SRK handle */
 #define TPM2_SRK_HANDLE 0x81000001