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From 3047d3fed460b6df83cb0713d5ef25169fdebb4e Mon Sep 17 00:00:00 2001
From: Dan Streetman <ddstreet@ieee.org>
Date: Thu, 15 Dec 2022 12:56:35 -0500
Subject: [PATCH] tpm2: add tpm2_calculate_sealing_policy()
This adds a function to fully calculate the authPolicy needed to seal a secret,
and updates tpm2_seal() to use the new function instead of a trial policy.
(cherry picked from commit d9a1f1a724a08defb70dbc6f44aa578983a66ac8)
Related: RHEL-16182
---
src/shared/tpm2-util.c | 118 ++++++++++++++++++++++++-----------------
1 file changed, 70 insertions(+), 48 deletions(-)
diff --git a/src/shared/tpm2-util.c b/src/shared/tpm2-util.c
index 2747cf0b53..f638c18223 100644
--- a/src/shared/tpm2-util.c
+++ b/src/shared/tpm2-util.c
@@ -2263,6 +2263,40 @@ static int tpm2_policy_authorize(
return tpm2_get_policy_digest(c, session, ret_policy_digest);
}
+/* Extend 'digest' with the calculated policy hash. */
+static int tpm2_calculate_sealing_policy(
+ const TPML_PCR_SELECTION *hash_pcr_selection,
+ const TPM2B_DIGEST *hash_pcr_values,
+ size_t n_hash_pcr_values,
+ const TPM2B_PUBLIC *public,
+ const char *pin,
+ TPM2B_DIGEST *digest) {
+
+ int r;
+
+ assert(digest);
+
+ if (public) {
+ r = tpm2_calculate_policy_authorize(public, NULL, digest);
+ if (r < 0)
+ return r;
+ }
+
+ if (hash_pcr_selection && !tpm2_tpml_pcr_selection_is_empty(hash_pcr_selection)) {
+ r = tpm2_calculate_policy_pcr(hash_pcr_selection, hash_pcr_values, n_hash_pcr_values, digest);
+ if (r < 0)
+ return r;
+ }
+
+ if (pin) {
+ r = tpm2_calculate_policy_auth_value(digest);
+ if (r < 0)
+ return r;
+ }
+
+ return 0;
+}
+
static int tpm2_build_sealing_policy(
Tpm2Context *c,
const Tpm2Handle *session,
@@ -2345,7 +2379,6 @@ int tpm2_seal(const char *device,
_cleanup_(erase_and_freep) void *secret = NULL;
_cleanup_free_ void *hash = NULL;
TPM2B_SENSITIVE_CREATE hmac_sensitive;
- TPMI_ALG_PUBLIC primary_alg;
TPM2B_PUBLIC hmac_template;
usec_t start;
TSS2_RC rc;
@@ -2398,59 +2431,37 @@ int tpm2_seal(const char *device,
return r;
}
+ TPML_PCR_SELECTION hash_pcr_selection = {};
+ _cleanup_free_ TPM2B_DIGEST *hash_pcr_values = NULL;
+ size_t n_hash_pcr_values = 0;
+ if (hash_pcr_mask) {
+ /* For now, we just read the current values from the system; we need to be able to specify
+ * expected values, eventually. */
+ tpm2_tpml_pcr_selection_from_mask(hash_pcr_mask, pcr_bank, &hash_pcr_selection);
+ r = tpm2_pcr_read(c, &hash_pcr_selection, &hash_pcr_selection, &hash_pcr_values, &n_hash_pcr_values);
+ if (r < 0)
+ return r;
+ }
+
TPM2B_PUBLIC pubkey_tpm2, *authorize_key = NULL;
- _cleanup_free_ void *fp = NULL;
- size_t fp_size = 0;
if (pubkey) {
- r = openssl_pubkey_to_tpm2_pubkey(pubkey, pubkey_size, &pubkey_tpm2, &fp, &fp_size);
+ r = openssl_pubkey_to_tpm2_pubkey(pubkey, pubkey_size, &pubkey_tpm2, NULL, NULL);
if (r < 0)
return r;
authorize_key = &pubkey_tpm2;
}
- _cleanup_tpm2_handle_ Tpm2Handle *primary = NULL;
- r = tpm2_make_primary(c, /* alg = */0, !!ret_srk_buf, &primary_alg, &primary);
+ TPM2B_DIGEST policy_digest;
+ r = tpm2_digest_init(TPM2_ALG_SHA256, &policy_digest);
if (r < 0)
return r;
- /* we cannot use the bind key before its created */
- _cleanup_tpm2_handle_ Tpm2Handle *encryption_session = NULL;
- r = tpm2_make_encryption_session(c, primary, &TPM2_HANDLE_NONE, &encryption_session);
- if (r < 0)
- return r;
-
- /* So apparently some TPM implementations don't implement trial mode correctly. To avoid issues let's
- * avoid it when it is easy to. At the moment we only really need trial mode for the signed PCR
- * policies (since only then we need to shove PCR values into the policy that don't match current
- * state anyway), hence if we have none of those we don't need to bother. Hence, let's patch in
- * TPM2_SE_POLICY even if trial mode is requested unless a pubkey PCR mask is specified that is
- * non-zero, i.e. signed PCR policy is requested.
- *
- * One day we should switch to calculating policy hashes client side when trial mode is requested, to
- * avoid this mess. */
- bool trial = (pubkey_pcr_mask != 0);
-
- _cleanup_tpm2_handle_ Tpm2Handle *policy_session = NULL;
- r = tpm2_make_policy_session(
- c,
- primary,
- encryption_session,
- trial,
- &policy_session);
- if (r < 0)
- return r;
-
- _cleanup_(Esys_Freep) TPM2B_DIGEST *policy_digest = NULL;
- r = tpm2_build_sealing_policy(
- c,
- policy_session,
- hash_pcr_mask,
- pcr_bank,
+ r = tpm2_calculate_sealing_policy(
+ &hash_pcr_selection,
+ hash_pcr_values,
+ n_hash_pcr_values,
authorize_key,
- fp, fp_size,
- pubkey_pcr_mask,
- /* signature_json= */ NULL,
- !!pin,
+ pin,
&policy_digest);
if (r < 0)
return r;
@@ -2466,7 +2477,7 @@ int tpm2_seal(const char *device,
.objectAttributes = TPMA_OBJECT_FIXEDTPM | TPMA_OBJECT_FIXEDPARENT,
.parameters.keyedHashDetail.scheme.scheme = TPM2_ALG_NULL,
.unique.keyedHash.size = SHA256_DIGEST_SIZE,
- .authPolicy = *policy_digest,
+ .authPolicy = policy_digest,
},
};
@@ -2490,11 +2501,22 @@ int tpm2_seal(const char *device,
if (r < 0)
return log_error_errno(r, "Failed to generate secret key: %m");
+ _cleanup_tpm2_handle_ Tpm2Handle *primary_handle = NULL;
+ TPMI_ALG_PUBLIC primary_alg;
+ r = tpm2_make_primary(c, /* alg = */0, !!ret_srk_buf, &primary_alg, &primary_handle);
+ if (r < 0)
+ return r;
+
+ _cleanup_tpm2_handle_ Tpm2Handle *encryption_session = NULL;
+ r = tpm2_make_encryption_session(c, primary_handle, &TPM2_HANDLE_NONE, &encryption_session);
+ if (r < 0)
+ return r;
+
log_debug("Creating HMAC key.");
rc = sym_Esys_Create(
c->esys_context,
- primary->esys_handle,
+ primary_handle->esys_handle,
encryption_session->esys_handle, /* use HMAC session to enable parameter encryption */
ESYS_TR_NONE,
ESYS_TR_NONE,
@@ -2534,7 +2556,7 @@ int tpm2_seal(const char *device,
return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE),
"Failed to marshal public key: %s", sym_Tss2_RC_Decode(rc));
- hash = memdup(policy_digest->buffer, policy_digest->size);
+ hash = memdup(policy_digest.buffer, policy_digest.size);
if (!hash)
return log_oom();
@@ -2544,7 +2566,7 @@ int tpm2_seal(const char *device,
*/
if (ret_srk_buf) {
log_debug("Serializing SRK ESYS_TR reference");
- rc = sym_Esys_TR_Serialize(c->esys_context, primary->esys_handle, &srk_buf, &srk_buf_size);
+ rc = sym_Esys_TR_Serialize(c->esys_context, primary_handle->esys_handle, &srk_buf, &srk_buf_size);
if (rc != TSS2_RC_SUCCESS)
return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE),
"Failed to serialize primary key: %s", sym_Tss2_RC_Decode(rc));
@@ -2572,7 +2594,7 @@ int tpm2_seal(const char *device,
*ret_blob = TAKE_PTR(blob);
*ret_blob_size = blob_size;
*ret_pcr_hash = TAKE_PTR(hash);
- *ret_pcr_hash_size = policy_digest->size;
+ *ret_pcr_hash_size = policy_digest.size;
*ret_pcr_bank = pcr_bank;
*ret_primary_alg = primary_alg;
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