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tpm2: add tpm2_set_auth()

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This provides a function to perform the SetAuth TPM function, which provides
the authValue for a key.
This commit is contained in:
Dan Streetman
2023-05-26 11:06:53 -04:00
parent 94a4ff2dc1
commit 409a65f829
1 changed files with 38 additions and 27 deletions
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src/shared/tpm2-util.c
+38 -27
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@@ -1457,6 +1457,31 @@ int tpm2_digest_many_digests(
return tpm2_digest_many(alg, digest, iovecs, n_data, extend);
}
static int tpm2_set_auth(Tpm2Context *c, const Tpm2Handle *handle, const char *pin) {
TPM2B_AUTH auth = {};
TSS2_RC rc;
int r;
assert(c);
assert(handle);
if (!pin)
return 0;
CLEANUP_ERASE(auth);
r = tpm2_digest_buffer(TPM2_ALG_SHA256, &auth, pin, strlen(pin), /* extend= */ false);
if (r < 0)
return r;
rc = sym_Esys_TR_SetAuth(c->esys_context, handle->esys_handle, &auth);
if (rc != TSS2_RC_SUCCESS)
return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE),
"Failed to load PIN in TPM: %s", sym_Tss2_RC_Decode(rc));
return 0;
}
static bool tpm2_is_encryption_session(Tpm2Context *c, const Tpm2Handle *session) {
TPMA_SESSION flags = 0;
TSS2_RC rc;
@@ -1475,7 +1500,6 @@ static int tpm2_make_encryption_session(
Tpm2Context *c,
const Tpm2Handle *primary,
const Tpm2Handle *bind_key,
const char *pin,
Tpm2Handle **ret_session) {
static const TPMT_SYM_DEF symmetric = {
@@ -1491,30 +1515,6 @@ static int tpm2_make_encryption_session(
assert(c);
assert(ret_session);
/*
* if a pin is set for the seal object, use it to bind the session
* key to that object. This prevents active bus interposers from
* faking a TPM and seeing the unsealed value. An active interposer
* could fake a TPM, satisfying the encrypted session, and just
* forward everything to the *real* TPM.
*/
if (pin) {
TPM2B_AUTH auth = {};
CLEANUP_ERASE(auth);
r = tpm2_digest_buffer(TPM2_ALG_SHA256, &auth, pin, strlen(pin), /* extend= */ false);
if (r < 0)
return r;
rc = sym_Esys_TR_SetAuth(c->esys_context, bind_key->esys_handle, &auth);
if (rc != TSS2_RC_SUCCESS)
return log_error_errno(
SYNTHETIC_ERRNO(ENOTRECOVERABLE),
"Failed to load PIN in TPM: %s",
sym_Tss2_RC_Decode(rc));
}
log_debug("Starting HMAC encryption session.");
/* Start a salted, unbound HMAC session with a well-known key (e.g. primary key) as tpmKey, which
@@ -2122,7 +2122,7 @@ int tpm2_seal(const char *device,
/* 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, NULL, &encryption_session);
r = tpm2_make_encryption_session(c, primary, &TPM2_HANDLE_NONE, &encryption_session);
if (r < 0)
return r;
@@ -2419,8 +2419,19 @@ int tpm2_unseal(const char *device,
sym_Tss2_RC_Decode(rc));
}
/*
* if a pin is set for the seal object, use it to bind the session
* key to that object. This prevents active bus interposers from
* faking a TPM and seeing the unsealed value. An active interposer
* could fake a TPM, satisfying the encrypted session, and just
* forward everything to the *real* TPM.
*/
r = tpm2_set_auth(c, hmac_key, pin);
if (r < 0)
return r;
_cleanup_tpm2_handle_ Tpm2Handle *encryption_session = NULL;
r = tpm2_make_encryption_session(c, primary, hmac_key, pin, &encryption_session);
r = tpm2_make_encryption_session(c, primary, hmac_key, &encryption_session);
if (r < 0)
return r;