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Secure Boot (Root of Trust) - Part 2 #289

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merged 2 commits into from
Aug 11, 2023
Merged

Secure Boot (Root of Trust) - Part 2 #289

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847e0ae
Fix for wolfTPM2_EncryptSecret to not loose error code.
dgarske Aug 10, 2023
00c8ffc
Avoid using heap (malloc/free) for ecc_point.
dgarske Aug 10, 2023
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60 changes: 32 additions & 28 deletions src/tpm2_wrap.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1044,7 +1044,12 @@ static int TPM2_KDFe(
return ret;
}

/* returns both the plaintext and encrypted salt, based on the salt public key */
#ifdef ALT_ECC_SIZE
#error use of ecc_point below does not support ALT_ECC_SIZE
#endif
/* returns both the plaintext and encrypted value */
/* ECC: data = derived symmetric key
* secret = exported public point */
static int wolfTPM2_EncryptSecret_ECC(WOLFTPM2_DEV* dev, const WOLFTPM2_KEY* tpmKey,
TPM2B_DATA *data, TPM2B_ENCRYPTED_SECRET *secret,
const char* label)
Expand All @@ -1054,7 +1059,7 @@ static int wolfTPM2_EncryptSecret_ECC(WOLFTPM2_DEV* dev, const WOLFTPM2_KEY* tpm
ecc_key eccKeyPriv, eccKeyPub;
const TPMT_PUBLIC *publicArea;
TPM2B_ECC_POINT pubPoint, secretPoint;
ecc_point* r = NULL;
ecc_point r[1];
mp_int prime, a;

publicArea = &tpmKey->pub.publicArea;
Expand All @@ -1063,6 +1068,9 @@ static int wolfTPM2_EncryptSecret_ECC(WOLFTPM2_DEV* dev, const WOLFTPM2_KEY* tpm
XMEMSET(&eccKeyPriv, 0, sizeof(eccKeyPriv));
XMEMSET(&pubPoint, 0, sizeof(pubPoint));
XMEMSET(&secretPoint, 0, sizeof(secretPoint));
XMEMSET(r, 0, sizeof(r));
XMEMSET(&prime, 0, sizeof(prime));
XMEMSET(&a, 0, sizeof(a));

rc = wc_InitRng_ex(&rng, NULL, INVALID_DEVID);
if (rc == 0) {
Expand Down Expand Up @@ -1100,25 +1108,25 @@ static int wolfTPM2_EncryptSecret_ECC(WOLFTPM2_DEV* dev, const WOLFTPM2_KEY* tpm
secret->size = packet.pos;
}
if (rc == 0) {
r = wc_ecc_new_point();
if (r == NULL)
rc = MEMORY_E;
rc = mp_init_multi(&prime, &a, r->x, r->y, r->z, NULL);
}
if (rc == 0) {
rc = mp_read_radix(&prime, eccKeyPriv.dp->prime, MP_RADIX_HEX);
}
if (rc == 0) {
rc = mp_read_radix(&a, eccKeyPriv.dp->Af, MP_RADIX_HEX);
}
if (rc == 0) {
mp_init(&prime);
mp_init(&a);
mp_read_radix(&prime, eccKeyPriv.dp->prime, MP_RADIX_HEX);
mp_read_radix(&a, eccKeyPriv.dp->Af, MP_RADIX_HEX);

/* perform point multiply */
rc = wc_ecc_mulmod(wc_ecc_key_get_priv(&eccKeyPriv), &eccKeyPub.pubkey,
r, &a, &prime, 1);
}
if (rc == 0) {
/* export shared secret x */
secretPoint.point.x.size = mp_unsigned_bin_size(r->x);
mp_to_unsigned_bin(r->x, secretPoint.point.x.buffer);

rc = mp_to_unsigned_bin(r->x, secretPoint.point.x.buffer);
}
if (rc == 0) {
/* set size encryption key */
data->size = TPM2_GetHashDigestSize(publicArea->nameAlg);

Expand All @@ -1133,28 +1141,27 @@ static int wolfTPM2_EncryptSecret_ECC(WOLFTPM2_DEV* dev, const WOLFTPM2_KEY* tpm
);
}

if (r != NULL) {
mp_free(&a);
mp_free(&prime);
wc_ecc_del_point(r);
}
mp_clear(r->x);
mp_clear(r->y);
mp_clear(r->z);
mp_clear(&a);
mp_clear(&prime);
wc_ecc_free(&eccKeyPub);
wc_ecc_free(&eccKeyPriv);
wc_FreeRng(&rng);

if (rc == data->size) {
rc = 0; /* success */
}
else {
rc = BUFFER_E;
if (rc >= 0) {
rc = (rc == data->size) ? 0 /* success */ : BUFFER_E /* fail */;
}

return rc;
}
#endif /* !WOLFTPM2_NO_WOLFCRYPT && HAVE_ECC && !WC_NO_RNG */

#if !defined(WOLFTPM2_NO_WOLFCRYPT) && !defined(NO_RSA) && !defined(WC_NO_RNG)
/* returns both the plaintext and encrypted salt, based on the salt public key */
/* returns both the plaintext and encrypted value */
/* RSA: data = input to encrypt or generated random value
* secret = RSA encrypted random */
static int wolfTPM2_EncryptSecret_RSA(WOLFTPM2_DEV* dev, const WOLFTPM2_KEY* tpmKey,
TPM2B_DATA *data, TPM2B_ENCRYPTED_SECRET *secret, const char* label)
{
Expand Down Expand Up @@ -1217,11 +1224,8 @@ static int wolfTPM2_EncryptSecret_RSA(WOLFTPM2_DEV* dev, const WOLFTPM2_KEY* tpm
wc_FreeRsaKey(&rsaKey);
wc_FreeRng(&rng);

if (rc == secret->size) {
rc = 0; /* success */
}
else if (rc >= 0) {
rc = BUFFER_E;
if (rc > 0) {
rc = (rc == secret->size) ? 0 /* success */ : BUFFER_E /* fail */;
}

return rc;
Expand Down