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ecc.c: small stack refactor for mp_int on the stack in wc_ecc_gen_deterministic_k().

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This commit is contained in:
Daniel Pouzzner 2021-12-16 00:51:17 -06:00
parent fed5eb1d94
commit b7307e0ca5
1 changed files with 18 additions and 9 deletions
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27
wolfcrypt/src/ecc.c
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@ -6100,15 +6100,16 @@ int wc_ecc_gen_deterministic_k(const byte* hash, word32 hashSz,
byte V[WC_MAX_DIGEST_SIZE];
byte K[WC_MAX_DIGEST_SIZE];
byte x[MAX_ECC_BYTES];
mp_int z1[1];
#else
byte *h1 = NULL;
byte *V = NULL;
byte *K = NULL;
byte *x = NULL;
mp_int *z1 = NULL;
#endif
word32 xSz, VSz, KSz, h1len;
byte intOct;
mp_int z1;
if (hash == NULL || k == NULL || order == NULL) {
return BAD_FUNC_ARG;
@ -6148,6 +6149,12 @@ int wc_ecc_gen_deterministic_k(const byte* hash, word32 hashSz,
ret = MEMORY_E;
}
if (ret == 0) {
z1 = (mp_int *)XMALLOC(sizeof(z1), heap, DYNAMIC_TYPE_ECC_BUFFER);
if (z1 == NULL)
ret = MEMORY_E;
}
/* bail out if any error has been hit at this point */
if (ret != 0) {
if (x != NULL)
@ -6170,17 +6177,17 @@ int wc_ecc_gen_deterministic_k(const byte* hash, word32 hashSz,
/* 3.2 c. Set K = 0x00 0x00 ... */
XMEMSET(K, 0x00, KSz);
mp_init(&z1); /* always init z1 and free z1 */
mp_init(z1); /* always init z1 and free z1 */
ret = mp_to_unsigned_bin_len(priv, x, hashSz);
if (ret == 0) {
qbits = mp_count_bits(order);
ret = mp_read_unsigned_bin(&z1, hash, hashSz);
ret = mp_read_unsigned_bin(z1, hash, hashSz);
}
/* bits2octets on h1 */
if (ret == 0) {
/* right shift by bits in hash minus bits in order */
mp_rshb(&z1, (hashSz * WOLFSSL_BIT_SIZE) - qbits);
mp_rshb(z1, (hashSz * WOLFSSL_BIT_SIZE) - qbits);
XMEMSET(h1, 0, WC_MAX_DIGEST_SIZE);
#if !defined(WOLFSSL_ECDSA_DETERMINISTIC_K_VARIANT)
@ -6188,14 +6195,14 @@ int wc_ecc_gen_deterministic_k(const byte* hash, word32 hashSz,
* RFC6979 lists a variant that uses the hash directly instead of
* doing bits2octets(H(m)), when variant macro is used avoid this
* bits2octets operation */
if (mp_cmp(&z1, order) == MP_GT) {
mp_sub(&z1, order, &z1);
h1len = mp_unsigned_bin_size(&z1);
if (mp_cmp(z1, order) == MP_GT) {
mp_sub(z1, order, z1);
h1len = mp_unsigned_bin_size(z1);
if (h1len < 0 || h1len > WC_MAX_DIGEST_SIZE) {
ret = BUFFER_E;
}
else {
ret = mp_to_unsigned_bin(&z1, h1);
ret = mp_to_unsigned_bin(z1, h1);
}
}
else
@ -6206,7 +6213,7 @@ int wc_ecc_gen_deterministic_k(const byte* hash, word32 hashSz,
XMEMCPY(h1, hash, hashSz);
}
}
mp_free(&z1);
mp_free(z1);
/* 3.2 step d. K = HMAC_K(V || 0x00 || int2octests(x) || bits2octests(h1) */
if (ret == 0) {
@ -6282,6 +6289,8 @@ int wc_ecc_gen_deterministic_k(const byte* hash, word32 hashSz,
}
#ifdef WOLFSSL_SMALL_STACK
if (z1 != NULL)
XFREE(z1, heap, DYNAMIC_TYPE_ECC_BUFFER);
if (x != NULL)
XFREE(x, heap, DYNAMIC_TYPE_PRIVATE_KEY);
if (K != NULL)