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better comments on RFC steps and fixes for combining code blocks, fix for check on sign_k value

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This commit is contained in:
Jacob Barthelmeh
2021-05-27 17:27:15 +07:00
parent 4a7434a56d
commit 252971aad7
1 changed files with 41 additions and 39 deletions
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54
wolfcrypt/src/ecc.c
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@ -5312,9 +5312,14 @@ static int deterministic_sign_helper(const byte* in, word32 inlen, ecc_key* key)
/* get curve order */
err = wc_ecc_curve_load(key->dp, &curve, ECC_CURVE_FIELD_ORDER);
if (err == MP_OKAY) {
/* if key->sign_k is NULL then create a buffer for the mp_int
* if not NULL then assume the user correctly set deterministic flag and
* that the key->sign_k holds a previously malloc'd mp_int buffer */
if (key->sign_k == NULL) {
key->sign_k = (mp_int*)XMALLOC(sizeof(mp_int), key->heap,
DYNAMIC_TYPE_ECC);
}
if (key->sign_k) {
/* currently limiting to SHA256 for auto create */
if (mp_init(key->sign_k) != MP_OKAY ||
@ -5324,16 +5329,11 @@ static int deterministic_sign_helper(const byte* in, word32 inlen, ecc_key* key)
mp_free(key->sign_k);
XFREE(key->sign_k, key->heap, DYNAMIC_TYPE_ECC);
key->sign_k = NULL;
wc_ecc_curve_free(curve);
FREE_CURVE_SPECS();
return ECC_PRIV_KEY_E;
err = ECC_PRIV_KEY_E;
}
}
else {
wc_ecc_curve_free(curve);
FREE_CURVE_SPECS();
return MEMORY_E;
}
err = MEMORY_E;
}
}
@ -5855,7 +5855,7 @@ static int _HMAC_K(byte* K, word32 KSz, byte* V, word32 VSz,
}
/* Generates a deterministic key based of the message using RFC6967
/* Generates a deterministic key based of the message using RFC6979
* @param [in] hash Hash value to sign
* @param [in] hashSz Size of 'hash' buffer passed in
* @param [in] hashType Type of hash to use with deterministic k gen, i.e.
@ -5938,27 +5938,26 @@ int wc_ecc_gen_deterministic_k(const byte* hash, word32 hashSz,
#endif
VSz = KSz = h1len = hashSz;
/* 3.2 b. Set V = 0x01 0x01 ... */
XMEMSET(V, 0x01, VSz);
/* 3.2 c. Set K = 0x00 0x00 ... */
XMEMSET(K, 0x00, KSz);
ret = mp_to_unsigned_bin(priv, x);
mp_init(&z1); /* always init z1 and free z1 */
ret = mp_to_unsigned_bin(priv, x);
if (ret == 0) {
qbits = mp_count_bits(order);
}
if (ret == 0) {
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);
XMEMSET(h1, 0, sizeof(h1));
}
if (ret == 0) {
/* mod reduce by order using conditional subtract */
if (mp_cmp(&z1, order) == MP_GT) {
mp_sub(&z1, order, &z1);
@ -5978,66 +5977,69 @@ int wc_ecc_gen_deterministic_k(const byte* hash, word32 hashSz,
}
mp_free(&z1);
/* step d. */
/* 3.2 step d. K = HMAC_K(V || 0x00 || int2octests(x) || bits2octests(h1) */
if (ret == 0) {
intOct = 0x00;
ret = _HMAC_K(K, KSz, V, VSz, h1, h1len, x, xSz, &intOct, K,
hashType, heap);
}
/* step e. */
/* 3.2 step e. V = HMAC_K(V) */
if (ret == 0) {
ret = _HMAC_K(K, KSz, V, VSz, NULL, 0, NULL, 0, NULL, V, hashType,
heap);
}
/* step f. */
/* 3.2 step f. K = HMAC_K(V || 0x01 || int2octests(x) || bits2octests(h1) */
if (ret == 0) {
intOct = 0x01;
ret = _HMAC_K(K, KSz, V, VSz, h1, h1len, x, xSz, &intOct, K, hashType,
heap);
}
/* step g. */
/* 3.2 step g. V = HMAC_K(V) */
if (ret == 0) {
ret = _HMAC_K(K, KSz, V, VSz, NULL, 0, NULL, 0, NULL, V, hashType,
heap);
}
/* step h. */
/* 3.2 step h. loop through the next steps until a valid value is found */
if (ret == 0 ) {
int err;
intOct = 0x00;
do {
err = 0; /* start as good until generated k is tested */
/* 3.2 step h.2 when tlen < qlen do V = HMAC_K(V); T = T || V */
ret = _HMAC_K(K, KSz, V, VSz, NULL, 0, NULL, 0, NULL, V, hashType,
heap);
if (ret == 0) {
mp_clear(k);
mp_clear(k); /* 3.2 step h.1 clear T */
ret = mp_read_unsigned_bin(k, V, VSz);
}
if ((ret == 0) && ((int)(VSz * WOLFSSL_BIT_SIZE) != qbits)) {
/* handle odd case where shift of 'k' is needed */
/* handle odd case where shift of 'k' is needed with RFC 6979
* k = bits2int(T) in section 3.2 h.3 */
mp_rshb(k, (VSz * WOLFSSL_BIT_SIZE) - qbits);
}
/* the key should be smaller than the order of base point */
/* 3.2 step h.3 the key should be smaller than the order of base
* point */
if (ret == 0) {
if (mp_cmp(k, order) != MP_LT) {
err = MP_VAL;
}
}
/* no 0 key's */
if (ret == 0) {
if (mp_iszero(k) == MP_YES)
err = MP_ZERO_E;
}
/* if there was a problem with 'k' generated then try again */
/* 3.2 step h.3 if there was a problem with 'k' generated then try
* again K = HMAC_K(V || 0x00) and V = HMAC_K(V) */
if (ret == 0 && err != 0) {
ret = _HMAC_K(K, KSz, V, VSz, NULL, 0, NULL, 0, &intOct, K,
hashType, heap);