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/* Copyright 2015 The Chromium OS Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "internal.h"
/* p256_base_point_mul sets {out_x,out_y} = nG, where n is < the
* order of the group. */
int DCRYPTO_p256_base_point_mul(p256_int *out_x, p256_int *out_y,
const p256_int *n)
{
if (p256_is_zero(n) != 0) {
p256_clear(out_x);
p256_clear(out_y);
return 0;
}
return dcrypto_p256_base_point_mul(n, out_x, out_y);
}
enum dcrypto_result DCRYPTO_p256_is_valid_point(const p256_int *x,
const p256_int *y)
{
return dcrypto_p256_is_valid_point(x, y);
}
/* DCRYPTO_p256_point_mul sets {out_x,out_y} = n*{in_x,in_y}, where n is <
* the order of the group. */
int DCRYPTO_p256_point_mul(p256_int *out_x, p256_int *out_y, const p256_int *n,
const p256_int *in_x, const p256_int *in_y)
{
if (p256_is_zero(n) != 0 ||
(dcrypto_p256_is_valid_point(in_x, in_y) != DCRYPTO_OK)) {
p256_clear(out_x);
p256_clear(out_y);
return 0;
}
return dcrypto_p256_point_mul(n, in_x, in_y, out_x, out_y);
}
int dcrypto_p256_fips_sign_internal(struct drbg_ctx *drbg, const p256_int *key,
const p256_int *message, p256_int *r,
p256_int *s)
{
int result;
p256_int k;
/* Pick uniform 0 < k < R */
result = fips_p256_hmac_drbg_generate(drbg, &k) - HMAC_DRBG_SUCCESS;
result |= dcrypto_p256_ecdsa_sign_raw(&k, key, message, r, s) - 1;
/* Wipe temp k */
p256_clear(&k);
return result == 0;
}
int DCRYPTO_p256_key_pwct(struct drbg_ctx *drbg, const p256_int *d,
const p256_int *x, const p256_int *y)
{
p256_int message, r, s;
int result;
if (p256_is_zero(d))
return 0;
/* set some pseudo-random message. */
p256_fast_random(&message);
if (dcrypto_p256_fips_sign_internal(drbg, d, &message, &r, &s) == 0)
return 0;
#ifdef CRYPTO_TEST_SETUP
if (fips_break_cmd == FIPS_BREAK_ECDSA_PWCT)
message.a[0] = ~message.a[0];
#endif
result = dcrypto_p256_ecdsa_verify(x, y, &message, &r, &s);
return result;
}
/**
* Key selection based on FIPS-186-4, section B.4.2 (Key Pair
* Generation by Testing Candidates).
*/
int DCRYPTO_p256_key_from_bytes(p256_int *x, p256_int *y, p256_int *d,
const uint8_t key_bytes[P256_NBYTES])
{
p256_int key;
p256_int tx, ty;
p256_from_bin(key_bytes, &key);
/**
* We need key to be in the range 0 < key < SECP256r1 - 1.
* To achieve that, first check key < SECP256r1 - 2, and
* then add 1 to key. Since key is unsigned number this will
* bring key in proper range.
*/
if (p256_lt_blinded(&key, &SECP256r1_nMin2) >= 0)
return 0;
p256_add_d(&key, 1, d);
always_memset(&key, 0, sizeof(key));
/* We need public key anyway for pair-wise consistency test. */
if (!x)
x = &tx;
if (!y)
y = &ty;
/* Compute public key (x,y) = d * G */
if (dcrypto_p256_base_point_mul(d, x, y) == 0)
return 0;
return DCRYPTO_p256_key_pwct(&fips_drbg, d, x, y);
}
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