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Map the Jacobian point back to affine space in wolfSSL_EC_POINT_get_affine_coordinates_GFp

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This commit is contained in:
Juliusz Sosinowicz
2019-11-28 13:05:36 +01:00
parent aea95232d1
commit 84a2ca7a4e
3 changed files with 29 additions and 2 deletions
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24
src/ssl.c
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@@ -34413,12 +34413,14 @@ int wolfSSL_EC_POINT_get_affine_coordinates_GFp(const WOLFSSL_EC_GROUP *group,
WOLFSSL_BIGNUM *y,
WOLFSSL_BN_CTX *ctx)
{
mp_digit mp;
mp_int modulus;
(void)ctx;
WOLFSSL_ENTER("wolfSSL_EC_POINT_get_affine_coordinates_GFp");
if (group == NULL || point == NULL || point->internal == NULL ||
x == NULL || y == NULL) {
x == NULL || y == NULL || wolfSSL_EC_POINT_is_at_infinity(group, point)) {
WOLFSSL_MSG("wolfSSL_EC_POINT_get_affine_coordinates_GFp NULL error");
return WOLFSSL_FAILURE;
}
@@ -34432,6 +34434,26 @@ int wolfSSL_EC_POINT_get_affine_coordinates_GFp(const WOLFSSL_EC_GROUP *group,
}
}
if (!wolfSSL_BN_is_one(point->Z)) {
/* Map the Jacobian point back to affine space */
if (mp_read_radix(&modulus, ecc_sets[group->curve_idx].prime, MP_RADIX_HEX) != MP_OKAY) {
WOLFSSL_MSG("mp_read_radix failed");
return WOLFSSL_FAILURE;
}
if (mp_montgomery_setup(&modulus, &mp) != MP_OKAY) {
WOLFSSL_MSG("mp_montgomery_setup failed");
return WOLFSSL_FAILURE;
}
if (ecc_map((ecc_point*)point->internal, &modulus, mp) != MP_OKAY) {
WOLFSSL_MSG("ecc_map failed");
return WOLFSSL_FAILURE;
}
if (SetECPointExternal((WOLFSSL_EC_POINT *)point) != WOLFSSL_SUCCESS) {
WOLFSSL_MSG("SetECPointExternal failed");
return WOLFSSL_FAILURE;
}
}
BN_copy(x, point->X);
BN_copy(y, point->Y);

5
tests/api.c
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@@ -1825,6 +1825,11 @@ static void test_wolfSSL_EC(void)
/* check if point X coordinate is zero */
AssertIntEQ(BN_is_zero(new_point->X), WOLFSSL_FAILURE);
/* Force non-affine coordinates */
AssertIntEQ(wolfSSL_BN_add(new_point->Z, (WOLFSSL_BIGNUM*)BN_value_one(),
(WOLFSSL_BIGNUM*)BN_value_one()), 1);
new_point->inSet = 0;
/* extract the coordinates from point */
AssertIntEQ(EC_POINT_get_affine_coordinates_GFp(group, new_point, X, Y, ctx), WOLFSSL_SUCCESS);

2
wolfcrypt/src/ecc.c
View File

@@ -2281,7 +2281,7 @@ int ecc_projective_dbl_point(ecc_point *P, ecc_point *R, mp_int* a,
/**
Map a projective jacbobian point back to affine space
Map a projective Jacobian point back to affine space
P [in/out] The point to map
modulus The modulus of the field the ECC curve is in
mp The "b" value from montgomery_setup()