03ab2a90b
Denys Vlasenko
2021-04-26
Subject
tls: simplify array manipulations in sp_256_ecc_mulmod_10
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Commit Diff GitHub →
networking/tls_sp_c32.c+17 -18
| @@ -788,29 +788,25 @@ static void sp_256_proj_point_add_10(sp_point* r, sp_point* p, sp_point* q, | |
| * r Resulting point. | |
| * g Point to multiply. | |
| * k Scalar to multiply by. | |
| + | * map Indicates whether to convert result to affine. |
| */ | |
| static void sp_256_ecc_mulmod_10(sp_point* r, const sp_point* g, const sp_digit* k /*, int map*/) | |
| { | |
| enum { map = 1 }; /* we always convert result to affine coordinates */ | |
| - | sp_point td[3]; |
| - | sp_point* t[3]; |
| + | sp_point t[3]; |
| sp_digit tmp[2 * 10 * 5]; | |
| sp_digit n; | |
| int i; | |
| int c, y; | |
| - | memset(td, 0, sizeof(td)); |
| - | |
| - | t[0] = &td[0]; |
| - | t[1] = &td[1]; |
| - | t[2] = &td[2]; |
| + | memset(t, 0, sizeof(t)); |
| /* t[0] = {0, 0, 1} * norm */ | |
| - | t[0]->infinity = 1; |
| + | t[0].infinity = 1; |
| /* t[1] = {g->x, g->y, g->z} * norm */ | |
| - | sp_256_mod_mul_norm_10(t[1]->x, g->x); |
| - | sp_256_mod_mul_norm_10(t[1]->y, g->y); |
| - | sp_256_mod_mul_norm_10(t[1]->z, g->z); |
| + | sp_256_mod_mul_norm_10(t[1].x, g->x); |
| + | sp_256_mod_mul_norm_10(t[1].y, g->y); |
| + | sp_256_mod_mul_norm_10(t[1].z, g->z); |
| i = 9; | |
| c = 22; | |
| @@ -827,19 +823,21 @@ static void sp_256_ecc_mulmod_10(sp_point* r, const sp_point* g, const sp_digit* | |
| y = (n >> 25) & 1; | |
| n <<= 1; | |
| - | sp_256_proj_point_add_10(t[y^1], t[0], t[1], tmp); |
| - | memcpy(t[2], t[y], sizeof(sp_point)); |
| - | sp_256_proj_point_dbl_10(t[2], t[2], tmp); |
| - | memcpy(t[y], t[2], sizeof(sp_point)); |
| + | //FIXME: what's "tmp" and why do we pass it down? |
| + | //is it scratch space for "sensitive" data, to be memset(0) after we are done? |
| + | sp_256_proj_point_add_10(&t[y^1], &t[0], &t[1], tmp); |
| + | memcpy(&t[2], &t[y], sizeof(sp_point)); |
| + | sp_256_proj_point_dbl_10(&t[2], &t[2], tmp); |
| + | memcpy(&t[y], &t[2], sizeof(sp_point)); |
| } | |
| if (map) | |
| - | sp_256_map_10(r, t[0], tmp); |
| + | sp_256_map_10(r, &t[0], tmp); |
| else | |
| - | memcpy(r, t[0], sizeof(sp_point)); |
| + | memcpy(r, &t[0], sizeof(sp_point)); |
| memset(tmp, 0, sizeof(tmp)); //paranoia | |
| - | memset(td, 0, sizeof(td)); //paranoia |
| + | memset(t, 0, sizeof(t)); //paranoia |
| } | |
| /* Multiply the base point of P256 by the scalar and return the result. | |
| @@ -847,6 +845,7 @@ static void sp_256_ecc_mulmod_10(sp_point* r, const sp_point* g, const sp_digit* | |
| * | |
| * r Resulting point. | |
| * k Scalar to multiply by. | |
| + | * map Indicates whether to convert result to affine. |
| */ | |
| static void sp_256_ecc_mulmod_base_10(sp_point* r, sp_digit* k /*, int map*/) | |
| { | |