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tls: stop passing temporary buffer address in P256 code

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function                                             old     new   delta
sp_256_proj_point_dbl_10                             435     453     +18
sp_256_ecc_mulmod_10                                1300    1237     -63
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/1 up/down: 18/-63)            Total: -45 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2021-04-26 17:41:43 +02:00
parent 772e18775e
commit 6381f3d4f6
1 changed files with 26 additions and 35 deletions
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47
networking/tls_sp_c32.c
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@ -553,16 +553,15 @@ static void sp_256_mont_sqr_10(sp_digit* r, const sp_digit* a, const sp_digit* m
*
* r Inverse result.
* a Number to invert.
* td Temporary data.
*/
/* Mod-2 for the P256 curve. */
static const uint32_t p256_mod_2[8] = {
0xfffffffd,0xffffffff,0xffffffff,0x00000000,
0x00000000,0x00000000,0x00000001,0xffffffff,
};
static void sp_256_mont_inv_10(sp_digit* r, sp_digit* a, sp_digit* td)
static void sp_256_mont_inv_10(sp_digit* r, sp_digit* a)
{
sp_digit* t = td;
sp_digit t[2*10]; //can be just [10]?
int i;
memcpy(t, a, sizeof(sp_digit) * 10);
@ -578,15 +577,14 @@ static void sp_256_mont_inv_10(sp_digit* r, sp_digit* a, sp_digit* td)
*
* r Resulting affine co-ordinate point.
* p Montgomery form projective co-ordinate point.
* t Temporary ordinate data.
*/
static void sp_256_map_10(sp_point* r, sp_point* p, sp_digit* t)
static void sp_256_map_10(sp_point* r, sp_point* p)
{
sp_digit* t1 = t;
sp_digit* t2 = t + 2*10;
sp_digit t1[2*10];
sp_digit t2[2*10];
int32_t n;
sp_256_mont_inv_10(t1, p->z, t + 2*10);
sp_256_mont_inv_10(t1, p->z);
sp_256_mont_sqr_10(t2, t1, p256_mod, p256_mp_mod);
sp_256_mont_mul_10(t1, t2, t1, p256_mod, p256_mp_mod);
@ -617,13 +615,12 @@ static void sp_256_map_10(sp_point* r, sp_point* p, sp_digit* t)
*
* r Result of doubling point.
* p Point to double.
* t Temporary ordinate data.
*/
static void sp_256_proj_point_dbl_10(sp_point* r, sp_point* p, sp_digit* t)
static void sp_256_proj_point_dbl_10(sp_point* r, sp_point* p)
{
sp_point tp;
sp_digit* t1 = t;
sp_digit* t2 = t + 2*10;
sp_digit t1[2*10];
sp_digit t2[2*10];
/* Put point to double into result */
if (r != p)
@ -676,16 +673,14 @@ static void sp_256_proj_point_dbl_10(sp_point* r, sp_point* p, sp_digit* t)
* r Result of addition.
* p Frist point to add.
* q Second point to add.
* t Temporary ordinate data.
*/
static void sp_256_proj_point_add_10(sp_point* r, sp_point* p, sp_point* q,
sp_digit* t)
static void sp_256_proj_point_add_10(sp_point* r, sp_point* p, sp_point* q)
{
sp_digit* t1 = t;
sp_digit* t2 = t + 2*10;
sp_digit* t3 = t + 4*10;
sp_digit* t4 = t + 6*10;
sp_digit* t5 = t + 8*10;
sp_digit t1[2*10];
sp_digit t2[2*10];
sp_digit t3[2*10];
sp_digit t4[2*10];
sp_digit t5[2*10];
/* Ensure only the first point is the same as the result. */
if (q == r) {
@ -701,7 +696,7 @@ static void sp_256_proj_point_add_10(sp_point* r, sp_point* p, sp_point* q,
&& sp_256_cmp_equal_10(p->z, q->z)
&& (sp_256_cmp_equal_10(p->y, q->y) || sp_256_cmp_equal_10(p->y, t1))
) {
sp_256_proj_point_dbl_10(r, p, t);
sp_256_proj_point_dbl_10(r, p);
}
else {
sp_point tp;
@ -762,7 +757,6 @@ static void sp_256_ecc_mulmod_10(sp_point* r, const sp_point* g, const sp_digit*
{
enum { map = 1 }; /* we always convert result to affine coordinates */
sp_point t[3];
sp_digit tmp[2 * 10 * 5];
sp_digit n;
int i;
int c, y;
@ -791,20 +785,17 @@ static void sp_256_ecc_mulmod_10(sp_point* r, const sp_point* g, const sp_digit*
y = (n >> 25) & 1;
n <<= 1;
//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);
sp_256_proj_point_add_10(&t[y^1], &t[0], &t[1]);
memcpy(&t[2], &t[y], sizeof(sp_point));
sp_256_proj_point_dbl_10(&t[2], &t[2], tmp);
sp_256_proj_point_dbl_10(&t[2], &t[2]);
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]);
else
memcpy(r, &t[0], sizeof(sp_point));
memset(tmp, 0, sizeof(tmp)); //paranoia
memset(t, 0, sizeof(t)); //paranoia
}