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wolfcrypt/src/ge_448.c: redo small stack refactor of ge448_double_scalarmult_vartime(), so that when -UWOLFSSL_SMALL_STACK, code is effectively unchanged.

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This commit is contained in:
Daniel Pouzzner
2020-09-03 00:01:33 -05:00
parent f4981d4c91
commit 76cba38971
1 changed files with 40 additions and 37 deletions
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77
wolfcrypt/src/ge_448.c
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@ -10655,7 +10655,7 @@ static void slide(int8_t *r, const uint8_t *a)
}
}
/* Perform a scalar multplication of the base point and public point.
/* Perform a scalar multiplication of the base point and public point.
* r = a * p + b * base
* Uses a sliding window of 5 bits.
* Not constant time.
@ -10667,25 +10667,24 @@ int ge448_double_scalarmult_vartime(ge448_p2 *r, const uint8_t *a,
const ge448_p2 *p, const uint8_t *b)
{
#define GE448_WINDOW_BUF_SIZE 448
#if !defined(WOLFSSL_SMALL_STACK) || (defined(WOLFSSL_NO_MALLOC) && !defined(XMALLOC_USER))
int8_t aslide[GE448_WINDOW_BUF_SIZE];
int8_t bslide[GE448_WINDOW_BUF_SIZE];
ge448_p2 pi[16]; /* p,3p,..,31p */
ge448_p2 p2;
int i;
#define PI_PTR(pi) (&(pi))
#else
int8_t *aslide = NULL;
int8_t *bslide = NULL;
ge448_p2 *pi[16]; /* p,3p,..,31p */
ge448_p2 *p2 = NULL;
int i;
int ret;
int i, ret;
#if defined(WOLFSSL_NO_MALLOC) && !defined(XMALLOC_USER)
int8_t aslide_buf[GE448_WINDOW_BUF_SIZE];
int8_t bslide_buf[GE448_WINDOW_BUF_SIZE];
ge448_p2 pi_buf[16];
ge448_p2 p2_buf;
#define PI_PTR(pi) (pi)
aslide = &aslide_buf[0];
bslide = &bslide_buf[0];
for (i = 0; i < (int)(sizeof pi / sizeof pi[0]); ++i)
pi[i] = &pi_buf[i];
p2 = &p2_buf;
#else
XMEMSET(pi, 0, sizeof pi);
aslide = (int8_t *)XMALLOC(GE448_WINDOW_BUF_SIZE, NULL, DYNAMIC_TYPE_TMP_BUFFER);
if (! aslide) {
@ -10714,25 +10713,25 @@ int ge448_double_scalarmult_vartime(ge448_p2 *r, const uint8_t *a,
slide(aslide, a);
slide(bslide, b);
fe448_copy(pi[0]->X, p->X);
fe448_copy(pi[0]->Y, p->Y);
fe448_copy(pi[0]->Z, p->Z);
ge448_dbl(p2, p);
ge448_add(pi[1], p2, pi[0]);
ge448_add(pi[2], p2, pi[1]);
ge448_add(pi[3], p2, pi[2]);
ge448_add(pi[4], p2, pi[3]);
ge448_add(pi[5], p2, pi[4]);
ge448_add(pi[6], p2, pi[5]);
ge448_add(pi[7], p2, pi[6]);
ge448_add(pi[8], p2, pi[7]);
ge448_add(pi[9], p2, pi[8]);
ge448_add(pi[10], p2, pi[9]);
ge448_add(pi[11], p2, pi[10]);
ge448_add(pi[12], p2, pi[11]);
ge448_add(pi[13], p2, pi[12]);
ge448_add(pi[14], p2, pi[13]);
ge448_add(pi[15], p2, pi[14]);
fe448_copy(PI_PTR(pi[0])->X, p->X);
fe448_copy(PI_PTR(pi[0])->Y, p->Y);
fe448_copy(PI_PTR(pi[0])->Z, p->Z);
ge448_dbl(PI_PTR(p2), p);
ge448_add(PI_PTR(pi[1]), PI_PTR(p2), PI_PTR(pi[0]));
ge448_add(PI_PTR(pi[2]), PI_PTR(p2), PI_PTR(pi[1]));
ge448_add(PI_PTR(pi[3]), PI_PTR(p2), PI_PTR(pi[2]));
ge448_add(PI_PTR(pi[4]), PI_PTR(p2), PI_PTR(pi[3]));
ge448_add(PI_PTR(pi[5]), PI_PTR(p2), PI_PTR(pi[4]));
ge448_add(PI_PTR(pi[6]), PI_PTR(p2), PI_PTR(pi[5]));
ge448_add(PI_PTR(pi[7]), PI_PTR(p2), PI_PTR(pi[6]));
ge448_add(PI_PTR(pi[8]), PI_PTR(p2), PI_PTR(pi[7]));
ge448_add(PI_PTR(pi[9]), PI_PTR(p2), PI_PTR(pi[8]));
ge448_add(PI_PTR(pi[10]), PI_PTR(p2), PI_PTR(pi[9]));
ge448_add(PI_PTR(pi[11]), PI_PTR(p2), PI_PTR(pi[10]));
ge448_add(PI_PTR(pi[12]), PI_PTR(p2), PI_PTR(pi[11]));
ge448_add(PI_PTR(pi[13]), PI_PTR(p2), PI_PTR(pi[12]));
ge448_add(PI_PTR(pi[14]), PI_PTR(p2), PI_PTR(pi[13]));
ge448_add(PI_PTR(pi[15]), PI_PTR(p2), PI_PTR(pi[14]));
ge448_0(r);
@ -10747,9 +10746,9 @@ int ge448_double_scalarmult_vartime(ge448_p2 *r, const uint8_t *a,
ge448_dbl(r, r);
if (aslide[i] > 0)
ge448_add(r, r, pi[aslide[i]/2]);
ge448_add(r, r, PI_PTR(pi[aslide[i]/2]));
else if (aslide[i] < 0)
ge448_sub(r, r ,pi[(-aslide[i])/2]);
ge448_sub(r, r ,PI_PTR(pi[(-aslide[i])/2]));
if (bslide[i] > 0)
ge448_madd(r, r, &base_i[bslide[i]/2]);
@ -10757,9 +10756,9 @@ int ge448_double_scalarmult_vartime(ge448_p2 *r, const uint8_t *a,
ge448_msub(r, r, &base_i[(-bslide[i])/2]);
}
#if defined(WOLFSSL_SMALL_STACK) && !(defined(WOLFSSL_NO_MALLOC) && !defined(XMALLOC_USER))
ret = 0;
#if !defined(WOLFSSL_NO_MALLOC) || defined(XMALLOC_USER)
out:
if (aslide)
@ -10772,9 +10771,13 @@ int ge448_double_scalarmult_vartime(ge448_p2 *r, const uint8_t *a,
}
if (p2)
XFREE(p2, NULL, DYNAMIC_TYPE_TMP_BUFFER);
#endif
return ret;
#else
return 0;
#endif
#undef PI_PTR
#undef GE448_WINDOW_BUF_SIZE
}