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Start introducing optblockers to prevent unwanted conditional jumps

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This commit is contained in:
Frank Denis 2024-08-01 14:25:32 +02:00
parent fb80cbfa59
commit 0217d07326
2 changed files with 6 additions and 2 deletions
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4
src/libsodium/crypto_core/ed25519/ref10/ed25519_ref10.c
View File

@ -288,6 +288,8 @@ slide_vartime(signed char *r, const unsigned char *a)
}
}
static volatile unsigned char optblocker_u8;
int
ge25519_frombytes(ge25519_p3 *h, const unsigned char *s)
{
@ -320,7 +322,7 @@ ge25519_frombytes(ge25519_p3 *h, const unsigned char *s)
fe25519_cmov(h->X, x_sqrtm1, 1 - has_m_root);
fe25519_neg(negx, h->X);
fe25519_cmov(h->X, negx, fe25519_isnegative(h->X) ^ (s[31] >> 7));
fe25519_cmov(h->X, negx, fe25519_isnegative(h->X) ^ (((s[31] >> 5) ^ optblocker_u8) >> 2));
fe25519_mul(h->T, h->X, h->Y);
return (has_m_root | has_p_root) - 1;

4
src/libsodium/crypto_onetimeauth/poly1305/sse2/poly1305_sse2.c
View File

@ -194,6 +194,8 @@ poly1305_init_ext(poly1305_state_internal_t *st, const unsigned char key[32],
st->leftover = 0U;
}
static volatile uint64_t optblocker_u64;
static POLY1305_NOINLINE void
poly1305_blocks(poly1305_state_internal_t *st, const unsigned char *m,
unsigned long long bytes)
@ -745,7 +747,7 @@ poly1305_blocks(poly1305_state_internal_t *st, const unsigned char *m,
g1 &= 0xfffffffffff;
g2 = h2 + c - ((uint64_t) 1 << 42);
c = (g2 >> 63) - 1;
c = (((g2 >> 61) ^ optblocker_u64) >> 2) - 1;
nc = ~c;
h0 = (h0 & nc) | (g0 & c);
h1 = (h1 & nc) | (g1 & c);