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ct: Be cautious and use volatile trick in more "conditional" paths

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- secp256k1_scalar_cadd_bit
 - secp256k1_modinvXX_normalize_YY
 - secp256k1_modinvXX_divsteps_ZZ
 - ECMULT_CONST_TABLE_GET_GE

Even though those code loations are not problematic right now
(with current compilers).
This commit is contained in:
Tim Ruffing
2023-05-10 16:25:37 +02:00
parent 5fb336f9ce
commit 17fa21733a
5 changed files with 40 additions and 32 deletions
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2
src/ecmult_const_impl.h
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@@ -29,7 +29,7 @@ static void secp256k1_ecmult_odd_multiples_table_globalz_windowa(secp256k1_ge *p
#define ECMULT_CONST_TABLE_GET_GE(r,pre,n,w) do { \
int m = 0; \
/* Extract the sign-bit for a constant time absolute-value. */ \
int mask = (n) >> (sizeof(n) * CHAR_BIT - 1); \
int volatile mask = (n) >> (sizeof(n) * CHAR_BIT - 1); \
int abs_n = ((n) + mask) ^ mask; \
int idx_n = abs_n >> 1; \
secp256k1_fe neg_y; \