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Prevent possible optimizations in sodium_compare()

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Frank Denis
2017-04-21 00:30:19 +02:00
parent 4809639ae1
commit 68d576cc95
1 changed files with 8 additions and 5 deletions
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src/libsodium/sodium/utils.c
+8 -5
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@@ -160,9 +160,10 @@ sodium_compare(const unsigned char *b1_, const unsigned char *b2_, size_t len)
const volatile unsigned char *volatile b2 =
(const volatile unsigned char *volatile) b2_;
#endif
unsigned char gt = 0U;
unsigned char eq = 1U;
size_t i;
size_t i;
volatile unsigned char gt = 0U;
volatile unsigned char eq = 1U;
volatile uint16_t x1, x2;
#if HAVE_WEAK_SYMBOLS
_sodium_dummy_symbol_to_prevent_compare_lto(b1, b2, len);
@@ -170,8 +171,10 @@ sodium_compare(const unsigned char *b1_, const unsigned char *b2_, size_t len)
i = len;
while (i != 0U) {
i--;
gt |= ((b2[i] - b1[i]) >> 8) & eq;
eq &= ((b2[i] ^ b1[i]) - 1) >> 8;
x1 = b1[i];
x2 = b2[i];
gt |= ((x2 - x1) >> 8) & eq;
eq &= ((x2 ^ x1) - 1) >> 8;
}
return (int) (gt + gt + eq) - 1;
}