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Simplify mbedtls_ct_memcmp_partial

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Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
This commit is contained in:
Dave Rodgman 2023-09-19 14:13:41 +01:00
parent 66d6ac92e6
commit c2630fac52
1 changed files with 4 additions and 2 deletions
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6
library/constant_time.c
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@ -158,13 +158,15 @@ int mbedtls_ct_memcmp_partial(const void *a,
for (size_t i = 0; i < n; i++) {
unsigned char x = A[i], y = B[i];
int d = x ^ y;
unsigned int d = x ^ y;
mbedtls_ct_condition_t valid = mbedtls_ct_bool_and(mbedtls_ct_uint_ge(i, skip_head),
mbedtls_ct_uint_lt(i, valid_end));
diff |= mbedtls_ct_uint_if_else_0(valid, d);
}
return (int) ((diff & 0xffff) | (diff >> 16));
/* Since we go byte-by-byte, the only bits set will be in the bottom 8 bits, so the
* cast from uint to int is safe. */
return (int) diff;
}
#endif