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Merge pull request #7579 from daverodgman/safer-ct-asm

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Arm assembly implementation of constant time primitives
This commit is contained in:
Dave Rodgman
2023-08-28 08:26:29 +00:00
committed by GitHub
parent 8ca2041145 e20d688463
commit d395590597
4 changed files with 170 additions and 4 deletions
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13
library/constant_time.c
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@ -150,8 +150,13 @@ void mbedtls_ct_memcpy_if(mbedtls_ct_condition_t condition,
const unsigned char *src2,
size_t len)
{
#if defined(MBEDTLS_CT_SIZE_64)
const uint64_t mask = (uint64_t) condition;
const uint64_t not_mask = (uint64_t) ~mbedtls_ct_compiler_opaque(condition);
#else
const uint32_t mask = (uint32_t) condition;
const uint32_t not_mask = (uint32_t) ~mbedtls_ct_compiler_opaque(condition);
#endif
/* If src2 is NULL, setup src2 so that we read from the destination address.
*
@ -165,11 +170,19 @@ void mbedtls_ct_memcpy_if(mbedtls_ct_condition_t condition,
/* dest[i] = c1 == c2 ? src[i] : dest[i] */
size_t i = 0;
#if defined(MBEDTLS_EFFICIENT_UNALIGNED_ACCESS)
#if defined(MBEDTLS_CT_SIZE_64)
for (; (i + 8) <= len; i += 8) {
uint64_t a = mbedtls_get_unaligned_uint64(src1 + i) & mask;
uint64_t b = mbedtls_get_unaligned_uint64(src2 + i) & not_mask;
mbedtls_put_unaligned_uint64(dest + i, a | b);
}
#else
for (; (i + 4) <= len; i += 4) {
uint32_t a = mbedtls_get_unaligned_uint32(src1 + i) & mask;
uint32_t b = mbedtls_get_unaligned_uint32(src2 + i) & not_mask;
mbedtls_put_unaligned_uint32(dest + i, a | b);
}
#endif /* defined(MBEDTLS_CT_SIZE_64) */
#endif /* MBEDTLS_EFFICIENT_UNALIGNED_ACCESS */
for (; i < len; i++) {
dest[i] = (src1[i] & mask) | (src2[i] & not_mask);