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Use new interface in mbedtls_ct_memmove_left

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Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
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Dave Rodgman
2023-05-17 12:20:11 +01:00
parent 6cee26db16
commit 15c142b58d
1 changed files with 7 additions and 13 deletions
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18
library/constant_time.c
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@@ -327,26 +327,20 @@ void mbedtls_ct_mpi_uint_cond_assign(size_t n,
#if defined(MBEDTLS_PKCS1_V15) && defined(MBEDTLS_RSA_C) && !defined(MBEDTLS_RSA_ALT) #if defined(MBEDTLS_PKCS1_V15) && defined(MBEDTLS_RSA_C) && !defined(MBEDTLS_RSA_ALT)
void mbedtls_ct_memmove_left(void *start, void mbedtls_ct_memmove_left(void *start, size_t total, size_t offset)
size_t total,
size_t offset)
{ {
volatile unsigned char *buf = start; volatile unsigned char *buf = start;
size_t i, n; for (size_t i = 0; i < total; i++) {
if (total == 0) { mbedtls_ct_condition_t no_op = mbedtls_ct_bool_gt(total - offset, i);
return;
}
for (i = 0; i < total; i++) {
unsigned no_op = mbedtls_ct_size_gt(total - offset, i);
/* The first `total - offset` passes are a no-op. The last /* The first `total - offset` passes are a no-op. The last
* `offset` passes shift the data one byte to the left and * `offset` passes shift the data one byte to the left and
* zero out the last byte. */ * zero out the last byte. */
for (n = 0; n < total - 1; n++) { for (size_t n = 0; n < total - 1; n++) {
unsigned char current = buf[n]; unsigned char current = buf[n];
unsigned char next = buf[n+1]; unsigned char next = buf[n+1];
buf[n] = mbedtls_ct_uint_if(no_op, current, next); buf[n] = mbedtls_ct_uint_if_new(no_op, current, next);
} }
buf[total-1] = mbedtls_ct_uint_if(no_op, buf[total-1], 0); buf[total-1] = mbedtls_ct_uint_if0(no_op, buf[total-1]);
} }
} }