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Merge pull request #1166 from daverodgman/ct-cmac

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Use ct module from cmac
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Tom Cosgrove 2024-01-30 09:54:02 +01:00 committed by GitHub
commit f35d24479e
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1 changed files with 4 additions and 16 deletions
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20
library/cmac.c
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@ -34,6 +34,7 @@
#include "mbedtls/platform_util.h"
#include "mbedtls/error.h"
#include "mbedtls/platform.h"
#include "constant_time_internal.h"
#include <string.h>
@ -57,7 +58,7 @@ static int cmac_multiply_by_u(unsigned char *output,
{
const unsigned char R_128 = 0x87;
const unsigned char R_64 = 0x1B;
unsigned char R_n, mask;
unsigned char R_n;
unsigned char overflow = 0x00;
int i;
@ -74,21 +75,8 @@ static int cmac_multiply_by_u(unsigned char *output,
overflow = input[i] >> 7;
}
/* mask = ( input[0] >> 7 ) ? 0xff : 0x00
* using bit operations to avoid branches */
/* MSVC has a warning about unary minus on unsigned, but this is
* well-defined and precisely what we want to do here */
#if defined(_MSC_VER)
#pragma warning( push )
#pragma warning( disable : 4146 )
#endif
mask = -(input[0] >> 7);
#if defined(_MSC_VER)
#pragma warning( pop )
#endif
output[blocksize - 1] ^= R_n & mask;
R_n = (unsigned char) mbedtls_ct_uint_if_else_0(mbedtls_ct_bool(input[0] >> 7), R_n);
output[blocksize - 1] ^= R_n;
return 0;
}