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Add basic shuffling and masking to CCM operations

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Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
This commit is contained in:
Andrzej Kurek 2020-10-30 12:18:21 +01:00
parent 938d4d3fa3
commit 8bef87ee5e
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GPG key ID: 89A90840DC388527
1 changed files with 50 additions and 4 deletions
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54
library/ccm.c
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@ -113,6 +113,41 @@ void mbedtls_ccm_free( mbedtls_ccm_context *ctx )
mbedtls_platform_zeroize( ctx, sizeof( mbedtls_ccm_context ) ); mbedtls_platform_zeroize( ctx, sizeof( mbedtls_ccm_context ) );
} }
/* Durstenfeld's version of Fisher-Yates shuffle */
static void mbedtls_generate_permutation( unsigned char* table, size_t size )
{
size_t i, j;
for( i = 0; i < size; i++ )
{
table[i] = (unsigned char) i;
}
if( size < 2 )
{
return;
}
for( i = size - 1; i > 0; i-- )
{
unsigned char tmp;
j = mbedtls_platform_random_uint32() % ( i + 1 );
tmp = table[i];
table[i] = table[j];
table[j] = tmp;
}
}
static void mbedtls_generate_masks( unsigned char* table, size_t size )
{
size_t i;
for( i = 0; i < size; i++ )
{
table[i] = mbedtls_platform_random_uint32() % ( 256 );
}
}
/* /*
* Macros for common operations. * Macros for common operations.
* Results in smaller compiled code than static inline functions. * Results in smaller compiled code than static inline functions.
@ -123,8 +158,11 @@ void mbedtls_ccm_free( mbedtls_ccm_context *ctx )
* (Always using b as the source helps the compiler optimise a bit better.) * (Always using b as the source helps the compiler optimise a bit better.)
*/ */
#define UPDATE_CBC_MAC \ #define UPDATE_CBC_MAC \
mbedtls_generate_permutation( perm_table, 16 ); \
for( i = 0; i < 16; i++ ) \ for( i = 0; i < 16; i++ ) \
y[i] ^= b[i]; \ { \
y[perm_table[i]] ^= b[perm_table[i]]; \
} \
\ \
if( ( ret = mbedtls_cipher_update( &ctx->cipher_ctx, y, 16, y, &olen ) ) != 0 ) \ if( ( ret = mbedtls_cipher_update( &ctx->cipher_ctx, y, 16, y, &olen ) ) != 0 ) \
return( ret ); return( ret );
@ -134,17 +172,23 @@ void mbedtls_ccm_free( mbedtls_ccm_context *ctx )
* Warning: using b for temporary storage! src and dst must not be b! * Warning: using b for temporary storage! src and dst must not be b!
* This avoids allocating one more 16 bytes buffer while allowing src == dst. * This avoids allocating one more 16 bytes buffer while allowing src == dst.
*/ */
#define CTR_CRYPT( dst, src, len ) \ #define CTR_CRYPT( dst, src, len ) \
do \ do \
{ \ { \
mbedtls_generate_permutation( perm_table, len ); \
mbedtls_generate_masks( mask_table, len ); \
if( ( ret = mbedtls_cipher_update( &ctx->cipher_ctx, ctr, \ if( ( ret = mbedtls_cipher_update( &ctx->cipher_ctx, ctr, \
16, b, &olen ) ) != 0 ) \ 16, b, &olen ) ) != 0 ) \
{ \ { \
return( ret ); \ return( ret ); \
} \ } \
\ \
for( i = 0; i < (len); i++ ) \ for( i = 0; i < len; i++ ) \
(dst)[i] = (src)[i] ^ b[i]; \ { \
(dst)[perm_table[i]] = (src)[perm_table[i]] ^ mask_table[perm_table[i]];\
(dst)[perm_table[i]] ^= b[perm_table[i]]; \
(dst)[perm_table[i]] ^= mask_table[perm_table[i]]; \
} \
} while( 0 ) } while( 0 )
/* /*
@ -163,6 +207,8 @@ static int ccm_auth_crypt( mbedtls_ccm_context *ctx, int mode, size_t length,
unsigned char b[16]; unsigned char b[16];
unsigned char y[16]; unsigned char y[16];
unsigned char ctr[16]; unsigned char ctr[16];
unsigned char perm_table[16];
unsigned char mask_table[16];
const unsigned char *src; const unsigned char *src;
unsigned char *dst; unsigned char *dst;