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Have mbedtls_mpi_core_exp_mod() take a temporary instead of allocating memory

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Last PR needed for #6293

Signed-off-by: Tom Cosgrove <tom.cosgrove@arm.com>
This commit is contained in:
Tom Cosgrove
2022-12-06 14:37:18 +00:00
parent 21d459d26a
commit 0a0ddedfb7
3 changed files with 92 additions and 53 deletions
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57
library/bignum_core.c
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@ -596,6 +596,19 @@ static size_t exp_mod_get_window_size( size_t Ebits )
return( wsize );
}
size_t mbedtls_mpi_core_exp_mod_working_limbs( size_t AN_limbs, size_t E_limbs )
{
const size_t wsize = exp_mod_get_window_size( E_limbs * biL );
const size_t welem = ( (size_t) 1 ) << wsize;
/* How big does each part of the working memory pool need to be? */
const size_t table_limbs = welem * AN_limbs;
const size_t select_limbs = AN_limbs;
const size_t temp_limbs = 2 * AN_limbs + 1;
return( table_limbs + select_limbs + temp_limbs );
}
static void exp_mod_precompute_window( const mbedtls_mpi_uint *A,
const mbedtls_mpi_uint *N,
size_t AN_limbs,
@ -636,35 +649,27 @@ static void exp_mod_precompute_window( const mbedtls_mpi_uint *A,
* (The difference is that the body in our loop processes a single bit instead
* of a full window.)
*/
int mbedtls_mpi_core_exp_mod( mbedtls_mpi_uint *X,
const mbedtls_mpi_uint *A,
const mbedtls_mpi_uint *N,
size_t AN_limbs,
const mbedtls_mpi_uint *E,
size_t E_limbs,
const mbedtls_mpi_uint *RR )
void mbedtls_mpi_core_exp_mod( mbedtls_mpi_uint *X,
const mbedtls_mpi_uint *A,
const mbedtls_mpi_uint *N,
size_t AN_limbs,
const mbedtls_mpi_uint *E,
size_t E_limbs,
const mbedtls_mpi_uint *RR,
mbedtls_mpi_uint *T )
{
const size_t wsize = exp_mod_get_window_size( E_limbs * biL );
const size_t welem = ( (size_t) 1 ) << wsize;
/* Allocate memory pool and set pointers to parts of it */
const size_t table_limbs = welem * AN_limbs;
const size_t temp_limbs = 2 * AN_limbs + 1;
const size_t select_limbs = AN_limbs;
const size_t total_limbs = table_limbs + temp_limbs + select_limbs;
/* This is how we will use the temporary storage T, which must have space
* for table_limbs, select_limbs and (2 * AN_limbs + 1) for montmul. */
const size_t table_limbs = welem * AN_limbs;
const size_t select_limbs = AN_limbs;
/* heap allocated memory pool */
mbedtls_mpi_uint *mempool =
mbedtls_calloc( total_limbs, sizeof(mbedtls_mpi_uint) );
if( mempool == NULL )
{
return( MBEDTLS_ERR_MPI_ALLOC_FAILED );
}
/* pointers to temporaries within memory pool */
mbedtls_mpi_uint *const Wtable = mempool;
mbedtls_mpi_uint *const Wselect = Wtable + table_limbs;
mbedtls_mpi_uint *const temp = Wselect + select_limbs;
/* Pointers to specific parts of the temporary working memory pool */
mbedtls_mpi_uint *const Wtable = T;
mbedtls_mpi_uint *const Wselect = Wtable + table_limbs;
mbedtls_mpi_uint *const temp = Wselect + select_limbs;
/*
* Window precomputation
@ -731,10 +736,6 @@ int mbedtls_mpi_core_exp_mod( mbedtls_mpi_uint *X,
}
}
while( ! ( E_bit_index == 0 && E_limb_index == 0 ) );
mbedtls_platform_zeroize( mempool, total_limbs * sizeof(mbedtls_mpi_uint) );
mbedtls_free( mempool );
return( 0 );
}
/* END MERGE SLOT 1 */