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Change mpi_safe_cond_assign() for more const-ness

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Manuel Pégourié-Gonnard
2013-11-25 18:28:53 +01:00
parent 3e3d2b818c
commit 96c7a92b08
3 changed files with 9 additions and 8 deletions
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11
library/bignum.c
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@ -206,8 +206,10 @@ void mpi_swap( mpi *X, mpi *Y )
/*
* Conditionally assign X = Y, without leaking information
* about whether the assignment was made or not.
* (Leaking information about the respective sizes of X and Y is ok however.)
*/
int mpi_safe_cond_assign( mpi *X, mpi *Y, unsigned char assign )
int mpi_safe_cond_assign( mpi *X, const mpi *Y, unsigned char assign )
{
int ret = 0;
size_t i;
@ -215,16 +217,15 @@ int mpi_safe_cond_assign( mpi *X, mpi *Y, unsigned char assign )
if( assign * ( 1 - assign ) != 0 )
return( POLARSSL_ERR_MPI_BAD_INPUT_DATA );
/* Make sure both MPIs have the same size */
if( X->n > Y->n )
MPI_CHK( mpi_grow( Y, X->n ) );
if( Y->n > X->n )
MPI_CHK( mpi_grow( X, Y->n ) );
/* Do the conditional assign safely */
X->s = X->s * (1 - assign) + Y->s * assign;
for( i = 0; i < X->n; i++ )
for( i = 0; i < Y->n; i++ )
X->p[i] = X->p[i] * (1 - assign) + Y->p[i] * assign;
for( ; i < X->n; i++ )
X->p[i] *= (1 - assign);
cleanup:
return( ret );