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- Fixed incorrect handling of negative first input value in mpi_mod_mpi() and mpi_mod_int(). Resulting change also affects mpi_write_string() (found by code coverage tests).

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This commit is contained in:
Paul Bakker 2009-06-23 19:46:08 +00:00
parent 1ef7a53fa2
commit ce40a6d21d
3 changed files with 25 additions and 3 deletions
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16
library/bignum.c
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@ -382,6 +382,10 @@ int mpi_write_string( mpi *X, int radix, char *s, int *slen )
else
{
MPI_CHK( mpi_copy( &T, X ) );
if( T.s == -1 )
T.s = 1;
MPI_CHK( mpi_write_hlp( &T, radix, &p ) );
}
@ -1180,6 +1184,9 @@ int mpi_mod_mpi( mpi *R, mpi *A, mpi *B )
{
int ret;
if( mpi_cmp_int( B, 0 ) < 0 )
return POLARSSL_ERR_MPI_NEGATIVE_VALUE;
MPI_CHK( mpi_div_mpi( NULL, R, A, B ) );
while( mpi_cmp_int( R, 0 ) < 0 )
@ -1205,7 +1212,7 @@ int mpi_mod_int( t_int *r, mpi *A, int b )
return( POLARSSL_ERR_MPI_DIVISION_BY_ZERO );
if( b < 0 )
b = -b;
return POLARSSL_ERR_MPI_NEGATIVE_VALUE;
/*
* handle trivial cases
@ -1238,6 +1245,13 @@ int mpi_mod_int( t_int *r, mpi *A, int b )
y -= z * b;
}
/*
* If A is negative, then the current y represents a negative value.
* Flipping it to the positive side.
*/
if( A->s < 0 && y != 0 )
y = b - y;
*r = y;
return( 0 );