[PATCH 2/3] mpi: fix missing fields in an empty point and the mpi_clear requires a non-empty argument.

[Jussi Kivilinna]

Hello,

On 22.12.2019 11.15, Tianjia Zhang via Gcrypt-devel wrote:
> * mpi/ec.c (_gcry_mpi_point_set): Assign value to missing fields.
> 
> The problem is triggered when using the following code by
> mpi_ec_get_elliptic_curve:
> 
>   elliptic_curve_t E;
>   memset (&E, 0, sizeof E);
>   mpi_point_set (&E->G, G->x, G->y, G->z);

I think this issue should be fixed in 'mpi_ec_get_elliptic_curve' rather than in '_gcry_mpi_point_set'. '_gcry_mpi_point_set' expects POINT to be either properly initialized point structure or NULL. 'mpi_ec_get_elliptic_curve' however is passing point structure that has not been initialized with '_gcry_mpi_point_init'.

So, I'd change 

            {
              mpi_point_set (&E->G, G->x, G->y, G->z);
              mpi_point_set (G, NULL, NULL, NULL);
              mpi_point_release (G);
            }

to

            {
              _gcry_mpi_point_init (&E->G);
              mpi_point_set (&E->G, G->x, G->y, G->z);
              mpi_point_set (G, NULL, NULL, NULL);
              mpi_point_release (G);
            }

-Jussi

> 
> Signed-off-by: Tianjia Zhang <tianjia.zhang at linux.alibaba.com>
> ---
>  mpi/ec.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/mpi/ec.c b/mpi/ec.c
> index d4c4f953..94d93354 100644
> --- a/mpi/ec.c
> +++ b/mpi/ec.c
> @@ -224,16 +224,16 @@ _gcry_mpi_point_set (mpi_point_t point,
>      point = mpi_point_new (0);
>  
>    if (x)
> -    mpi_set (point->x, x);
> -  else
> +    point->x = mpi_set (point->x, x);
> +  else if (point->x)
>      mpi_clear (point->x);
>    if (y)
> -    mpi_set (point->y, y);
> -  else
> +    point->y = mpi_set (point->y, y);
> +  else if (point->y)
>      mpi_clear (point->y);
>    if (z)
> -    mpi_set (point->z, z);
> -  else
> +    point->z = mpi_set (point->z, z);
> +  else if (point->z)
>      mpi_clear (point->z);
>  
>    return point;
>