Mailing List Archive: [PATCH 2/3] mpi: fix missing fields in an empty point and the mpi

* 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);

Signed-off-by: Tianjia Zhang <tianjia.zhang@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;
--
2.17.1

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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@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;
>

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