Fix ecdh_get_params with mismatching group
If mbedtls_ecdh_get_params is called with keys belonging to
different groups, make it return an error the second time, rather than
silently interpret the first key as being on the second curve.
This makes the non-regression test added by the previous commit pass.
diff --git a/library/ecdh.c b/library/ecdh.c
index 61380b6..75630bd 100644
--- a/library/ecdh.c
+++ b/library/ecdh.c
@@ -179,8 +179,20 @@
{
int ret;
- if( ( ret = mbedtls_ecp_group_copy( &ctx->grp, &key->grp ) ) != 0 )
- return( ret );
+ if( ctx->grp.id == MBEDTLS_ECP_DP_NONE )
+ {
+ /* This is the first call to get_params(). Copy the group information
+ * into the context. */
+ if( ( ret = mbedtls_ecp_group_copy( &ctx->grp, &key->grp ) ) != 0 )
+ return( ret );
+ }
+ else
+ {
+ /* This is not the first call to get_params(). Check that the group
+ * is the same as the first time. */
+ if( ctx->grp.id != key->grp.id )
+ return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
+ }
/* If it's not our key, just import the public part as Qp */
if( side == MBEDTLS_ECDH_THEIRS )