EC Oddity

[Bill Colvin]

I have been doing some EC test code with the Sept. 5 snapshot and have
observed something that I find a little odd.  So I thought I would
mention it so someone could take a look to see if it is a bug or what is
supposed to occur.

 

I have a PEM file with an EC private key.

I want to create an ephemeral private key for the same group.

So my code fragments are as follows:

 

    EC_KEY          *ecc_A=NULL;

    EC_KEY          *ecc_E=NULL;

    const EC_GROUP  *group=NULL;

 

    ecc_A = PEM_read_bio_ECPrivateKey( bio_in, NULL, NULL, NULL );

 

    group = EC_KEY_get0_group(ecc_A);

    ecc_E = EC_KEY_new();

    EC_KEY_set_group( ecc_E, group );

    EC_KEY_generate_key( ecc_E );

 

Now the oddity occurs when I free the objects.  If I have:

 

    if( ecc_E != NULL )     {EC_KEY_free( ecc_E ); printf("ecc_E
freed\n");}

    if( ecc_A != NULL )     {EC_KEY_free( ecc_A ); printf("ecc_A
freed\n");}

    if( group != NULL )     {EC_GROUP_free( (EC_GROUP*)group );
printf("group freed\n");}

 

I see the messages:

 

            ecc_E freed

            ecc_A freed

            Killed

 

If I reverse the order of the last two:

 

    if( ecc_E != NULL )     {EC_KEY_free( ecc_E ); printf("ecc_E
freed\n");}

    if( group != NULL )     {EC_GROUP_free( (EC_GROUP*)group);
printf("group freed\n");}

    if( ecc_A != NULL )     {EC_KEY_free( ecc_A ); printf("ecc_A
freed\n");}

 

I see the messages:

 

            ecc_E freed

            group freed

            Killed

 

It is almost as if the group object and the ec key object are combined,
such that freeing one automatically frees the other.

 

Is this the way it is supposed to be?

 

Also when doing the group free, I had to add the cast to prevent
compiler warnings.  It seems that EC_GROUP is inconsistently defined in
the include files between its various uses.  Is this also expected?

 

Bill