Re: Query related to SSL_CTX_set_msg_callback_arg

"J. J. Farrell" <jeremy.farrell@xxxxxxxxxx> · Mon, 10 Jun 2019 15:21:29 +0100

    On 10/06/2019 11:05, Jeremy Harris wrote:

      On 10/06/2019 09:32, Viktor Dukhovni wrote:

        On Mon, Jun 10, 2019 at 07:16:26AM +0000, shalu dhamija via openssl-users wrote:

          Actually while setting the callback, we can not pass the user-defined/application data.

        You can however attach it to the SSL connection handle as "ex_data":

      I fail to see the point.  You don't need to pass the data, only a
pointer to the data.

    Well ... obviously ...

      Any time you set the callback, you can set the callback-arg.

    How? As Shalu quoted, the prototype of the call to set the callback
    is

    void SSL_CTX_sess_set_new_cb(SSL_CTX *ctx,
                              int (*new_session_cb)(SSL *, SSL_SESSION *));

    How do we specify a user-defined callback data pointer in that call?

      When the callback is called it is given the arg;

    Where? According to the prototype which Shalu quoted the callback
    gets just a pointer to an SSL and a pointer to an SSL_SESSION;
    neither of those is a user-defined data pointer.

      if the arg was a pointer you can deref to get the data... which could
have been manipulated as needed in the interim.

Using the ex_data facility is not needed.

    I may be missing something, but I can't see any other way to do it.

    -- 
J. J. Farrell
Not speaking for Oracle