[openssl-dev] How to do reneg with client certs in 1.1.0 API

[Matt Caswell]

On 08/02/16 14:36, Viktor Dukhovni wrote:
> 
>> On Feb 8, 2016, at 9:26 AM, Matt Caswell <matt at openssl.org> wrote:
>>
>> SSL_renegotiate(ssl);
>> SSL_do_handshake(ssl);
>> do {
>>    read_some_app_data();
>>    if(no_client_cert_yet()) {
>>        discard_app_data();
>>    }
>> } while(no_client_cert_yet());
> 
> At what point in the handshake would a query for client
> certificates show their presence?  Is it always strictly
> after the new "finished" message?  An additional check for
> the completion of the handshake may be appropriate.
> 

Actually, yes that is a good point. There could be some subtle security
issues there. You probably need to additionally check that you are not
halfway through a handshake:

SSL_renegotiate(ssl);
SSL_do_handshake(ssl);
do {
    read_some_app_data();
    if(no_client_cert_yet() || SSL_in_init(ssl)) {
        discard_app_data();
    }
} while(no_client_cert_yet() || SSL_in_init(ssl));

Matt