Hello  Matt,

I am interested in your issue with:
SSL_shutdown(ssl);
SSL_free(ssl);

causing disruption of other SSL connections open within the same 
application.

There should be nothing wrong not checking the return values of 
SSL_shutdown() is your application does not need a guaranteed end of 
session and doesn't need to ensure the SSL session cache keeps the 
session-id around to be re-used again.

A guaranteed end of session are for applications that must ensure 
(cryptographically / securely) that all the data the other end was going 
to send has been received, and allows your end to signal to the other 
end its not going to send any more data. This is what the SSL_shutdown() 
provides, a secure end of transmission indication.  This is to stop an 
attacker from prematurely terminating a network connection (man in the 
middle) to make each end presume the other end had finished.  Most 
applications dont need this facility.

The two calls above like that, would make the SSL_shutdown() attempt to 
send the shutdown notify alert, which may or may not get commited from 
application into kernel buffer (to be sent to your peer).  You then 
SSL_free() and presumably a close(fd) takes place.

I am thinking your SSL_ERROR_SSL on an SSL_read() of a different (SSL *) 
is an application programming error.  Maybe you can indicate how many 
other SSL connections the application had open at the time, the amount 
of throughput/data traffic it was doing, the amount of time a connection 
stayed open.



If you are using:

SSL_set_shutdown(c->ssl, SSL_SENT_SHUTDOWN|SSL_RECEIVED_SHUTDOWN);
SSL_free(c->ssl);


I belive the SSL_set_shutdown() call is redundant in that situation. 
Since SSL_free() does not initiate an automatic shutdown it just tears 
down the resources for the SSL socket and you can do no futher work with 
it. AFAIK SSL_free() will not cause a read() or write() to take place.


Best Regards,

Darryl


-- 
Darryl L. Miles


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