Server application hangs on SS_read, even when client disconnects

Matt Caswell matt at
Tue Nov 17 14:06:17 UTC 2020

On 17/11/2020 13:56, Michael Wojcik wrote:
>> From: Kyle Hamilton <aerowolf at>
>> Sent: Tuesday, 17 November, 2020 02:37
>> On Fri, Nov 13, 2020 at 11:51 AM Michael Wojcik
>> <Michael.Wojcik at> wrote:
>>>> From: Brice André <brice at>
>>>> Sent: Friday, 13 November, 2020 09:13
>>>> "Does the server parent process close its copy of the conversation socket?"
>>>> I checked in my code, but it seems that no. Is it needed?
>>> You'll want to do it, for a few reasons: ...
>> There's another reason why you'll want to close your socket with
>> SSL_close(): SSL (and TLS) view a prematurely-closed stream as an
>> exceptional condition to be reported to the application. This is to
>> prevent truncation attacks against the data communication layer.
>> While your application may not need that level of protection, it helps
>> to keep the state of your application in lockstep with the state of
>> the TLS protocol.  If your application doesn't expect to send any more
>> data, SSL_close() sends another record across the TCP connection to
>> tell the remote side that it should not keep the descriptor open.
> This is true, but not what we're talking about here. When the
> application is done with the conversation, it should use SSL_close
> to terminate the conversation.
> Here, though, we're talking about the server parent process closing
> its descriptor for the socket after forking the child process. At that
> point the application is not done with the conversation, and calling
> SSL_close in the server would be a mistake.
> Now, if the server is unable to start a child process (e.g. fork fails
> because the user's process limit has been reached), or if for whatever
> other reason it decides to terminate the conversation without further
> processing, SSL_close would be appropriate.

Just for clarity, there is no such function as SSL_close. I assume
SSL_shutdown is what people mean.


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