[openssl-users] Root-Level queries while using SSL-connections wrapping "sockets"

[Viktor Dukhovni]

On Fri, Oct 07, 2016 at 08:51:24AM +0530, Ajay Garg wrote:

> However, I am a bit unsure about certain implementations.
> In particular (let's talk only about the client-side), I wonder how do
> the following methods work internally ::
> 
> 
>       * SSL_connect (implicitly involving underlying-socket-reads and
> underlying-socket-writes)

Correct.

>       * SSL_write (involving underlying-socket-writes)

This can also involve socket reads, e.g. when the peer requests
renegotiation.  Hence, on non-blocking sockets this can fail with
SSL_ERROR_WANT_READ.  The application should then retry the write
(generally with the identitical data) when the socket becomes
*readable*.

>       * SSL_read (involving underlying-socket-reads)

This can also involve socket writes, e.g. when the peer requests
renegotiation.  Hence, on non-blocking sockets this can fail with
SSL_ERROR_WANT_WRITE.  The application should then retry the read
when the socket becomes *writable*.

> We have a framework which we have ported to a variety of devices,
> involving GPRS-connectivity, and devices without operating-systems.
> I know that there is "no one universal socket-write" and "no one
> universal socket-read" implementations.

No idea what "root-level" means.  Perhaps you mean something
analogous to a system-call?  If so OpenSSL can either be handed
the socket to use, or plugged into some other way of moving data
via the BIO pair interface.

    https://www.openssl.org/docs/manmaster/crypto/BIO_s_bio.html

-- 
	Viktor.