msan detected an uninit read.
Reviewed-by: NRichard Levitte <levitte@openssl.org>

Split the create_ssl_connection() helper function into two steps: one to
create the SSL objects, and one to actually create the connection. This
provides the ability to make changes to the SSL object before the
connection is actually made.
Reviewed-by: NRichard Levitte <levitte@openssl.org>

Fix some bogus "may be used uninitialized" warnings on some compilers.
Reviewed-by: NRich Salz <rsalz@openssl.org>

SSL_set_rbio() and SSL_set_wbio() are new functions in 1.1.0 and really
should be called SSL_set0_rbio() and SSL_set0_wbio(). The old
implementation was not consistent with what "set0" means though as there
were special cases around what happens if the rbio and wbio are the same.
We were only ever taking one reference on the BIO, and checking everywhere
whether the rbio and wbio are the same so as not to double free.

A better approach is to rename the functions to SSL_set0_rbio() and
SSL_set0_wbio(). If an existing BIO is present it is *always* freed
regardless of whether the rbio and wbio are the same or not. It is
therefore the callers responsibility to ensure that a reference is taken
for *each* usage, i.e. one for the rbio and one for the wbio.

The legacy function SSL_set_bio() takes both the rbio and wbio in one go
and sets them both. We can wrap up the old behaviour in the implementation
of that function, i.e. previously if the rbio and wbio are the same in the
call to this function then the caller only needed to ensure one reference
was passed. This behaviour is retained by internally upping the ref count.

This commit was inspired by BoringSSL commit f715c423224.

RT#4572
Reviewed-by: NRich Salz <rsalz@openssl.org>

This adds some simple SSL BIO tests that check for pushing and popping of
BIOs into the chain. These tests would have caught the bugs fixed in the
previous three commits, if combined with a crypto-mdebug build.
Reviewed-by: NRich Salz <rsalz@openssl.org>

The SSL_set_bio() function has some complicated ownership rules. This adds a
test to make sure it all works as expected.
Reviewed-by: NRich Salz <rsalz@openssl.org>

Misc fixes impacting no-tls1_2. Also fixes no-dtls1_2.
Reviewed-by: NRich Salz <rsalz@openssl.org>

Add some more tests for sessions following on from the previous commit
to ensure the callbacks are called when appropriate.
Reviewed-by: NRichard Levitte <levitte@openssl.org>

Reviewed-by: NRich Salz <rsalz@openssl.org>

This commit adds some session API tests, and in particular tests the
modified behaviour of SSL_set_session() introduced in the last commit. To
do this I have factored out some common code from the asynciotest into a
new ssltestlib.c file. I've also renamed getsettest to sslapitest as this
more closely matches what it now is!
Reviewed-by: NRich Salz <rsalz@openssl.org>