I need to write a test for my client to make sure it's non-blocking ssl interactions are able to survive SSL renegotiation. However, I can't seem to find anything in our python ssl API that calls `SSL_renegotiate()` in order to force renegotiation.

Since it's a feature request, I have changed the version number to 3.8.

By the way, renegotiation is a problematic and has been replaced by rekeying in TLS 1.3.

> By the way, renegotiation is a problematic and has been replaced by rekeying in TLS 1.3

How can I trigger rekeying via python ssl? Many thanks.

You can't.

Rekeying is not available yet. SSL_key_update() is only available with OpenSSL 1.1.1 and TLS 1.3. Both are still in beta phase.

I have also wanted to force renegotation for testing with Python.

As a workaround, I have used the "openssl s_server" program, which I described at <https://bugs.python.org/issue25919#msg257508> (use the lower-case "r" command). More recently I did a similar thing with "s_client", where you have to use capital "R".

PyOpenSSL supports renegotiation, and I've used it for writing exactly this kind of test. Might be easier than wrapping a test harness around the 'openssl' command.

For extra fun, openssl itself doesn't fully support renegotiation on duplex connections, even if your code works correctly: http://openssl.6102.n7.nabble.com/TLS-renegotiation-failure-on-receiving-application-data-during-handshake-td48127.html

> For extra fun, openssl itself doesn't fully support renegotiation on duplex connections ...

The necessitated modification to the application protocol on that thread sounds like an OpenSSL cop-out. There is no good reason that OpenSSL shouldn't be able to cache incoming application data during the client-initiated handshake just as it does at other times. It should be able to cache the incoming pre-negotiation records, decoding them. The pending() check would inform the client that they need to reap the incoming data during the handshake too.

> an OpenSSL cop-out

Perhaps, but they've been doing it this way for a decade+, and we're living in a time when other libraries like BoringSSL are flat-out removing renegotiation support, so good luck convincing them to fix things. Anyway, it's nothing to do with Python, just a friendly heads-up; I ran into this when trying to do renegotiation tests on my non-blocking code using the 'ssl' module and was *very* confused for a while until I realized it wasn't my code's fault at all.