[TLS 1.3] Enable post-handshake auth for OpenSSL 1.1.1

[tiran]

Curl does neither call SSL_CTX_set_post_handshake_auth() nor SSL_set_post_handshake_auth() to enable TLS 1.3's post handshake authentication feature. TLS 1.3 does no longer support renegotiation, therefore PHA is required when the server requires TLS client cert auth depending on HTTP method and/or path. OpenSSL 1.1.1 changed PHA to opt-in.

I noticed the issue while I was working on PHA support for Python. I wanted to verify my implementation with curl...

Resources:

• openssl/openssl#6938
• https://www.openssl.org/docs/manmaster/man3/SSL_CTX_set_post_handshake_auth.html
• https://bugs.python.org/issue34670
• https://github.com/apache/httpd/blob/trunk/modules/ssl/ssl_engine_kernel.c#L1207

[tiran]

It might be sufficient to just call the function. I'm not fully sure how the actual PHA handshake works with HTTP. If I understand the Apache mod_ssl implementation correctly, then it's like HTTP STARTTLS. The server sends a HTTP connection upgrade request along a CertRequest TLS message. The client response with an upgrade confirmation along with Certificate, CertificateVerify, and Finish TLS message.