OpenSSL: Negotiate TLS version by default

[taboege]

If no $version was given to OpenSSL.new, it would use the highest TLS version implemented in the OpenSSL library. This is a problem when you access, via e.g. the WWW module which gives you no access to the OpenSSL instance, a server which only implements older TLS.

Now, a version negotiating TLS method is used instead if no explicit $version is requested. Prior to OpenSSL 1.1.0, this was SSLv23_method() and was then renamed to TLS_method(). See https://wiki.openssl.org/index.php/SSL/TLS_Client#Context_Setup

The OpenSSL documentation SSL_CTX_new(3) recommends to use the version-flexible methods in applications, so this module should at least make it available in some form. The manpage even says that the version-specific methods are deprecated with OpenSSL 1.1.0, so I guess it isn't too poor practice to potentially allow protocol downgrades by default.

Now, the 'new 3/3' test in 01-basic.t probes the version selected by default, so I had to adjust that as well. With OpenSSL 1.1.0, there is a special method version 0x10000 indicating version negotiation. Prior to that, the version was set to the same as the highest implemented method. See:

• Added TLSv1.1: https://github.com/openssl/openssl/blob/637f374ad49d5f6d4f81d87d7cdd226428aa470c/ssl/ssl_locl.h#L673
• Added TLSv1.2: https://github.com/openssl/openssl/blob/49f6cb968ff63793f6671d9026fb2a7034dad79a/ssl/ssl_locl.h#L694

Here's an example that's failing with master but working with this commit:

use WWW
use Test
lives-ok { get <https://www.studentenwerk-magdeburg.de/> }

err code: 337056010
error:1417110A:SSL routines:tls_process_server_hello:wrong ssl version
not ok 1 -
# Failed test at <unknown file> line 1
# Internal Error: 'server returned no data'

[taboege]

I'm trying to figure out how the CIers OpenSSLs differ from my local one.

[taboege]

It was missing a vital unspace...

[sergot]

Thanks a lot for your contribution! :)