MDEV-33834 Add TLS version to audit plugin available variables

[Chupsy]

MDEV: https://jira.mariadb.org/browse/MDEV-33834

Description

Add tls_version and tls_version_length variables to the audit plugin so they can be logged. This is useful to help identify suspicious or malformed connections attempting to use unsupported TLS versions. A log with this information will allow to detect and block more malicious connection attempts.

Users with 'server_audit_events' empty will have these two new variables automatically visible in their logs, but if users don't want them, they can always configure what fields to include by listing the fields in 'server_audit_events'.

Release Notes

None. This just adds more possibilities for users.

How can this PR be tested?

Modified the server audit plugin to include this new info, and updated the server audit plugin MTR tests.

Basing the PR against the correct MariaDB version

• This is a new feature and the PR is based against the latest MariaDB development branch.

PR quality check

• I checked the CODING_STANDARDS.md file and my PR conforms to this where appropriate.
• For any trivial modifications to the PR, I am ok with the reviewer making the changes themselves.

Copyright

All new code of the whole pull request, including one or several files that are either new files or modified ones, are contributed under the BSD-new license. I am contributing on behalf of my employer Amazon Web Services, Inc.

[CLAassistant]

All committers have signed the CLA.

[grooverdan]

good idea. Can you create a MDEV with the use case?

Is it logical to log cipher at the same time?

[LinuxJedi]

Requested changes have been made. The MDEV is assigned to @holyfoot to review, so I have assigned here too.

[vuvova]

@Chupsy just to set the expectations: new features go into 10.6, we start working on 10.6 features in early May and finish it in min-June. Somewhere in that time @holyfoot should review and (if all good) merge your PR.

[Chupsy]

@LinuxJedi not sure I understand the changes that you have made to the PR, maybe another commit or modifying current commit message could help ?

[Chupsy]

Are you sure it's 10.6 and not 11.6 ?

[LinuxJedi]

@LinuxJedi not sure I understand the changes that you have made to the PR, maybe another commit or modifying current commit message could help ?

I did an automatic rebase onto the top of the branch. I have not altered the code. I also added the MDEV to the title of the PR, as this makes things much easier for us.

And yes, @vuvova would have meant 11.6.

[Chupsy]

Hello @LinuxJedi @vuvova, any update on the validation of this PR ? Do you need me to do some modifications ?

[vuvova]

To repeat, what I wrote above (with a s/10/11/ typo fix):

@Chupsy just to set the expectations: new features go into 11.6, we start working on 11.6 features in early May and finish it in min-June. Somewhere in that time @holyfoot should review and (if all good) merge your PR.

So, if nothing happens now — it's normal, the PR is not forgotten, please, wait until May-June