Fix some ipv6proxy issues

[drwetter]

Describe your changes

As a quick hack this PR enables basically the IPv6 proxy which results that testssl.sh will use an IPv6 proxy when

• the binary supports that
• the binary is used and not tls_sockets()
• there's no A record but an AAAA record of the proxy or an IPv6 address as proxy address was specified.

The latter should guarantee that it doesn't break anything.

Command line should be ./testssl.sh --proxy='IPV6PROXY:PORT' TARGET whereas IPV6PROXY should be an IPv6 address . A IPv6 only hostname should work too but wasn't tested.

See #1105

Done:

• Distinguished between LibreSSL and OpenSSL IPv6 proxy (for the binaries which can deal with an IPv6 proxy: when sending an openssl s_client connect the square bracket's were missing when using LibreSSL)
• Parser problem for IPv6 and proxy port fixed
• Seemed like when specifying an IPv6 proxy via DNS and an IPv4 target the CONNECT method used IPv4 only (on a dual stack client) -- looks like the bash sockets are to blame
• docu added

What is your pull request about?

• Bug fix
• Improvement
• New feature (adds functionality)
• Breaking change (bug fix, feature or improvement that would cause existing functionality to not work as expected)
• Typo fix
• Documentation update
• Update of other files

If it's a code change please check the boxes which are applicable

• For the main program: My edits contain no tabs, indentation is five spaces and any line endings do not contain any blank chars
• I've read CONTRIBUTING.md and Coding_Convention.md
• I have tested this fix or improvement against >=2 hosts and I couldn't spot a problem
• I have tested this new feature against >=2 hosts which show this feature and >=2 host which does not (in order to avoid side effects) . I couldn't spot a problem
• For the new feature I have made corresponding changes to the documentation and / or to help()
• If it's a bigger change: I added myself to CREDITS.md (alphabetical order) and the change to CHANGELOG.md

[drwetter]

@dcooper16 : Do you know by any chance since when (in OpenSSL and LibreSSL) IPv6 is supported for the proxy? I'd like to add a check here. Unfortunately that probably needs to be version-based rather as testing-based as we normally do.

[dcooper16]

@dcooper16 : Do you know by any chance since when (in OpenSSL and LibreSSL) IPv6 is supported for the proxy? I'd like to add a check here. Unfortunately that probably needs to be version-based rather as testing-based as we normally do.

Sorry, no. I haven't really worked with IPv6 or proxies.

[drwetter]

Thanks anyway. PS: The git log (of openssl) wasn't really helpful. As I didn't find even less in the git log of LibreSSL I guess it was implemented before the fork. Edit: 1.1.1 works, and 1.1.0m as well