Add default certificate store when none given

[nanaya]

References:

• https://ruby-doc.org/stdlib-2.4.0/libdoc/openssl/rdoc/OpenSSL/SSL/SSLContext.html#method-i-set_params
• https://gitlab.com/gitlab-org/gitlab-ce/issues/1558#note_1185132

[nanaya]

Unfortunately this will set verify_mode to system default as well which is peer in my system.

Updated to default to none as per current behavior (which honor SSLContext#verify_mode default instead of system default).

I'm not sure anymore what the default should be. I switched to just adding default cert store when neither ca_path nor ca_file is specified and mode isn't none.

Alternatively:

      Net::SMTP.default_ssl_context.tap do |context|
        params = {}
        params[:verify_mode] = openssl_verify_mode if openssl_verify_mode
        params[:ca_path] = settings[:ca_path] if settings[:ca_path]
        params[:ca_file] = settings[:ca_file] if settings[:ca_file]

        context.set_params(params)
      end

[jeremy]

Can we test this?

[jeremy]

Can we always set the cert store? Does it need to be mutually exclusive with provided CA path/file settings?

[nanaya]

Good question. Unfortunately I'm not sure myself. I based this off #set_params which checks all three settings (including cert_store itself).