(MAINT) pdksync: fix for net-ssh 5 host_key check

Author: florindragos

spec/spec_helper_acceptance.rb

@@ -28,7 +28,30 @@
     options[:port] = node_config.dig('ssh', 'port') unless node_config.dig('ssh', 'port').nil?
     options[:keys] = node_config.dig('ssh', 'private-key') unless node_config.dig('ssh', 'private-key').nil?
     options[:password] = node_config.dig('ssh', 'password') unless node_config.dig('ssh', 'password').nil?
-    options[:verify_host_key] = Net::SSH::Verifiers::Null.new unless node_config.dig('ssh', 'host-key-check').nil?
+    # Support both net-ssh 4 and 5.
+    # rubocop:disable Metrics/BlockNesting
+    options[:verify_host_key] = if node_config.dig('ssh', 'host-key-check').nil?
+                                  # Fall back to SSH behavior. This variable will only be set in net-ssh 5.3+.
+                                  if @strict_host_key_checking.nil? || @strict_host_key_checking
+                                    Net::SSH::Verifiers::Always.new
+                                  else
+                                    # SSH's behavior with StrictHostKeyChecking=no: adds new keys to known_hosts.
+                                    # If known_hosts points to /dev/null, then equivalent to :never where it
+                                    # accepts any key beacuse they're all new.
+                                    Net::SSH::Verifiers::AcceptNewOrLocalTunnel.new
+                                  end
+                                elsif node_config.dig('ssh', 'host-key-check')
+                                  if defined?(Net::SSH::Verifiers::Always)
+                                    Net::SSH::Verifiers::Always.new
+                                  else
+                                    Net::SSH::Verifiers::Secure.new
+                                  end
+                                elsif defined?(Net::SSH::Verifiers::Never)
+                                  Net::SSH::Verifiers::Never.new
+                                else
+                                  Net::SSH::Verifiers::Null.new
+                                end
+    # rubocop:enable Metrics/BlockNesting
     host = if ENV['TARGET_HOST'].include?(':')
              ENV['TARGET_HOST'].split(':').first
            else