core: guard against SSH to localhost:22 [GH-4070]

CHANGELOG.md

@@ -19,6 +19,7 @@ IMPROVEMENTS:
 
 BUG FIXES:
 
+  - core: Guard against SSHing to localhost:22 [GH-4070]
   - core: Downloading box files should resume in more cases since the
       temporary file is preserved in more cases. [GH-4301]
   - core: Windows is not detected as NixOS in some cases. [GH-4302]

lib/vagrant/machine.rb

@@ -434,6 +434,13 @@ module Vagrant
         File.expand_path(path, @env.root_path)
       end
 
+      # If we're connecting to localhost:22, then short-circuit
+      # and return nil here since this is something that nobody ever
+      # really wants.
+      if info[:host] == "127.0.0.1" && info[:port] == 22
+        return nil
+      end
+
       # Return the final compiled SSH info data
       info
     end

test/unit/vagrant/machine_test.rb

@@ -605,6 +605,13 @@ describe Vagrant::Machine do
         expect(instance.ssh_info[:password]).to eql("")
       end
 
+      it "should return nil if localhost:22" do
+        provider_ssh_info[:host] = "127.0.0.1"
+        instance.config.ssh.port = 22
+
+        expect(instance.ssh_info).to be_nil
+      end
+
       context "with no data dir" do
         let(:base)     { true }
         let(:data_dir) { nil }