Added a negative test of PROXY enabled

Author: donovanhubbard

server_test.go

@@ -133,7 +133,7 @@ func TestServerClose(t *testing.T) {
 	}
 }
 
-func TestProxyProtocol(t *testing.T) {
+func TestProxyProtocolEnabled(t *testing.T) {
 	const (
 		CORRECT_IP   = "1.1.1.1"
 		CORRECT_PORT = 55555
@@ -232,3 +232,103 @@ func TestProxyProtocol(t *testing.T) {
 		t.Fatal(testResult)
 	}
 }
+
+func TestProxyProtocolDisabled(t *testing.T) {
+	const (
+		INCORRECT_IP   = "1.1.1.1"
+		INCORRECT_PORT = 55555
+	)
+	handlerDone := make(chan struct{})
+	var testResult error
+
+	handler := func(sess Session) {
+		defer close(handlerDone)
+		sourceAddress := sess.RemoteAddr()
+
+		index := strings.Index(sourceAddress.String(), ":")
+		ip := sourceAddress.String()[:index]
+		portStr := sourceAddress.String()[index+1:]
+
+		if ip == INCORRECT_IP {
+			errorMsg := fmt.Sprintf("Expected source address to be anything but '%s' but got '%s'", INCORRECT_IP, ip)
+			testResult = errors.Join(testResult, fmt.Errorf("%s", errorMsg))
+		}
+		port, err := strconv.Atoi(portStr)
+		if err != nil {
+			testResult = errors.Join(testResult, fmt.Errorf("%s", err))
+		} else if port == INCORRECT_PORT {
+			errorMsg := fmt.Sprintf("Expected source port anything but '%d' but got '%d'", INCORRECT_PORT, port)
+			testResult = errors.Join(testResult, fmt.Errorf("%s", errorMsg))
+		}
+	}
+
+	// Bind the port before starting the goroutine so net.Dial never races
+	// with the server not yet listening.
+	l := newLocalListener()
+	srv := &Server{Handler: handler}
+
+	serverDone := make(chan error, 1)
+
+	go func() {
+		serverDone <- srv.Serve(l)
+	}()
+
+	defer func() {
+		srv.Close()
+		if err := <-serverDone; err != nil && err != ErrServerClosed {
+			t.Error(err)
+		}
+	}()
+
+	serverIP, serverPortStr, _ := net.SplitHostPort(l.Addr().String())
+	serverPort, _ := strconv.Atoi(serverPortStr)
+	conn, err := net.Dial("tcp", l.Addr().String())
+
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	//Set the PROXY header information. The server should not read it
+	header := &proxyproto.Header{
+		Version:           1,
+		Command:           proxyproto.PROXY,
+		TransportProtocol: proxyproto.TCPv4,
+		SourceAddr: &net.TCPAddr{
+			IP:   net.ParseIP(INCORRECT_IP),
+			Port: INCORRECT_PORT,
+		},
+		DestinationAddr: &net.TCPAddr{
+			IP:   net.ParseIP(serverIP),
+			Port: serverPort,
+		},
+	}
+
+	// Writes the PROXY header to the TCP stream before SSH begins
+	_, err = header.WriteTo(conn)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Hand the same conn to the SSH stack — handshake starts from here.
+	clientConn, chans, reqs, err := gossh.NewClientConn(conn, l.Addr().String(), &gossh.ClientConfig{
+		User:            "testuser",
+		HostKeyCallback: gossh.InsecureIgnoreHostKey(),
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	client := gossh.NewClient(clientConn, chans, reqs)
+	defer client.Close()
+
+	session, err := client.NewSession()
+	if err != nil {
+		t.Fatal(err)
+	}
+	session.Run("") // triggers the handler; ignore exec error
+
+	<-handlerDone
+
+	if testResult != nil {
+		t.Fatal(testResult)
+	}
+}