multiserver/ban.go

package main

import (
	"database/sql"
	"errors"
	"fmt"
	"net"

	_ "github.com/mattn/go-sqlite3"
)

var ErrInvalidAddress = errors.New("invalid ip address format")

// addBanItem inserts a ban DB entry
func addBanItem(db *sql.DB, addr, name string) error {
	_, err := db.Exec(`INSERT INTO ban (
		addr,
		name
	) VALUES (
		?,
		?
	);`, name)
	return err
}

// readBanItem selects and reads a ban DB entry
func readBanItem(db *sql.DB, addr string) (string, error) {
	var r string
	err := db.QueryRow(`SELECT name FROM ban WHERE addr = ?;`, addr).Scan(&r)
	if err != nil && !errors.Is(err, sql.ErrNoRows) {
		return "", err
	}

	return r, nil
}

// deleteBanItem deletes a ban DB entry
func deleteBanItem(db *sql.DB, name string) error {
	_, err := db.Exec(`DELETE FROM ban WHERE name = ? OR addr = ?;`, name)
	return err
}

// BanList returns the list of banned players and IP addresses
func BanList() (map[string]string, error) {
	db, err := initAuthDB()
	if err != nil {
		return nil, err
	}
	defer db.Close()

	rows, err := db.Query(`SELECT addr, name FROM ban;`)
	if err != nil {
		return nil, err
	}

	r := make(map[string]string)

	for rows.Next() {
		var addr, name string

		if err = rows.Scan(&addr, &name); err != nil {
			return nil, err
		}

		r[addr] = name
	}

	return r, nil
}

// IsBanned reports whether a Conn is banned
func (c *Conn) IsBanned() (bool, string, error) {
	db, err := initAuthDB()
	if err != nil {
		return true, "", err
	}
	defer db.Close()

	addr := c.Addr().(*net.UDPAddr).IP.String()

	name, err := readBanItem(db, addr)
	if err != nil {
		return true, "", err
	}

	return name != "", name, nil
}

// Ban adds a Conn to the ban list
func (c *Conn) Ban() error {
	banned, _, err := c.IsBanned()
	if err != nil {
		return err
	}

	if banned {
		return fmt.Errorf("ip address %s is already banned", c.Addr().String())
	}

	db, err := initAuthDB()
	if err != nil {
		return err
	}
	defer db.Close()

	name := c.Username()
	addr := c.Addr().(*net.UDPAddr).IP.String()

	err = addBanItem(db, addr, name)
	if err != nil {
		return err
	}

	c.CloseWith(AccessDeniedCustomString, "Banned.", false)
	return nil
}

func Ban(addr string) error {
	db, err := initAuthDB()
	if err != nil {
		return err
	}
	defer db.Close()

	name := "not known"

	if net.ParseIP(addr) == nil {
		return ErrInvalidAddress
	}

	err = addBanItem(db, addr, name)
	if err != nil {
		return err
	}

	return nil
}

func Unban(name string) error {
	db, err := initAuthDB()
	if err != nil {
		return err
	}
	defer db.Close()

	err = deleteBanItem(db, name)
	if err != nil {
		return err
	}

	return nil
}