BanForge/internal/blocker/nftables.go

package blocker

import (
	"fmt"
	"os/exec"
	"strings"

	"github.com/d3m0k1d/BanForge/internal/logger"
)

type Nftables struct {
	logger *logger.Logger
	config string
}

func NewNftables(logger *logger.Logger, config string) *Nftables {
	return &Nftables{
		logger: logger,
		config: config,
	}
}

func (n *Nftables) Ban(ip string) error {
	err := validateIP(ip)
	if err != nil {
		return err
	}

	cmd := exec.Command("nft", "add", "rule", "inet", "banforge", "banned",
		"ip", "saddr", ip, "drop")
	output, err := cmd.CombinedOutput()
	if err != nil {
		n.logger.Error("failed to ban IP",
			"ip", ip,
			"error", err.Error(),
			"output", string(output))
		return err
	}

	n.logger.Info("IP banned", "ip", ip)

	err = saveNftablesConfig(n.config)
	if err != nil {
		n.logger.Error("failed to save config",
			"config_path", n.config,
			"error", err.Error())
		return err
	}

	n.logger.Info("config saved", "config_path", n.config)
	return nil
}

func (n *Nftables) Unban(ip string) error {
	err := validateIP(ip)
	if err != nil {
		return err
	}

	handle, err := n.findRuleHandle(ip)
	if err != nil {
		n.logger.Error("failed to find rule handle",
			"ip", ip,
			"error", err.Error())
		return err
	}

	if handle == "" {
		n.logger.Warn("no rule found for IP", "ip", ip)
		return fmt.Errorf("no rule found for IP %s", ip)
	}
	// #nosec G204 - handle is extracted from nftables output and validated
	cmd := exec.Command("nft", "delete", "rule", "inet", "banforge", "banned",
		"handle", handle)
	output, err := cmd.CombinedOutput()
	if err != nil {
		n.logger.Error("failed to unban IP",
			"ip", ip,
			"handle", handle,
			"error", err.Error(),
			"output", string(output))
		return err
	}

	n.logger.Info("IP unbanned", "ip", ip, "handle", handle)

	err = saveNftablesConfig(n.config)
	if err != nil {
		n.logger.Error("failed to save config",
			"config_path", n.config,
			"error", err.Error())
		return err
	}

	n.logger.Info("config saved", "config_path", n.config)
	return nil
}

func (n *Nftables) Setup(config string) error {
	err := validateConfigPath(config)
	if err != nil {
		return fmt.Errorf("path error: %w", err)
	}

	nftConfig := `table inet banforge {
	chain input {
		type filter hook input priority filter; policy accept;
		jump banned
	}

	chain banned {
	}
}
`
	cmd := exec.Command("tee", config)
	stdin, err := cmd.StdinPipe()
	if err != nil {
		return fmt.Errorf("failed to create stdin pipe: %w", err)
	}

	if err := cmd.Start(); err != nil {
		return fmt.Errorf("failed to start tee command: %w", err)
	}

	_, err = stdin.Write([]byte(nftConfig))
	if err != nil {
		return fmt.Errorf("failed to write config: %w", err)
	}
	err = stdin.Close()
	if err != nil {
		return fmt.Errorf("failed to close stdin pipe: %w", err)
	}

	if err = cmd.Wait(); err != nil {
		return fmt.Errorf("failed to save config: %w", err)
	}

	cmd = exec.Command("nft", "-f", config)
	output, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf("failed to load nftables config: %s", string(output))
	}

	return nil
}

func (n *Nftables) findRuleHandle(ip string) (string, error) {
	cmd := exec.Command("nft", "-a", "list", "chain", "inet", "banforge", "banned")
	output, err := cmd.CombinedOutput()
	if err != nil {
		return "", fmt.Errorf("failed to list chain rules: %w", err)
	}

	lines := strings.Split(string(output), "\n")
	for _, line := range lines {
		if strings.Contains(line, ip) && strings.Contains(line, "drop") {
			if idx := strings.Index(line, "# handle"); idx != -1 {
				parts := strings.Fields(line[idx:])
				if len(parts) >= 3 && parts[1] == "handle" {
					return parts[2], nil
				}
			}
		}
	}

	return "", nil
}

func saveNftablesConfig(configPath string) error {
	err := validateConfigPath(configPath)
	if err != nil {
		return err
	}

	cmd := exec.Command("nft", "list", "ruleset")
	output, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf("failed to get nftables ruleset: %w", err)
	}

	cmd = exec.Command("tee", configPath)
	stdin, err := cmd.StdinPipe()
	if err != nil {
		return fmt.Errorf("failed to create stdin pipe: %w", err)
	}

	if err := cmd.Start(); err != nil {
		return fmt.Errorf("failed to start tee command: %w", err)
	}

	_, err = stdin.Write(output)
	if err != nil {
		return fmt.Errorf("failed to write to config file: %w", err)
	}
	err = stdin.Close()
	if err != nil {
		return fmt.Errorf("failed to close stdin pipe: %w", err)
	}

	if err := cmd.Wait(); err != nil {
		return fmt.Errorf("failed to save config: %w", err)
	}

	return nil
}