fscan/plugins/services/telnet.go

package services

import (
	"context"
	"fmt"
	"net"
	"strings"
	"time"

	"github.com/shadow1ng/fscan/common"
)

type TelnetPlugin struct {
	name  string
	ports []int
}

func NewTelnetPlugin() *TelnetPlugin {
	return &TelnetPlugin{
		name:  "telnet",
		ports: []int{23, 2323},
	}
}

func (p *TelnetPlugin) Name() string {
	return p.name
}

func (p *TelnetPlugin) GetPorts() []int {
	return p.ports
}

func (p *TelnetPlugin) Scan(ctx context.Context, info *common.HostInfo) *ScanResult {
	target := fmt.Sprintf("%s:%s", info.Host, info.Ports)

	if common.DisableBrute {
		return p.identifyService(ctx, info)
	}

	if result := p.testUnauthAccess(ctx, info); result != nil && result.Success {
		common.LogSuccess(fmt.Sprintf("Telnet %s 未授权访问", target))
		return result
	}

	credentials := GenerateCredentials("telnet")
	if len(credentials) == 0 {
		return &ScanResult{
			Success: false,
			Service: "telnet",
			Error:   fmt.Errorf("没有可用的测试凭据"),
		}
	}

	for _, cred := range credentials {
		if p.testCredential(ctx, info, cred) {
			common.LogSuccess(fmt.Sprintf("Telnet %s %s:%s", target, cred.Username, cred.Password))

			return &ScanResult{
				Success:  true,
				Service:  "telnet",
				Username: cred.Username,
				Password: cred.Password,
			}
		}
	}

	return &ScanResult{
		Success: false,
		Service: "telnet",
		Error:   fmt.Errorf("未发现弱密码"),
	}
}


func (p *TelnetPlugin) testUnauthAccess(ctx context.Context, info *common.HostInfo) *ScanResult {
	target := fmt.Sprintf("%s:%s", info.Host, info.Ports)
	
	conn, err := net.DialTimeout("tcp", target, time.Duration(common.Timeout)*time.Second)
	if err != nil {
		return nil
	}
	defer conn.Close()

	conn.SetDeadline(time.Now().Add(time.Duration(common.Timeout) * time.Second))

	buffer := make([]byte, 1024)
	n, err := conn.Read(buffer)
	if err != nil {
		return nil
	}

	welcome := string(buffer[:n])
	
	if strings.Contains(welcome, "$") || strings.Contains(welcome, "#") || strings.Contains(welcome, ">") {
		return &ScanResult{
			Success: true,
			Service: "telnet",
			Banner:  "未授权访问",
		}
	}

	return nil
}

func (p *TelnetPlugin) testCredential(ctx context.Context, info *common.HostInfo, cred Credential) bool {
	target := fmt.Sprintf("%s:%s", info.Host, info.Ports)
	
	conn, err := net.DialTimeout("tcp", target, time.Duration(common.Timeout)*time.Second)
	if err != nil {
		return false
	}
	defer conn.Close()

	conn.SetDeadline(time.Now().Add(time.Duration(common.Timeout) * time.Second))

	buffer := make([]byte, 1024)
	n, err := conn.Read(buffer)
	if err != nil {
		return false
	}

	data := string(buffer[:n])
	data = p.cleanTelnetData(data)
	
	if strings.Contains(strings.ToLower(data), "login") || strings.Contains(strings.ToLower(data), "username") {
		conn.Write([]byte(cred.Username + "\r\n"))
		time.Sleep(500 * time.Millisecond)
		
		n, err = conn.Read(buffer)
		if err != nil {
			return false
		}
		
		data = string(buffer[:n])
		if strings.Contains(strings.ToLower(data), "password") {
			conn.Write([]byte(cred.Password + "\r\n"))
			time.Sleep(1 * time.Second)
			
			n, err = conn.Read(buffer)
			if err != nil {
				return false
			}
			
			result := string(buffer[:n])
			result = p.cleanTelnetData(result)
			
			return p.isLoginSuccessful(result)
		}
	}

	return false
}


func (p *TelnetPlugin) cleanTelnetData(data string) string {
	cleaned := ""
	for i := 0; i < len(data); i++ {
		b := data[i]
		if b == 255 && i+2 < len(data) {
			i += 2
			continue
		}
		if b >= 32 && b <= 126 || b == '\r' || b == '\n' {
			cleaned += string(b)
		}
	}
	return cleaned
}

func (p *TelnetPlugin) isLoginSuccessful(data string) bool {
	data = strings.ToLower(data)
	
	successIndicators := []string{"$", "#", ">", "welcome", "last login"}
	for _, indicator := range successIndicators {
		if strings.Contains(data, indicator) {
			return true
		}
	}
	
	failIndicators := []string{"incorrect", "failed", "denied", "invalid", "login:"}
	for _, indicator := range failIndicators {
		if strings.Contains(data, indicator) {
			return false
		}
	}
	
	return false
}

func (p *TelnetPlugin) identifyService(ctx context.Context, info *common.HostInfo) *ScanResult {
	target := fmt.Sprintf("%s:%s", info.Host, info.Ports)

	conn, err := net.DialTimeout("tcp", target, time.Duration(common.Timeout)*time.Second)
	if err != nil {
		return &ScanResult{
			Success: false,
			Service: "telnet",
			Error:   err,
		}
	}
	defer conn.Close()

	conn.SetDeadline(time.Now().Add(time.Duration(common.Timeout) * time.Second))

	buffer := make([]byte, 1024)
	n, err := conn.Read(buffer)
	if err != nil {
		return &ScanResult{
			Success: false,
			Service: "telnet",
			Error:   err,
		}
	}

	data := string(buffer[:n])
	data = p.cleanTelnetData(data)
	
	var banner string
	if strings.Contains(strings.ToLower(data), "login") || strings.Contains(strings.ToLower(data), "username") {
		banner = "Telnet远程终端服务"
	} else if strings.Contains(data, "$") || strings.Contains(data, "#") || strings.Contains(data, ">") {
		banner = "Telnet远程终端服务 (无认证)"
	} else {
		banner = "Telnet远程终端服务"
	}

	common.LogSuccess(fmt.Sprintf("Telnet %s %s", target, banner))

	return &ScanResult{
		Success: true,
		Service: "telnet",
		Banner:  banner,
	}
}

func init() {
	// 使用高效注册方式：直接传递端口信息，避免实例创建
	RegisterPluginWithPorts("telnet", func() Plugin {
		return NewTelnetPlugin()
	}, []int{23, 2323})
}