feat: add JDWP plugin for Java debug port detection

Detects exposed JDWP (Java Debug Wire Protocol) services on ports
5005/8000/8787/5050. Performs protocol handshake and reports as VULN
since an exposed debug port allows remote code execution.

pkg/fscan/scanner.go

@@ -39,6 +39,7 @@ var defaultSafePlugins = []string{
 	"rabbitmq",
 	"rdp",
 	"redis",
+	"jdwp",
 	"rsync",
 	"smb",
 	"smtp",

plugins/services/jdwp.go

@@ -0,0 +1,111 @@
+//go:build plugin_jdwp || !plugin_selective
+
+package services
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/shadow1ng/fscan/common"
+	"github.com/shadow1ng/fscan/plugins"
+)
+
+var jdwpHandshake = []byte("JDWP-Handshake")
+
+type JDWPPlugin struct {
+	plugins.BasePlugin
+}
+
+func NewJDWPPlugin() *JDWPPlugin {
+	return &JDWPPlugin{BasePlugin: plugins.NewBasePlugin("jdwp")}
+}
+
+func (p *JDWPPlugin) Scan(ctx context.Context, info *common.HostInfo, session *common.ScanSession) *ScanResult {
+	timeout := session.Config.Timeout
+	if timeout <= 0 {
+		timeout = 3 * time.Second
+	}
+
+	addr := fmt.Sprintf("%s:%d", info.Host, info.Port)
+	conn, err := session.DialTCP(ctx, "tcp", addr, timeout)
+	if err != nil {
+		return &ScanResult{Success: false, Service: "jdwp"}
+	}
+	defer conn.Close()
+
+	_ = conn.SetDeadline(time.Now().Add(timeout))
+	if _, err := conn.Write(jdwpHandshake); err != nil {
+		return &ScanResult{Success: false, Service: "jdwp"}
+	}
+
+	buf := make([]byte, len(jdwpHandshake))
+	n, err := conn.Read(buf)
+	if err != nil || !bytes.Equal(buf[:n], jdwpHandshake) {
+		return &ScanResult{Success: false, Service: "jdwp"}
+	}
+
+	version := p.getVersion(conn, timeout)
+
+	return &ScanResult{
+		Success: true,
+		Type:    plugins.ResultTypeVuln,
+		Service: "jdwp",
+		VulInfo: "JDWP Remote Debug Port Exposed",
+		Banner:  version,
+	}
+}
+
+func (p *JDWPPlugin) getVersion(conn interface{ Read([]byte) (int, error); Write([]byte) (int, error); SetDeadline(time.Time) error }, timeout time.Duration) string {
+	_ = conn.SetDeadline(time.Now().Add(timeout))
+
+	// JDWP Version command: length=11, id=1, flags=0, commandSet=1, command=1
+	pkt := []byte{
+		0x00, 0x00, 0x00, 0x0b, // length = 11
+		0x00, 0x00, 0x00, 0x01, // id = 1
+		0x00,                   // flags = 0 (request)
+		0x01,                   // commandSet = 1 (VirtualMachine)
+		0x01,                   // command = 1 (Version)
+	}
+	if _, err := conn.Write(pkt); err != nil {
+		return ""
+	}
+
+	header := make([]byte, 11)
+	if _, err := conn.Read(header); err != nil {
+		return ""
+	}
+	replyLen := int(header[0])<<24 | int(header[1])<<16 | int(header[2])<<8 | int(header[3])
+	if replyLen <= 11 || replyLen > 4096 {
+		return ""
+	}
+
+	body := make([]byte, replyLen-11)
+	if _, err := conn.Read(body); err != nil {
+		return ""
+	}
+
+	return parseJDWPVersionString(body)
+}
+
+func parseJDWPVersionString(data []byte) string {
+	if len(data) < 4 {
+		return ""
+	}
+	strLen := int(data[0])<<24 | int(data[1])<<16 | int(data[2])<<8 | int(data[3])
+	if strLen <= 0 || strLen > len(data)-4 {
+		return ""
+	}
+	s := string(data[4 : 4+strLen])
+	if len(s) > 200 {
+		s = s[:200]
+	}
+	return s
+}
+
+func init() {
+	RegisterPluginWithPorts("jdwp", func() Plugin {
+		return NewJDWPPlugin()
+	}, []int{5005, 8000, 8787, 5050})
+}