fix ms17010 legacy packet decoding (#574)

plugins/services/ms17010_test.go

@@ -3,6 +3,7 @@
 package services
 
 import (
+	"bytes"
 	"context"
 	"net"
 	"testing"
@@ -11,6 +12,34 @@ import (
 	"github.com/shadow1ng/fscan/common"
 )
 
+func TestMS17010LegacyRequestsDecodeToSMB1Packets(t *testing.T) {
+	requests := map[string][]byte{
+		"negotiate":          negotiateProtocolRequest,
+		"sessionSetup":       sessionSetupRequest,
+		"treeConnect":        treeConnectRequest,
+		"transNamedPipe":     transNamedPipeRequest,
+		"trans2SessionSetup": trans2SessionSetupRequest,
+	}
+
+	for name, request := range requests {
+		t.Run(name, func(t *testing.T) {
+			if len(request) < 36 {
+				t.Fatalf("request length = %d, want at least 36", len(request))
+			}
+			if request[0] != 0x00 {
+				t.Fatalf("NetBIOS message type = 0x%02x, want 0x00", request[0])
+			}
+			payloadLen := int(request[1])<<16 | int(request[2])<<8 | int(request[3])
+			if payloadLen != len(request)-4 {
+				t.Fatalf("NetBIOS payload length = %d, want %d", payloadLen, len(request)-4)
+			}
+			if !bytes.Equal(request[4:8], []byte{0xff, 0x53, 0x4d, 0x42}) {
+				t.Fatalf("SMB signature = % x, want ff 53 4d 42", request[4:8])
+			}
+		})
+	}
+}
+
 func TestMS17010CheckDetectsVulnerableStatus(t *testing.T) {
 	addr, cleanup := startMS17010FakeServer(t, true, 45)
 	defer cleanup()