add vncscreenshot script. note: vncscreenshotting is still not implemented

Author: superswan

vncscreen.py

@@ -0,0 +1,53 @@
+"""
+Code is based on slyd0g's pwnVNC
+https://github.com/slyd0g/pwnVNC
+
+More info here:
+https://grumpy-sec.blogspot.com/2017/02/scanning-entire-internet.html
+"""
+import socket
+import os
+
+from bcolors import bcolors
+
+# takes a screen screenshot of VNC connection. Will only connect when authentication is disabled on VNC
+def getVncScreen(ip_addr, port):
+    vnc_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    vnc_socket.settimeout(0.5)
+    try:
+        # attmept to create TCP handshake and do authentication check using RFB protocol
+        vnc_socket.connect((ip_addr, port))
+        RFB_VERSION = vnc_socket.recv(12)
+        rfb_version_string = RFB_VERSION.decode('UTF-8')
+        if "RFB" not in rfb_version_string:
+            print("Unable to capture screenshot")
+            return
+        
+        vnc_socket.send(RFB_VERSION)
+        auth_required = vnc_socket.recv(1)
+        
+        if not auth_required:
+            print("Unable to capture screenshot")
+            return
+
+        # 0x01 received from server signifies that no authentication is required  
+        if auth_required == b'\x01':
+            filename = ip_addr.replace('.', '_') + '_scrot' + '.jpg'
+            print(f"Saving VNC snapshot as {filename}")
+            vnc_snapshot = f"timeout 10 vncsnapshot -allowblank -port {str(port)} {ip_addr}:0 {filename}" 
+            print(vnc_snapshot) 
+
+            # close authentication check socket and then run command. command must be run after or vncsnapshot will end prematurely
+            vnc_socket.shutdown(socket.SHUT_WR)
+            vnc_socket.close()
+            
+            os.system(vnc_snapshot)
+            return filename
+        
+
+    except socket.error:
+        vnc_socket.close()
+        pass
+    except socket.timeout:
+        vnc_socket.close()
+        pass