1 files changed, 74 insertions, 0 deletions
diff --git a/scripts/x11-access.nse b/scripts/x11-access.nse
new file mode 100644
index 0000000..f434956
--- /dev/null
+++ b/scripts/x11-access.nse
@@ -0,0 +1,74 @@
+local nmap = require "nmap"
+local string = require "string"
+
+-- NSE x11-access v1.3
+
+description = [[
+Checks if you're allowed to connect to the X server.
+
+If the X server is listening on TCP port 6000+n (where n is the display
+number), it is possible to check if you're able to get connected to the
+remote display by sending a X11 initial connection request.
+
+In reply, the success byte (0x00 or 0x01) will determine if you are in
+the <code>xhost +</code> list. In this case, script will display the message:
+<code>X server access is granted</code>.
+]]
+
+---
+-- @output
+-- Host script results:
+-- |_ x11-access: X server access is granted
+--
+-- @xmloutput
+-- true
+
+author = "vladz"
+license = "Same as Nmap--See https://nmap.org/book/man-legal.html"
+categories = {"default", "safe", "auth"}
+
+portrule = function(host, port)
+  return ((port.number >= 6000 and port.number <= 6009)
+    or (port.service and string.match(port.service, "^X11")))
+  -- If port.version.product is not equal to nil, version
+  -- detection "-sV" has already done this X server test.
+  and port.version.product == nil
+end
+
+action = function(host, port)
+
+  local result, socket, try, catch
+  socket = nmap.new_socket()
+  catch = function()
+    socket:close()
+  end
+
+  try = nmap.new_try(catch)
+  try(socket:connect(host, port))
+
+  -- Sending the network dump of a x11 connection request (captured
+  -- from the XOpenDisplay() function):
+  --
+  --    0x6c 0x00 0x0b 0x00 0x00 0x00 0x00
+  --    0x00 0x00 0x00 0x00 0x00 0x00
+  try(socket:send("\108\000\011\000\000\000\000\000\000\000\000\000"))
+
+  -- According to the XOpenDisplay() sources, server answer is
+  -- stored in a xConnSetupPrefix structure [1]. The function
+  -- returns NULL if it does not succeed, and more precisely: When
+  -- the success field of this structure (stored on 1 byte) is not
+  -- equal to xTrue [2]. For more information, see the Xlib
+  -- programming Manual [3].
+  --
+  -- [1] xConnSetupPrefix structure is defined in X11/Xproto.h.
+  -- [2] xTrue = 0x01 according to X11/Xproto.h.
+  -- [3] http://www.sbin.org/doc/Xlib
+
+  result = try(socket:receive_bytes(1))
+  socket:close()
+
+  -- Check if first byte received is 0x01 (xTrue: succeed).
+  if string.match(result, "^\001") then
+    return true, "X server access is granted"
+  end
+end