Hi,
I'm still quite new to using lua as a dissector language. I managed to
write a first dissector for our specific messages. The message itself is
encrypted so for passing the data to the next layer (dissector) I have
to decrypt the data. How do I do that?
My code so far:
function mpiccom7_proto.dissector(buffer,pinfo,tree)
pinfo.cols.protocol = "com7" -- fill protocol column
local data = buffer():string() -- string version of the buffer
local datalen = buffer:len()
-- fill info pane -----------------------
local t = tree:add(mpiccom7_proto,buffer())
t:add(f_len,datalen)
t:add(f_checksum,buffer(datalen-1,1))
-- evaluate checksum --------------------
local framecheck
framecheck = 0
for i = 1, data:len()-1 -- for all the chars in buffer string
do
framecheck = framecheck + buffer(i,1):uint()
end
if framecheck == 0 then -- no frameerror! continue!
t:add(f_frameerror,0)
... do some decryption here?!
else -- frameerror!
t:add(f_frameerror,1)
end
end
That works so far. Now, if the checksum is ok (no frameerror) I would
like to decrypt the data and pass it to the next dissector to evaluate
the content of the frame further.
--
Christian Gurk
Electronics Working Group / Research & Development
Max-Planck-Insitute for Chemistry, Mainz, Germany
+49-6131-305387 / christian.gurk@xxxxxxx
