Companion scripts written for the Sharkfest conference

1 files changed, 127 insertions, 0 deletions

diff --git a/wireshark/sharkfest_scripts/tcp_no_data_exchanged.lua b/wireshark/sharkfest_scripts/tcp_no_data_exchanged.lua
new file mode 100644
index 000000000..7d9ac9839
--- /dev/null
+++ b/wireshark/sharkfest_scripts/tcp_no_data_exchanged.lua
@@ -0,0 +1,127 @@
+
+--
+-- Sharkfest 2021
+--
+-- This is going to be an example of a lua script that can be written for cybersecurity reasons.
+-- TCP No Data Exchanged:
+-- The TCP No Data Exchanged is a really important script to check if flows are suspicious
+-- Because usually, a typic TCP traffic, have some payload and it is not 0. Instead, in some attacks,
+-- for example the TCP SYN Scan or SYN Flood, there is a lot of TCP traffic with no data.
+
+local f_tcp_traffic = Field.new("tcp")
+local f_tcp_payload = Field.new("tcp.len")
+local f_ip_src = Field.new("ip.src")
+local f_ip_dst = Field.new("ip.dst")
+local f_port_src = Field.new("tcp.srcport")
+local f_port_dst = Field.new("tcp.dstport")
+local f_conn_fin = Field.new("tcp.flags.fin")
+
+--############################################
+
+local function getstring(finfo)
+	local ok, val = pcall(tostring, finfo)
+	if not ok then val = "(unknown)" end
+	return val
+end
+
+--############################################
+
+local function processResponse(tcp_table, src, src_port, dst, dst_port, payload)
+    local key = src .. ":" .. src_port .. "->" .. dst .. ":" .. dst_port
+
+    -- Create the table entry if needed
+    if not tcp_table[key] then
+        local key2 = dst .. ":" .. dst_port .. "->" ..  src .. ":" .. src_port
+        if not tcp_table[key2] then
+            tcp_table[key] = {
+                payload = 0,
+                fin = false
+            }
+        else
+            key = key2
+        end
+    end
+
+    -- Increase the stats
+    tcp_table[key]["payload"] = tcp_table[key]["payload"] + getstring(payload.value)
+
+    if getstring(f_conn_fin().value) == true then
+        tcp_table[key]["fin"] = true
+    end
+
+    return tcp_table
+end
+
+--############################################
+
+local function processPackets(pinfo,tvb, tcp_table) 
+    -- Call the function that extracts the field
+    local tcp_traffic = f_tcp_traffic()
+    local tcp_payload = f_tcp_payload()
+
+    --Check if there is an HTTP request or reply
+    if tcp_traffic then
+        local src = getstring(f_ip_src().value)
+        local dst = getstring(f_ip_dst().value)
+        local src_port = getstring(f_port_src().value)
+        local dst_port = getstring(f_port_dst().value)
+
+        tcp_table = processResponse(tcp_table, src, src_port, dst, dst_port, tcp_payload)
+    end
+
+    return tcp_table
+end
+
+--############################################
+
+local function tcpPayload()
+	-- Declare the window we will use
+	local tw = TextWindow.new("TCP No Data Exchanged")
+
+	local tcp_table = {}
+
+	local tap = Listener.new();
+
+	local function removeListener()
+		-- This way we remove the listener that otherwise will remain running indefinitely
+		tap:remove();
+	end
+
+	-- We tell the window to call the remove() function when closed
+	tw:set_atclose(removeListener)
+
+	-- This function will be called once for each packet
+	function tap.packet(pinfo,tvb)
+        tcp_table = processPackets(pinfo,tvb, tcp_table)
+	end
+
+	-- This function will be called once every few seconds to update our window
+	function tap.draw(t)
+		tw:clear()
+		
+        for flow in pairs(tcp_table) do
+			local payload = tcp_table[flow]["payload"]
+            local fin = tcp_table[flow]["fin"]
+            local danger = ""
+
+            if tonumber(payload) == 0 then
+                danger = "-- DANGER: NO DATA EXCHANGED FOR THIS FLOW --\n"
+            end
+
+			tw:append(danger .. flow .. ":\n\tPayload: " .. payload .. "\n\tFlow Ended: " .. tostring(fin) .. "\n\n");
+		end
+	end
+
+	-- This function will be called whenever a reset is needed
+	-- e.g. when reloading the capture file
+	function tap.reset()
+		tw:clear()
+		tcp_table = {}
+	end
+
+	-- Ensure that all existing packets are processed.
+	retap_packets()
+end
+
+-- Register the menu Entry
+register_menu("Sharkfest/TCP No Data Exchanged", tcpPayload, MENU_TOOLS_UNSORTED)
\ No newline at end of file