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grab_beacon_config.nse
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grab_beacon_config.nse
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-- Head
local shortport = require "shortport"
local http = require "http"
local string = require "string"
local rand = require "rand"
local openssl = require "openssl"
local stdnse = require "stdnse"
local json = require "json"
description = [[
Simple PoC script to scan and acquire CobaltStrike Beacon configurations.
Based on :
JPCERT :: cobaltstrikescan.py
Sentinel-One :: parse_beacon_config.py
Didier Stevens :: 1768.py
Roman Emelynaov :: L8_get_beacon.py
]]
categories = {"safe"}
author = "Wade Hickey, Zach Stanford"
-- Rule
portrule = shortport.http
-- Action
local function generate_checksum(input)
-- 92 and 93 are options
local trial = ""
local total = 0
local i = 1
while (total ~= input) do
total = 0
trial = rand.random_string(4,"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890")
for i = 1, 4 do
total = (total + string.byte(string.sub(trial,i,i))) % 256
i = i + 1
end
end
return "/" .. trial
end
local function xor_finder()
end
local function extract_value(key_name, format, hex_identifier, content)
local port_index = string.find(content,"\x00\x02\x00\x01\x00\x02",1,true)
if (port_index) then
local port = string.unpack(">H",content,port_index + 6)
return port
end
end
local function parse_field(key_name,contents,hex_flag,format)
local index = ""
local beacon_types = {}
beacon_types[0] = "0 (HTTP)"
beacon_types[1] = "1 (Hybrid HTTP DNS)"
beacon_types[2] = "2 (SMB)"
beacon_types[3] = "3 (Unknown)"
beacon_types[4] = "4 (TCP)"
beacon_types[5] = "5 (Unknown)"
beacon_types[6] = "6 (Unknown)"
beacon_types[7] = "7 (Unknown)"
beacon_types[8] = "8 (HTTPS)"
beacon_types[9] = "9 (Unkown)"
beacon_types[10] = "10 (Bind TCP)"
local access_types = {}
access_types[0] = "0 (Unknown)"
access_types[1] = "1 (Use direct connection)"
access_types[2] = "2 (Use IE settings)"
access_types[3] = "3 (Unknown)"
access_types[4] = "4 (Use proxy server)"
if key_name == "Beacon Type" then
index = string.find(contents,hex_flag,1,true)
if index == nil then
return nil
end
return beacon_types[string.unpack(format,contents,index + string.len(hex_flag))]
elseif key_name == "Proxy Access Type" then
index = string.find(contents,hex_flag,1,true)
if index == nil then
return nil
end
return access_types[string.unpack(format,contents,index + string.len(hex_flag))]
elseif key_name == "DNS Idle" then
index = string.find(contents,hex_flag,1,true)
if index == nil then
return nil
end
local address = ""
address = address .. string.unpack(format,contents,index + string.len(hex_flag) + 0) .. "."
address = address .. string.unpack(format,contents,index + string.len(hex_flag) + 1) .. "."
address = address .. string.unpack(format,contents,index + string.len(hex_flag) + 2) .. "."
address = address .. string.unpack(format,contents,index + string.len(hex_flag) + 3)
return address
else
index = string.find(contents,hex_flag,1,true)
if index == nil then
return nil
end
return string.unpack(format,contents,index + string.len(hex_flag))
end
end
local function grab_beacon(response)
local output = {}
local test_string = string.char(0xFF) .. string.char(0xFF) .. string.char(0xFF)
local return_string = ""
if (response.status == 200) then
if (http.response_contains(response, test_string, true)) then
local offset = string.find(response.rawbody, test_string) + 3
local endian = "<I"
local key = string.unpack(endian,response.rawbody,offset)
local size = string.unpack(endian,response.rawbody,offset+4) ~ key
local c = string.unpack(endian,response.rawbody,offset+8) ~ key
local mz = c & 0xffff
local x = math.floor(2 + (offset / 4))
local y = math.floor((string.len(response.rawbody)/4)-4)
local repacked = ""
local repacked2 = ""
for var=x,y do
a = string.unpack(endian,response.rawbody,var*4)
b = string.unpack(endian,response.rawbody,var*4+4)
z = tonumber(a) ~ tonumber(b)
repacked = repacked .. string.pack(endian,z ~ 0x2e2e2e2e) --version 4
repacked2 = repacked2 .. string.pack(endian,z ~ 0x69696969) --version 3
end
output["Beacon Type"] = parse_field("Beacon Type",repacked,"\x00\x01\x00\x01\x00\x02",">H")
if not output["Beacon Type"] then
output["Beacon Type"] = parse_field("Beacon Type",repacked2,"\x00\x01\x00\x01\x00\x02",">H")
repacked = repacked2
end
output["Port"] = parse_field("Port",repacked,"\x00\x02\x00\x01\x00\x02",">H")
output["Polling"] = parse_field("Polling",repacked,"\x00\x03\x00\x02\x00\x04",">I")
output["Jitter"] = parse_field("Jitter",repacked,"\x00\x05\x00\x01\x00\x02",">H")
output["Max DNS"] = parse_field("Max DNS",repacked,"\x00\x06\x00\x01\x00\x02",">H")
output["C2 Server"] = parse_field("C2 Server",repacked,"\x00\x08\x00\x03\x01\x00","z")
output["User Agent"] = parse_field("User Agent",repacked,"\x00\x09\x00\x03\x00\x80","z")
output["HTTP Method Path 2"] = parse_field("HTTP Method Path 2",repacked,"\x00\x0a\x00\x03\x00\x40","z")
output["Header 1"] = parse_field("Header 1",repacked,"\x00\x0c\x00\x03\x01\x00","z")
output["Header 2"] = parse_field("Header 2",repacked,"\x00\x0d\x00\x03\x01\x00","z")
output["Injection Process"] = parse_field("Injection Process",repacked,"\x00\x0e\x00\x03\x00\x40","z")
output["Pipe Name"] = parse_field("Pipe Name",repacked,"\x00\x0f\x00\x03\x00\x80","z")
output["Year"] = parse_field("Year",repacked,"\x00\x10\x00\x01\x00\x02",">H")
output["Month"] = parse_field("Month",repacked,"\x00\x11\x00\x01\x00\x02",">H")
output["Day"] = parse_field("Day",repacked,"\x00\x12\x00\x01\x00\x02",">H")
output["DNS Idle"] = parse_field("DNS Idle",repacked,"\x00\x13\x00\x02\x00\x04","B")
output["DNS Sleep"] = parse_field("DNS Sleep",repacked,"\x00\x14\x00\x02\x00\x04",">H")
output["Method 1"] = parse_field("Method 1",repacked,"\x00\x1a\x00\x03\x00\x10","z")
output["Method 2"] = parse_field("Method 2",repacked,"\x00\x1b\x00\x03\x00\x10","z")
output["Spawn To x86"] = parse_field("Spawn To x86",repacked,"\x00\x1d\x00\x03\x00\x40","z")
output["Spawn To x64"] = parse_field("Spawn To x64",repacked,"\x00\x1e\x00\x03\x00\x40","z")
output["Proxy Hostname"] = parse_field("Proxy Hostname",repacked,"\x00\x20\x00\x03\x00\x80","z")
output["Proxy Username"] = parse_field("Proxy Username",repacked,"\x00\x21\x00\x03\x00\x40","z")
output["Proxy Password"] = parse_field("Proxy Password",repacked,"\x00\x22\x00\x03\x00\x40","z")
output["Proxy Access Type"] = parse_field("Proxy Access Type",repacked,"\x00\x23\x00\x01\x00\x02","z")
output["CreateRemoteThread"] = parse_field("CreateRemoteThread",repacked,"\x00\x24\x00\x01\x00\x02","z")
output["Watermark"] = parse_field("Watermark",repacked,"\x00\x25\x00\x02\x00\x04",">I")
output["C2 Host Header"] = parse_field("C2 Host Header",repacked,"\x00\x36\x00\x03\x00\x80","z")
if (stdnse.get_script_args("save")) == "true" then
local write_out = io.open(stdnse.tohex(openssl.digest("sha256",response.body)) .. ".bin","w")
io.output(write_out)
io.write(response.body)
end
end
end
return output
end
action = function(host,port)
local json_output = {}
local uri_x86 = generate_checksum(92)
local uri_x64 = generate_checksum(93)
local response_x86 = http.get(host,port,uri_x86)
if response_x86.body == nil then
return "No Valid Response"
end
json_output['x86'] = {}
json_output['x86']['uri_queried'] = uri_x86
json_output['x86']['sha256'] = stdnse.tohex(openssl.digest("sha256",response_x86.body))
json_output['x86']['sha1'] = stdnse.tohex(openssl.digest("sha1",response_x86.body))
json_output['x86']['md5'] = stdnse.tohex(openssl.digest("md5",response_x86.body))
json_output['x86']['time'] = stdnse.clock_ms()
json_output['x86']['config'] = grab_beacon(response_x86)
local response_x64 = http.get(host,port,uri_x64)
if response_x64.body == nil then
return "No Valid Response"
end
json_output['x64'] = {}
json_output['x64']['uri_queried'] = uri_x64
json_output['x64']['sha256'] = stdnse.tohex(openssl.digest("sha256",response_x64.body))
json_output['x64']['sha1'] = stdnse.tohex(openssl.digest("sha1",response_x64.body))
json_output['x64']['md5'] = stdnse.tohex(openssl.digest("md5",response_x64.body))
json_output['x64']['time'] = stdnse.clock_ms()
json_output['x64']['config'] = grab_beacon(response_x64)
json_output = json.generate(json_output)
return json_output
end