dissector.lua

package.path = package.path .. ";./lockbox/?.lua"

local String = require("string");

local Array = require("lockbox.util.array");
local Stream = require("lockbox.util.stream");

local CBCMode = require("lockbox.cipher.mode.cbc");

local PKCS7Padding = require("lockbox.padding.pkcs7");
local ZeroPadding = require("lockbox.padding.zero");

local AES256Cipher = require("lockbox.cipher.aes256");


validity90_proto = Proto("validity90", "Validity 90 fingerprint reader protocol")

local f = validity90_proto.fields
f.f_magic_header = ProtoField.uint24("validity90.magic", "Magic Header", base.HEX)
f.f_length = ProtoField.uint16("validity90.length", "Packet length bytes", base.DEC)
f.f_iv = ProtoField.bytes("validity90.iv", "Encryption AES IV")
f.f_data = ProtoField.bytes("validity90.data", "Encrypted data")
f.f_dec_data = ProtoField.bytes("validity90.dec_data", "Decrypted data")
f.f_particial = ProtoField.bool("validity90.partial", "Is partial", base.NONE, {[0] = "no", [1] = "yes"})

local f_direction = Field.new("usb.endpoint_number.direction")

local CONST_MAGIC_HEADER_44 = ByteArray.new("44000000")
local CONST_MAGIC_HEADER = ByteArray.new("170303")
local CONST_MAGIC_HEADER_TLS_DATA = ByteArray.new("17")
local CONST_MAGIC_HEADER_TLS = ByteArray.new("16")
local CONST_MAGIC_HEADER_TLS15 = ByteArray.new("15")
local CONST_MAGIC_HEADER_TLS14 = ByteArray.new("14")

local packetDb = {}
local partialBuffer = nil
local sslDissector = Dissector.get('ssl')

local function decode_aes(ivStr, dataStr)
    -- body
    local decipher = CBCMode.Decipher()
    
    local key = nil
    local dir = f_direction()
    
    if tostring(f_direction()) == "1" then
        key = Array.fromHex(validity90_proto.prefs["aes_in"])
    else
        key = Array.fromHex(validity90_proto.prefs["aes_out"])
    end

    local iv = Array.fromHex(ivStr)
    local ciphertext = Array.fromHex(dataStr)
    decipher
            .setKey(key)
            .setBlockCipher(AES256Cipher)
            .setPadding(PKCS7Padding);

    local plainOutput = decipher
                        .init()
                        .update(Stream.fromArray(iv))
                        .update(Stream.fromArray(ciphertext))
                        .finish()
                        .asHex();

    return plainOutput
end

function parseSsl(buffer, pinfo, tree)
    sslDissector:call(buffer, pinfo, tree)
end

function validity90_proto.dissector(buffer, pinfo, tree)
    local buf = nil

    if packetDb[pinfo.number] == nil or packetDb[pinfo.number].buf == nil then
        packetDb[pinfo.number] = {};

        if partialBuffer == nil then
            partialBuffer = buffer:bytes()
            buf = partialBuffer:tvb("New joint packet")
        else
            partialBuffer:append(buffer:bytes())
            buf = partialBuffer:tvb("Joint packet")
        end
    else
        local state = packetDb[pinfo.number]

        buf = state.buf:tvb("Joint packet [loaded]")
    end

    -- buf = buffer:bytes():tvb("Joint packet")
    -- buf = buffer

    pinfo.cols["protocol"] = "Validity90"

    -- create protocol tree
    local t_validity90 = tree:add(validity90_proto, buf())
    local offset = 0

    -- pinfo.cols["src"] = 'CLIENT'
    -- pinfo.cols["dst"] = 'SERVER'
    -- pinfo.cols["port_type"] = "2"
    -- pinfo.cols["src_port"] = "0"
    -- pinfo.cols["dst_port"] = "443"
    

    -- Header
    local magic_header = buf(offset, 3)
    local magic_header4 = buf(offset, 4)
    local magic_header1 = buf(offset, 1)

    if magic_header1:bytes() == CONST_MAGIC_HEADER_TLS 
        or magic_header1:bytes() == CONST_MAGIC_HEADER_TLS_DATA 
        or magic_header1:bytes() == CONST_MAGIC_HEADER_TLS14
        or magic_header1:bytes() == CONST_MAGIC_HEADER_TLS15
        then
        offset = offset + 3

        pcall(parseSsl, buf, pinfo, tree)

        if magic_header:bytes() == CONST_MAGIC_HEADER then
            t_validity90:add(f.f_magic_header, magic_header)

            -- Len
            local len = buf(offset, 2)
            offset = offset + 2
            t_validity90:add(f.f_length, len)
            
            if buf:len() - 5 < len:uint() then
                pinfo.cols["info"]:append(string.format(" INCOMPLETE %d left", len:uint() - buf:len() + 5))
                t_validity90:add(f.f_particial, true)
            elseif buf:len() - 5 == len:uint() then
                pinfo.cols["info"]:append(string.format(" COMPLETED", len:uint() - buf:len() + 5))
                partialBuffer = nil

                t_validity90:add(f.f_particial, 0)

                -- iv
                local iv = buf(offset, 16)
                offset = offset + 16
                t_validity90:add(f.f_iv, iv)

                -- Raw Data
                local data = buf(offset)
                t_validity90:add(f.f_data, data)

                -- Decode
                local dec_data = ByteArray.new(decode_aes(iv:bytes():tohex(), data:bytes():tohex()))
                local res = dec_data:tvb("Decrypted")

                local pad_len = dec_data:get_index(dec_data:len() - 1) + 1
                dec_data:subset(0, dec_data:len() - 0x20 - pad_len):tvb("Unpadded")

                t_validity90:add(f.f_dec_data, res())
            else
                pinfo.cols["info"]:append(string.format(" INVALID", len:uint() - buf:len() + 5))
                partialBuffer = nil
            end
        else
            t_validity90:add(f.f_magic_header, magic_header)
            -- pinfo.cols["info"]:append(string.format(" Invalid header %#03x", magic_header:le_uint()))        

            partialBuffer = nil
        end

        packetDb[pinfo.number].buf = buf:bytes()
    elseif magic_header4:bytes() == CONST_MAGIC_HEADER_44 then
        offset = offset + 4
        partialBuffer = nil
        pcall(parseSsl, buf:bytes(offset):tvb("44 data"), pinfo, tree)
    else
        partialBuffer = nil
    end
end


-- preferences
validity90_proto.prefs["aes_in"] = Pref.string("IN AES Key", "", "")
validity90_proto.prefs["aes_out"] = Pref.string("OUT AES Key", "", "")


usb_table = DissectorTable.get("usb.bulk")
usb_table:add(0xFF, validity90_proto)
usb_table:add(0xFFFF, validity90_proto)