CRFv3.1 - LAN Client Side

-- Local Area Networking w/ CRFv3.1, Client Side
-- Most of the explanations are in the CRFv3.1 source code.

local identStr = "LAN"
local freq = 0xC01D

local router_id = -1
local modemSide = ""
local modem = {}
local lan_key = {}
local networks_available = {}

local svcRunning = false

if not fs.exists("AES") then
    print("AES library does not exist, attempting to download...")
    if http then
        local wHandle = http.get("http://pastebin.com/raw.php?i=rCYDnCxn")
        if wHandle then
            local fHandle = fs.open("AES", "w")
            if fHandle then
                fHandle.write(wHandle.readAll())
                fHandle.close()
            else
                print("Could not open AES for writing.")
            end
            wHandle.close()
        else
            print("Could not connect to pastebin.")
        end
    else
        print("HTTP is disabled.")
    end
end

if not fs.exists("SHA2") then
    print("SHA2 library does not exist, attempting to download...")
    if http then
        local wHandle = http.get("http://pastebin.com/raw.php?i=9c1h7812")
        if wHandle then
            local fHandle = fs.open("SHA2", "w")
            if fHandle then
                fHandle.write(wHandle.readAll())
                fHandle.close()
            else
                print("Could not open SHA2 for writing.")
            end
            wHandle.close()
        else
            print("Could not connect to pastebin.")
        end
    else
        print("HTTP is disabled.")
    end
end

local secureLANEnabled = true

if (not ((AES ~= nil) or os.loadAPI("AES"))) or (not ((SHA2 ~= nil) or os.loadAPI("SHA2"))) then
    print("Could not load encryption libraries; encrypted LAN functionality disabled!")
    secureLANEnabled = false
end


local function raw_recv(timeout, id)
    local t = {}
    if timeout then
        t = os.startTimer(timeout)
    end
    while true do
        local event, side, sCH, rCh, data = os.pullEvent()
        if event == "modem_message" then
            data = textutils.unserialize(data)
            if type(data) == "table" then
                if data[1] == identStr then
                    if data[4] == os.computerID() then
                        if ((id ~= nil) and (id == data[2])) or (id == nil) then
                            return side, data
                        end
                    end
                end
            end
        elseif event == "timer" then
            if side == t then
                return
            end
        end
    end
end

function authenticate(side, id, key)
    assert((type(key) == "string"), "authenticate: key type must be a string")
    local _, k = SHA2.digestStr(key)
    lan_key = SHA2.hashToBytes(k)
    if peripheral.isPresent(side) then
        modem = peripheral.wrap(side)
        modem.open(freq)
        modemSide = side
        modem.transmit(freq, freq, textutils.serialize( {identStr, os.computerID(), "auth_req", id} ))
        while true do
            local sender, data = raw_recv(10, id)
            if data then
                if data[3] == "auth_challenge" then
                    local challenge = data[5]
                    local response = AES.encrypt_block(challenge, lan_key)
                    modem.transmit(freq, freq, textutils.serialize( {identStr, os.computerID(), "auth_response", id, response} ))
                elseif data[3] == "auth_good" then
                    return true
                elseif data[3] == "auth_fail" then
                    --modem.closeAll()
                    lan_key = {}
                    --modem = {}
                    --modemSide = ""
                    return false
                end
            else
                return false
            end
        end
    end
end

function associate(side, id)
    if peripheral.isPresent(side) then
        modem = peripheral.wrap(side)
        modem.open(freq)
        modemSide = side
        modem.transmit(freq, freq, textutils.serialize( {identStr, os.computerID(), "assoc", id} ))
        local s, data = raw_recv(10, id)
        if data then
            if data[3] == "assoc_ack" then
                router_id = id
                return true
            end
        end
    end
    modem = {}
    modemSide = ""
    return false
end

function disassociate()
    if modem.transmit and (router_id > -1) then
        modem.transmit(freq, freq, textutils.serialize( {identStr, os.computerID(), "disassoc", router_id} ))
        local s, data = raw_recv(10, router_id)
        if data then
            if data[3] == "disassoc_ack" then
                modem.closeAll()
                router_id = -1
                modem = {}
                modemSide = ""
                return true
            end
        end
    end
    return false
end

function requiresAuth(side, id)
    if networks_available[id] then
        return networks_available[id][2]
    end
    if peripheral.isPresent(side) then
        local m = peripheral.wrap(side)
        m.open(freq)
        m.transmit(freq, freq, textutils.serialize( {identStr, os.computerID(), "auth_required", id} ))
        while true do
            local sender, data = raw_recv(10, id)
            if data then
                if data[3] == "auth_not_required" then
                    m.closeAll()
                    networks_available[id] = {"", false, os.clock()}
                    return false
                elseif data[3] == "auth_required" then
                    m.closeAll()
                    networks_available[id] = {"", true, os.clock()}
                    return true
                end
            else
                return false
            end
        end
    end
end

function connect(side, id, key)
    if requiresAuth(side, id) then
        if not authenticate(side, id, key) then
            return false
        end
    end
    return associate(side, id)
end

function force_disconnect()
    if modem.transmit and (router_id > -1) then
        if not disconnect() then
            modem.closeAll()
            router_id = -1
            modem = {}
            modemSide = ""
        end
        return true
    end
    return false
end

function get_router()
    return router_id
end

function get_id_list()
    if modem.transmit and (router_id > -1) then
        modem.transmit(freq, freq, textutils.serialize( {identStr, os.computerID(), "id_list", router_id} ))
        local s, data = raw_recv(10, router_id)
        if data then
            if data[3] == "id_list" then
                return data[5]
            end
        end
    end
    return
end

function get_lan_list()
    if modem.transmit and (router_id > -1) then
        modem.transmit(freq, freq, textutils.serialize( {identStr, os.computerID(), "lan_list", router_id} ))
        local s, data = raw_recv(10, router_id)
        if data then
            if data[3] == "id_list" then
                return data[5]
            end
        end
    end
    return
end

function send(id, data)
    if modem.transmit and (router_id > -1) then
        if (#lan_key == 0) then
            modem.transmit(freq, freq, textutils.serialize( {identStr, os.computerID(), "data", router_id, id, data} ))
            local s, data = raw_recv(10, router_id)
            if data then
                if data[3] == "data_ack" then
                    return true
                elseif data[3] == "data_fail" then
                    return false
                end
            end
        else
            local packet = {id, data}
            local plain_data = {}
            local plain_data_str = textutils.serialize(packet)
            local iv = {}
            for i=1, 16 do
                iv[i] = math.random(0, 255)
            end
            for i=1, #plain_data_str do
                plain_data[i] = string.byte(plain_data_str, i, i)
            end
            local enc_packet = AES.encrypt_bytestream(plain_data, lan_key, iv)
            modem.transmit(freq, freq, textutils.serialize( {identStr, os.computerID(), "encrypted_data", router_id, iv, enc_packet} ))
            local s, data = raw_recv(10, router_id)
            if data then
                if data[3] == "data_ack" then
                    return true
                elseif data[3] == "data_fail" then
                    return false
                end
            end
        end
    end
    return false
end

function broadcast(data)
    return send(-1, data)
end

function backgroundLoop()
    svcRunning = true
    local timer = os.startTimer(30)
    while true do
        local event, side, sCh, rCh, data = os.pullEvent()
        if event == "modem_message" then
            --print(data)
            data = textutils.unserialize(data)
            if type(data) == "table" then
                if (data[1] == identStr) and ((data[4] == os.computerID()) or (data[4] == -1)) then
                    if (data[3] == "data") then
                        os.queueEvent("routed_message", data[5], data[6])
                    elseif (data[3] == "encrypted_data") then
                        local iv = data[5]
                        local enc_data = data[6]
                        if (#lan_key ~= 0) then
                            local dec_data = AES.decrypt_bytestream(enc_data, lan_key, iv)
                            local dec_str = ""
                            for i=1, #dec_data do
                                dec_str = dec_str..string.char(dec_data[i])
                            end
                            dec_packet = textutils.unserialize(dec_str)
                            if type(dec_packet) == "table" then
                                os.queueEvent("routed_message", dec_packet[1], dec_packet[2])
                                --handle_datagram(side, {data[1], data[2], "data", data[4]}, dec_packet[1], dec_packet[2])
                            end
                        end
                    elseif (data[3] == "rekey") then
                        os.queueEvent("LAN_network_rekey")
                    elseif (data[3] == "beacon") then
                        if not networks_available[data[2]] then
                            os.queueEvent("LAN_new_network", data[2], data[5], data[6])
                        end
                        networks_available[data[2]] = {data[5], data[6], os.clock()}
                    end
                end
            end
        elseif event == "timer" then
            if side == timer then
                local removeList = {}
                for i,v in pairs(networks_available) do
                    if v[3] then
                        if (os.clock() - v[3]) >= 45 then
                            table.insert(removeList, i)
                        end
                    end
                end
                for i=1, #removeList do
                    networks_available[removeList[i]] = nil
                end
            end
        end
    end
end

function receive(timeout, id)
    while true do
        local side, data = raw_recv(timeout, router_id)
        if type(data) == "table" then
            if (data[1] == "LAN") and ((data[3] == "data") or (data[3] == "encrypted_data")) and (data[4] == os.computerID()) and ((id == nil) or (data[5] == id)) then -- In order: Ident string checking, packet type checking, recipient checking, and non-local sender checking if applicable.
                if (data[3] == "encrypted_data") then
                    local iv = data[5]
                    local enc_data = data[6]
                    if (#lan_key ~= 0) then
                        local dec_data = AES.decrypt_bytestream(enc_data, lan_key, iv)
                        local dec_str = ""
                        for i=1, #dec_data do
                            dec_str = dec_str..string.char(dec_data[i])
                        end
                        dec_packet = textutils.unserialize(dec_str)
                        if type(dec_packet) == "table" then
                            return dec_packet[1], dec_packet[2]
                            --handle_datagram(side, {data[1], data[2], "data", data[4]}, dec_packet[1], dec_packet[2])
                        end
                    end
                else
                    return data[5], data[6]
                end
            end
        elseif side == nil then
            return
        end
    end
end

function join_group(group)
    if modem.transmit and (router_id > -1) then
        modem.transmit(freq, freq, textutils.serialize( {identStr, os.computerID(), "join_group", router_id, group} ))
        local s, data = raw_recv(10, router_id)
        if data then
            if data[3] == "group_ack" then
                return true
            elseif data[3] == "group_fail" then
                return false
            end
        end
    else
        return false
    end
end

function leave_group(group)
    if modem.transmit and (router_id > -1) then
        modem.transmit(freq, freq, textutils.serialize( {identStr, os.computerID(), "leave_group", router_id, group} ))
        local s, data = raw_recv(10, router_id)
        if data then
            if data[3] == "group_ack" then
                return true
            elseif data[3] == "group_fail" then
                return false
            end
        end
    else
        return false
    end
end

function get_networks()
    return networks_available
end

if shell then
    local file = fs.open(shell.getRunningProgram(), "r")
    if file then
        local l = file.readLine()
        file.close()
        if string.match(l, "Local Area Network") and string.match(l, "Client Side") then
            local apiName = fs.getName(shell.getRunningProgram())
            if not _G[apiName] then
                os.loadAPI(shell.getRunningProgram())
            end
            local args = {...}
            if args[1] == "connect" then
                connect(args[2], args[3], args[4])
            elseif (args[1] == "disconnect") or (args[1] == "disassociate") then
                disassociate()
            elseif (args[1] == "receive") or (args[1] == "recv") then
                receive(tonumber(args[2]))
            elseif (args[1] == "send") then
                if (tonumber(args[2]) ~= nil) and (type(args[3]) == "string") then
                    send(tonumber(args[2]), args[3])
                end
            elseif (args[1] == "help") or (#args == 0) then
                print("LANClient -- CRFv3.1 LAN API and basic interface")
                print(string.rep("-", term.getSize()))
                print("Usage: LANClient [action] [args]")
                print("Actions:")
                print("connect (\"connect [side] [id] [key]\"): Connect to a LAN.")
                print("disconnect (\"disconnect\"): Disconnect from a LAN.  ")
                print("receive / recv (\"recv [timeout]\"): Receive from a LAN.")
                print("send (\"send [id] [data]\"): Send simple messages via a LAN.")
                print("Information on the API can be found on the ComputerCraft forum topic.")
            end
        end
    end
end