Firewolf Encrypted Rednet Receive Demo

--  RC4
    --    RC4
    --    Implementation by AgentE382


    local cryptWrapper = function(plaintext, salt)
        local key = type(salt) == "table" and {unpack(salt)} or {string.byte(salt, 1, #salt)}
        local S = {}
        for i = 0, 255 do
            S[i] = i
        end

        local j, keylength = 0, #key
        for i = 0, 255 do
            j = (j + S[i] + key[i % keylength + 1]) % 256
            S[i], S[j] = S[j], S[i]
        end

        local i = 0
        j = 0
        local chars, astable = type(plaintext) == "table" and {unpack(plaintext)} or {string.byte(plaintext, 1, #plaintext)}, false

        for n = 1, #chars do
            i = (i + 1) % 256
            j = (j + S[i]) % 256
            S[i], S[j] = S[j], S[i]
            chars[n] = bit.bxor(S[(S[i] + S[j]) % 256], chars[n])
            if chars[n] > 127 or chars[n] == 13 then
                astable = true
            end
        end

        return astable and chars or string.char(unpack(chars))
    end


    local crypt = function(text, key)
        local resp, msg = pcall(cryptWrapper, text, key)
        if resp then
            return msg
        else
            return nil
        end
    end


--  Base64
    --
    --  Base64 Encryption/Decryption
    --  By KillaVanilla
    --  http://www.computercraft.info/forums2/index.php?/topic/12450-killavanillas-various-apis/
    --  http://pastebin.com/rCYDnCxn
    --



    local alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"


    local function sixBitToBase64(input)
        return string.sub(alphabet, input+1, input+1)
    end


    local function base64ToSixBit(input)
        for i=1, 64 do
            if input == string.sub(alphabet, i, i) then
                return i-1
            end
        end
    end


    local function octetToBase64(o1, o2, o3)
        local shifted = bit.brshift(bit.band(o1, 0xFC), 2)
        local i1 = sixBitToBase64(shifted)
        local i2 = "A"
        local i3 = "="
        local i4 = "="
        if o2 then
            i2 = sixBitToBase64(bit.bor( bit.blshift(bit.band(o1, 3), 4), bit.brshift(bit.band(o2, 0xF0), 4) ))
            if not o3 then
                i3 = sixBitToBase64(bit.blshift(bit.band(o2, 0x0F), 2))
            else
                i3 = sixBitToBase64(bit.bor( bit.blshift(bit.band(o2, 0x0F), 2), bit.brshift(bit.band(o3, 0xC0), 6) ))
            end
        else
            i2 = sixBitToBase64(bit.blshift(bit.band(o1, 3), 4))
        end
        if o3 then
            i4 = sixBitToBase64(bit.band(o3, 0x3F))
        end

        return i1..i2..i3..i4
    end


    local function base64ToThreeOctet(s1)
        local c1 = base64ToSixBit(string.sub(s1, 1, 1))
        local c2 = base64ToSixBit(string.sub(s1, 2, 2))
        local c3 = 0
        local c4 = 0
        local o1 = 0
        local o2 = 0
        local o3 = 0
        if string.sub(s1, 3, 3) == "=" then
            c3 = nil
            c4 = nil
        elseif string.sub(s1, 4, 4) == "=" then
            c3 = base64ToSixBit(string.sub(s1, 3, 3))
            c4 = nil
        else
            c3 = base64ToSixBit(string.sub(s1, 3, 3))
            c4 = base64ToSixBit(string.sub(s1, 4, 4))
        end
        o1 = bit.bor( bit.blshift(c1, 2), bit.brshift(bit.band( c2, 0x30 ), 4) )
        if c3 then
            o2 = bit.bor( bit.blshift(bit.band(c2, 0x0F), 4), bit.brshift(bit.band( c3, 0x3C ), 2) )
        else
            o2 = nil
        end
        if c4 then
            o3 = bit.bor( bit.blshift(bit.band(c3, 3), 6), c4 )
        else
            o3 = nil
        end
        return o1, o2, o3
    end


    local function splitIntoBlocks(bytes)
        local blockNum = 1
        local blocks = {}
        for i=1, #bytes, 3 do
            blocks[blockNum] = {bytes[i], bytes[i+1], bytes[i+2]}
            blockNum = blockNum+1
        end
        return blocks
    end


    function base64Encode(bytes)
        local blocks = splitIntoBlocks(bytes)
        local output = ""
        for i=1, #blocks do
            output = output..octetToBase64( unpack(blocks[i]) )
        end
        return output
    end


    function base64Decode(str)
        local bytes = {}
        local blocks = {}
        local blockNum = 1

        for i=1, #str, 4 do
            blocks[blockNum] = string.sub(str, i, i+3)
            blockNum = blockNum+1
        end

        for i=1, #blocks do
            local o1, o2, o3 = base64ToThreeOctet(blocks[i])
            table.insert(bytes, o1)
            table.insert(bytes, o2)
            table.insert(bytes, o3)
        end

        return bytes
    end


--  SHA-256
    --
    --  Adaptation of the Secure Hashing Algorithm (SHA-244/256)
    --  Found Here: http://lua-users.org/wiki/SecureHashAlgorithm
    --
    --  Using an adapted version of the bit library
    --  Found Here: https://bitbucket.org/Boolsheet/bslf/src/1ee664885805/bit.lua
    --



    local MOD = 2^32
    local MODM = MOD-1


    local function memoize(f)
        local mt = {}
        local t = setmetatable({}, mt)
        function mt:__index(k)
            local v = f(k)
            t[k] = v
            return v
        end
        return t
    end


    local function make_bitop_uncached(t, m)
        local function bitop(a, b)
            local res,p = 0,1
            while a ~= 0 and b ~= 0 do
                local am, bm = a % m, b % m
                res = res + t[am][bm] * p
                a = (a - am) / m
                b = (b - bm) / m
                p = p * m
            end
            res = res + (a + b) * p
            return res
        end

        return bitop
    end


    local function make_bitop(t)
        local op1 = make_bitop_uncached(t,2^1)
        local op2 = memoize(function(a)
            return memoize(function(b)
                return op1(a, b)
            end)
        end)
        return make_bitop_uncached(op2, 2 ^ (t.n or 1))
    end


    local customBxor1 = make_bitop({[0] = {[0] = 0,[1] = 1}, [1] = {[0] = 1, [1] = 0}, n = 4})

    local function customBxor(a, b, c, ...)
        local z = nil
        if b then
            a = a % MOD
            b = b % MOD
            z = customBxor1(a, b)
            if c then
                z = customBxor(z, c, ...)
            end
            return z
        elseif a then
            return a % MOD
        else
            return 0
        end
    end


    local function customBand(a, b, c, ...)
        local z
        if b then
            a = a % MOD
            b = b % MOD
            z = ((a + b) - customBxor1(a,b)) / 2
            if c then
                z = customBand(z, c, ...)
            end
            return z
        elseif a then
            return a % MOD
        else
            return MODM
        end
    end


    local function bnot(x)
        return (-1 - x) % MOD
    end


    local function rshift1(a, disp)
        if disp < 0 then
            return lshift(a, -disp)
        end
        return math.floor(a % 2 ^ 32 / 2 ^ disp)
    end


    local function rshift(x, disp)
        if disp > 31 or disp < -31 then
            return 0
        end
        return rshift1(x % MOD, disp)
    end


    local function lshift(a, disp)
        if disp < 0 then
            return rshift(a, -disp)
        end
        return (a * 2 ^ disp) % 2 ^ 32
    end


    local function rrotate(x, disp)
        x = x % MOD
        disp = disp % 32
        local low = customBand(x, 2 ^ disp - 1)
        return rshift(x, disp) + lshift(low, 32 - disp)
    end


    local k = {
        0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5,
        0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
        0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
        0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
        0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc,
        0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
        0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7,
        0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
        0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
        0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
        0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3,
        0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
        0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5,
        0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
        0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
        0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2,
    }


    local function str2hexa(s)
        return (string.gsub(s, ".", function(c)
            return string.format("%02x", string.byte(c))
        end))
    end


    local function num2s(l, n)
        local s = ""
        for i = 1, n do
            local rem = l % 256
            s = string.char(rem) .. s
            l = (l - rem) / 256
        end
        return s
    end


    local function s232num(s, i)
        local n = 0
        for i = i, i + 3 do
            n = n*256 + string.byte(s, i)
        end
        return n
    end


    local function preproc(msg, len)
        local extra = 64 - ((len + 9) % 64)
        len = num2s(8 * len, 8)
        msg = msg .. "\128" .. string.rep("\0", extra) .. len
        assert(#msg % 64 == 0)
        return msg
    end


    local function initH256(H)
        H[1] = 0x6a09e667
        H[2] = 0xbb67ae85
        H[3] = 0x3c6ef372
        H[4] = 0xa54ff53a
        H[5] = 0x510e527f
        H[6] = 0x9b05688c
        H[7] = 0x1f83d9ab
        H[8] = 0x5be0cd19
        return H
    end


    local function digestblock(msg, i, H)
        local w = {}
        for j = 1, 16 do
            w[j] = s232num(msg, i + (j - 1)*4)
        end
        for j = 17, 64 do
            local v = w[j - 15]
            local s0 = customBxor(rrotate(v, 7), rrotate(v, 18), rshift(v, 3))
            v = w[j - 2]
            w[j] = w[j - 16] + s0 + w[j - 7] + customBxor(rrotate(v, 17), rrotate(v, 19), rshift(v, 10))
        end

        local a, b, c, d, e, f, g, h = H[1], H[2], H[3], H[4], H[5], H[6], H[7], H[8]
        for i = 1, 64 do
            local s0 = customBxor(rrotate(a, 2), rrotate(a, 13), rrotate(a, 22))
            local maj = customBxor(customBand(a, b), customBand(a, c), customBand(b, c))
            local t2 = s0 + maj
            local s1 = customBxor(rrotate(e, 6), rrotate(e, 11), rrotate(e, 25))
            local ch = customBxor (customBand(e, f), customBand(bnot(e), g))
            local t1 = h + s1 + ch + k[i] + w[i]
            h, g, f, e, d, c, b, a = g, f, e, d + t1, c, b, a, t1 + t2
        end

        H[1] = customBand(H[1] + a)
        H[2] = customBand(H[2] + b)
        H[3] = customBand(H[3] + c)
        H[4] = customBand(H[4] + d)
        H[5] = customBand(H[5] + e)
        H[6] = customBand(H[6] + f)
        H[7] = customBand(H[7] + g)
        H[8] = customBand(H[8] + h)
    end


    local function sha256(msg)
        msg = preproc(msg, #msg)
        local H = initH256({})
        for i = 1, #msg, 64 do
            digestblock(msg, i, H)
        end
        return str2hexa(num2s(H[1], 4) .. num2s(H[2], 4) .. num2s(H[3], 4) .. num2s(H[4], 4) ..
            num2s(H[5], 4) .. num2s(H[6], 4) .. num2s(H[7], 4) .. num2s(H[8], 4))
    end


local protocolName = "Firewolf"


--  Cryptography
    local Cryptography = {}
    Cryptography.sha = {}
    Cryptography.base64 = {}
    Cryptography.aes = {}


    function Cryptography.bytesFromMessage(msg)
        local bytes = {}

        for i = 1, msg:len() do
            local letter = string.byte(msg:sub(i, i))
            table.insert(bytes, letter)
        end

        return bytes
    end


    function Cryptography.messageFromBytes(bytes)
        local msg = ""

        for i = 1, #bytes do
            local letter = string.char(bytes[i])
            msg = msg .. letter
        end

        return msg
    end


    function Cryptography.bytesFromKey(key)
        local bytes = {}

        for i = 1, key:len() / 2 do
            local group = key:sub((i - 1) * 2 + 1, (i - 1) * 2 + 1)
            local num = tonumber(group, 16)
            table.insert(bytes, num)
        end

        return bytes
    end


    function Cryptography.sha.sha256(msg)
        return sha256(msg)
    end


    function Cryptography.aes.encrypt(msg, key)
        return base64Encode(crypt(msg, key))
    end


    function Cryptography.aes.decrypt(msg, key)
        return crypt(base64Decode(msg), key)
    end


    function Cryptography.base64.encode(msg)
        return base64Encode(Cryptography.bytesFromMessage(msg))
    end


    function Cryptography.base64.decode(msg)
        return Cryptography.messageFromBytes(base64Decode(msg))
    end


--  Modem
    local Modem = {}

    Modem.modems = {}

    function Modem.exists()
        Modem.exists = false
        for _, side in pairs(rs.getSides()) do
            if peripheral.isPresent(side) and peripheral.getType(side) == "modem" then
                Modem.exists = true

                if not Modem.modems[side] then
                    Modem.modems[side] = peripheral.wrap(side)
                end
            end
        end

        return Modem.exists
    end


    function Modem.open(channel)
        if not Modem.exists then
            return false
        end

        for side, modem in pairs(Modem.modems) do
            modem.open(channel)
        end

        return true
    end


    function Modem.close(channel)
        if not Modem.exists then
            return false
        end

        for side, modem in pairs(Modem.modems) do
            modem.close(channel)
        end

        return true
    end


    function Modem.isOpen(channel)
        if not Modem.exists then
            return false
        end

        local isOpen = false
        for side, modem in pairs(Modem.modems) do
            if modem.isOpen(channel) then
                isOpen = true
                break
            end
        end

        return isOpen
    end


    function Modem.send(channel, msg)
        if not Modem.exists then
            return false
        end

        if not Modem.isOpen(channel) then
            Modem.open(channel)
        end

        for side, modem in pairs(Modem.modems) do
            modem.transmit(channel, channel, msg)
        end

        return true
    end


--  Handshake
    local Handshake = {}

    Handshake.prime = 625210769
    Handshake.channel = 54569
    Handshake.base = -1
    Handshake.secret = -1
    Handshake.sharedSecret = -1
    Handshake.packetHeader = "["..protocolName.."-Handshake-Packet Header]"
    Handshake.packetMatch = "%["..protocolName.."%-Handshake%-Packet Header%](.+)"

    function Handshake.exponentWithModulo(base, exponent, modulo)
        local remainder = base

        for i = 1, exponent-1 do
            remainder = remainder * remainder
            if remainder >= modulo then
                remainder = remainder % modulo
            end
        end

        return remainder
    end


    function Handshake.clear()
        Handshake.base = -1
        Handshake.secret = -1
        Handshake.sharedSecret = -1
    end

    function Handshake.generateInitiatorData()
        Handshake.base = math.random(10,99999)
        Handshake.secret = math.random(10,99999)
        return {
            type = "initiate",
            prime = Handshake.prime,
            base = Handshake.base,
            moddedSecret = Handshake.exponentWithModulo(Handshake.base, Handshake.secret, Handshake.prime)
        }
    end

    function Handshake.generateResponseData(initiatorData)
        local isPrimeANumber = type(initiatorData.prime) == "number"
        local isPrimeMatching = initiatorData.prime == Handshake.prime
        local isBaseANumber = type(initiatorData.base) == "number"
        local isInitiator = initiatorData.type == "initiate"
        local isModdedSecretANumber = type(initiatorData.moddedSecret) == "number"
        local areAllNumbersNumbers = isPrimeANumber and isBaseANumber and isModdedSecretANumber

        if areAllNumbersNumbers and isPrimeMatching then
            if isInitiator then
                Handshake.base = initiatorData.base
                Handshake.secret = math.random(10,99999)
                Handshake.sharedSecret = Handshake.exponentWithModulo(initiatorData.moddedSecret, Handshake.secret, Handshake.prime)
                return {
                    type = "response",
                    prime = Handshake.prime,
                    base = Handshake.base,
                    moddedSecret = Handshake.exponentWithModulo(Handshake.base, Handshake.secret, Handshake.prime)
                }, Handshake.sharedSecret
            elseif initiatorData.type == "response" and Handshake.base > 0 and Handshake.secret > 0 then
                Handshake.sharedSecret = Handshake.exponentWithModulo(initiatorData.moddedSecret, Handshake.secret, Handshake.prime)
                return Handshake.sharedSecret
            else
                return false
            end
        else
            return false
        end
    end


--  Secure Connection
    local SecureConnection = {}
    SecureConnection.__index = SecureConnection


    SecureConnection.packetHeader = "["..protocolName.."-SecureConnection-Packet Header]"
    SecureConnection.packetMatch = "%["..protocolName.."%-SecureConnection%-Packet Header%](.+)"
    SecureConnection.connectionTimeout = 0.1
    SecureConnection.successPacketTimeout = 0.1


    function SecureConnection.new(secret, key, distance)
        local self = setmetatable({}, SecureConnection)
        self:setup(secret, key, distance)
        return self
    end


    function SecureConnection.verifyHeader(msg)
        if msg:match(SecureConnection.packetMatch) then
            return true
        else
            return false
        end
    end


    function SecureConnection:setup(secret, key, distance)
        local rawSecret

        if not distance or distance < 0 then
            self.isRednet = true
            self.distance = -1
            rawSecret = tostring(secret) .. "|" .. tostring(key)
        else
            self.isRednet = false
            self.distance = distance
            rawSecret = tostring(secret) .. "|" .. tostring(key) .. "|" .. tostring(distance)
        end

        self.secret = Cryptography.sha.sha256(rawSecret)

        if not self.isRednet then
            local total = 0

            for i = 1, self.secret:len() do
                local letter = string.byte(self.secret:sub(i, i))
                total = total + letter
            end

            self.channel = total % 65530
            Modem.open(self.channel)
        else
            self.channel = nil
        end
    end


    function SecureConnection:sendMessage(msg, id)
        if self.isRednet and not id then
            return false
        else
            local rawEncryptedMsg = Cryptography.aes.encrypt(SecureConnection.packetHeader .. msg, self.secret)
            local encryptedMsg = SecureConnection.packetHeader .. rawEncryptedMsg

            if self.isRednet then
                rednet.send(id, encryptedMsg)
                return true
            else
                return Modem.send(self.channel, encryptedMsg)
            end
        end
    end

    function SecureConnection:decryptMessage(msg)
        if SecureConnection.verifyHeader(msg) then
            local encrypted = msg:match(SecureConnection.packetMatch)

            local unencryptedMsg = nil
            pcall(function() unencryptedMsg = Cryptography.aes.decrypt(encrypted, self.secret) end)
            if not unencryptedMsg then
                return false, "Could not decrypt"
            end

            if SecureConnection.verifyHeader(unencryptedMsg) then
                return unencryptedMsg:match(SecureConnection.packetMatch)
            else
                return false, "Could not verify"
            end
        end
    end


--  Testing

print(Modem.exists())

Modem.open(Handshake.channel)
Handshake.clear()

local secret = nil
local distance = 0

while true do
    local e, p1, p2, p3, msg, p5 = os.pullEvent()
    if e == "modem_message" then
        if msg:match(Handshake.packetMatch) then
            local unserialized = textutils.unserialize(msg:match(Handshake.packetMatch))
            local data, key = Handshake.generateResponseData(unserialized)
            print("key: ",key)
            distance = p5
            secret = key
            if type(data) == "table" then
                local toSend = Handshake.packetHeader .. textutils.serialize(data)
                Modem.send(Handshake.channel, toSend)
            end
            break
        end
    end
end

local connection = SecureConnection.new(secret, "1lann.com", distance)

while true do
    local e, p1, p2, p3, msg, p5 = os.pullEvent()
    print(e)
    if e == "modem_message" then
        print("message received")
        if SecureConnection.verifyHeader(msg) then
            print("Header verified")
            local resp, data = connection:decryptMessage(msg)
            if not resp then
                print(data)
            else
                print(resp)
            end
            break
        end
    end
end