CG Clear Serv

--CGClearServ v.0.0.3
--Credential Passing Server
--Must be saved as startup
--Full Documentation unavailable.

--Begin Variable Config Block
local reqChan = 1 -- The channel the server will want to receive requests on.
local userChan = 2 -- the channel the server will send username information on
local passChan = 3 -- The channel the server uses to send password information
local credChan = 4 -- the channel the server uses to send credential information
local keyChan = 5 -- the channel that the administrator uses to send current tables to the server.
local downChan = 6 -- the channel that the server uses to talk to the client.
local saltChan = 7 -- the channel that the server uses to talk to the client.
local trust = "anything" -- the trust variable that is expected for requests.
local mside = "direction" -- the direction of the modem.

--SHA-256 Hashing Implementation via GravityScore
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 bxor1 = make_bitop({[0] = {[0] = 0,[1] = 1}, [1] = {[0] = 1, [1] = 0}, n = 4})

local function bxor(a, b, c, ...)
        local z = nil
        if b then
                a = a % MOD
                b = b % MOD
                z = bxor1(a, b)
                if c then z = bxor(z, c, ...) end
                return z
        elseif a then return a % MOD
        else return 0 end
end

local function band(a, b, c, ...)
        local z
        if b then
                a = a % MOD
                b = b % MOD
                z = ((a + b) - bxor1(a,b)) / 2
                if c then z = bit32_band(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 = band(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 = bxor(rrotate(v, 7), rrotate(v, 18), rshift(v, 3))
                v = w[j - 2]
                w[j] = w[j - 16] + s0 + w[j - 7] + bxor(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 = bxor(rrotate(a, 2), rrotate(a, 13), rrotate(a, 22))
                local maj = bxor(band(a, b), band(a, c), band(b, c))
                local t2 = s0 + maj
                local s1 = bxor(rrotate(e, 6), rrotate(e, 11), rrotate(e, 25))
                local ch = bxor (band(e, f), band(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] = band(H[1] + a)
        H[2] = band(H[2] + b)
        H[3] = band(H[3] + c)
        H[4] = band(H[4] + d)
        H[5] = band(H[5] + e)
        H[6] = band(H[6] + f)
        H[7] = band(H[7] + g)
        H[8] = band(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

--Table/File Handling Protocols
local function load(name)
local file = fs.open(name, "r")
local data = file.readAll()
file.close()
return textutils.unserialize(data)
end

local function save(table, name)
local file = fs.open(name, "w")
file.write(textutils.serialize(table))
file.close()
end

--First Boot//Install Block
--Checks for an existing database. If it can't find one, it creates a random one.
if fs.exists("userhash") == false then
    userHash = {[1]=sha256(tostring(math.random(1, 2^16))), }
    save(userHash, "userhash")
    print("Intializing Users.")
end
if fs.exists("passhash") == false then
    passHash = {[1]=sha256(tostring(math.random(1, 2^16))), }
    save(passHash, "passhash")
    print("Intializing Passwords.")
end
if fs.exists("credhash") == false then
    credHash = {[1]=sha256(tostring(math.random(1, 2^16))), } -- Virtually ensures that the default password won't be credentialled for anything anyway.
    save(credHash, "credhash")
    print("Initializing Credentials")
end
if fs.exists("tablesalt") == false then
    tableSalt = {[1]=sha256(tostring(math.random(1, 2^16))), }
    save(tableSalt, "tablesalt")
    print("Salting Database")
end

--Initialization
modem = peripheral.wrap(mside)
modem.open(reqChan)
modem.open(keyChan)
modem.open(userChan)
modem.open(passChan)
modem.open(credChan)
modem.open(saltChan)
print("Credentials Server Ready.")

while true do
        local event, modemSide, senderChannel, replyChannel, message, senderDistance = os.pullEvent("modem_message") -- Waits for a message, in this case a request.
        if senderChannel == reqChan then -- Request Handling Block
                if message == sha256(trust) then -- this verified that the requester is allowed to have the data.
                        print("Recieved Request for Credentials from" ..tostring(senderDistance) .."Away") -- For detection of bad machines.
                        modem.transmit(downChan, reqChan, sha256(trust)) -- tells the client it is a valid server.
                        os.pullEvent("modem_message") -- waits to be told to continue.
                        local userHash = load("userHash")
                        modem.transmit(userChan, reqChan, userHash) -- sends the userHash file as a string.
                        os.pullEvent("modem_message")
                        local passHash = load("passHash")
                        modem.transmit(passChan, reqChan, passHash) -- sends passHash
                        os.pullEvent("modem_message")
                        local credHash = load("credhash")
                        modem.transmit(credChan, reqChan, credHash) -- sends credHash
                        os.pullEvent("modem_message")
                        local tableSalt = load("tableSalt")
                        modem.transmit(saltChan, reqChan, tableSalt) -- sends the salt.
                        print("Update sent to Client upon Request.")
                else
                print("Unauthorized Request.")
                end
        elseif senderChannel == keyChan then
        print("Receiving Credentials Update.")
                if message == sha256(trust) then -- validates the admin machine.
                        modem.close(reqChan) -- stops other requests from interrupting the system.
                        modem.transmit(downChan, keyChan, sha256(trust)) -- tells the admin machine this is a valid server.
                        os.pullEvent("modem_message")
                        local userUpdate = textutils.unserialize(message)
                        save(userUpdate, "userHash")
                        print("Usernames Updated")
                        modem.transmit(downChan, downChan, "ping") -- asks for the next packet.
                        os.pullEvent("modem_message")
                        local passUpdate = textutils.unserialize(message)
                        save(passUpdate, "passHash")
                        print("Passwords Updated")
                        modem.transmit(downChan, keyChan, "ping")
                        os.pullEvent("modem_message")
                        local credUpdate = textutils.unserialize(message)
                        save(credUpdate, "credHash")
                        print("Credentials List Updated")
                        modem.transmit(downChan, keyChan, "ping")
                        os.pullEvent("modem_message")
                        local saltUpdate = textutils.unserialize(message)
                        save(saltUpdate, "tableSalt")
                        print("Salts Updated")
                        modem.open(reqChan) -- because people are going to need the new files.
                        end
                else
                        print("Spoofing Attempt Detected.")
                end
                print("Credentials server ready.")
        end