Door lock program for ComputerCraft using secure remote servers, supporting optional key expiration & use limits

client.lua

-- Save this as startup.lua on each client computer with a drive and modem attached. You can also optionally attach a speaker for audio feedback.
local secret = "" -- Set this to the same secret that was set in the server file.
local redstoneSide = "left" -- Set this to the side the redstone signal should be output on.
local openTime = 5 -- Set this to the number of seconds to keep the door open for.
local defaultOutput = false -- Set this to the default redstone state for the door. If set to true, this means power will be cut when unlocking.
                            -- This allows you to place a door sideways, and then have it stay closed even when power is applied externally.

if not secret or secret == "" then error("Please set some keys inside the script before running.") end

local ok, err = pcall(function()
os.pullEvent = os.pullEventRaw
settings.set("shell.allow_disk_startup", false)

local sha256

do
    local MOD = 2^32

    local function rrotate(x, disp)
        x = x % MOD
        disp = disp % 32
        local low = bit32.band(x, 2 ^ disp - 1)
        return bit32.rshift(x, disp) + bit32.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 = bit32.bxor(rrotate(v, 7), rrotate(v, 18), bit32.rshift(v, 3))
            v = w[j - 2]
            w[j] = w[j - 16] + s0 + w[j - 7] + bit32.bxor(rrotate(v, 17), rrotate(v, 19), bit32.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 = bit32.bxor(rrotate(a, 2), rrotate(a, 13), rrotate(a, 22))
            local maj = bit32.bxor(bit32.band(a, b), bit32.band(a, c), bit32.band(b, c))
            local t2 = s0 + maj
            local s1 = bit32.bxor(rrotate(e, 6), rrotate(e, 11), rrotate(e, 25))
            local ch = bit32.bxor(bit32.band(e, f), bit32.band(bit32.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] = bit32.band(H[1] + a)
        H[2] = bit32.band(H[2] + b)
        H[3] = bit32.band(H[3] + c)
        H[4] = bit32.band(H[4] + d)
        H[5] = bit32.band(H[5] + e)
        H[6] = bit32.band(H[6] + f)
        H[7] = bit32.band(H[7] + g)
        H[8] = bit32.band(H[8] + h)
    end

    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
end

local speaker = peripheral.find("speaker")
local modem = peripheral.find("modem")
modem.open(74)
redstone.setOutput(redstoneSide, defaultOutput)

while true do
    local ev, side = os.pullEvent()
    if ev == "disk" then
        sleep(0.25)
        local found = false
        local file = fs.open("disk/id", "r")
        if file ~= nil then
            local id = file.readAll()
            file.close()
            local msg = sha256("?:" .. id .. tostring(math.floor(os.epoch("utc") / 1000) .. secret))
            local channel = math.random(0, 65533)
            while channel == 74 do channel = math.random(0, 65533) end
            modem.open(channel)
            modem.transmit(74, channel, "?:" .. msg)
            local timer = os.startTimer(3)
            while true do
                local ev2, side2, port, reply, message = os.pullEvent()
                if ev2 == "timer" and side2 == timer then break
                elseif ev2 == "modem_message" and port == channel and reply == 74 and type(message) == "string" and message:sub(1, 2) == "=:" then
                    if message == "=:" .. sha256("=:" .. id .. tostring(math.floor(os.epoch("utc") / 1000)) .. secret .. "true") or
                       message == "=:" .. sha256("=:" .. id .. tostring(math.floor(os.epoch("utc") / 1000) - 1) .. secret .. "true") then found = true break
                    elseif message == "=:" .. sha256("=:" .. msg .. secret .. "false") then found = false break end
                end
            end
            modem.close(channel)
        end
        disk.eject(side)
        if found then
            redstone.setOutput(redstoneSide, not defaultOutput)
            if speaker then speaker.playNote("bit", 1, 24) end
            sleep(openTime)
            redstone.setOutput(redstoneSide, defaultOutput)
        elseif speaker then
            for i = 1, 3 do 
                speaker.playNote("bit", 1, 12) 
                if i < 3 then sleep(0.2) end
            end
        end
        disk.eject(side)
    end
end
end)

if not ok then
    printError(err)
    sleep(5)
end

os.reboot()

server.lua

-- Save this as startup.lua on the server computer with a modem attached to the computer. You can also optionally attach a drive to be able to create and erase ID cards.
local addIDPassword = "" -- Set this to a password that can be used to create a new ID card.
local secret = "" -- Set this to a randomly-generated secret code. This code should be copied to the secret variable for all clients.

if not addIDPassword or not secret or addIDPassword == "" or secret == "" then error("Please set some keys inside the script before running.") end

if not fs.exists("ids.lua") then
    local file = fs.open("ids.lua", "w")
    file.write("return {}")
    file.close()
end

local ok, err = pcall(function()
os.pullEvent = os.pullEventRaw
settings.set("shell.allow_disk_startup", false)

local sha256, base64encode

do
    local MOD = 2^32

    local function rrotate(x, disp)
        x = x % MOD
        disp = disp % 32
        local low = bit32.band(x, 2 ^ disp - 1)
        return bit32.rshift(x, disp) + bit32.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 = bit32.bxor(rrotate(v, 7), rrotate(v, 18), bit32.rshift(v, 3))
            v = w[j - 2]
            w[j] = w[j - 16] + s0 + w[j - 7] + bit32.bxor(rrotate(v, 17), rrotate(v, 19), bit32.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 = bit32.bxor(rrotate(a, 2), rrotate(a, 13), rrotate(a, 22))
            local maj = bit32.bxor(bit32.band(a, b), bit32.band(a, c), bit32.band(b, c))
            local t2 = s0 + maj
            local s1 = bit32.bxor(rrotate(e, 6), rrotate(e, 11), rrotate(e, 25))
            local ch = bit32.bxor(bit32.band(e, f), bit32.band(bit32.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] = bit32.band(H[1] + a)
        H[2] = bit32.band(H[2] + b)
        H[3] = bit32.band(H[3] + c)
        H[4] = bit32.band(H[4] + d)
        H[5] = bit32.band(H[5] + e)
        H[6] = bit32.band(H[6] + f)
        H[7] = bit32.band(H[7] + g)
        H[8] = bit32.band(H[8] + h)
    end

    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
end

do
    local extract = _G.bit32 and _G.bit32.extract
    if not extract then
        if _G.bit then
            local shl, shr, band = _G.bit.blshift, _G.bit.brshift, _G.bit.band
            extract = function( v, from, width )
                return band( shr( v, from ), shl( 1, width ) - 1 )
            end
        elseif _G._VERSION >= "Lua 5.3" then
            extract = load[[return function( v, from, width )
                return ( v >> from ) & ((1 << width) - 1)
            end]]()
        else
            extract = function( v, from, width )
                local w = 0
                local flag = 2^from
                for i = 0, width-1 do
                    local flag2 = flag + flag
                    if v % flag2 >= flag then
                        w = w + 2^i
                    end
                    flag = flag2
                end
                return w
            end
        end
    end

    local DEFAULT_ENCODER = (function( s62, s63, spad )
        local encoder = {}
        for b64code, char in pairs{[0]='A','B','C','D','E','F','G','H','I','J',
            'K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y',
            'Z','a','b','c','d','e','f','g','h','i','j','k','l','m','n',
            'o','p','q','r','s','t','u','v','w','x','y','z','0','1','2',
            '3','4','5','6','7','8','9',s62 or '+',s63 or'/',spad or'='} do
            encoder[b64code] = char:byte()
        end
        return encoder
    end)()

    local char, concat = string.char, table.concat

    function base64encode( str, encoder, usecaching )
        encoder = encoder or DEFAULT_ENCODER
        local t, k, n = {}, 1, #str
        local lastn = n % 3
        local cache = {}
        for i = 1, n-lastn, 3 do
            local a, b, c = str:byte( i, i+2 )
            local v = a*0x10000 + b*0x100 + c
            local s
            if usecaching then
                s = cache[v]
                if not s then
                    s = char(encoder[extract(v,18,6)], encoder[extract(v,12,6)], encoder[extract(v,6,6)], encoder[extract(v,0,6)])
                    cache[v] = s
                end
            else
                s = char(encoder[extract(v,18,6)], encoder[extract(v,12,6)], encoder[extract(v,6,6)], encoder[extract(v,0,6)])
            end
            t[k] = s
            k = k + 1
        end
        if lastn == 2 then
            local a, b = str:byte( n-1, n )
            local v = a*0x10000 + b*0x100
            t[k] = char(encoder[extract(v,18,6)], encoder[extract(v,12,6)], encoder[extract(v,6,6)], encoder[64])
        elseif lastn == 1 then
            local v = str:byte( n )*0x10000
            t[k] = char(encoder[extract(v,18,6)], encoder[extract(v,12,6)], encoder[64], encoder[64])
        end
        return concat( t )
    end
end

local modem = peripheral.find("modem")
modem.open(74)

while true do
    local ev, side, port, reply, message = os.pullEvent()
    if ev == "modem_message" and port == 74 and type(message) == "string" and message:sub(1, 2) == "?:" then
        local found = false
        local ids = dofile("ids.lua")
        local delete = {}
        modem.open(reply)
        for i,id in ipairs(ids) do
            if (id.expiration == 0 or id.expiration > os.epoch("utc")) and (id.uses ~= 0) then
                if message == "?:" .. sha256("?:" .. id.id .. tostring(math.floor(os.epoch("utc") / 1000)) .. secret) or
                message == "?:" .. sha256("?:" .. id.id .. tostring(math.floor(os.epoch("utc") / 1000) - 1) .. secret) then
                    found = true
                    modem.transmit(reply, 74, "=:" .. sha256("=:" .. id.id .. tostring(math.floor(os.epoch("utc") / 1000)) .. secret .. "true"))
                    if id.uses > 0 then
                        ids[i].uses = id.uses - 1
                        local file = fs.open("ids.lua", "w")
                        file.write("return " .. textutils.serialize(ids))
                        file.close()
                    end
                    break
                end
            else table.insert(delete, i) end
        end
        if not found then modem.transmit(reply, 74, "=:" .. sha256("=:" .. message:sub(3) .. secret .. "false")) end
        if reply ~= 74 then modem.close(reply) end
        if #delete > 0 then
            for _,i in ipairs(delete) do ids[i] = nil end
            local file = fs.open("ids.lua", "w")
            file.write("return " .. textutils.serialize(ids))
            file.close()
        end
    elseif ev == "disk" then
        if fs.exists("disk/id") then
            write("Erasing ID card, please enter the password.\n: ")
            local password
            parallel.waitForAny(function() sleep(15) end, function() password = read("*") end)
            if password == addIDPassword then
                local file = fs.open("disk/id", "r")
                local id = file.readAll()
                file.close()
                local ids = dofile("ids.lua")
                for i,v in ipairs(ids) do if v.id == id then ids[i] = nil break end end
                file = fs.open("ids.lua", "w")
                file.write("return " .. textutils.serialize(ids))
                file.close()
                fs.delete("disk/id")
                disk.setLabel(side, nil)
                print("Erased ID card.")
            else print("Incorrect password.") end
        else
            write("Writing new ID card, please enter the password.\n: ")
            local password
            parallel.waitForAny(function() sleep(15) end, function() password = read("*") end)
            if password == addIDPassword then
                print("To skip a value, just press enter without typing anything.")
                write("Seconds valid? ")
                local exp = read()
                write("Maximum uses? ")
                local uses = read()
                local id = ""
                for i = 1, 12 do id = id .. string.char(math.random(0, 255)) end
                id = base64encode(id)
                local ids = dofile("ids.lua")
                ids[#ids+1] = {id = id, expiration = exp == "" and 0 or os.epoch("utc") + (tonumber(exp) * 1000), uses = uses == "" and -1 or tonumber(uses)}
                local file = fs.open("ids.lua", "w")
                file.write("return " .. textutils.serialize(ids))
                file.close()
                file = fs.open("disk/id", "w")
                file.write(id)
                file.close()
                disk.setLabel(side, "ID Card #" .. #ids)
                print("Successfully wrote new ID card.")
            else print("Incorrect password.") end
        end
        disk.eject(side)
    end
end
end)

if not ok then
    printError(err)
    sleep(5)
end

os.reboot()