FTP Server ComputerCraft

local connections = {}
local validusers = {}
local protected= {"/users", "/logs"}
local userdir = "/users"
local logdir = "/logs"
local logfile

--[[
rednet_message:
    source id
    message
    distance
]]

local function validUser(username)
    for k,v in pairs(validusers) do
        if k == username then return true end
    end
    return false
end

local function split(s, del)
    local ret = {}
    local del = del or " "
    local pattern = string.format("([^%s]+)", del)
    s:gsub(pattern, function(c) ret[#ret+1] = c end)
    return ret
end

local function log(s)
    logfile:write(s .. "\n")
    print(s)
    --logfile:flush()
end

local function send(id, message)
    os.sleep(0.1)
    rednet.send(id, message)
end

local function canRead(user)
    if not user.permissions.read then
        send(id, "532 Permission denied.")
        return false
    end
    return true
end

local function canWrite(user)
    if not user.permissions.write then
        send(id, "532 Permission denied.")
        return false
    end
    return true
end

local function isProtected(f)
    for k,v in pairs(protected) do
        if shell.resolve(v) == shell.resolve(f) then return true end
    end
    return false
end

-- Load users
local list = fs.list(userdir)
for k,v in pairs(list) do
    local filename = fs.combine(userdir, v)
    local file = io.open(filename, "r")

    local user = {
        username = file:read():lower(),
        password = file:read(),
        permissions = {
            read = file:read() == "1",
            write = file:read() == "1"
        }
    }

    validusers[user.username:lower()] = user
end

-- Open log
local i = 1
while true do
    list = fs.list(logdir)
    local found = true
    for k,v in pairs(list) do
        if tonumber(v) == i then
            found = false
            break
        end
    end
    if found then
        logfile = io.open(fs.combine(logdir,i),"w")
        break
    end
    i = i + 1
end

-- Clear terminal
rednet.open("top")
term.clear()
term.setCursorPos(1,1)

print("Server started")

-- Mainloop
while true do
    local event,id,message,distance = os.pullEvent()
    if event == "rednet_message" then
        local conn = connections[id]
        local user
        if conn ~= nil then user = conn.user end
        if conn == nil then
            -- New connection
            if validUser(message:lower()) then
                local newconnection = {}
                newconnection.id = id
                newconnection.user = validusers[message:lower()]
                newconnection.idle = 0

                local pwd = validusers[message:lower()].password
                if pwd == "" or pwd == nil then
                    send(id, "230 Login successful.")
                    newconnection.connected = true
                    newconnection.dir = "/"
                    newconnection.waiting = false
                    log(message:lower() .. " logged in from " .. id .. ".")
                else
                    send(id, "331 Password required for " .. message .. ".")
                    newconnection.connected = false
                end
                connections[id] = newconnection
            else
                send(id, "332 Need account for login.")
            end
        elseif conn.connected == false or conn.connected == nil then
            -- Password
            local username = user.username
            if validusers[username].password == message then
                conn.connected = true
                conn.waiting = false
                conn.dir = "/"
                send(id, "230 Login successful.")
                log(username .. " logged in from " .. id .. ".")
            else
                send(id, "332 Need account for login.")
                connections[id] = nil
                log("Connection from " .. id .. " entered wrong password for " .. username .. ".")
            end
        else
            if conn.waiting then
                conn.waiting = false
                local handle = conn.handle
                conn.handle = nil

                handle:write(message)
                handle:close()
                send(id, "200 OK.")
            else
                local username = user.username
                local cmdparams = split(message, " ")
                local cmd = cmdparams[1] or ""
                cmd = cmd:lower()

                if cmd == "bye" or cmd == "quit" then
                    send(id, "221 Goodbye.")
                    connections[id] = nil
                elseif cmd == "cd" then
                    if canRead(user) then
                        local dir = cmdparams[2]
                        if dir == nil then
                            send(id, "501 Not enough parameters.")
                        else
                            local path = fs.combine(conn.dir, dir)
                            if not fs.exists(path) then
                                send(id, "501 File or directory does not exist.")
                            else
                                if not fs.isDir(path) then
                                    send(id, "501 Not a directory.")
                                else
                                    if isProtected(path) then
                                        send(id, "532 Permission denied.")
                                    else
                                        conn.dir = "/" .. path
                                        send(id, "200 CD command successful.")
                                    end
                                end
                            end
                        end
                    end
                elseif cmd == "rm" then
                    if canWrite(user) then
                        local file = cmdparams[2]
                        if file == nil then
                            send(id, "501 Not enough parameters.")
                        else
                            file = fs.combine(conn.dir,file)
                            if not fs.exists(file) then
                                send(id, "501 File or directory not found")
                            else
                                if isProtected(file) then
                                    send(id, "532 Permission denied.")
                                else
                                    if fs.isReadOnly(file) then
                                        send(id, "532 Permission denied.")
                                    else
                                        fs.delete(file)
                                        send(id, "200 RM command successful.")
                                        log(username .. " from " .. id .. " deleted " .. file .. ".")
                                    end
                                end
                            end
                        end
                    end
                elseif cmd == "get" then
                    if canRead(user) then
                        local file = cmdparams[2]
                        if file == nil then
                            send(id, "501 Not enough parameters.")
                        else
                            file = fs.combine(conn.dir,file)
                            if not fs.exists(file) then
                                send(id, "501 File or directory not found.")
                            else
                                if isProtected(file) then
                                    send(id, "532 Permission denied.")
                                else
                                    local handle = io.open(file, "r")
                                    if not handle then
                                        send(id, "501 Could not open file for reading.")
                                    else
                                        local content = handle:read("*a")
                                        handle:close()
                                        send(id, content)
                                        send(id, "200 OK.")
                                        log(username .. " from " .. id .. " downloaded " .. file .. ".")
                                    end
                                end
                            end
                        end
                    end
                elseif cmd == "ls" then
                    if canRead(user) then
                        local dir = cmdparams[2]
                        if dir == nil then
                            dir = conn.dir
                        else
                            dir = fs.combine(conn.dir, dir)
                        end

                        if not fs.exists(dir) then
                            send(id, "501 File or directory not found.")
                        else
                            if isProtected(dir) then
                                send(id, "532 Permission denied.")
                            else
                                local list = fs.list(dir)
                                for k,v in pairs(list) do
                                    if fs.isDir(fs.combine(dir,v)) then
                                        list[k] = "[" .. v .. "]"
                                    end
                                end
                                local ret = table.concat(list, " ")
                                send(id, ret)
                                send(id, "200 LS command successful.")
                            end
                        end
                    end
                elseif cmd == "mkdir" then
                    if canWrite(user) then
                        local file = cmdparams[2]
                        if file == nil then
                            send(id, "501 Not enough parameters.")
                        else
                            file = fs.combine(conn.dir, file)
                            if fs.exists(file) then
                                send(id, "501 File exists.")
                            else
                                if fs.isReadOnly(file) then
                                    send(id, "532 Permission denied.")
                                else
                                    fs.makeDir(file)
                                    send(id, "200 MKDIR command successful.")
                                    log(username .. " from " .. id .. " created directory " .. file .. ".")
                                end
                            end
                        end
                    end
                elseif cmd == "put" then
                    if canWrite(user) then
                        local file = cmdparams[2]
                        if file == nil then
                            send(id, "501 Not enough parameters.")
                        else
                            file = fs.combine(conn.dir, file)
                            if fs.isReadOnly(file) then
                                send(id, "532 Permission denied.")
                            else
                                if isProtected(file) then
                                    send(id, "532 Permission denied.")
                                else
                                    conn.handle = io.open(file, "w")
                                    if not conn.handle then
                                        send(id, "501 Could not open file for writing.")
                                    else
                                        conn.waiting = true
                                        send(id, "150 OK.")
                                        log(username .. " from " .. id .. " uploaded " .. file .. ".")
                                    end
                                end
                            end
                        end
                    end
                elseif cmd == "pwd" then
                    send(id, conn.dir)
                    send(id, "200 OK.")
                else
                    send(id, "500 Unknown command.")
                end
            end
        end
    end
end