VaultShell - ComputerCraft Secure Shell

-- Vault Shell v1.0
-- by Majd123mc
-- Licensed under CCPL which may be found here: https://github.com/dan200/ComputerCraft/blob/master/LICENSE

os.loadAPI("sha256.lua")

local _os_pullEvent = os.pullEvent
os.pullEvent = os.pullEventRaw

function printColor(text,color)
    local _color = term.getTextColor()
    term.setTextColor(color)
    print(text)
    term.setTextColor(_color)
end

function flushSettings()
    settings.save("/.settings")
end

function clearScreen()
    term.setCursorPos(1,1)
    term.clear()
end

-- Taken from shell.lua
local function createShellEnv( sDir )
    local tEnv = {}
    tEnv[ "shell" ] = shell
    tEnv[ "multishell" ] = multishell

    local package = {}
    package.loaded = {
        _G = _G,
        bit32 = bit32,
        coroutine = coroutine,
        math = math,
        package = package,
        string = string,
        table = table,
    }
    package.path = "?;?.lua;?/init.lua;/rom/modules/main/?;/rom/modules/main/?.lua;/rom/modules/main/?/init.lua"
    if turtle then
        package.path = package.path..";/rom/modules/turtle/?;/rom/modules/turtle/?.lua;/rom/modules/turtle/?/init.lua"
    elseif command then
        package.path = package.path..";/rom/modules/command/?;/rom/modules/command/?.lua;/rom/modules/command/?/init.lua"
    end
    package.config = "/\n;\n?\n!\n-"
    package.preload = {}
    package.loaders = {
        function( name )
            if package.preload[name] then
                return package.preload[name]
            else
                return nil, "no field package.preload['" .. name .. "']"
            end
        end,
        function( name )
            local fname = string.gsub(name, "%.", "/")
            local sError = ""
            for pattern in string.gmatch(package.path, "[^;]+") do
                local sPath = string.gsub(pattern, "%?", fname)
                if sPath:sub(1,1) ~= "/" then
                    sPath = fs.combine(sDir, sPath)
                end
                if fs.exists(sPath) and not fs.isDir(sPath) then
                    local fnFile, sError = loadfile( sPath, tEnv )
                    if fnFile then
                        return fnFile, sPath
                    else
                        return nil, sError
                    end
                else
                    if #sError > 0 then
                        sError = sError .. "\n"
                    end
                    sError = sError .. "no file '" .. sPath .. "'"
                end
            end
            return nil, sError
        end
    }

    local sentinel = {}
    local function require( name )
        if type( name ) ~= "string" then
            error( "bad argument #1 (expected string, got " .. type( name ) .. ")", 2 )
        end
        if package.loaded[name] == sentinel then
            error("Loop detected requiring '" .. name .. "'", 0)
        end
        if package.loaded[name] then
            return package.loaded[name]
        end

        local sError = "Error loading module '" .. name .. "':"
        for n,searcher in ipairs(package.loaders) do
            local loader, err = searcher(name)
            if loader then
                package.loaded[name] = sentinel
                local result = loader( err )
                if result ~= nil then
                    package.loaded[name] = result
                    return result
                else
                    package.loaded[name] = true
                    return true
                end
            else
                sError = sError .. "\n" .. err
            end
        end
        error(sError, 2)
    end

    tEnv["package"] = package
    tEnv["require"] = require

    return tEnv
end

-- Prompting

function promptUsername()
    term.write("Username> ")
    local usr = read()

    if not usr then
        return nil
    end

    if not usr:match("[a-zA-Z0-9_]+") then
        print("Invalid username. Usernames may only contain letters, numbers, and underscores")
        return promptUsername()
    end

    return usr
end

function promptPassword()
    term.write("Password> ")
    return read("*")
end

function promptLogin()
    print("Please enter your credentials:")
    local usr = promptUsername()
    if not usr then return false end
    local pwd = promptPassword()

    return true,usr,pwd
end

function promptConfirmPwd(new)
    term.write((new and "New " or "") .. "Password> ")
    local pwd = read("*")
    term.write("Confirm> ")
    local con = read("*")

    if pwd == con then
        return pwd
    else
        print("Passowrds do not match. Please try again")
        return promptConfirmPwd()
    end
end

function promptChangePassword()
    print("Please enter username and new credentials")
    local usr = promptUsername()

    if not usr then
        return false
    elseif not userExists(usr) then
        print("No such user exists")
        return false
    end

    local pwd = promptConfirmPwd(true)

    return true,usr,pwd
end

function promptDeleteUser()
    print("Enter the username for the account to be deleted")
    local usr = promptUsername()

    if not usr then
        return false
    elseif not userExists(usr) then
        print("No such user exists")
        return false
    end

    return true, usr
end

function promptCreateUser()
    --print("It looks like this is the first time you have run Vault Shell")
    print("Please enter credentials for new account")
    local usr = promptUsername()

    if not usr then
        return false
    elseif userExists(usr) then
        print("A user with that name already exists. Please try again")
        return promptCreateUser()
    end

    local pwd = promptConfirmPwd()

    return true,usr,pwd
end

function promptSetup()
    print("It looks like this is the first time you have run Vault Shell")
    return promptCreateUser()
end

-- User accounts

function getUserHash(usr)
    return settings.get("vsh.login." .. usr)
end

function userExists(usr)
    return getUserHash(usr) ~= nil
end

function verifyLogin(usr,pwd)
    local test_hash = getUserHash(usr)
    local input_hash = sha256.digestStr(pwd)

    return test_hash == input_hash
end

function createUser(usr,pwd)
    local hash = sha256.digestStr(pwd)
    settings.set("vsh.login." .. usr,hash)

    local users = settings.get("vsh.users") or {}
    table.insert(users, usr)
    settings.set("vsh.users", users)

    flushSettings()
    return true
end

function setPassword(usr, pwd)
    local hash = sha256.digestStr(pwd)
    settings.set("vsh.login." .. usr,hash)
    flushSettings()
    return true
end

function deleteUser(usr)
    settings.unset("vsh.login." .. usr)

    local users = settings.get("vsh.users") or {}
    for i, usr2 in ipairs(users) do
        if usr2 == usr then
            table.remove(users, i)
        end
    end
    settings.set("vsh.users", users)

    flushSettings()
    return true
end

-- Main

function loginShell(usr)
    os.pullEvent = _os_pullEvent

    shell.run("rom/programs/shell.lua")

    os.pullEvent = os.pullEventRaw
end

function mainLogin()
    local success,usr,pwd = promptLogin()
    if not success then
        print("Please enter a username to log in")
        mainLogin()
    end

    local validLogin = verifyLogin(usr,pwd)
    if validLogin then
        print("Login successful!\n")

        _G.vsh.usr = usr
        loginShell(usr,pwd)
        _G.vsh.usr = nil

        clearScreen()
        mainLogin()
    else
        print("Invalid credentials. Please try again")
        mainLogin()
    end
end

function init()
    clearScreen()
    printColor("Vault Shell v1.0 - Majd123mc 2022\n",colors.yellow)

    multishell.setTitle(multishell.getCurrent(), "vsh")

    local setupComplete = settings.get("vsh.setup")

    if not setupComplete then
        local success,usr,pwd = promptSetup()
        if not success then
            print("You must create a user to use Vault Shell. Exiting to CraftOS")
            shell.run("sh")
            return
        end

        createUser(usr,pwd)
        settings.set("vsh.setup",true)
        flushSettings()

        print("Account created successfully. You must reenter your credentials to log in.\n")
    end

    mainLogin()
end

_G.vsh = _G.vsh or {}

local arg = ...

if not arg then
    if not _G.vsh.usr then
        init()
    else
        print("Already logged in. Type exit to log out")
    end
elseif arg == "help" then
    print("vsh help - View help")
    print("vsh chpwd - Change password")
    print("vsh add - Add user")
    print("vsh del - Remove user")
    print("vsh users - List users")
elseif arg == "chpwd" then
    local success, usr, pwd = promptChangePassword()

    if not success then
        return
    end

    createUser(usr, pwd)
elseif arg == "add" then
    local success, usr, pwd = promptCreateUser()
    if not success then
        print("Error")
        return
    end

    createUser(usr, pwd)
    print("Account created successfully.")
elseif arg == "del" then
    if #settings.get("vsh.users") <= 1 then
        print("At least one user must exist on the system")
        return
    end

    local success, usr = promptDeleteUser()

    if not success then
        return
    end

    deleteUser(usr)
elseif arg == "users" then
    for _, user in ipairs(settings.get("vsh.users")) do
        print(user)
    end
else
    print("Unknown argument " .. arg .. ". Type vsh help for more info")
end