computercraft/packages/auth_server.lua

settings.define("auth_server.salt", {
    description = "Salt for hashing passwords",
    type = "string",
    default = "3m&LmNm7"
})

local data = {
    users = {}
}
-- Schema:
-- data = {
--     users = {
--         ["username"] = {
--             token = "token",
--             password = "hashed password",
--             groups = {
--                 ["group"] = true
--             },
--     },
-- }

function save_data()
    db = fs.open("auth.db", "w")
    db.write(textutils.serialize(data))
    db.close()
end

function load_data()
    if fs.exists("auth.db") then
        db = fs.open("auth.db", "r")
        db_contents = db.readAll()
        db.close()

        data = textutils.unserialize(db_contents)
    end
end

function generate_token(user)
    local token = sha256.sha256(user .. os.time() .. math.random())
    data.users[user].token = token

    return token
end

function convert_password(password)
    local salt = settings.get("auth_server.salt")
    return sha256.sha256(password .. salt)
end

function log(str)
    io.write("[" .. os.time() .. "] " .. str .. "\n")
end

function countElements(table)
    local count = 0
    for key, value in pairs(table) do
        count = count + 1
    end
    return count
end

load_data()
math.randomseed(os.time())

while true do
    client_id, msg = rednet.receive("auth")
    request = msg

    if request.action == nil then
        rednet.send(client_id, "invalid request", "auth")
    end

    if request.action == "register" then
        if request.username == nil or request.password == nil then
            rednet.send(client_id, "invalid request", "auth")
        end

        if data.users[request.username] ~= nil then
            rednet.send(client_id, "user already exists", "auth")
        end

        data.users[request.username] = {
            password = convert_password(request.password)
        }
        
        local user_count = countElements(data.users)
        if user_count == 1 then
            log("Promoting " .. request.username .. " to admin")
            data.users[request.username].groups = {
                ["admin"] = true
            }
        end

        save_data()

        rednet.send(client_id, "ok", "auth")
        log(request.username .. " registered")
    end

    if request.action == "login" then
        if request.username == nil or request.password == nil then
            rednet.send(client_id, "invalid request", "auth")
            
        elseif data.users[request.username] == nil then
            rednet.send(client_id, "user not found", "auth")

            log(request.username .. " failed log in attempt")
        elseif convert_password(request.password) == data.users[request.username].password then
            local token = generate_token(request.username)

            rednet.send(client_id, token, "auth")

            log(request.username .. " logged in")
        else
            rednet.send(client_id, "invalid password", "auth")
        end

    end

    if request.action == "token" then
        if request.token == nil or request.token == "" or request.token == -1 then
            rednet.send(client_id, "invalid request", "auth")
        else

            local found = false
            for user, userdata in pairs(data.users) do
                if userdata.token == request.token then
                    rednet.send(client_id, user, "auth")
                    found = true
                end
            end

            if not found then
                rednet.send(client_id, "invalid token", "auth")
            end
        end
    end

    if request.action == "profile" then
        if request.username == nil then
            rednet.send(client_id, "invalid request", "auth")
        end

        local profile = {}

        if data.users[request.username].profile_data ~= nil then
            profile = data.users[request.username].profile_data
        else
            profile.display_name = request.username
        end

        profile.username = request.username

        rednet.send(client_id, data.users[request.username], "auth")
    end

    if request.action == "update_profile" then
        if request.username == nil or request.token == nil then
            rednet.send(client_id, "invalid request", "auth")
        end

        if data.users[request.username].token == request.token then
            if request.profile_data ~= nil then
                data.users[request.username].profile_data = request.profile_data
            end

            save_data()

            rednet.send(client_id, "ok")
            log(request.username .. " updated their profile", "auth")
        else
            rednet.send(client_id, "invalid token", "auth")
        end
    end

    if request.action == "check_group" then
        if request.username == nil or request.group == nil then
            rednet.send(client_id, "invalid request", "auth")
        end

        if data.users[request.username].groups == nil or data.users[request.username].groups[request.group] == nil or data.users[request.username].groups[request.group] == false then
            rednet.send(client_id, false, "auth")
        else
            rednet.send(client_id, true, "auth")
        end
    end

    if request.action == "list_groups" then
        if request.username == nil then
            rednet.send(client_id, "invalid request", "auth")
        end

        if data.users[request.username].groups == nil then
            rednet.send(client_id, {}, "auth")
        else
            rednet.send(client_id, data.users[request.username].groups, "auth")
        end
    end

    -- Only if in group admin
    if request.action == "add_group" then
        if request.username == nil or request.group == nil or request.token == nil then
            rednet.send(client_id, "invalid request", "auth")
        else
            local found = false
            local acting_user = nil
            for user, userdata in pairs(data.users) do
                if userdata.token == request.token then
                    acting_user = user
                    found = true
                end
            end

            if not found then
                rednet.send(client_id, "invalid token", "auth")
            elseif data.users[acting_user]["groups"] == nil or data.users[acting_user].groups["admin"] == nil then
                rednet.send(client_id, "invalid privileges", "auth")
            else
                if data.users[request.username].groups == nil then
                    data.users[request.username].groups = {}
                end

                data.users[request.username].groups[request.group] = true

                save_data()

                rednet.send(client_id, "ok", "auth")
                log(request.username .. " added to group " .. request.group, "auth")
            end
        end
    end
end