bevy free trial demo

anti_dbg.rs

// A bevy 0.14 plugin which sets a date of death for an alpha release of your game.
// helps fight against old alpha builds from being used when product goes comercial.
// Somewhat of a "free trial" system, or a "birthday bomb" causing the program to fail.
// Especially effective in networked scenarios where system time cannot be changed as easily.
//
// Plugin Usage:
// App::new()
//     .insert_resource(ClearColor(Color::NONE))
//     .add_plugins((
//         DefaultPlugins,
//         anti_dbg::AntiDbg
//     )).run();

pub struct AntiDbg;

use bevy::{prelude::*, time::Stopwatch};

use chrono::{DateTime, Duration, Utc};

fn check_date_system(
    mut sw: Local<Stopwatch>,
    time: Res<Time>,
) {
    // tick the time each frame by frame delta
    sw.tick(time.delta());

    // only check if birthday has arrived every 5 seconds
    if sw.elapsed_secs() > 5. {
        // make this program dead in the water after 30 days
        let deadline = Utc::now() - Duration::days(30);
        // let deadline = Utc::now() - Duration::minutes(2); // for testing that it works
        let build_date = DateTime::<Utc>::from_timestamp(std::env!("DATE").parse().unwrap(),0).unwrap();

        // debug output our UTC times for demonstration purposes. (Remove this for serious usages)
        println!("Got build date: {} and 30 days ago {}", build_date, deadline);
        if deadline > build_date {
            std::process::exit(0);
            // backup panic in case exit is skipped somehow
            panic!("");
            // 2nd backup anti-debug catcher
            unsafe {
            asm!(
                "xor  eax, eax",
                "push offset l2",
                "push d fs:[eax]",
                "mov  fs:[eax], esp" ,
                "push fs",
                "pop  ss",
                "xchg [eax], cl", 
                "xchg [eax], cl",
                "int 3", // force breakpoint
                "int 29h" // fast fail on windows
            );
            }
        }
        // reset the stopwatch timer when we have reached 5 seconds
        sw.reset();
    }
}

// this allows this system to simply be added as a plugin on bevy init
impl Plugin for AntiDbg {
    fn build(&self, app: &mut App) {
        app.add_systems(PreUpdate, (check_date_system));
    }
}

build.rs

use std::process::Command;
// chrono package must be in build-dependencies
use chrono::Utc;
fn main() {
    println!("cargo:rerun-if-changed=.git/HEAD");
    // note: add error checking yourself.
    let output = Command::new("git")
        .args(&["rev-parse", "HEAD"])
        .output()
        .unwrap();
    let git_hash = String::from_utf8(output.stdout).unwrap();
    println!("cargo:rustc-env=GIT_HASH={}", git_hash);

    let date = Utc::now();

    println!("cargo:rustc-env=DATE={}", date.timestamp());
    //println!("cargo:rerun-if-env-changed=DATE");
    println!("cargo:rerun-if-changed=./*");
}