initrd/src/cmd/init.rs

use eyre::{format_err, Result};
use log::{error, info, warn};
use std::collections::BTreeSet as Set;
use std::os::unix::fs::symlink;
use tokio::sync::Mutex;
use tokio::{fs, process::Command};

use crate::{bootstrap::config::Config, cmd::version::version_string, dklog, input};

mod bootstrap;
mod dmcrypt;
mod lvm;
mod networks;
mod sshd;

// devices used by any block target (DM, LVM...)
static USED_DEVS: Mutex<Set<String>> = Mutex::const_new(Set::new());

pub async fn run() {
    if std::process::id() != 1 {
        error!("init must run as PID 1, not {}", std::process::id());
        std::process::exit(1);
    }

    unsafe {
        use std::env;
        env::set_var("PATH", "/bin:/sbin:/usr/bin:/usr/sbin");
        env::set_var("HOME", "/root");
    }

    info!("Welcome to {}", version_string());

    let uname = nix::sys::utsname::uname().expect("uname should work");
    let kernel_version = uname.release().to_string_lossy();
    info!("Linux version {kernel_version}");

    let cfg: Config = retry(async || {
        let cfg = (fs::read("config.yaml").await)
            .map_err(|e| format_err!("failed to read config: {e}"))?;
        serde_yaml::from_slice(cfg.as_slice())
            .map_err(|e| format_err!("failed to parse config: {e}"))
    })
    .await;

    info!("config loaded");
    info!("anti-phishing-code: {}", cfg.anti_phishing_code);

    // seem to occasionaly race with Child::wait
    // tokio::spawn(child_reaper());

    // open input channels
    tokio::spawn(crate::input::answer_requests_from_stdin());
    tokio::spawn(crate::input::answer_requests_from_socket());

    // mount basic filesystems
    mount("none", "/proc", "proc", None).await;
    mount("none", "/sys", "sysfs", None).await;
    mount("none", "/dev", "devtmpfs", None).await;
    mount("none", "/dev/pts", "devpts", Some("gid=5,mode=620")).await;

    // mount modules
    if let Some(ref modules) = cfg.modules {
        retry_or_ignore(async || {
            info!("mounting modules");
            mount(modules, "/modules", "squashfs", None).await;

            fs::create_dir_all("/lib/modules").await?;
            let modules_path = &format!("/modules/lib/modules/{kernel_version}");

            if !std::fs::exists(modules_path)? {
                return Err(format_err!(
                    "invalid modules package: {modules_path} should exist"
                ));
            }

            symlink(modules_path, format!("/lib/modules/{kernel_version}"))?;
            Ok(())
        })
        .await;
    } else {
        warn!("modules NOT mounted (not configured)");
    }

    // init devices
    info!("initializing devices");
    start_daemon("udevd", &[]).await;

    exec("udevadm", &["trigger", "-c", "add", "-t", "devices"]).await;
    exec("udevadm", &["trigger", "-c", "add", "-t", "subsystems"]).await;
    exec("udevadm", &["settle"]).await;

    // Wireguard VPN
    // TODO startVPN()

    // SSH service
    sshd::start(&cfg).await;

    // networks
    networks::setup(&cfg).await;

    // pre-lvm dmcrypt devs
    dmcrypt::setup(&cfg.pre_lvm_crypt).await;

    // LVM
    lvm::setup(&cfg).await;

    // post-lvm dmcrypt devs
    dmcrypt::setup(&cfg.crypt).await;

    // bootstrap the system
    bootstrap::bootstrap(cfg).await;

    // finalize
    retry(async || switch_root("/system").await).await;
}

async fn switch_root(root: &str) -> Result<()> {
    use std::ffi::CString;

    macro_rules! c {
        ($s:expr) => {
            CString::new($s)?.as_c_str()
        };
    }

    info!("switching root");
    dklog::LOG.close().await;

    nix::unistd::execv(
        c!("/sbin/switch_root"),
        &[
            c!("switch_root"),
            c!("-c"),
            c!("/dev/console"),
            c!(root),
            c!("/sbin/init"),
        ],
    )?;
    Ok(())
}

async fn mount(src: &str, dst: &str, fstype: &str, opts: Option<&str>) {
    if let Err(e) = fs::create_dir_all(dst).await {
        error!("failed to create dir {dst}: {e}");
    }

    match fstype {
        "ext4" => {
            exec("fsck", &["-p", src]).await;
        }
        _ => {}
    }

    let mut args = vec![src, dst];
    if !fstype.is_empty() {
        args.extend(&["-t", fstype]);
    }
    if let Some(opts) = opts {
        args.extend(["-o", opts]);
    }
    exec("mount", &args).await;
}

async fn start_daemon(prog: &str, args: &[&str]) {
    let (cmd_str, mut cmd) = cmd_str(prog, args);
    retry_or_ignore(async || {
        info!("starting as daemon: {cmd_str}");
        cmd.spawn()?;
        Ok(())
    })
    .await;
}

async fn try_exec(prog: &str, args: &[&str]) -> Result<()> {
    let (cmd_str, mut cmd) = cmd_str(prog, args);
    info!("# {cmd_str}");

    let s = cmd.status().await?;
    if s.success() {
        Ok(())
    } else {
        Err(format_err!("command failed: {s}"))
    }
}

async fn exec(prog: &str, args: &[&str]) {
    retry_or_ignore(async || try_exec(prog, args).await).await;
}

async fn retry_or_ignore(mut action: impl AsyncFnMut() -> Result<()>) {
    loop {
        match action().await {
            Ok(_) => return,
            Err(e) => {
                error!("{e}");

                match input::read_choice(["[r]etry", "[i]gnore", "[s]hell"]).await {
                    'r' => {}
                    'i' => return,
                    's' => exec_shell().await,
                    _ => unreachable!(),
                }
            }
        }
    }
}

async fn retry<T>(mut action: impl AsyncFnMut() -> Result<T>) -> T {
    loop {
        match action().await {
            Ok(v) => return v,
            Err(e) => {
                error!("{e}");

                match input::read_choice(["[r]etry", "[s]hell"]).await {
                    'r' => {}
                    's' => exec_shell().await,
                    _ => unreachable!(),
                }
            }
        }
    }
}

async fn exec_shell() {
    let mut child = match Command::new("ash").spawn() {
        Ok(c) => c,
        Err(e) => {
            error!("failed to exec shell: {e}");
            return;
        }
    };

    let _ = child.wait().await;
}

fn cmd_str(prog: &str, args: &[&str]) -> (String, Command) {
    use std::borrow::Cow;

    let mut buf = String::new();

    buf.push_str(&shell_escape::escape(Cow::Borrowed(prog)));

    for &arg in args {
        buf.push(' ');
        buf.push_str(&shell_escape::escape(Cow::Borrowed(arg)));
    }

    let mut cmd = Command::new(prog);
    cmd.args(args);

    (buf, cmd)
}

#[allow(unused)]
async fn child_reaper() {
    use nix::sys::wait::{waitpid, WaitPidFlag};
    use nix::unistd::Pid;
    use tokio::signal::unix::{signal, SignalKind};

    let Ok(mut sigs) =
        signal(SignalKind::child()).inspect_err(|e| warn!("failed to setup SIGCHLD handler: {e}"))
    else {
        return;
    };

    loop {
        sigs.recv().await;
        let _ = waitpid(Some(Pid::from_raw(-1)), Some(WaitPidFlag::WNOHANG));
    }
}