Red Bear OS
403 lines
13 KiB
Rust
403 lines
13 KiB
Rust
use std::collections::HashMap;
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use std::env;
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use std::io::{self, Write};
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use std::os::fd::{AsRawFd, FromRawFd, OwnedFd, RawFd};
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use std::os::unix::process::CommandExt;
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use std::process::{Command, exit};
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use extra::option::OptionalExt;
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use libredox::flag::O_CLOEXEC;
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use libredox::protocol::ProcCall;
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use redox_rt::sys::proc_call;
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use redox_scheme::scheme::{SchemeSync, register_sync_scheme};
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use redox_scheme::{
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CallerCtx, OpenResult, RequestKind, Response, SendFdRequest, SignalBehavior, Socket,
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};
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use redox_users::{All, AllGroups, AllUsers, Config, get_uid};
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use syscall::error::*;
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use syscall::flag::*;
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use syscall::schemev2::NewFdFlags;
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use termion::input::TermRead;
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const MAX_ATTEMPTS: u16 = 3;
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const _MAN_PAGE: &'static str = /* @MANSTART{sudo} */
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r#"
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NAME
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sudo - execute a command as another user
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SYNOPSIS
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sudo command
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sudo [ -h | --help ]
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DESCRIPTION
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The sudo utility allows a permitted user to execute a command as the
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superuser or another user, as specified by the security policy.
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EXIT STATUS
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Upon successful execution of a command, the exit status from sudo will
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be the exit status of the program that was executed. In case of error
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the exit status will be >0.
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AUTHOR
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Written by Jeremy Soller, Jose Narvaez, bjorn3.
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"#; /* @MANEND */
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fn main() {
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if env::args().nth(1).as_deref() == Some("--daemon") {
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daemon_main();
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}
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let mut args = env::args().skip(1);
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let cmd = args.next().unwrap_or_else(|| {
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eprintln!("sudo: no command provided");
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exit(1);
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});
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let users = AllUsers::basic(Config::default()).unwrap_or_exit(1);
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let uid = get_uid().unwrap_or_exit(1);
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let user = users.get_by_id(uid).unwrap_or_exit(1);
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if uid == 0 {
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// We are root already. No need to elevate privileges
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run_command_as_root(&cmd, &args.collect());
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}
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let file = libredox::call::open("/scheme/sudo", O_CLOEXEC, 0).unwrap();
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let mut attempts = 0;
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loop {
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print!("[sudo] password for {}: ", user.user);
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let _ = io::stdout().flush();
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match io::stdin().read_passwd(&mut io::stdout()).unwrap() {
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Some(password) => {
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println!();
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match libredox::call::write(file, password.as_bytes()) {
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Ok(_) => break,
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Err(err) if err.errno() == EPERM => {
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attempts += 1;
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eprintln!(
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"sudo: incorrect password or not in sudo group ({}/{})",
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attempts, MAX_ATTEMPTS,
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);
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if attempts >= MAX_ATTEMPTS {
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exit(1);
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}
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}
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Err(err) => panic!("{err}"),
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}
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}
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None => {
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println!();
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exit(1);
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}
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}
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}
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// FIXME move to libredox
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unsafe extern "C" {
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safe fn redox_cur_procfd_v0() -> usize;
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}
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// Elevate privileges of our own process with help from the sudo daemon
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syscall::sendfd(
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file,
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syscall::dup(redox_cur_procfd_v0(), &[]).unwrap(),
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0,
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0,
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)
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.unwrap();
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// FIXME perhaps keep the original namespace available in a subdirectory of the namespace we switch to?
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let ns = syscall::openat(file, "ns", 0, syscall::O_CLOEXEC).unwrap();
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libredox::call::setns(ns).unwrap();
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run_command_as_root(&cmd, &args.collect());
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}
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enum Policy {
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Deny,
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Authenticate,
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}
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fn policy_for_user(uid: u32) -> Policy {
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let users = AllUsers::authenticator(Config::default()).unwrap_or_exit(1);
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let groups = AllGroups::new(Config::default()).unwrap_or_exit(1);
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let user = users.get_by_id(uid as usize).unwrap_or_exit(1);
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let sudo_group = groups.get_by_name("sudo").unwrap_or_exit(1);
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if !sudo_group.users.iter().any(|name| name == &user.user) {
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return Policy::Deny;
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}
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Policy::Authenticate
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}
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fn run_command_as_root(cmd: &str, args: &Vec<String>) -> ! {
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let mut command = Command::new(&cmd);
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for arg in args {
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command.arg(&arg);
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}
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command.uid(0);
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command.gid(0);
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command.env("USER", "root");
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command.env("UID", "0");
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command.env("GROUPS", "0");
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let err = command.exec();
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eprintln!("sudo: failed to execute {}: {}", cmd, err);
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exit(1);
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}
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struct Scheme {
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next_fd: usize,
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handles: HashMap<usize, Handle>,
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}
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enum Handle {
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AwaitingPassword { uid: u32 },
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AwaitingRootPassword,
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AwaitingContextFd,
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AwaitingNamespaceFetch { ns: libredox::Fd },
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AwaitingPasswordForPasswd { uid: u32 },
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AwaitingNewPassword { uid: u32 },
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Placeholder,
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SchemeRoot,
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}
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impl SchemeSync for Scheme {
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fn scheme_root(&mut self) -> Result<usize> {
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let fd = self.next_fd;
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self.next_fd = self.next_fd.checked_add(1).ok_or(Error::new(EMFILE))?;
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self.handles.insert(fd, Handle::SchemeRoot);
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Ok(fd)
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}
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fn openat(
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&mut self,
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dirfd: usize,
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path: &str,
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_flags: usize,
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_fcntl_flags: u32,
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ctx: &CallerCtx,
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) -> Result<OpenResult> {
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let handle = match self.handles.get_mut(&dirfd).ok_or(Error::new(EBADF))? {
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Handle::SchemeRoot => match path {
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"" => Handle::AwaitingPassword { uid: ctx.uid },
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"su" => Handle::AwaitingRootPassword,
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"passwd" => Handle::AwaitingPasswordForPasswd { uid: ctx.uid },
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_ => return Err(Error::new(ENOENT)),
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},
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Handle::AwaitingNamespaceFetch { .. } => {
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if path != "ns" {
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return Err(Error::new(ENOENT));
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}
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let ns = match self.handles.insert(dirfd, Handle::Placeholder).unwrap() {
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Handle::AwaitingNamespaceFetch { ns } => ns,
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_ => unreachable!(),
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};
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return Ok(OpenResult::OtherScheme { fd: ns.into_raw() });
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}
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_ => return Err(Error::new(EINVAL)),
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};
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let fd = self.next_fd;
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self.next_fd = self.next_fd.checked_add(1).ok_or(Error::new(EMFILE))?;
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self.handles.insert(fd, handle);
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Ok(OpenResult::ThisScheme {
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number: fd,
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flags: NewFdFlags::empty(),
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})
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}
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fn write(
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&mut self,
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id: usize,
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buf: &[u8],
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_off: u64,
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_flags: u32,
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_ctx: &CallerCtx,
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) -> Result<usize> {
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let handle = self.handles.get_mut(&id).ok_or(Error::new(EBADF))?;
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let validate_utf8 = |buf| std::str::from_utf8(buf).map_err(|_| Error::new(EINVAL));
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match std::mem::replace(handle, Handle::Placeholder) {
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Handle::AwaitingPassword { uid } => {
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let users = AllUsers::authenticator(Config::default()).unwrap_or_exit(1);
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let user = users.get_by_id(uid as usize).unwrap_or_exit(1);
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match policy_for_user(uid) {
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Policy::Deny => {
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*handle = Handle::AwaitingPassword { uid };
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return Err(Error::new(EPERM));
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}
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Policy::Authenticate => {
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let password = validate_utf8(buf)?;
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if user.verify_passwd(&password) {
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*handle = Handle::AwaitingContextFd
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} else {
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*handle = Handle::AwaitingPassword { uid };
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return Err(Error::new(EPERM));
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}
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}
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}
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}
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Handle::AwaitingRootPassword => {
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let users = AllUsers::authenticator(Config::default()).unwrap_or_exit(1);
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let user = users.get_by_id(0).unwrap_or_exit(1);
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let password = validate_utf8(buf)?;
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if user.verify_passwd(&password) {
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*handle = Handle::AwaitingContextFd
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} else {
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*handle = Handle::AwaitingRootPassword;
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return Err(Error::new(EPERM));
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}
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}
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Handle::AwaitingContextFd => {
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*handle = Handle::AwaitingContextFd;
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return Err(Error::new(EINVAL));
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}
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Handle::AwaitingPasswordForPasswd { uid } => {
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let users =
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AllUsers::authenticator(Config::default()).map_err(|_| Error::new(ENOLCK))?;
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let user = users.get_by_id(uid as usize).ok_or(Error::new(EEXIST))?;
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let password = validate_utf8(buf)?;
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if user.verify_passwd(&password) {
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*handle = Handle::AwaitingNewPassword { uid }
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} else {
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*handle = Handle::AwaitingPasswordForPasswd { uid };
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return Err(Error::new(EPERM));
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}
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}
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Handle::AwaitingNewPassword { uid } => {
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let mut users = AllUsers::authenticator(Config::default().writeable(true))
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.map_err(|_| Error::new(ENOLCK))?;
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let user = users
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.get_mut_by_id(uid as usize)
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.ok_or(Error::new(EEXIST))?;
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let new_password = validate_utf8(buf)?;
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if user.set_passwd(&new_password).is_ok() {
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users.save().map_err(|_| Error::new(ENOLCK))?;
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*handle = Handle::Placeholder
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} else {
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*handle = Handle::AwaitingNewPassword { uid };
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return Err(Error::new(EPERM));
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}
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}
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Handle::AwaitingNamespaceFetch { .. } => {
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eprintln!("sudo: found namespace fetch handle with ID {id}");
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return Err(Error::new(EBADFD));
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}
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Handle::Placeholder => {
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eprintln!("sudo: found placeholder handle with ID {id}");
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return Err(Error::new(EBADFD));
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}
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Handle::SchemeRoot => {
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eprintln!("sudo: found Scheme root handle with ID {id}");
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return Err(Error::new(EBADFD));
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}
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}
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Ok(buf.len())
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}
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}
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impl Scheme {
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fn on_close(&mut self, id: usize) {
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self.handles.remove(&id);
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}
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fn on_sendfd(&mut self, socket: &Socket, req: &SendFdRequest) -> Result<usize> {
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let handle = self.handles.get_mut(&req.id()).ok_or(Error::new(EBADF))?;
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match std::mem::replace(handle, Handle::Placeholder) {
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Handle::AwaitingContextFd => {
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let mut proc_fd = usize::MAX;
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req.obtain_fd(
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socket,
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FobtainFdFlags::empty(),
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std::slice::from_mut(&mut proc_fd),
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)?;
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let proc_fd = unsafe { OwnedFd::from_raw_fd(proc_fd as RawFd) };
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let [ruid, euid, suid] = [0, 0, 0];
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let [rgid, egid, sgid] = [0, 0, 0];
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let mut payload = [0; size_of::<u32>() * 6];
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plain::slice_from_mut_bytes(&mut payload)
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.unwrap()
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.copy_from_slice(&[ruid, euid, suid, rgid, egid, sgid]);
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if let Err(err) = proc_call(
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proc_fd.as_raw_fd() as usize,
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&mut payload,
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CallFlags::empty(),
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&[ProcCall::SetResugid as u64],
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) {
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eprintln!("failed to setresugid: {err}");
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}
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*handle = Handle::AwaitingNamespaceFetch {
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ns: libredox::Fd::new(
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syscall::dup(libredox::call::getns().unwrap(), b"").unwrap(),
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),
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};
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}
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old => {
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*handle = old;
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return Err(Error::new(EBADF));
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}
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}
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Ok(0)
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}
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}
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fn daemon_main() -> ! {
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// TODO: Linux kernel audit-like logging?
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let socket = Socket::create().expect("failed to open scheme socket");
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let mut scheme = Scheme {
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next_fd: 1,
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handles: HashMap::new(),
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};
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let mut scheme_state = redox_scheme::scheme::SchemeState::new();
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register_sync_scheme(&socket, "sudo", &mut scheme)
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.expect("failed to register sudo scheme to namespace");
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loop {
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let Some(req) = socket
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.next_request(SignalBehavior::Restart)
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.expect("failed to get request")
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else {
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break;
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};
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let response = match req.kind() {
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RequestKind::Call(call) => call.handle_sync(&mut scheme, &mut scheme_state),
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RequestKind::SendFd(req) => Response::new(scheme.on_sendfd(&socket, &req), req),
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RequestKind::OnClose { id } => {
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scheme.on_close(id);
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continue;
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}
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_ => continue,
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};
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socket
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.write_response(response, SignalBehavior::Restart)
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.expect("sudo: scheme write failed");
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}
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std::process::exit(0)
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}
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