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// -*- coding: utf-8 -*-
//
// Copyright (C) 2024 Michael Büsch <m@bues.ch>
//
// Licensed under the Apache License version 2.0
// or the MIT license, at your option.
// SPDX-License-Identifier: Apache-2.0 OR MIT
#![forbid(unsafe_code)]
#[cfg(not(any(target_os = "linux", target_os = "android")))]
std::compile_error!("letmeind server and letmein-seccomp do not support non-Linux platforms.");
use anyhow::{self as ah, Context as _};
use seccompiler::{
apply_filter_all_threads, BpfProgram, SeccompAction, SeccompFilter, SeccompRule,
};
use std::{collections::BTreeMap, env::consts::ARCH};
macro_rules! sys {
($ident:ident) => {{
#[allow(clippy::useless_conversion)]
let id: i64 = libc::$ident.into();
id
}};
}
/// Returns `true` if seccomp is supported on this platform.
pub fn seccomp_supported() -> bool {
// This is what `seccompiler` currently supports:
cfg!(any(target_arch = "x86_64", target_arch = "aarch64"))
}
/// Abstract allow-list features that map to one or more syscalls each.
#[derive(Clone, Debug)]
pub enum Allow {
Mmap,
Mprotect,
UnixConnect,
TcpAccept,
Read,
Write,
Recv,
Send,
Prctl,
Signal,
Futex,
}
/// Action to be performed, if a syscall is executed that is not in the allow-list.
#[derive(Clone, Debug)]
pub enum Action {
/// Kill the process.
Kill,
/// Only log the event and keep running. See the kernel logs.
Log,
}
/// A compiled seccomp filter program.
pub struct Filter(BpfProgram);
impl Filter {
pub fn compile(allow: &[Allow], deny_action: Action) -> ah::Result<Self> {
Self::compile_for_arch(allow, deny_action, ARCH)
}
pub fn compile_for_arch(allow: &[Allow], deny_action: Action, arch: &str) -> ah::Result<Self> {
let mut rules: BTreeMap<i64, Vec<SeccompRule>> = [
(sys!(SYS_brk), vec![]),
(sys!(SYS_close), vec![]),
#[cfg(not(target_os = "android"))]
(sys!(SYS_close_range), vec![]),
(sys!(SYS_exit), vec![]),
(sys!(SYS_exit_group), vec![]),
(sys!(SYS_getpid), vec![]),
(sys!(SYS_getrandom), vec![]),
(sys!(SYS_gettid), vec![]),
(sys!(SYS_madvise), vec![]),
(sys!(SYS_munmap), vec![]),
(sys!(SYS_sched_getaffinity), vec![]),
(sys!(SYS_sigaltstack), vec![]),
(sys!(SYS_nanosleep), vec![]),
(sys!(SYS_clock_gettime), vec![]),
(sys!(SYS_clock_getres), vec![]),
(sys!(SYS_clock_nanosleep), vec![]),
(sys!(SYS_gettimeofday), vec![]),
]
.into();
let add_read_write_rules = |rules: &mut BTreeMap<_, _>| {
rules.insert(sys!(SYS_epoll_create1), vec![]);
rules.insert(sys!(SYS_epoll_ctl), vec![]);
rules.insert(sys!(SYS_epoll_pwait), vec![]);
#[cfg(all(any(target_arch = "x86_64", target_arch = "arm"), target_os = "linux"))]
rules.insert(sys!(SYS_epoll_pwait2), vec![]);
rules.insert(sys!(SYS_epoll_wait), vec![]);
rules.insert(sys!(SYS_lseek), vec![]);
rules.insert(sys!(SYS_ppoll), vec![]);
rules.insert(sys!(SYS_pselect6), vec![]);
};
for allow in allow {
match *allow {
Allow::Mmap => {
#[cfg(any(
target_arch = "x86",
target_arch = "x86_64",
target_arch = "aarch64"
))]
rules.insert(sys!(SYS_mmap), vec![]);
#[cfg(any(target_arch = "x86", target_arch = "arm"))]
rules.insert(sys!(SYS_mmap2), vec![]);
rules.insert(sys!(SYS_mremap), vec![]);
rules.insert(sys!(SYS_munmap), vec![]);
}
Allow::Mprotect => {
rules.insert(sys!(SYS_mprotect), vec![]);
}
Allow::UnixConnect => {
rules.insert(sys!(SYS_connect), vec![]);
rules.insert(sys!(SYS_socket), vec![]); //TODO: Restrict to AF_UNIX
rules.insert(sys!(SYS_getsockopt), vec![]);
}
Allow::TcpAccept => {
rules.insert(sys!(SYS_accept4), vec![]);
rules.insert(sys!(SYS_socket), vec![]); //TODO: Restrict to AF_UNIX
rules.insert(sys!(SYS_getsockopt), vec![]);
}
Allow::Read => {
rules.insert(sys!(SYS_pread64), vec![]);
rules.insert(sys!(SYS_preadv2), vec![]);
rules.insert(sys!(SYS_read), vec![]);
rules.insert(sys!(SYS_readv), vec![]);
add_read_write_rules(&mut rules);
}
Allow::Write => {
rules.insert(sys!(SYS_fdatasync), vec![]);
rules.insert(sys!(SYS_fsync), vec![]);
rules.insert(sys!(SYS_pwrite64), vec![]);
rules.insert(sys!(SYS_pwritev2), vec![]);
rules.insert(sys!(SYS_write), vec![]);
rules.insert(sys!(SYS_writev), vec![]);
add_read_write_rules(&mut rules);
}
Allow::Recv => {
rules.insert(sys!(SYS_recvfrom), vec![]);
rules.insert(sys!(SYS_recvmsg), vec![]);
rules.insert(sys!(SYS_recvmmsg), vec![]);
}
Allow::Send => {
rules.insert(sys!(SYS_sendto), vec![]);
rules.insert(sys!(SYS_sendmsg), vec![]);
rules.insert(sys!(SYS_sendmmsg), vec![]);
}
Allow::Prctl => {
//TODO: The arguments should be restricted to what is needed.
rules.insert(sys!(SYS_prctl), vec![]);
}
Allow::Signal => {
rules.insert(sys!(SYS_rt_sigaction), vec![]);
rules.insert(sys!(SYS_rt_sigreturn), vec![]);
rules.insert(sys!(SYS_rt_sigprocmask), vec![]);
}
Allow::Futex => {
rules.insert(sys!(SYS_futex), vec![]);
rules.insert(sys!(SYS_get_robust_list), vec![]);
rules.insert(sys!(SYS_set_robust_list), vec![]);
#[cfg(all(
any(target_arch = "x86", target_arch = "x86_64", target_arch = "arm"),
target_os = "linux"
))]
rules.insert(sys!(SYS_futex_waitv), vec![]);
//rules.insert(sys!(SYS_futex_wake), vec![]);
//rules.insert(sys!(SYS_futex_wait), vec![]);
//rules.insert(sys!(SYS_futex_requeue), vec![]);
}
}
}
let filter = SeccompFilter::new(
rules,
match deny_action {
Action::Kill => SeccompAction::KillProcess,
Action::Log => SeccompAction::Log,
},
SeccompAction::Allow,
arch.try_into().context("Unsupported CPU ARCH")?,
)
.context("Create seccomp filter")?;
let filter: BpfProgram = filter.try_into().context("Seccomp to BPF")?;
Ok(Self(filter))
}
pub fn install(&self) -> ah::Result<()> {
apply_filter_all_threads(&self.0).context("Apply seccomp filter")
}
}
// vim: ts=4 sw=4 expandtab
|
