mirror of
https://github.com/containers/youki
synced 2024-05-05 23:26:32 +02:00
515 lines
19 KiB
Rust
515 lines
19 KiB
Rust
use super::args::ContainerArgs;
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use crate::apparmor;
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use crate::{
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capabilities, hooks, namespaces::Namespaces, process::channel, rootfs, rootless::Rootless,
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seccomp, tty, utils,
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};
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use anyhow::{bail, Context, Result};
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use nix::mount::mount as nix_mount;
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use nix::mount::MsFlags;
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use nix::sched::CloneFlags;
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use nix::{
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fcntl,
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unistd::{self, Gid, Uid},
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};
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use oci_spec::runtime::{LinuxNamespaceType, User};
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use std::collections::HashMap;
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use std::{
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env, fs,
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path::{Path, PathBuf},
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};
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// Get a list of open fds for the calling process.
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fn get_open_fds() -> Result<Vec<i32>> {
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const PROCFS_FD_PATH: &str = "/proc/self/fd";
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utils::ensure_procfs(Path::new(PROCFS_FD_PATH))
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.with_context(|| format!("{} is not the actual procfs", PROCFS_FD_PATH))?;
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let fds: Vec<i32> = fs::read_dir(PROCFS_FD_PATH)?
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.filter_map(|entry| match entry {
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Ok(entry) => Some(entry.path()),
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Err(_) => None,
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})
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.filter_map(|path| path.file_name().map(|file_name| file_name.to_owned()))
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.filter_map(|file_name| file_name.to_str().map(String::from))
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.filter_map(|file_name| -> Option<i32> {
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// Convert the file name from string into i32. Since we are looking
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// at /proc/<pid>/fd, anything that's not a number (i32) can be
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// ignored. We are only interested in opened fds.
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match file_name.parse() {
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Ok(fd) => Some(fd),
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Err(_) => None,
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}
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})
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.collect();
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Ok(fds)
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}
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// Cleanup any extra file descriptors, so the new container process will not
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// leak a file descriptor from before execve gets executed. The first 3 fd will
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// stay open: stdio, stdout, and stderr. We would further preserve the next
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// "preserve_fds" number of fds. Set the rest of fd with CLOEXEC flag, so they
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// will be closed after execve into the container payload. We can't close the
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// fds immediatly since we at least still need it for the pipe used to wait on
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// starting the container.
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fn cleanup_file_descriptors(preserve_fds: i32) -> Result<()> {
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let open_fds = get_open_fds().with_context(|| "Failed to obtain opened fds")?;
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// Include stdin, stdout, and stderr for fd 0, 1, and 2 respectively.
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let min_fd = preserve_fds + 3;
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let to_be_cleaned_up_fds: Vec<i32> = open_fds
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.iter()
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.filter_map(|&fd| if fd >= min_fd { Some(fd) } else { None })
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.collect();
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to_be_cleaned_up_fds.iter().for_each(|&fd| {
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// Intentionally ignore errors here -- the cases where this might fail
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// are basically file descriptors that have already been closed.
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let _ = fcntl::fcntl(fd, fcntl::F_SETFD(fcntl::FdFlag::FD_CLOEXEC));
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});
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Ok(())
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}
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fn sysctl(kernel_params: &HashMap<String, String>) -> Result<()> {
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let sys = PathBuf::from("/proc/sys");
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for (kernel_param, value) in kernel_params {
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let path = sys.join(kernel_param.replace(".", "/"));
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log::debug!(
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"apply value {} to kernel parameter {}.",
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value,
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kernel_param
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);
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fs::write(path, value.as_bytes())
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.with_context(|| format!("failed to set sysctl {}={}", kernel_param, value))?;
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}
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Ok(())
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}
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// make a read only path
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// The first time we bind mount, other flags are ignored,
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// so we need to mount it once and then remount it with the necessary flags specified.
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// https://man7.org/linux/man-pages/man2/mount.2.html
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fn readonly_path(path: &str) -> Result<()> {
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match nix_mount::<str, str, str, str>(
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Some(path),
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path,
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None::<&str>,
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MsFlags::MS_BIND | MsFlags::MS_REC,
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None::<&str>,
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) {
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// ignore error if path is not exist.
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Err(nix::errno::Errno::ENOENT) => {
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log::warn!("readonly path {:?} not exist", path);
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return Ok(());
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}
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Err(err) => bail!(err),
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Ok(_) => {}
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}
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nix_mount::<str, str, str, str>(
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Some(path),
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path,
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None::<&str>,
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MsFlags::MS_NOSUID
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| MsFlags::MS_NODEV
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| MsFlags::MS_NOEXEC
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| MsFlags::MS_BIND
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| MsFlags::MS_REMOUNT
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| MsFlags::MS_RDONLY,
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None::<&str>,
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)?;
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log::debug!("readonly path {:?} mounted", path);
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Ok(())
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}
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// For files, bind mounts /dev/null over the top of the specified path.
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// For directories, mounts read-only tmpfs over the top of the specified path.
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fn masked_path(path: &str, mount_label: &Option<String>) -> Result<()> {
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match nix_mount::<str, str, str, str>(
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Some("/dev/null"),
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path,
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None::<&str>,
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MsFlags::MS_BIND,
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None::<&str>,
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) {
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// ignore error if path is not exist.
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Err(nix::errno::Errno::ENOENT) => {
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log::warn!("masked path {:?} not exist", path);
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return Ok(());
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}
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Err(nix::errno::Errno::ENOTDIR) => {
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let label = match mount_label {
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Some(l) => format!("context={}", l),
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None => "".to_string(),
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};
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let _ = nix_mount(
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Some("tmpfs"),
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path,
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Some("tmpfs"),
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MsFlags::MS_RDONLY,
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Some(label.as_str()),
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);
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}
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Err(err) => bail!(err),
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Ok(_) => {}
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};
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Ok(())
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}
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pub fn container_init(
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args: ContainerArgs,
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sender_to_intermediate: &mut channel::SenderInitToIntermediate,
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) -> Result<()> {
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let command = args.syscall;
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let spec = &args.spec;
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let linux = spec.linux().as_ref().context("no linux in spec")?;
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let proc = spec.process().as_ref().context("no process in spec")?;
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let mut envs: Vec<String> = proc.env().as_ref().unwrap_or(&vec![]).clone();
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let rootfs = &args.rootfs;
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let hooks = spec.hooks().as_ref();
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let container = args.container.as_ref();
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let namespaces = Namespaces::from(linux.namespaces().as_ref());
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// set up tty if specified
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if let Some(csocketfd) = args.console_socket {
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tty::setup_console(&csocketfd).with_context(|| "Failed to set up tty")?;
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}
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// Enter into rest of namespace. Note, we already entered into user and pid
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// namespace. We also have to enter into mount namespace last since
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// namespace may be bind to /proc path. The /proc path will need to be
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// accessed before pivot_root.
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namespaces
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.apply_namespaces(|ns_type| -> bool {
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ns_type != CloneFlags::CLONE_NEWUSER
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&& ns_type != CloneFlags::CLONE_NEWPID
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&& ns_type != CloneFlags::CLONE_NEWNS
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})
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.with_context(|| "Failed to apply namespaces")?;
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if let Some(mount_namespace) = namespaces.get(LinuxNamespaceType::Mount) {
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namespaces
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.unshare_or_setns(mount_namespace)
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.with_context(|| format!("Failed to enter mount namespace: {:?}", mount_namespace))?;
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}
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// Only set the host name if entering into a new uts namespace
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if let Some(uts_namespace) = namespaces.get(LinuxNamespaceType::Uts) {
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if uts_namespace.path().is_none() {
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if let Some(hostname) = spec.hostname() {
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command.set_hostname(hostname)?;
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}
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}
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}
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if let Some(true) = proc.no_new_privileges() {
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let _ = prctl::set_no_new_privileges(true);
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}
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if args.init {
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// create_container hook needs to be called after the namespace setup, but
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// before pivot_root is called. This runs in the container namespaces.
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if let Some(hooks) = hooks {
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hooks::run_hooks(hooks.create_container().as_ref(), container)
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.context("Failed to run create container hooks")?;
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}
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let bind_service = namespaces.get(LinuxNamespaceType::User).is_some();
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rootfs::prepare_rootfs(spec, rootfs, bind_service)
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.with_context(|| "Failed to prepare rootfs")?;
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// Entering into the rootfs jail. If mount namespace is specified, then
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// we use pivot_root, but if we are on the host mount namespace, we will
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// use simple chroot. Scary things will happen if you try to pivot_root
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// in the host mount namespace...
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if namespaces.get(LinuxNamespaceType::Mount).is_some() {
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// change the root of filesystem of the process to the rootfs
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command
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.pivot_rootfs(rootfs)
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.with_context(|| format!("Failed to pivot root to {:?}", rootfs))?;
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} else {
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command
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.chroot(rootfs)
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.with_context(|| format!("Failed to chroot to {:?}", rootfs))?;
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}
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rootfs::adjust_root_mount_propagation(linux)
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.context("Failed to set propagation type of root mount")?;
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if let Some(kernel_params) = linux.sysctl() {
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sysctl(kernel_params)
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.with_context(|| format!("Failed to sysctl: {:?}", kernel_params))?;
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}
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}
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if let Some(profile) = proc.apparmor_profile() {
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apparmor::apply_profile(profile)
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.with_context(|| format!("failed to apply apparmor profile {}", profile))?;
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}
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if let Some(true) = spec.root().as_ref().map(|r| r.readonly().unwrap_or(false)) {
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nix_mount(
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None::<&str>,
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"/",
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None::<&str>,
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MsFlags::MS_RDONLY | MsFlags::MS_REMOUNT | MsFlags::MS_BIND,
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None::<&str>,
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)?
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}
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if let Some(paths) = linux.readonly_paths() {
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// mount readonly path
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for path in paths {
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readonly_path(path).context("Failed to set read only path")?;
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}
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}
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if let Some(paths) = linux.masked_paths() {
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// mount masked path
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for path in paths {
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masked_path(path, linux.mount_label()).context("Failed to set masked path")?;
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}
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}
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let cwd = format!("{}", proc.cwd().display());
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let do_chdir = if cwd.is_empty() {
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false
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} else {
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// This chdir must run before setting up the user.
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// This may allow the user running youki to access directories
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// that the container user cannot access.
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match unistd::chdir(proc.cwd()) {
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Ok(_) => false,
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Err(nix::Error::EPERM) => true,
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Err(e) => bail!("Failed to chdir: {}", e),
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}
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};
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set_supplementary_gids(proc.user(), &args.rootless)
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.context("failed to set supplementary gids")?;
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command
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.set_id(
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Uid::from_raw(proc.user().uid()),
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Gid::from_raw(proc.user().gid()),
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)
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.context("Failed to configure uid and gid")?;
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// Without no new privileges, seccomp is a privileged operation. We have to
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// do this before dropping capabilities. Otherwise, we should do it later,
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// as close to exec as possible.
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if linux.seccomp().is_some() && proc.no_new_privileges().is_none() {
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seccomp::initialize_seccomp(linux.seccomp().as_ref().unwrap())
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.context("Failed to execute seccomp")?;
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}
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capabilities::reset_effective(command).context("Failed to reset effective capabilities")?;
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if let Some(caps) = proc.capabilities() {
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capabilities::drop_privileges(caps, command).context("Failed to drop capabilities")?;
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}
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// Take care of LISTEN_FDS used for systemd-active-socket. If the value is
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// not 0, then we have to preserve those fds as well, and set up the correct
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// environment variables.
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let preserve_fds: i32 = match env::var("LISTEN_FDS") {
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Ok(listen_fds_str) => {
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let listen_fds = match listen_fds_str.parse::<i32>() {
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Ok(v) => v,
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Err(error) => {
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log::warn!(
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"LISTEN_FDS entered is not a fd. Ignore the value. {:?}",
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error
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);
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0
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}
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};
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// The LISTEN_FDS will have to be passed to container init process.
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// The LISTEN_PID will be set to PID 1. Based on the spec, if
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// LISTEN_FDS is 0, the variable should be unset, so we just ignore
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// it here, if it is 0.
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if listen_fds > 0 {
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envs.append(&mut vec![
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format!("LISTEN_FDS={}", listen_fds),
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"LISTEN_PID=1".to_string(),
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]);
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}
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args.preserve_fds + listen_fds
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}
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Err(env::VarError::NotPresent) => args.preserve_fds,
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Err(env::VarError::NotUnicode(value)) => {
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log::warn!(
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"LISTEN_FDS entered is malformed: {:?}. Ignore the value.",
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&value
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);
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args.preserve_fds
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}
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};
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// clean up and handle perserved fds.
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cleanup_file_descriptors(preserve_fds).with_context(|| "Failed to clean up extra fds")?;
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// change directory to process.cwd if process.cwd is not empty
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if do_chdir {
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unistd::chdir(proc.cwd())
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.with_context(|| format!("Failed to chdir {}", proc.cwd().display()))?;
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}
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// Reset the process env based on oci spec.
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env::vars().for_each(|(key, _value)| std::env::remove_var(key));
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utils::parse_env(&envs)
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.iter()
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.for_each(|(key, value)| env::set_var(key, value));
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// notify parents that the init process is ready to execute the payload.
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// Note, we pass -1 here because we are already inside the pid namespace.
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// The pid outside the pid namespace should be recorded by the intermediate
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// process.
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sender_to_intermediate.init_ready()?;
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// listing on the notify socket for container start command
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let notify_socket = args.notify_socket;
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notify_socket.wait_for_container_start()?;
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// create_container hook needs to be called after the namespace setup, but
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// before pivot_root is called. This runs in the container namespaces.
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if args.init {
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if let Some(hooks) = hooks {
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hooks::run_hooks(hooks.start_container().as_ref(), container)?
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}
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}
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if linux.seccomp().is_some() && proc.no_new_privileges().is_some() {
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// Initialize seccomp profile right before we are ready to execute the
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// payload. The notify socket will still need network related syscalls.
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seccomp::initialize_seccomp(linux.seccomp().as_ref().unwrap())
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.context("Failed to execute seccomp")?;
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}
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if let Some(args) = proc.args() {
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utils::do_exec(&args[0], args)?;
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} else {
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bail!("On non-Windows, at least one process arg entry is required.")
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}
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// After do_exec is called, the process is replaced with the container
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// payload through execvp, so it should never reach here.
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unreachable!();
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}
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// Before 3.19 it was possible for an unprivileged user to enter an user namespace,
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// become root and then call setgroups in order to drop membership in supplementary
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// groups. This allowed access to files which blocked access based on being a member
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// of these groups (see CVE-2014-8989)
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//
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// This leaves us with three scenarios:
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//
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// Unprivileged user starting a rootless container: The main process is running as an
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// unprivileged user and therefore cannot write the mapping until "deny" has been written
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// to /proc/{pid}/setgroups. Once written /proc/{pid}/setgroups cannot be reset and the
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// setgroups system call will be disabled for all processes in this user namespace. This
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// also means that we should detect if the user is unprivileged and additional gids have
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// been specified and bail out early as this can never work. This is not handled here,
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// but during the validation for rootless containers.
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//
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// Privileged user starting a rootless container: It is not necessary to write "deny" to
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// /proc/setgroups in order to create the gid mapping and therefore we don't. This means
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// that setgroups could be used to drop groups, but this is fine as the user is privileged
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// and could do so anyway.
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// We already have checked during validation if the specified supplemental groups fall into
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// the range that are specified in the gid mapping and bail out early if they do not.
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//
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// Privileged user starting a normal container: Just add the supplementary groups.
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//
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fn set_supplementary_gids(user: &User, rootless: &Option<Rootless>) -> Result<()> {
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if let Some(additional_gids) = user.additional_gids() {
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if additional_gids.is_empty() {
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return Ok(());
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}
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let setgroups =
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fs::read_to_string("/proc/self/setgroups").context("failed to read setgroups")?;
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if setgroups.trim() == "deny" {
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bail!("cannot set supplementary gids, setgroup is disabled");
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}
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let gids: Vec<Gid> = additional_gids
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.iter()
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.map(|gid| Gid::from_raw(*gid))
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.collect();
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match rootless {
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Some(r) if r.privileged => {
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nix::unistd::setgroups(&gids).context("failed to set supplementary gids")?;
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}
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None => {
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nix::unistd::setgroups(&gids).context("failed to set supplementary gids")?;
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}
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// this should have been detected during validation
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_ => unreachable!(
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"unprivileged users cannot set supplementary gids in rootless container"
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),
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}
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}
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Ok(())
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use anyhow::{bail, Result};
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use nix::{fcntl, sys, unistd};
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use serial_test::serial;
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use std::{fs, os::unix::prelude::AsRawFd};
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|
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// Note: We have to run these tests here as serial. The main issue is that
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// these tests has a dependency on the system state. The
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// cleanup_file_descriptors test is especially evil when running with other
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// tests because it would ran around close down different fds.
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#[test]
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#[serial]
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fn test_get_open_fds() -> Result<()> {
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let file = fs::File::open("/dev/null")?;
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let fd = file.as_raw_fd();
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let open_fds = super::get_open_fds()?;
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if !open_fds.iter().any(|&v| v == fd) {
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bail!("Failed to find the opened dev null fds: {:?}", open_fds);
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}
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// explicitly close the file before the test case returns.
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drop(file);
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// The stdio fds should also be contained in the list of opened fds.
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if !vec![0, 1, 2]
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.iter()
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.all(|&stdio_fd| open_fds.iter().any(|&open_fd| open_fd == stdio_fd))
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{
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bail!("Failed to find the stdio fds: {:?}", open_fds);
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}
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Ok(())
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}
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#[test]
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#[serial]
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fn test_cleanup_file_descriptors() -> Result<()> {
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|
// Open a fd without the CLOEXEC flag. Rust automatically adds the flag,
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|
// so we use fcntl::open here for more control.
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let fd = fcntl::open("/dev/null", fcntl::OFlag::O_RDWR, sys::stat::Mode::empty())?;
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cleanup_file_descriptors(fd - 1).with_context(|| "Failed to clean up the fds")?;
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let fd_flag = fcntl::fcntl(fd, fcntl::F_GETFD)?;
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if (fd_flag & fcntl::FdFlag::FD_CLOEXEC.bits()) != 0 {
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|
bail!("CLOEXEC flag is not set correctly");
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|
}
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|
|
|
unistd::close(fd)?;
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Ok(())
|
|
}
|
|
}
|