1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533
// Copyright 2017 The ChromiumOS Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#![deny(missing_docs)]
#![allow(dead_code)]
use std::path::Path;
use std::str;
use anyhow::bail;
use anyhow::Context;
use anyhow::Result;
#[cfg(feature = "seccomp_trace")]
use base::debug;
use base::getegid;
use base::geteuid;
#[cfg(feature = "seccomp_trace")]
use base::warn;
use libc::c_ulong;
use minijail::Minijail;
use once_cell::sync::Lazy;
#[cfg(feature = "seccomp_trace")]
use static_assertions::const_assert;
#[cfg(feature = "seccomp_trace")]
use zerocopy::AsBytes;
use crate::config::JailConfig;
static EMBEDDED_BPFS: Lazy<std::collections::HashMap<&str, Vec<u8>>> =
Lazy::new(|| include!(concat!(env!("OUT_DIR"), "/bpf_includes.in")));
/// Most devices don't need to open many fds.
pub const MAX_OPEN_FILES_DEFAULT: u64 = 1024;
/// The max open files for gpu processes.
const MAX_OPEN_FILES_FOR_GPU: u64 = 32768;
/// The max open files for jail warden, matching FD_RAW_FAILURE.
pub const MAX_OPEN_FILES_FOR_JAIL_WARDEN: u64 = 65536;
/// The user in the jail to run as.
pub enum RunAsUser {
/// Do not specify the user
Unspecified,
/// Runs as the same user in the jail as the current user.
CurrentUser,
/// Runs as the root user in the jail.
Root,
/// Runs as the specified uid and gid.
/// This requires `SandboxConfig::ugid_map` to be set.
Specified(u32, u32),
}
/// Config for the sandbox to be created by [Minijail].
pub struct SandboxConfig<'a> {
/// Whether or not to drop all capabilities in the sandbox.
pub limit_caps: bool,
log_failures: bool,
seccomp_policy_dir: Option<&'a Path>,
seccomp_policy_name: &'a str,
/// The pair of `uid_map` and `gid_map`.
pub ugid_map: Option<(&'a str, &'a str)>,
/// The remount mode instead of default MS_PRIVATE.
pub remount_mode: Option<c_ulong>,
/// Whether to use empty net namespace. Enabled by default.
pub namespace_net: bool,
/// Whether or not to configure the jail to support bind-mounts.
///
/// Note that most device processes deny `open(2)` and `openat(2)` by seccomp policy and just
/// returns `ENOENT`. Passing opened file descriptors is recommended over opening files in the
/// sandbox.
pub bind_mounts: bool,
/// Specify the user in the jail to run as.
pub run_as: RunAsUser,
}
impl<'a> SandboxConfig<'a> {
/// Creates [SandboxConfig].
pub fn new(jail_config: &'a JailConfig, policy: &'a str) -> Self {
Self {
limit_caps: true,
log_failures: jail_config.seccomp_log_failures,
seccomp_policy_dir: jail_config.seccomp_policy_dir.as_ref().map(Path::new),
seccomp_policy_name: policy,
ugid_map: None,
remount_mode: None,
namespace_net: true,
bind_mounts: false,
run_as: RunAsUser::Unspecified,
}
}
}
/// Wrapper that cleans up a [Minijail] when it is dropped
pub struct ScopedMinijail(pub Minijail);
impl Drop for ScopedMinijail {
fn drop(&mut self) {
let _ = self.0.kill();
}
}
/// Creates a [Minijail] instance which just changes the root using pivot_root(2) path and
/// `max_open_files` using `RLIMIT_NOFILE`.
///
/// If `root` path is "/", the minijail don't change the root.
///
/// # Arguments
///
/// * `root` - The root path to be changed to by minijail.
/// * `max_open_files` - The maximum number of file descriptors to allow a jailed process to open.
#[allow(clippy::unnecessary_cast)]
pub fn create_base_minijail(root: &Path, max_open_files: u64) -> Result<Minijail> {
// Validate new root directory. Path::is_dir() also checks the existence.
if !root.is_dir() {
bail!("{:?} is not a directory, cannot create jail", root);
}
// chroot accepts absolute path only.
if !root.is_absolute() {
bail!("{:?} is not absolute path", root);
}
let mut jail = Minijail::new().context("failed to jail device")?;
// Only pivot_root if we are not re-using the current root directory.
if root != Path::new("/") {
// Run in a new mount namespace.
jail.namespace_vfs();
jail.enter_pivot_root(root)
.context("failed to pivot root device")?;
}
jail.set_rlimit(libc::RLIMIT_NOFILE as i32, max_open_files, max_open_files)
.context("error setting max open files")?;
Ok(jail)
}
/// Creates a [Minijail] instance which just invokes a jail process and sets
/// `max_open_files` using `RLIMIT_NOFILE`. This is helpful with crosvm process
/// runs as a non-root user without SYS_ADMIN capabilities.
///
/// Unlike `create_base_minijail`, this function doesn't call `pivot_root`
/// and `mount namespace`. So, it runs as a non-root user without
/// SYS_ADMIN capabilities.
///
/// Note that since there is no file system isolation provided by this function,
/// caller of this function should enforce other security mechanisum such as selinux
/// on the host to protect directories.
///
/// # Arguments
///
/// * `root` - The root path to checked before the process is jailed
/// * `max_open_files` - The maximum number of file descriptors to allow a jailed process to open.
#[allow(clippy::unnecessary_cast)]
pub fn create_base_minijail_without_pivot_root(
root: &Path,
max_open_files: u64,
) -> Result<Minijail> {
// Validate new root directory. Path::is_dir() also checks the existence.
if !root.is_dir() {
bail!("{:?} is not a directory, cannot create jail", root);
}
if !root.is_absolute() {
bail!("{:?} is not absolute path", root);
}
let mut jail = Minijail::new().context("failed to jail device")?;
jail.set_rlimit(libc::RLIMIT_NOFILE as i32, max_open_files, max_open_files)
.context("error setting max open files")?;
Ok(jail)
}
/// Creates a [Minijail] instance which creates a sandbox.
///
/// # Arguments
///
/// * `root` - The root path to be changed to by minijail.
/// * `max_open_files` - The maximum number of file descriptors to allow a jailed process to open.
/// * `config` - The [SandboxConfig] to control details of the sandbox.
pub fn create_sandbox_minijail(
root: &Path,
max_open_files: u64,
config: &SandboxConfig,
) -> Result<Minijail> {
let mut jail = create_base_minijail(root, max_open_files)?;
jail.namespace_pids();
jail.namespace_user();
jail.namespace_user_disable_setgroups();
if config.limit_caps {
// Don't need any capabilities.
jail.use_caps(0);
}
match config.run_as {
RunAsUser::Unspecified => {
if config.bind_mounts && config.ugid_map.is_none() {
// Minijail requires to set user/group map to mount extra directories.
add_current_user_to_jail(&mut jail)?;
}
}
RunAsUser::CurrentUser => {
add_current_user_to_jail(&mut jail)?;
}
RunAsUser::Root => {
// Add the current user as root in the jail.
let crosvm_uid = geteuid();
let crosvm_gid = getegid();
jail.uidmap(&format!("0 {} 1", crosvm_uid))
.context("error setting UID map")?;
jail.gidmap(&format!("0 {} 1", crosvm_gid))
.context("error setting GID map")?;
}
RunAsUser::Specified(uid, gid) => {
if uid != 0 {
jail.change_uid(uid)
}
if gid != 0 {
jail.change_gid(gid)
}
}
}
if config.bind_mounts {
// Create a tmpfs in the device's root directory so that we can bind mount files.
// The size=67108864 is size=64*1024*1024 or size=64MB.
// TODO(b/267581374): Use appropriate size for tmpfs.
jail.mount_with_data(
Path::new("none"),
Path::new("/"),
"tmpfs",
(libc::MS_NOSUID | libc::MS_NODEV | libc::MS_NOEXEC) as usize,
"size=67108864",
)?;
}
if let Some((uid_map, gid_map)) = config.ugid_map {
jail.uidmap(uid_map).context("error setting UID map")?;
jail.gidmap(gid_map).context("error setting GID map")?;
}
// Run in a new mount namespace.
jail.namespace_vfs();
if config.namespace_net {
// Run in an empty network namespace.
jail.namespace_net();
}
// Don't allow the device to gain new privileges.
jail.no_new_privs();
#[cfg(feature = "seccomp_trace")]
{
#[repr(C)]
#[derive(AsBytes)]
struct sock_filter {
/* Filter block */
code: u16, /* Actual filter code */
jt: u8, /* Jump true */
jf: u8, /* Jump false */
k: u32, /* Generic multiuse field */
}
// BPF constant is defined in https://elixir.bootlin.com/linux/latest/source/include/uapi/linux/bpf_common.h
// BPF parser/assembler is defined in https://elixir.bootlin.com/linux/v4.9/source/tools/net/bpf_exp.y
const SECCOMP_RET_TRACE: u32 = 0x7ff00000;
const SECCOMP_RET_LOG: u32 = 0x7ffc0000;
const BPF_RET: u16 = 0x06;
const BPF_K: u16 = 0x00;
// return SECCOMP_RET_LOG for all syscalls
const FILTER_RET_LOG_BLOCK: sock_filter = sock_filter {
code: BPF_RET | BPF_K,
jt: 0,
jf: 0,
k: SECCOMP_RET_LOG,
};
warn!("The running crosvm is compiled with seccomp_trace feature, and is striclty used for debugging purpose only. DO NOT USE IN PRODUCTION!!!");
debug!(
"seccomp_trace {{\"event\": \"minijail_create\", \"name\": \"{}\", \"jail_addr\": \"0x{:x}\"}}",
config.seccomp_policy_name,
read_jail_addr(&jail),
);
jail.parse_seccomp_bytes(FILTER_RET_LOG_BLOCK.as_bytes())
.unwrap();
}
#[cfg(not(feature = "seccomp_trace"))]
if let Some(seccomp_policy_dir) = config.seccomp_policy_dir {
let seccomp_policy_path = seccomp_policy_dir.join(config.seccomp_policy_name);
// By default we'll prioritize using the pre-compiled .bpf over the .policy file (the .bpf
// is expected to be compiled using "trap" as the failure behavior instead of the default
// "kill" behavior) when a policy path is supplied in the command line arugments. Otherwise
// the built-in pre-compiled policies will be used.
// Refer to the code comment for the "seccomp-log-failures" command-line parameter for an
// explanation about why the |log_failures| flag forces the use of .policy files (and the
// build-time alternative to this run-time flag).
let bpf_policy_file = seccomp_policy_path.with_extension("bpf");
if bpf_policy_file.exists() && !config.log_failures {
jail.parse_seccomp_program(&bpf_policy_file)
.with_context(|| {
format!(
"failed to parse precompiled seccomp policy: {}",
bpf_policy_file.display()
)
})?;
} else {
// Use TSYNC only for the side effect of it using SECCOMP_RET_TRAP, which will correctly
// kill the entire device process if a worker thread commits a seccomp violation.
jail.set_seccomp_filter_tsync();
if config.log_failures {
jail.log_seccomp_filter_failures();
}
let bpf_policy_file = seccomp_policy_path.with_extension("policy");
jail.parse_seccomp_filters(&bpf_policy_file)
.with_context(|| {
format!(
"failed to parse seccomp policy: {}",
bpf_policy_file.display()
)
})?;
}
} else {
set_embedded_bpf_program(&mut jail, config.seccomp_policy_name)?;
}
jail.use_seccomp_filter();
// Don't do init setup.
jail.run_as_init();
// Set up requested remount mode instead of default MS_PRIVATE.
if let Some(mode) = config.remount_mode {
jail.set_remount_mode(mode);
}
Ok(jail)
}
/// Creates a basic [Minijail] if `jail_config` is present.
///
/// Returns `None` if `jail_config` is none.
pub fn simple_jail(jail_config: &Option<JailConfig>, policy: &str) -> Result<Option<Minijail>> {
if let Some(jail_config) = jail_config {
let config = SandboxConfig::new(jail_config, policy);
Ok(Some(create_sandbox_minijail(
&jail_config.pivot_root,
MAX_OPEN_FILES_DEFAULT,
&config,
)?))
} else {
Ok(None)
}
}
/// Creates [Minijail] for gpu processes.
pub fn create_gpu_minijail(
root: &Path,
config: &SandboxConfig,
render_node_only: bool,
snapshot_scratch_directory: Option<&Path>,
) -> Result<Minijail> {
let mut jail = create_sandbox_minijail(root, MAX_OPEN_FILES_FOR_GPU, config)?;
// Device nodes required for DRM.
let sys_dev_char_path = Path::new("/sys/dev/char");
jail.mount_bind(sys_dev_char_path, sys_dev_char_path, false)?;
// Necessary for CGROUP control of the vGPU threads
// This is not necessary UNLESS one wants to make use
// of the gpu cgroup command line options.
let sys_cpuset_path = Path::new("/sys/fs/cgroup/cpuset");
if sys_cpuset_path.exists() {
jail.mount_bind(sys_cpuset_path, sys_cpuset_path, true)?;
}
let sys_devices_path = Path::new("/sys/devices");
jail.mount_bind(sys_devices_path, sys_devices_path, false)?;
jail_mount_bind_drm(&mut jail, render_node_only)?;
// If the ARM specific devices exist on the host, bind mount them in.
let mali0_path = Path::new("/dev/mali0");
if mali0_path.exists() {
jail.mount_bind(mali0_path, mali0_path, true)?;
}
let pvr_sync_path = Path::new("/dev/pvr_sync");
if pvr_sync_path.exists() {
jail.mount_bind(pvr_sync_path, pvr_sync_path, true)?;
}
// If the udmabuf driver exists on the host, bind mount it in.
let udmabuf_path = Path::new("/dev/udmabuf");
if udmabuf_path.exists() {
jail.mount_bind(udmabuf_path, udmabuf_path, true)?;
}
// Libraries that are required when mesa drivers are dynamically loaded.
jail_mount_bind_if_exists(
&mut jail,
&[
"/usr/lib",
"/usr/lib64",
"/lib",
"/lib64",
"/usr/share/drirc.d",
"/usr/share/glvnd",
"/usr/share/libdrm",
"/usr/share/vulkan",
],
)?;
// pvr driver requires read access to /proc/self/task/*/comm.
mount_proc(&mut jail)?;
// To enable perfetto tracing, we need to give access to the perfetto service IPC
// endpoints.
let perfetto_path = Path::new("/run/perfetto");
if perfetto_path.exists() {
jail.mount_bind(perfetto_path, perfetto_path, true)?;
}
// Provide scratch space for the GPU device to build or unpack snapshots.
if let Some(snapshot_scratch_directory) = snapshot_scratch_directory {
jail.mount_with_data(
Path::new("none"),
snapshot_scratch_directory,
"tmpfs",
(libc::MS_NOSUID | libc::MS_NODEV | libc::MS_NOEXEC) as usize,
"size=4294967296",
)?;
}
Ok(jail)
}
/// Selectively bind mount drm nodes into `jail` based on `render_node_only`
///
/// This function will not return an error if drm nodes don't exist
pub fn jail_mount_bind_drm(jail: &mut Minijail, render_node_only: bool) -> Result<()> {
if render_node_only {
const DRM_NUM_NODES: u32 = 63;
const DRM_RENDER_NODE_START: u32 = 128;
for offset in 0..DRM_NUM_NODES {
let path_str = format!("/dev/dri/renderD{}", DRM_RENDER_NODE_START + offset);
let drm_dri_path = Path::new(&path_str);
if !drm_dri_path.exists() {
break;
}
jail.mount_bind(drm_dri_path, drm_dri_path, false)?;
}
} else {
let drm_dri_path = Path::new("/dev/dri");
if drm_dri_path.exists() {
jail.mount_bind(drm_dri_path, drm_dri_path, false)?;
}
}
Ok(())
}
/// Mirror-mount all the directories in `dirs` into `jail` on a best-effort basis.
///
/// This function will not return an error if any of the directories in `dirs` is missing.
pub fn jail_mount_bind_if_exists<P: AsRef<std::ffi::OsStr>>(
jail: &mut Minijail,
dirs: &[P],
) -> Result<()> {
for dir in dirs {
let dir_path = Path::new(dir);
if dir_path.exists() {
jail.mount_bind(dir_path, dir_path, false)?;
}
}
Ok(())
}
/// Mount proc in the sandbox.
pub fn mount_proc(jail: &mut Minijail) -> Result<()> {
jail.mount(
Path::new("proc"),
Path::new("/proc"),
"proc",
(libc::MS_NOSUID | libc::MS_NODEV | libc::MS_NOEXEC | libc::MS_RDONLY) as usize,
)?;
Ok(())
}
/// Read minijail internal struct address for uniquely identifying and tracking jail's lifetime
#[cfg(feature = "seccomp_trace")]
pub fn read_jail_addr(jail: &Minijail) -> usize {
// We can only hope minijail's rust object will always contain a pointer to C jail struct as the
// first field.
const_assert!(std::mem::size_of::<Minijail>() >= std::mem::size_of::<usize>());
// Safe because it's only doing a read within bound checked by static assert
unsafe { *(jail as *const Minijail as *const usize) }
}
/// Set the uid/gid for the jailed process and give a basic id map. This is
/// required for bind mounts to work.
fn add_current_user_to_jail(jail: &mut Minijail) -> Result<()> {
let crosvm_uid = geteuid();
let crosvm_gid = getegid();
jail.uidmap(&format!("{0} {0} 1", crosvm_uid))
.context("error setting UID map")?;
jail.gidmap(&format!("{0} {0} 1", crosvm_gid))
.context("error setting GID map")?;
if crosvm_uid != 0 {
jail.change_uid(crosvm_uid);
}
if crosvm_gid != 0 {
jail.change_gid(crosvm_gid);
}
Ok(())
}
/// Set the seccomp policy for a jail from embedded bpfs
pub fn set_embedded_bpf_program(jail: &mut Minijail, seccomp_policy_name: &str) -> Result<()> {
let bpf_program = EMBEDDED_BPFS.get(seccomp_policy_name).with_context(|| {
format!(
"failed to find embedded seccomp policy: {}",
seccomp_policy_name
)
})?;
jail.parse_seccomp_bytes(bpf_program).with_context(|| {
format!(
"failed to parse embedded seccomp policy: {}",
seccomp_policy_name
)
})?;
Ok(())
}