chromium/sandbox/linux/suid/sandbox.c

// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifdef UNSAFE_BUFFERS_BUILD
// TODO(crbug.com/351564777): Remove this and convert code to safer constructs.
#pragma allow_unsafe_buffers
#endif

// https://chromium.googlesource.com/chromium/src/+/main/docs/linux/suid_sandbox.md

#include "sandbox/linux/suid/common/sandbox.h"

#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif
#include <asm/unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <sched.h>
#include <signal.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/prctl.h>
#include <sys/resource.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/vfs.h>
#include <sys/wait.h>
#include <unistd.h>

#include "sandbox/linux/suid/common/suid_unsafe_environment_variables.h"
#include "sandbox/linux/suid/process_util.h"

#if !defined(CLONE_NEWPID)
#define CLONE_NEWPID …
#endif
#if !defined(CLONE_NEWNET)
#define CLONE_NEWNET …
#endif

static bool DropRoot();

#define HANDLE_EINTR(x) …

static void FatalError(const char* msg, ...)
    __attribute__((noreturn, format(printf, 1, 2)));

static void FatalError(const char* msg, ...) { … }

static void ExitWithErrorSignalHandler(int signal) { … }

// We will chroot() to the helper's /proc/self directory. Anything there will
// not exist anymore if we make sure to wait() for the helper.
//
// /proc/self/fdinfo or /proc/self/fd are especially safe and will be empty
// even if the helper survives as a zombie.
//
// There is very little reason to use fdinfo/ instead of fd/ but we are
// paranoid. fdinfo/ only exists since 2.6.22 so we allow fallback to fd/
#define SAFE_DIR …
#define SAFE_DIR2 …

static bool SpawnChrootHelper() { … }

// Block until child_pid exits, then exit. Try to preserve the exit code.
static void WaitForChildAndExit(pid_t child_pid) { … }

static bool MoveToNewNamespaces() { … }

static bool DropRoot() { … }

static bool SetupChildEnvironment() { … }

bool CheckAndExportApiVersion() { … }

int main(int argc, char** argv) { … }