baseline_policy_android.cc

// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "sandbox/linux/seccomp-bpf-helpers/baseline_policy_android.h"

#include <errno.h>
#include <fcntl.h>
#include <linux/net.h>
#include <sys/socket.h>
#include <sys/syscall.h>
#include <sys/types.h>

#include "build/build_config.h"
#include "sandbox/linux/bpf_dsl/bpf_dsl.h"
#include "sandbox/linux/seccomp-bpf-helpers/syscall_parameters_restrictions.h"
#include "sandbox/linux/seccomp-bpf-helpers/syscall_sets.h"
#include "sandbox/linux/system_headers/linux_syscalls.h"

#if defined(__x86_64__)
#include <asm/prctl.h>
#endif

using sandbox::bpf_dsl::AllOf;
using sandbox::bpf_dsl::Allow;
using sandbox::bpf_dsl::AnyOf;
using sandbox::bpf_dsl::Arg;
using sandbox::bpf_dsl::BoolExpr;
using sandbox::bpf_dsl::If;
using sandbox::bpf_dsl::Error;
using sandbox::bpf_dsl::ResultExpr;

namespace sandbox {

#ifndef SOCK_CLOEXEC
#define SOCK_CLOEXEC O_CLOEXEC
#endif

#ifndef SOCK_NONBLOCK
#define SOCK_NONBLOCK O_NONBLOCK
#endif

#define CASES SANDBOX_BPF_DSL_CASES

namespace {

#if !defined(__i386__)
// Restricts the arguments to sys_socket() to AF_UNIX. Returns a BoolExpr that
// evaluates to true if the syscall should be allowed.
BoolExpr RestrictSocketArguments(const Arg<int>& domain,
                                 const Arg<int>& type,
                                 const Arg<int>& protocol) {
  const int kSockFlags = SOCK_CLOEXEC | SOCK_NONBLOCK;
  return AllOf(domain == AF_UNIX,
               AnyOf((type & ~kSockFlags) == SOCK_DGRAM,
                     (type & ~kSockFlags) == SOCK_STREAM),
               protocol == 0);
}
#endif  // !defined(__i386__)

}  // namespace

BaselinePolicyAndroid::BaselinePolicyAndroid()
    : BaselinePolicy() {}

BaselinePolicyAndroid::~BaselinePolicyAndroid() {}

ResultExpr BaselinePolicyAndroid::EvaluateSyscall(int sysno) const {
  bool override_and_allow = false;

  switch (sysno) {
    // TODO(rsesek): restrict clone parameters.
    case __NR_clone:
    case __NR_epoll_pwait:
    case __NR_fdatasync:
    case __NR_flock:
    case __NR_fsync:
    case __NR_ftruncate:
#if defined(__i386__) || defined(__arm__) || defined(__mips32__)
    case __NR_ftruncate64:
#endif
#if defined(__x86_64__) || defined(__aarch64__)
    case __NR_newfstatat:
    case __NR_fstatfs:
#elif defined(__i386__) || defined(__arm__) || defined(__mips32__)
    case __NR_fstatat64:
    case __NR_fstatfs64:
#endif
#if defined(__i386__) || defined(__arm__) || defined(__mips__)
    case __NR_getdents:
#endif
    case __NR_getdents64:
    case __NR_getpriority:
    case __NR_ioctl:
    case __NR_mremap:
#if defined(__i386__)
    // Used on pre-N to initialize threads in ART.
    case __NR_modify_ldt:
#endif
    case __NR_msync:
    // File system access cannot be restricted with seccomp-bpf on Android,
    // since the JVM classloader and other Framework features require file
    // access. It may be possible to restrict the filesystem with SELinux.
    // Currently we rely on the app/service UID isolation to create a
    // filesystem "sandbox".
#if !defined(ARCH_CPU_ARM64)
    case __NR_open:
#endif
    case __NR_openat:
    case __NR_pread64:
    case __NR_pwrite64:
    case __NR_rt_sigtimedwait:
    case __NR_sched_getparam:
    case __NR_sched_getscheduler:
    case __NR_sched_setscheduler:
    case __NR_setpriority:
#if defined(__i386__)
    // Used on N+ instead of __NR_modify_ldt to initialize threads in ART.
    case __NR_set_thread_area:
#endif
    case __NR_set_tid_address:
    case __NR_sigaltstack:
#if defined(__i386__) || defined(__arm__)
    case __NR_ugetrlimit:
#else
    case __NR_getrlimit:
#endif
    case __NR_sysinfo:  // https://crbug.com/655277
    case __NR_uname:

    // Permit socket operations so that renderers can connect to logd and
    // debuggerd. The arguments to socket() are further restricted below.
    // Note that on i386, both of these calls map to __NR_socketcall, which
    // is demultiplexed below.
#if defined(__x86_64__) || defined(__arm__) || defined(__aarch64__) || \
      defined(__mips__)
    case __NR_getsockopt:
    case __NR_connect:
    case __NR_socket:
#endif

    // Ptrace is allowed so the Breakpad Microdumper can fork in a renderer
    // and then ptrace the parent.
    case __NR_ptrace:
      override_and_allow = true;
      break;
  }

  // https://crbug.com/772441 and https://crbug.com/760020.
  if (SyscallSets::IsEventFd(sysno)) {
    return Allow();
  }

  // https://crbug.com/644759
  if (sysno == __NR_rt_tgsigqueueinfo) {
    const Arg<pid_t> tgid(0);
    return If(tgid == policy_pid(), Allow())
           .Else(Error(EPERM));
  }

  // https://crbug.com/766245
  if (sysno == __NR_process_vm_readv) {
    const Arg<pid_t> pid(0);
    return If(pid == policy_pid(), Allow())
           .Else(Error(EPERM));
  }

  // https://crbug.com/655299
  if (sysno == __NR_clock_getres) {
    return RestrictClockID();
  }

  // https://crbug.com/826289
  if (sysno == __NR_getrusage) {
    return RestrictGetrusage();
  }

#if defined(__x86_64__)
  if (sysno == __NR_arch_prctl) {
    const Arg<int> code(0);
    return If(code == ARCH_SET_GS, Allow()).Else(Error(EPERM));
  }
#endif

  // Restrict socket-related operations. On non-i386 platforms, these are
  // individual syscalls. On i386, the socketcall syscall demultiplexes many
  // socket operations.
#if defined(__x86_64__) || defined(__arm__) || defined(__aarch64__) || \
      defined(__mips__)
  if (sysno == __NR_socket) {
    const Arg<int> domain(0);
    const Arg<int> type(1);
    const Arg<int> protocol(2);
    return If(RestrictSocketArguments(domain, type, protocol), Allow())
           .Else(Error(EPERM));
  }

  // https://crbug.com/655300
  if (sysno == __NR_getsockname) {
    // Rather than blocking with SIGSYS, just return an error. This is not
    // documented to be a valid errno, but we will use it anyways.
    return Error(EPERM);
  }

  // https://crbug.com/682488, https://crbug.com/701137
  if (sysno == __NR_setsockopt) {
    // The baseline policy applies other restrictions to setsockopt.
    const Arg<int> level(1);
    const Arg<int> option(2);
    return If(AllOf(level == SOL_SOCKET,
                    AnyOf(option == SO_SNDTIMEO,
                          option == SO_RCVTIMEO,
                          option == SO_SNDBUF,
                          option == SO_REUSEADDR)),
              Allow())
           .Else(BaselinePolicy::EvaluateSyscall(sysno));
  }
#elif defined(__i386__)
  if (sysno == __NR_socketcall) {
    // The baseline policy allows other socketcall sub-calls.
    const Arg<int> socketcall(0);
    return Switch(socketcall)
        .CASES((SYS_CONNECT,
                SYS_SOCKET,
                SYS_SETSOCKOPT,
                SYS_GETSOCKOPT),
               Allow())
        .Default(BaselinePolicy::EvaluateSyscall(sysno));
  }
#endif

  if (override_and_allow)
    return Allow();

  return BaselinePolicy::EvaluateSyscall(sysno);
}

}  // namespace sandbox