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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "SandboxFilter.h"
#include "SandboxFilterUtil.h"

#include "Sandbox.h"  // for ContentProcessSandboxParams
#include "SandboxBrokerClient.h"
#include "SandboxInfo.h"
#include "SandboxInternal.h"
#include "SandboxLogging.h"
#include "SandboxOpenedFiles.h"
#include "mozilla/Move.h"
#include "mozilla/PodOperations.h"
#include "mozilla/TemplateLib.h"
#include "mozilla/UniquePtr.h"
#include "prenv.h"

#include <errno.h>
#include <fcntl.h>
#include <linux/ioctl.h>
#include <linux/ipc.h>
#include <linux/net.h>
#include <linux/sched.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/prctl.h>
#include <sys/socket.h>
#include <sys/syscall.h>
#include <sys/un.h>
#include <sys/utsname.h>
#include <time.h>
#include <unistd.h>
#include <vector>
#include <algorithm>

#include "sandbox/linux/bpf_dsl/bpf_dsl.h"
#include "sandbox/linux/system_headers/linux_seccomp.h"
#include "sandbox/linux/system_headers/linux_syscalls.h"

using namespace sandbox::bpf_dsl;
#define CASES SANDBOX_BPF_DSL_CASES

// Fill in defines in case of old headers.
// (Warning: these are wrong on PA-RISC.)
#ifndef MADV_HUGEPAGE
#  define MADV_HUGEPAGE 14
#endif
#ifndef MADV_NOHUGEPAGE
#  define MADV_NOHUGEPAGE 15
#endif
#ifndef MADV_DONTDUMP
#  define MADV_DONTDUMP 16
#endif

// Added in Linux 4.5; see bug 1303813.
#ifndef MADV_FREE
#  define MADV_FREE 8
#endif

#ifndef PR_SET_PTRACER
#  define PR_SET_PTRACER 0x59616d61
#endif

// The headers define O_LARGEFILE as 0 on x86_64, but we need the
// actual value because it shows up in file flags.
#define O_LARGEFILE_REAL 00100000

// To avoid visual confusion between "ifdef ANDROID" and "ifndef ANDROID":
#ifndef ANDROID
#  define DESKTOP
#endif

// This file defines the seccomp-bpf system call filter policies.
// See also SandboxFilterUtil.h, for the CASES_FOR_* macros and
// SandboxFilterBase::Evaluate{Socket,Ipc}Call.
//
// One important difference from how Chromium bpf_dsl filters are
// normally interpreted: returning -ENOSYS from a Trap() handler
// indicates an unexpected system call; SigSysHandler() in Sandbox.cpp
// will detect this, request a crash dump, and terminate the process.
// This does not apply to using Error(ENOSYS) in the policy, so that
// can be used if returning an actual ENOSYS is needed.

namespace mozilla {

// This class allows everything used by the sandbox itself, by the
// core IPC code, by the crash reporter, or other core code.  It also
// contains support for brokering file operations, but file access is
// denied if no broker client is provided by the concrete class.
class SandboxPolicyCommon : public SandboxPolicyBase {
 protected:
  enum class ShmemUsage {
    MAY_CREATE,
    ONLY_USE,
  };

  SandboxBrokerClient* mBroker;
  ShmemUsage mShmemUsage;

  explicit SandboxPolicyCommon(SandboxBrokerClient* aBroker,
                               ShmemUsage aShmemUsage = ShmemUsage::MAY_CREATE)
      : mBroker(aBroker), mShmemUsage(aShmemUsage) {}

  SandboxPolicyCommon() : SandboxPolicyCommon(nullptr, ShmemUsage::ONLY_USE) {}

  typedef const sandbox::arch_seccomp_data& ArgsRef;

  static intptr_t BlockedSyscallTrap(ArgsRef aArgs, void* aux) {
    MOZ_ASSERT(!aux);
    return -ENOSYS;
  }

  // Convert Unix-style "return -1 and set errno" APIs back into the
  // Linux ABI "return -err" style.
  static intptr_t ConvertError(long rv) { return rv < 0 ? -errno : rv; }

  template <typename... Args>
  static intptr_t DoSyscall(long nr, Args... args) {
    static_assert(tl::And<(sizeof(Args) <= sizeof(void*))...>::value,
                  "each syscall arg is at most one word");
    return ConvertError(syscall(nr, args...));
  }

 private:
  // Bug 1093893: Translate tkill to tgkill for pthread_kill; fixed in
  // bionic commit 10c8ce59a (in JB and up; API level 16 = Android 4.1).
  // Bug 1376653: musl also needs this, and security-wise it's harmless.
  static intptr_t TKillCompatTrap(ArgsRef aArgs, void* aux) {
    auto tid = static_cast<pid_t>(aArgs.args[0]);
    auto sig = static_cast<int>(aArgs.args[1]);
    return DoSyscall(__NR_tgkill, getpid(), tid, sig);
  }

  static intptr_t SetNoNewPrivsTrap(ArgsRef& aArgs, void* aux) {
    if (gSetSandboxFilter == nullptr) {
      // Called after BroadcastSetThreadSandbox finished, therefore
      // not our doing and not expected.
      return BlockedSyscallTrap(aArgs, nullptr);
    }
    // Signal that the filter is already in place.
    return -ETXTBSY;
  }

  // Trap handlers for filesystem brokering.
  // (The amount of code duplication here could be improved....)
#ifdef __NR_open
  static intptr_t OpenTrap(ArgsRef aArgs, void* aux) {
    auto broker = static_cast<SandboxBrokerClient*>(aux);
    auto path = reinterpret_cast<const char*>(aArgs.args[0]);
    auto flags = static_cast<int>(aArgs.args[1]);
    return broker->Open(path, flags);
  }
#endif

  static intptr_t OpenAtTrap(ArgsRef aArgs, void* aux) {
    auto broker = static_cast<SandboxBrokerClient*>(aux);
    auto fd = static_cast<int>(aArgs.args[0]);
    auto path = reinterpret_cast<const char*>(aArgs.args[1]);
    auto flags = static_cast<int>(aArgs.args[2]);
    if (fd != AT_FDCWD && path[0] != '/') {
      SANDBOX_LOG_ERROR("unsupported fd-relative openat(%d, \"%s\", 0%o)", fd,
                        path, flags);
      return BlockedSyscallTrap(aArgs, nullptr);
    }
    return broker->Open(path, flags);
  }

#ifdef __NR_access
  static intptr_t AccessTrap(ArgsRef aArgs, void* aux) {
    auto broker = static_cast<SandboxBrokerClient*>(aux);
    auto path = reinterpret_cast<const char*>(aArgs.args[0]);
    auto mode = static_cast<int>(aArgs.args[1]);
    return broker->Access(path, mode);
  }
#endif

  static intptr_t AccessAtTrap(ArgsRef aArgs, void* aux) {
    auto broker = static_cast<SandboxBrokerClient*>(aux);
    auto fd = static_cast<int>(aArgs.args[0]);
    auto path = reinterpret_cast<const char*>(aArgs.args[1]);
    auto mode = static_cast<int>(aArgs.args[2]);
    // Linux's faccessat syscall has no "flags" argument.  Attempting
    // to handle the flags != 0 case is left to userspace; this is
    // impossible to do correctly in all cases, but that's not our
    // problem.
    if (fd != AT_FDCWD && path[0] != '/') {
      SANDBOX_LOG_ERROR("unsupported fd-relative faccessat(%d, \"%s\", %d)", fd,
                        path, mode);
      return BlockedSyscallTrap(aArgs, nullptr);
    }
    return broker->Access(path, mode);
  }

  static intptr_t StatTrap(ArgsRef aArgs, void* aux) {
    auto broker = static_cast<SandboxBrokerClient*>(aux);
    auto path = reinterpret_cast<const char*>(aArgs.args[0]);
    auto buf = reinterpret_cast<statstruct*>(aArgs.args[1]);
    return broker->Stat(path, buf);
  }

  static intptr_t LStatTrap(ArgsRef aArgs, void* aux) {
    auto broker = static_cast<SandboxBrokerClient*>(aux);
    auto path = reinterpret_cast<const char*>(aArgs.args[0]);
    auto buf = reinterpret_cast<statstruct*>(aArgs.args[1]);
    return broker->LStat(path, buf);
  }

  static intptr_t StatAtTrap(ArgsRef aArgs, void* aux) {
    auto broker = static_cast<SandboxBrokerClient*>(aux);
    auto fd = static_cast<int>(aArgs.args[0]);
    auto path = reinterpret_cast<const char*>(aArgs.args[1]);
    auto buf = reinterpret_cast<statstruct*>(aArgs.args[2]);
    auto flags = static_cast<int>(aArgs.args[3]);
    if (fd != AT_FDCWD && path[0] != '/') {
      SANDBOX_LOG_ERROR("unsupported fd-relative fstatat(%d, \"%s\", %p, %d)",
                        fd, path, buf, flags);
      return BlockedSyscallTrap(aArgs, nullptr);
    }
    if ((flags & ~AT_SYMLINK_NOFOLLOW) != 0) {
      SANDBOX_LOG_ERROR("unsupported flags %d in fstatat(%d, \"%s\", %p, %d)",
                        (flags & ~AT_SYMLINK_NOFOLLOW), fd, path, buf, flags);
      return BlockedSyscallTrap(aArgs, nullptr);
    }
    return (flags & AT_SYMLINK_NOFOLLOW) == 0 ? broker->Stat(path, buf)
                                              : broker->LStat(path, buf);
  }

  static intptr_t ChmodTrap(ArgsRef aArgs, void* aux) {
    auto broker = static_cast<SandboxBrokerClient*>(aux);
    auto path = reinterpret_cast<const char*>(aArgs.args[0]);
    auto mode = static_cast<mode_t>(aArgs.args[1]);
    return broker->Chmod(path, mode);
  }

  static intptr_t LinkTrap(ArgsRef aArgs, void* aux) {
    auto broker = static_cast<SandboxBrokerClient*>(aux);
    auto path = reinterpret_cast<const char*>(aArgs.args[0]);
    auto path2 = reinterpret_cast<const char*>(aArgs.args[1]);
    return broker->Link(path, path2);
  }

  static intptr_t SymlinkTrap(ArgsRef aArgs, void* aux) {
    auto broker = static_cast<SandboxBrokerClient*>(aux);
    auto path = reinterpret_cast<const char*>(aArgs.args[0]);
    auto path2 = reinterpret_cast<const char*>(aArgs.args[1]);
    return broker->Symlink(path, path2);
  }

  static intptr_t RenameTrap(ArgsRef aArgs, void* aux) {
    auto broker = static_cast<SandboxBrokerClient*>(aux);
    auto path = reinterpret_cast<const char*>(aArgs.args[0]);
    auto path2 = reinterpret_cast<const char*>(aArgs.args[1]);
    return broker->Rename(path, path2);
  }

  static intptr_t MkdirTrap(ArgsRef aArgs, void* aux) {
    auto broker = static_cast<SandboxBrokerClient*>(aux);
    auto path = reinterpret_cast<const char*>(aArgs.args[0]);
    auto mode = static_cast<mode_t>(aArgs.args[1]);
    return broker->Mkdir(path, mode);
  }

  static intptr_t RmdirTrap(ArgsRef aArgs, void* aux) {
    auto broker = static_cast<SandboxBrokerClient*>(aux);
    auto path = reinterpret_cast<const char*>(aArgs.args[0]);
    return broker->Rmdir(path);
  }

  static intptr_t UnlinkTrap(ArgsRef aArgs, void* aux) {
    auto broker = static_cast<SandboxBrokerClient*>(aux);
    auto path = reinterpret_cast<const char*>(aArgs.args[0]);
    return broker->Unlink(path);
  }

  static intptr_t ReadlinkTrap(ArgsRef aArgs, void* aux) {
    auto broker = static_cast<SandboxBrokerClient*>(aux);
    auto path = reinterpret_cast<const char*>(aArgs.args[0]);
    auto buf = reinterpret_cast<char*>(aArgs.args[1]);
    auto size = static_cast<size_t>(aArgs.args[2]);
    return broker->Readlink(path, buf, size);
  }

  static intptr_t ReadlinkAtTrap(ArgsRef aArgs, void* aux) {
    auto broker = static_cast<SandboxBrokerClient*>(aux);
    auto fd = static_cast<int>(aArgs.args[0]);
    auto path = reinterpret_cast<const char*>(aArgs.args[1]);
    auto buf = reinterpret_cast<char*>(aArgs.args[2]);
    auto size = static_cast<size_t>(aArgs.args[3]);
    if (fd != AT_FDCWD && path[0] != '/') {
      SANDBOX_LOG_ERROR("unsupported fd-relative readlinkat(%d, %s, %p, %u)",
                        fd, path, buf, size);
      return BlockedSyscallTrap(aArgs, nullptr);
    }
    return broker->Readlink(path, buf, size);
  }

  static intptr_t SocketpairDatagramTrap(ArgsRef aArgs, void* aux) {
    auto fds = reinterpret_cast<int*>(aArgs.args[3]);
    // Return sequential packet sockets instead of the expected
    // datagram sockets; see bug 1355274 for details.
    return ConvertError(socketpair(AF_UNIX, SOCK_SEQPACKET, 0, fds));
  }

  static intptr_t SocketpairUnpackTrap(ArgsRef aArgs, void* aux) {
#ifdef __NR_socketpair
    auto argsPtr = reinterpret_cast<unsigned long*>(aArgs.args[1]);
    return DoSyscall(__NR_socketpair, argsPtr[0], argsPtr[1], argsPtr[2],
                     argsPtr[3]);
#else
    MOZ_CRASH("unreachable?");
    return -ENOSYS;
#endif
  }

 public:
  ResultExpr InvalidSyscall() const override {
    return Trap(BlockedSyscallTrap, nullptr);
  }

  virtual ResultExpr ClonePolicy(ResultExpr failPolicy) const {
    // Allow use for simple thread creation (pthread_create) only.

    // WARNING: s390 and cris pass the flags in the second arg -- see
    // CLONE_BACKWARDS2 in arch/Kconfig in the kernel source -- but we
    // don't support seccomp-bpf on those archs yet.
    Arg<int> flags(0);

    // The exact flags used can vary.  CLONE_DETACHED is used by musl
    // and by old versions of Android (<= JB 4.2), but it's been
    // ignored by the kernel since the beginning of the Git history.
    //
    // If we ever need to support Android <= KK 4.4 again, SETTLS
    // and the *TID flags will need to be made optional.
    static const int flags_required =
        CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND | CLONE_THREAD |
        CLONE_SYSVSEM | CLONE_SETTLS | CLONE_PARENT_SETTID |
        CLONE_CHILD_CLEARTID;
    static const int flags_optional = CLONE_DETACHED;

    return If((flags & ~flags_optional) == flags_required, Allow())
        .Else(failPolicy);
  }

  virtual ResultExpr PrctlPolicy() const {
    // Note: this will probably need PR_SET_VMA if/when it's used on
    // Android without being overridden by an allow-all policy, and
    // the constant will need to be defined locally.
    Arg<int> op(0);
    return Switch(op)
        .CASES((PR_GET_SECCOMP,   // BroadcastSetThreadSandbox, etc.
                PR_SET_NAME,      // Thread creation
                PR_SET_DUMPABLE,  // Crash reporting
                PR_SET_PTRACER),  // Debug-mode crash handling
               Allow())
        .Default(InvalidSyscall());
  }

  Maybe<ResultExpr> EvaluateSocketCall(int aCall,
                                       bool aHasArgs) const override {
    switch (aCall) {
      case SYS_RECVMSG:
      case SYS_SENDMSG:
        return Some(Allow());

      case SYS_SOCKETPAIR: {
        // Allow "safe" (always connected) socketpairs when using the
        // file broker.
        if (mBroker == nullptr) {
          return Nothing();
        }
        // See bug 1066750.
        if (!aHasArgs) {
          // If this is a socketcall(2) platform, but the kernel also
          // supports separate syscalls (>= 4.2.0), we can unpack the
          // arguments and filter them.
          if (HasSeparateSocketCalls()) {
            return Some(Trap(SocketpairUnpackTrap, nullptr));
          }
          // Otherwise, we can't filter the args if the platform passes
          // them by pointer.
          return Some(Allow());
        }
        Arg<int> domain(0), type(1);
        return Some(
            If(domain == AF_UNIX,
               Switch(type & ~(SOCK_CLOEXEC | SOCK_NONBLOCK))
                   .Case(SOCK_STREAM, Allow())
                   .Case(SOCK_SEQPACKET, Allow())
                   // This is used only by content (and only for
                   // direct PulseAudio, which is deprecated) but it
                   // doesn't increase attack surface:
                   .Case(SOCK_DGRAM, Trap(SocketpairDatagramTrap, nullptr))
                   .Default(InvalidSyscall()))
                .Else(InvalidSyscall()));
      }

      default:
        return Nothing();
    }
  }

  ResultExpr EvaluateSyscall(int sysno) const override {
    // If a file broker client was provided, route syscalls to it;
    // otherwise, fall through to the main policy, which will deny
    // them.
    if (mBroker != nullptr) {
      switch (sysno) {
        case __NR_open:
          return Trap(OpenTrap, mBroker);
        case __NR_openat:
          return Trap(OpenAtTrap, mBroker);
        case __NR_access:
          return Trap(AccessTrap, mBroker);
        case __NR_faccessat:
          return Trap(AccessAtTrap, mBroker);
        CASES_FOR_stat:
          return Trap(StatTrap, mBroker);
        CASES_FOR_lstat:
          return Trap(LStatTrap, mBroker);
        CASES_FOR_fstatat:
          return Trap(StatAtTrap, mBroker);
        case __NR_chmod:
          return Trap(ChmodTrap, mBroker);
        case __NR_link:
          return Trap(LinkTrap, mBroker);
        case __NR_mkdir:
          return Trap(MkdirTrap, mBroker);
        case __NR_symlink:
          return Trap(SymlinkTrap, mBroker);
        case __NR_rename:
          return Trap(RenameTrap, mBroker);
        case __NR_rmdir:
          return Trap(RmdirTrap, mBroker);
        case __NR_unlink:
          return Trap(UnlinkTrap, mBroker);
        case __NR_readlink:
          return Trap(ReadlinkTrap, mBroker);
        case __NR_readlinkat:
          return Trap(ReadlinkAtTrap, mBroker);
      }
    }

    switch (sysno) {
        // Timekeeping
      case __NR_clock_gettime: {
        Arg<clockid_t> clk_id(0);
        return If(clk_id == CLOCK_MONOTONIC, Allow())
#ifdef CLOCK_MONOTONIC_COARSE
            // Used by SandboxReporter, among other things.
            .ElseIf(clk_id == CLOCK_MONOTONIC_COARSE, Allow())
#endif
            .ElseIf(clk_id == CLOCK_PROCESS_CPUTIME_ID, Allow())
            .ElseIf(clk_id == CLOCK_REALTIME, Allow())
#ifdef CLOCK_REALTIME_COARSE
            .ElseIf(clk_id == CLOCK_REALTIME_COARSE, Allow())
#endif
            .ElseIf(clk_id == CLOCK_THREAD_CPUTIME_ID, Allow())
            .Else(InvalidSyscall());
      }
      case __NR_gettimeofday:
#ifdef __NR_time
      case __NR_time:
#endif
      case __NR_nanosleep:
        return Allow();

        // Thread synchronization
      case __NR_futex:
        // FIXME: This could be more restrictive....
        return Allow();

        // Asynchronous I/O
      case __NR_epoll_create1:
      case __NR_epoll_create:
      case __NR_epoll_wait:
      case __NR_epoll_pwait:
      case __NR_epoll_ctl:
      case __NR_ppoll:
      case __NR_poll:
        return Allow();

        // Used when requesting a crash dump.
      case __NR_pipe:
        return Allow();

        // Metadata of opened files
      CASES_FOR_fstat:
        return Allow();

        // Simple I/O
      case __NR_write:
      case __NR_read:
      case __NR_readv:
      case __NR_writev:  // see SandboxLogging.cpp
      CASES_FOR_lseek:
        return Allow();

      CASES_FOR_ftruncate:
        switch (mShmemUsage) {
          case ShmemUsage::MAY_CREATE:
            return Allow();
          case ShmemUsage::ONLY_USE:
            return InvalidSyscall();
          default:
            MOZ_CRASH("unreachable");
        }

        // Used by our fd/shm classes
      case __NR_dup:
        return Allow();

        // Memory mapping
      CASES_FOR_mmap:
      case __NR_munmap:
        return Allow();

        // ipc::Shmem; also, glibc when creating threads:
      case __NR_mprotect:
        return Allow();

#if !defined(MOZ_MEMORY)
        // No jemalloc means using a system allocator like glibc
        // that might use brk.
      case __NR_brk:
        return Allow();
#endif

        // madvise hints used by malloc; see bug 1303813 and bug 1364533
      case __NR_madvise: {
        Arg<int> advice(2);
        return If(advice == MADV_DONTNEED, Allow())
            .ElseIf(advice == MADV_FREE, Allow())
            .ElseIf(advice == MADV_HUGEPAGE, Allow())
            .ElseIf(advice == MADV_NOHUGEPAGE, Allow())
#ifdef MOZ_ASAN
            .ElseIf(advice == MADV_DONTDUMP, Allow())
#endif
            .Else(InvalidSyscall());
      }

      // Signal handling
#if defined(ANDROID) || defined(MOZ_ASAN)
      case __NR_sigaltstack:
#endif
      CASES_FOR_sigreturn:
      CASES_FOR_sigprocmask:
      CASES_FOR_sigaction:
        return Allow();

        // Send signals within the process (raise(), profiling, etc.)
      case __NR_tgkill: {
        Arg<pid_t> tgid(0);
        return If(tgid == getpid(), Allow()).Else(InvalidSyscall());
      }

        // Polyfill with tgkill; see above.
      case __NR_tkill:
        return Trap(TKillCompatTrap, nullptr);

        // Yield
      case __NR_sched_yield:
        return Allow();

        // Thread creation.
      case __NR_clone:
        return ClonePolicy(InvalidSyscall());

        // More thread creation.
#ifdef __NR_set_robust_list
      case __NR_set_robust_list:
        return Allow();
#endif
#ifdef ANDROID
      case __NR_set_tid_address:
        return Allow();
#endif

        // prctl
      case __NR_prctl: {
        if (SandboxInfo::Get().Test(SandboxInfo::kHasSeccompTSync)) {
          return PrctlPolicy();
        }

        Arg<int> option(0);
        return If(option == PR_SET_NO_NEW_PRIVS,
                  Trap(SetNoNewPrivsTrap, nullptr))
            .Else(PrctlPolicy());
      }

        // NSPR can call this when creating a thread, but it will accept a
        // polite "no".
      case __NR_getpriority:
        // But if thread creation races with sandbox startup, that call
        // could succeed, and then we get one of these:
      case __NR_setpriority:
        return Error(EACCES);

        // Stack bounds are obtained via pthread_getattr_np, which calls
        // this but doesn't actually need it:
      case __NR_sched_getaffinity:
        return Error(ENOSYS);

        // Read own pid/tid.
      case __NR_getpid:
      case __NR_gettid:
        return Allow();

        // Discard capabilities
      case __NR_close:
        return Allow();

        // Machine-dependent stuff
#ifdef __arm__
      case __ARM_NR_breakpoint:
      case __ARM_NR_cacheflush:
      case __ARM_NR_usr26:  // FIXME: do we actually need this?
      case __ARM_NR_usr32:
      case __ARM_NR_set_tls:
        return Allow();
#endif

        // Needed when being debugged:
      case __NR_restart_syscall:
        return Allow();

        // Terminate threads or the process
      case __NR_exit:
      case __NR_exit_group:
        return Allow();

      case __NR_getrandom:
        return Allow();

#ifdef DESKTOP
        // Bug 1543858: glibc's qsort calls sysinfo to check the
        // memory size; it falls back to assuming there's enough RAM.
      case __NR_sysinfo:
        return Error(EPERM);
#endif

#ifdef MOZ_ASAN
        // ASAN's error reporter wants to know if stderr is a tty.
      case __NR_ioctl: {
        Arg<int> fd(0);
        return If(fd == STDERR_FILENO, Error(ENOTTY)).Else(InvalidSyscall());
      }

        // ...and before compiler-rt r209773, it will call readlink on
        // /proc/self/exe and use the cached value only if that fails:
      case __NR_readlink:
      case __NR_readlinkat:
        return Error(ENOENT);

        // ...and if it found an external symbolizer, it will try to run it:
        // (See also bug 1081242 comment #7.)
      CASES_FOR_stat:
        return Error(ENOENT);
#endif

      default:
        return SandboxPolicyBase::EvaluateSyscall(sysno);
    }
  }
};

// The process-type-specific syscall rules start here:

// The seccomp-bpf filter for content processes is not a true sandbox
// on its own; its purpose is attack surface reduction and syscall
// interception in support of a semantic sandboxing layer.  On B2G
// this is the Android process permission model; on desktop,
// namespaces and chroot() will be used.
class ContentSandboxPolicy : public SandboxPolicyCommon {
 private:
  ContentProcessSandboxParams mParams;
  bool mAllowSysV;
  bool mUsingRenderDoc;

  bool BelowLevel(int aLevel) const { return mParams.mLevel < aLevel; }
  ResultExpr AllowBelowLevel(int aLevel, ResultExpr aOrElse) const {
    return BelowLevel(aLevel) ? Allow() : std::move(aOrElse);
  }
  ResultExpr AllowBelowLevel(int aLevel) const {
    return AllowBelowLevel(aLevel, InvalidSyscall());
  }

  static intptr_t GetPPidTrap(ArgsRef aArgs, void* aux) {
    // In a pid namespace, getppid() will return 0. We will return 0 instead
    // of the real parent pid to see what breaks when we introduce the
    // pid namespace (Bug 1151624).
    return 0;
  }

  static intptr_t StatFsTrap(ArgsRef aArgs, void* aux) {
    // Warning: the kernel interface is not the C interface.  The
    // structs are different (<asm/statfs.h> vs. <sys/statfs.h>), and
    // the statfs64 version takes an additional size parameter.
    auto path = reinterpret_cast<const char*>(aArgs.args[0]);
    int fd = open(path, O_RDONLY | O_LARGEFILE);
    if (fd < 0) {
      return -errno;
    }

    intptr_t rv;
    switch (aArgs.nr) {
      case __NR_statfs: {
        auto buf = reinterpret_cast<void*>(aArgs.args[1]);
        rv = DoSyscall(__NR_fstatfs, fd, buf);
        break;
      }
#ifdef __NR_statfs64
      case __NR_statfs64: {
        auto sz = static_cast<size_t>(aArgs.args[1]);
        auto buf = reinterpret_cast<void*>(aArgs.args[2]);
        rv = DoSyscall(__NR_fstatfs64, fd, sz, buf);
        break;
      }
#endif
      default:
        MOZ_ASSERT(false);
        rv = -ENOSYS;
    }

    close(fd);
    return rv;
  }

  // This just needs to return something to stand in for the
  // unconnected socket until ConnectTrap, below, and keep track of
  // the socket type somehow.  Half a socketpair *is* a socket, so it
  // should result in minimal confusion in the caller.
  static intptr_t FakeSocketTrapCommon(int domain, int type, int protocol) {
    int fds[2];
    // X11 client libs will still try to getaddrinfo() even for a
    // local connection.  Also, WebRTC still has vestigial network
    // code trying to do things in the content process.  Politely tell
    // them no.
    if (domain != AF_UNIX) {
      return -EAFNOSUPPORT;
    }
    if (socketpair(domain, type, protocol, fds) != 0) {
      return -errno;
    }
    close(fds[1]);
    return fds[0];
  }

  static intptr_t FakeSocketTrap(ArgsRef aArgs, void* aux) {
    return FakeSocketTrapCommon(static_cast<int>(aArgs.args[0]),
                                static_cast<int>(aArgs.args[1]),
                                static_cast<int>(aArgs.args[2]));
  }

  static intptr_t FakeSocketTrapLegacy(ArgsRef aArgs, void* aux) {
    const auto innerArgs = reinterpret_cast<unsigned long*>(aArgs.args[1]);

    return FakeSocketTrapCommon(static_cast<int>(innerArgs[0]),
                                static_cast<int>(innerArgs[1]),
                                static_cast<int>(innerArgs[2]));
  }

  static Maybe<int> DoGetSockOpt(int fd, int optname) {
    int optval;
    socklen_t optlen = sizeof(optval);

    if (getsockopt(fd, SOL_SOCKET, optname, &optval, &optlen) != 0) {
      return Nothing();
    }
    MOZ_RELEASE_ASSERT(static_cast<size_t>(optlen) == sizeof(optval));
    return Some(optval);
  }

  // Substitute the newly connected socket from the broker for the
  // original socket.  This is meant to be used on a fd from
  // FakeSocketTrap, above, but it should also work to simulate
  // re-connect()ing a real connected socket.
  //
  // Warning: This isn't quite right if the socket is dup()ed, because
  // other duplicates will still be the original socket, but hopefully
  // nothing we're dealing with does that.
  static intptr_t ConnectTrapCommon(SandboxBrokerClient* aBroker, int aFd,
                                    const struct sockaddr_un* aAddr,
                                    socklen_t aLen) {
    if (aFd < 0) {
      return -EBADF;
    }
    const auto maybeDomain = DoGetSockOpt(aFd, SO_DOMAIN);
    if (!maybeDomain) {
      return -errno;
    }
    if (*maybeDomain != AF_UNIX) {
      return -EAFNOSUPPORT;
    }
    const auto maybeType = DoGetSockOpt(aFd, SO_TYPE);
    if (!maybeType) {
      return -errno;
    }
    const int oldFlags = fcntl(aFd, F_GETFL);
    if (oldFlags == -1) {
      return -errno;
    }
    const int newFd = aBroker->Connect(aAddr, aLen, *maybeType);
    if (newFd < 0) {
      return newFd;
    }
    // Copy over the nonblocking flag.  The connect() won't be
    // nonblocking in that case, but that shouldn't matter for
    // AF_UNIX.  The other fcntl-settable flags are either irrelevant
    // for sockets (e.g., O_APPEND) or would be blocked by this
    // seccomp-bpf policy, so they're ignored.
    if (fcntl(newFd, F_SETFL, oldFlags & O_NONBLOCK) != 0) {
      close(newFd);
      return -errno;
    }
    if (dup2(newFd, aFd) < 0) {
      close(newFd);
      return -errno;
    }
    close(newFd);
    return 0;
  }

  static intptr_t ConnectTrap(ArgsRef aArgs, void* aux) {
    typedef const struct sockaddr_un* AddrPtr;

    return ConnectTrapCommon(static_cast<SandboxBrokerClient*>(aux),
                             static_cast<int>(aArgs.args[0]),
                             reinterpret_cast<AddrPtr>(aArgs.args[1]),
                             static_cast<socklen_t>(aArgs.args[2]));
  }

  static intptr_t ConnectTrapLegacy(ArgsRef aArgs, void* aux) {
    const auto innerArgs = reinterpret_cast<unsigned long*>(aArgs.args[1]);
    typedef const struct sockaddr_un* AddrPtr;

    return ConnectTrapCommon(static_cast<SandboxBrokerClient*>(aux),
                             static_cast<int>(innerArgs[0]),
                             reinterpret_cast<AddrPtr>(innerArgs[1]),
                             static_cast<socklen_t>(innerArgs[2]));
  }

 public:
  ContentSandboxPolicy(SandboxBrokerClient* aBroker,
                       ContentProcessSandboxParams&& aParams)
      : SandboxPolicyCommon(aBroker),
        mParams(std::move(aParams)),
        mAllowSysV(PR_GetEnv("MOZ_SANDBOX_ALLOW_SYSV") != nullptr),
        mUsingRenderDoc(PR_GetEnv("RENDERDOC_CAPTUREOPTS") != nullptr) {}

  ~ContentSandboxPolicy() override = default;

  Maybe<ResultExpr> EvaluateSocketCall(int aCall,
                                       bool aHasArgs) const override {
    switch (aCall) {
      case SYS_RECVFROM:
      case SYS_SENDTO:
      case SYS_SENDMMSG:  // libresolv via libasyncns; see bug 1355274
        return Some(Allow());

#ifdef ANDROID
      case SYS_SOCKET:
        return Some(Error(EACCES));
#else  // #ifdef DESKTOP
      case SYS_SOCKET: {
        const auto trapFn = aHasArgs ? FakeSocketTrap : FakeSocketTrapLegacy;
        return Some(AllowBelowLevel(4, Trap(trapFn, nullptr)));
      }
      case SYS_CONNECT: {
        const auto trapFn = aHasArgs ? ConnectTrap : ConnectTrapLegacy;
        return Some(AllowBelowLevel(4, Trap(trapFn, mBroker)));
      }
      case SYS_ACCEPT:
      case SYS_ACCEPT4:
        if (mUsingRenderDoc) {
          return Some(Allow());
        }
        return SandboxPolicyCommon::EvaluateSocketCall(aCall, aHasArgs);
      case SYS_RECV:
      case SYS_SEND:
      case SYS_GETSOCKOPT:
      case SYS_SETSOCKOPT:
      case SYS_GETSOCKNAME:
      case SYS_GETPEERNAME:
      case SYS_SHUTDOWN:
        return Some(Allow());
#endif
      default:
        return SandboxPolicyCommon::EvaluateSocketCall(aCall, aHasArgs);
    }
  }

#ifdef DESKTOP
  Maybe<ResultExpr> EvaluateIpcCall(int aCall) const override {
    switch (aCall) {
        // These are a problem: SysV IPC follows the Unix "same uid
        // policy" and can't be restricted/brokered like file access.
        // We're not using it directly, but there are some library
        // dependencies that do; see ContentNeedsSysVIPC() in
        // SandboxLaunch.cpp.  Also, Cairo as used by GTK will sometimes
        // try to use MIT-SHM, so shmget() is a non-fatal error.  See
        // also bug 1376910 and bug 1438401.
      case SHMGET:
        return Some(mAllowSysV ? Allow() : Error(EPERM));
      case SHMCTL:
      case SHMAT:
      case SHMDT:
      case SEMGET:
      case SEMCTL:
      case SEMOP:
        if (mAllowSysV) {
          return Some(Allow());
        }
        return SandboxPolicyCommon::EvaluateIpcCall(aCall);
      default:
        return SandboxPolicyCommon::EvaluateIpcCall(aCall);
    }
  }
#endif

#ifdef MOZ_PULSEAUDIO
  ResultExpr PrctlPolicy() const override {
    if (BelowLevel(4)) {
      Arg<int> op(0);
      return If(op == PR_GET_NAME, Allow())
          .Else(SandboxPolicyCommon::PrctlPolicy());
    }
    return SandboxPolicyCommon::PrctlPolicy();
  }
#endif

  ResultExpr EvaluateSyscall(int sysno) const override {
    // Straight allow for anything that got overriden via prefs
    const auto& whitelist = mParams.mSyscallWhitelist;
    if (std::find(whitelist.begin(), whitelist.end(), sysno) !=
        whitelist.end()) {
      if (SandboxInfo::Get().Test(SandboxInfo::kVerbose)) {
        SANDBOX_LOG_ERROR("Allowing syscall nr %d via whitelist", sysno);
      }
      return Allow();
    }

    // Level 1 allows direct filesystem access; higher levels use
    // brokering (by falling through to the main policy and delegating
    // to SandboxPolicyCommon).
    if (BelowLevel(2)) {
      MOZ_ASSERT(mBroker == nullptr);
      switch (sysno) {
        case __NR_open:
        case __NR_openat:
        case __NR_access:
        case __NR_faccessat:
        CASES_FOR_stat:
        CASES_FOR_lstat:
        CASES_FOR_fstatat:
        case __NR_chmod:
        case __NR_link:
        case __NR_mkdir:
        case __NR_symlink:
        case __NR_rename:
        case __NR_rmdir:
        case __NR_unlink:
        case __NR_readlink:
        case __NR_readlinkat:
          return Allow();
      }
    }

    switch (sysno) {
#ifdef DESKTOP
      case __NR_getppid:
        return Trap(GetPPidTrap, nullptr);

      CASES_FOR_statfs:
        return Trap(StatFsTrap, nullptr);

        // GTK's theme parsing tries to getcwd() while sandboxed, but
        // only during Talos runs.
      case __NR_getcwd:
        return Error(ENOENT);

#  ifdef MOZ_PULSEAUDIO
      CASES_FOR_fchown:
      case __NR_fchmod:
        return AllowBelowLevel(4);
#  endif
      CASES_FOR_fstatfs:  // fontconfig, pulseaudio, GIO (see also statfs)
      case __NR_flock:    // graphics
        return Allow();

        // Bug 1354731: proprietary GL drivers try to mknod() their devices
#  ifdef __NR_mknod
      case __NR_mknod:
#  endif
      case __NR_mknodat: {
        Arg<mode_t> mode(sysno == __NR_mknodat ? 2 : 1);
        return If((mode & S_IFMT) == S_IFCHR, Error(EPERM))
            .Else(InvalidSyscall());
      }
      // Bug 1438389: ...and nvidia GL will sometimes try to chown the devices
#  ifdef __NR_chown
      case __NR_chown:
#  endif
      case __NR_fchownat:
        return Error(EPERM);

        // For ORBit called by GConf (on some systems) to get proxy
        // settings.  Can remove when bug 1325242 happens in some form.
      case __NR_utime:
        return Error(EPERM);
#endif

      CASES_FOR_select:
      case __NR_pselect6:
        return Allow();

      CASES_FOR_getdents:
      case __NR_writev:
      case __NR_pread64:
#ifdef DESKTOP
      case __NR_pwrite64:
      case __NR_readahead:
#endif
        return Allow();

      case __NR_ioctl: {
#ifdef MOZ_ALSA
        if (BelowLevel(4)) {
          return Allow();
        }
#endif
        static const unsigned long kTypeMask = _IOC_TYPEMASK << _IOC_TYPESHIFT;
        static const unsigned long kTtyIoctls = TIOCSTI & kTypeMask;
        // On some older architectures (but not x86 or ARM), ioctls are
        // assigned type fields differently, and the TIOC/TC/FIO group
        // isn't all the same type.  If/when we support those archs,
        // this would need to be revised (but really this should be a
        // default-deny policy; see below).
        static_assert(kTtyIoctls == (TCSETA & kTypeMask) &&
                          kTtyIoctls == (FIOASYNC & kTypeMask),
                      "tty-related ioctls use the same type");

        Arg<unsigned long> request(1);
        auto shifted_type = request & kTypeMask;

        // Rust's stdlib seems to use FIOCLEX instead of equivalent fcntls.
        return If(request == FIOCLEX, Allow())
            // Rust's stdlib also uses FIONBIO instead of equivalent fcntls.
            .ElseIf(request == FIONBIO, Allow())
            // ffmpeg, and anything else that calls isatty(), will be told
            // that nothing is a typewriter:
            .ElseIf(request == TCGETS, Error(ENOTTY))
            // Allow anything that isn't a tty ioctl, for now; bug 1302711
            // will cover changing this to a default-deny policy.
            .ElseIf(shifted_type != kTtyIoctls, Allow())
            .Else(SandboxPolicyCommon::EvaluateSyscall(sysno));
      }

      CASES_FOR_fcntl : {
        Arg<int> cmd(1);
        Arg<int> flags(2);
        // Typical use of F_SETFL is to modify the flags returned by
        // F_GETFL and write them back, including some flags that
        // F_SETFL ignores.  This is a default-deny policy in case any
        // new SETFL-able flags are added.  (In particular we want to
        // forbid O_ASYNC; see bug 1328896, but also see bug 1408438.)
        static const int ignored_flags =
            O_ACCMODE | O_LARGEFILE_REAL | O_CLOEXEC;
        static const int allowed_flags = ignored_flags | O_APPEND | O_NONBLOCK;
        return Switch(cmd)
            // Close-on-exec is meaningless when execve isn't allowed, but
            // NSPR reads the bit and asserts that it has the expected value.
            .Case(F_GETFD, Allow())
            .Case(
                F_SETFD,
                If((flags & ~FD_CLOEXEC) == 0, Allow()).Else(InvalidSyscall()))
            .Case(F_GETFL, Allow())
            .Case(F_SETFL, If((flags & ~allowed_flags) == 0, Allow())
                               .Else(InvalidSyscall()))
            .Case(F_DUPFD_CLOEXEC, Allow())
            // Nvidia GL and fontconfig (newer versions) use fcntl file locking.
            .Case(F_SETLK, Allow())
#ifdef F_SETLK64
            .Case(F_SETLK64, Allow())
#endif
            // Pulseaudio uses F_SETLKW, as does fontconfig.
            .Case(F_SETLKW, Allow())
#ifdef F_SETLKW64
            .Case(F_SETLKW64, Allow())
#endif
            .Default(SandboxPolicyCommon::EvaluateSyscall(sysno));
      }

      case __NR_brk:
        // FIXME(bug 1510861) are we using any hints that aren't allowed
        // in SandboxPolicyCommon now?
      case __NR_madvise:
        // libc's realloc uses mremap (Bug 1286119); wasm does too (bug
        // 1342385).
      case __NR_mremap:
        return Allow();

        // Bug 1462640: Mesa libEGL uses mincore to test whether values
        // are pointers, for reasons.
      case __NR_mincore: {
        Arg<size_t> length(1);
        return If(length == getpagesize(), Allow())
            .Else(SandboxPolicyCommon::EvaluateSyscall(sysno));
      }

      case __NR_sigaltstack:
        return Allow();

#ifdef __NR_set_thread_area
      case __NR_set_thread_area:
        return Allow();
#endif

      case __NR_getrusage:
      case __NR_times:
        return Allow();

      case __NR_dup2:  // See ConnectTrapCommon
        return Allow();

      CASES_FOR_getuid:
      CASES_FOR_getgid:
      CASES_FOR_geteuid:
      CASES_FOR_getegid:
        return Allow();

      case __NR_fsync:
      case __NR_msync:
        return Allow();

      case __NR_getpriority:
      case __NR_setpriority:
      case __NR_sched_get_priority_min:
      case __NR_sched_get_priority_max:
      case __NR_sched_getscheduler:
      case __NR_sched_setscheduler:
      case __NR_sched_getparam:
      case __NR_sched_setparam:
#ifdef DESKTOP
      case __NR_sched_getaffinity:
#endif
        return Allow();

#ifdef DESKTOP
      case __NR_sched_setaffinity:
        return Error(EPERM);
#endif

#ifdef DESKTOP
      case __NR_pipe2:
        return Allow();

      CASES_FOR_getrlimit:
      case __NR_clock_getres:
      CASES_FOR_getresuid:
      CASES_FOR_getresgid:
        return Allow();

      case __NR_prlimit64: {
        // Allow only the getrlimit() use case.  (glibc seems to use
        // only pid 0 to indicate the current process; pid == getpid()
        // is equivalent and could also be allowed if needed.)
        Arg<pid_t> pid(0);
        // This is really a const struct ::rlimit*, but Arg<> doesn't
        // work with pointers, only integer types.
        Arg<uintptr_t> new_limit(2);
        return If(AllOf(pid == 0, new_limit == 0), Allow())
            .Else(InvalidSyscall());
      }

        // PulseAudio calls umask, even though it's unsafe in
        // multithreaded applications.  But, allowing it here doesn't
        // really do anything one way or the other, now that file
        // accesses are brokered to another process.
      case __NR_umask:
        return AllowBelowLevel(4);

      case __NR_kill: {
        if (BelowLevel(4)) {
          Arg<int> sig(1);
          // PulseAudio uses kill(pid, 0) to check if purported owners of
          // shared memory files are still alive; see bug 1397753 for more
          // details.
          return If(sig == 0, Error(EPERM)).Else(InvalidSyscall());
        }
        return InvalidSyscall();
      }

      case __NR_wait4:
#  ifdef __NR_waitpid
      case __NR_waitpid:
#  endif
        // NSPR will start a thread to wait for child processes even if
        // fork() fails; see bug 227246 and bug 1299581.
        return Error(ECHILD);

      case __NR_eventfd2:
        return Allow();

#  ifdef __NR_memfd_create
      case __NR_memfd_create:
        return Allow();
#  endif

#  ifdef __NR_rt_tgsigqueueinfo
        // Only allow to send signals within the process.
      case __NR_rt_tgsigqueueinfo: {
        Arg<pid_t> tgid(0);
        return If(tgid == getpid(), Allow()).Else(InvalidSyscall());
      }
#  endif

      case __NR_mlock:
      case __NR_munlock:
        return Allow();

        // We can't usefully allow fork+exec, even on a temporary basis;
        // the child would inherit the seccomp-bpf policy and almost
        // certainly die from an unexpected SIGSYS.  We also can't have
        // fork() crash, currently, because there are too many system
        // libraries/plugins that try to run commands.  But they can
        // usually do something reasonable on error.
      case __NR_clone:
        return ClonePolicy(Error(EPERM));

#  ifdef __NR_fadvise64
      case __NR_fadvise64:
        return Allow();
#  endif

#  ifdef __NR_fadvise64_64
      case __NR_fadvise64_64:
        return Allow();
#  endif

      case __NR_fallocate:
        return Allow();

      case __NR_get_mempolicy:
        return Allow();

#endif  // DESKTOP

        // nsSystemInfo uses uname (and we cache an instance, so
        // the info remains present even if we block the syscall)
      case __NR_uname:
#ifdef DESKTOP
      case __NR_sysinfo:
#endif
        return Allow();

#ifdef MOZ_JPROF
      case __NR_setitimer:
        return Allow();
#endif  // MOZ_JPROF

      default:
        return SandboxPolicyCommon::EvaluateSyscall(sysno);
    }
  }
};

UniquePtr<sandbox::bpf_dsl::Policy> GetContentSandboxPolicy(
    SandboxBrokerClient* aMaybeBroker, ContentProcessSandboxParams&& aParams) {
  return MakeUnique<ContentSandboxPolicy>(aMaybeBroker, std::move(aParams));
}

// Unlike for content, the GeckoMediaPlugin seccomp-bpf policy needs
// to be an effective sandbox by itself, because we allow GMP on Linux
// systems where that's the only sandboxing mechanism we can use.
//
// Be especially careful about what this policy allows.
class GMPSandboxPolicy : public SandboxPolicyCommon {
  static intptr_t OpenTrap(const sandbox::arch_seccomp_data& aArgs, void* aux) {
    const auto files = static_cast<const SandboxOpenedFiles*>(aux);
    const char* path;
    int flags;

    switch (aArgs.nr) {
#ifdef __NR_open
      case __NR_open:
        path = reinterpret_cast<const char*>(aArgs.args[0]);
        flags = static_cast<int>(aArgs.args[1]);
        break;
#endif
      case __NR_openat:
        // The path has to be absolute to match the pre-opened file (see
        // assertion in ctor) so the dirfd argument is ignored.
        path = reinterpret_cast<const char*>(aArgs.args[1]);
        flags = static_cast<int>(aArgs.args[2]);
        break;
      default:
        MOZ_CRASH("unexpected syscall number");
    }

    if ((flags & O_ACCMODE) != O_RDONLY) {
      SANDBOX_LOG_ERROR("non-read-only open of file %s attempted (flags=0%o)",
                        path, flags);
      return -EROFS;
    }
    int fd = files->GetDesc(path);
    if (fd < 0) {
      // SandboxOpenedFile::GetDesc already logged about this, if appropriate.
      return -ENOENT;
    }
    return fd;
  }

  static intptr_t SchedTrap(ArgsRef aArgs, void* aux) {
    const pid_t tid = syscall(__NR_gettid);
    if (aArgs.args[0] == static_cast<uint64_t>(tid)) {
      return DoSyscall(aArgs.nr, 0, static_cast<uintptr_t>(aArgs.args[1]),
                       static_cast<uintptr_t>(aArgs.args[2]),
                       static_cast<uintptr_t>(aArgs.args[3]),
                       static_cast<uintptr_t>(aArgs.args[4]),
                       static_cast<uintptr_t>(aArgs.args[5]));
    }
    SANDBOX_LOG_ERROR("unsupported tid in SchedTrap");
    return BlockedSyscallTrap(aArgs, nullptr);
  }

  static intptr_t UnameTrap(const sandbox::arch_seccomp_data& aArgs,
                            void* aux) {
    const auto buf = reinterpret_cast<struct utsname*>(aArgs.args[0]);
    PodZero(buf);
    // The real uname() increases fingerprinting risk for no benefit.
    // This is close enough.
    strcpy(buf->sysname, "Linux");
    strcpy(buf->version, "3");
    return 0;
  };

  static intptr_t FcntlTrap(const sandbox::arch_seccomp_data& aArgs,
                            void* aux) {
    const auto cmd = static_cast<int>(aArgs.args[1]);
    switch (cmd) {
        // This process can't exec, so the actual close-on-exec flag
        // doesn't matter; have it always read as true and ignore writes.
      case F_GETFD:
        return O_CLOEXEC;
      case F_SETFD:
        return 0;
      default:
        return -ENOSYS;
    }
  }

  const SandboxOpenedFiles* mFiles;

 public:
  explicit GMPSandboxPolicy(const SandboxOpenedFiles* aFiles)
      : mFiles(aFiles) {}

  ~GMPSandboxPolicy() override = default;

  ResultExpr EvaluateSyscall(int sysno) const override {
    switch (sysno) {
      // Simulate opening the plugin file.
#ifdef __NR_open
      case __NR_open:
#endif
      case __NR_openat:
        return Trap(OpenTrap, mFiles);

      case __NR_brk:
      // Because Firefox on glibc resorts to the fallback implementation
      // mentioned in bug 1576006, we must explicitly allow the get*id()
      // functions in order to use NSS in the clearkey CDM.
      CASES_FOR_getuid:
      CASES_FOR_getgid:
      CASES_FOR_geteuid:
      CASES_FOR_getegid:
        return Allow();
      case __NR_sched_get_priority_min:
      case __NR_sched_get_priority_max:
        return Allow();
      case __NR_sched_getparam:
      case __NR_sched_getscheduler:
      case __NR_sched_setscheduler: {
        Arg<pid_t> pid(0);
        return If(pid == 0, Allow()).Else(Trap(SchedTrap, nullptr));
      }

      // For clock(3) on older glibcs; bug 1304220.
      case __NR_times:
        return Allow();

      // Bug 1372428
      case __NR_uname:
        return Trap(UnameTrap, nullptr);
      CASES_FOR_fcntl:
        return Trap(FcntlTrap, nullptr);

      default:
        return SandboxPolicyCommon::EvaluateSyscall(sysno);
    }
  }
};

UniquePtr<sandbox::bpf_dsl::Policy> GetMediaSandboxPolicy(
    const SandboxOpenedFiles* aFiles) {
  return UniquePtr<sandbox::bpf_dsl::Policy>(new GMPSandboxPolicy(aFiles));
}

// The policy for the data decoder process is similar to the one for
// media plugins, but the codec code is all in-tree so it's better
// behaved and doesn't need special exceptions (or the ability to load
// a plugin file).  However, it does directly create shared memory
// segments, so it may need file brokering.
class RDDSandboxPolicy final : public SandboxPolicyCommon {
 public:
  explicit RDDSandboxPolicy(SandboxBrokerClient* aBroker)
      : SandboxPolicyCommon(aBroker) {}

  static intptr_t FcntlTrap(const sandbox::arch_seccomp_data& aArgs,
                            void* aux) {
    const auto cmd = static_cast<int>(aArgs.args[1]);
    switch (cmd) {
        // This process can't exec, so the actual close-on-exec flag
        // doesn't matter; have it always read as true and ignore writes.
      case F_GETFD:
        return O_CLOEXEC;
      case F_SETFD:
        return 0;
      default:
        return -ENOSYS;
    }
  }

  ResultExpr EvaluateSyscall(int sysno) const override {
    switch (sysno) {
      case __NR_getrusage:
        return Allow();

      CASES_FOR_fcntl:
        return Trap(FcntlTrap, nullptr);

      // Pass through the common policy.
      default:
        return SandboxPolicyCommon::EvaluateSyscall(sysno);
    }
  }
};

UniquePtr<sandbox::bpf_dsl::Policy> GetDecoderSandboxPolicy(
    SandboxBrokerClient* aMaybeBroker) {
  return UniquePtr<sandbox::bpf_dsl::Policy>(
      new RDDSandboxPolicy(aMaybeBroker));
}

}  // namespace mozilla