gecko-dev/ipc/gtest/TestSharedMemory.cpp

/* -*- 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 "gtest/gtest.h"

#include "base/shared_memory.h"

#include "mozilla/RefPtr.h"
#include "mozilla/ipc/SharedMemory.h"
#include "mozilla/ipc/SharedMemoryBasic.h"

#ifdef XP_LINUX
#  include <errno.h>
#  include <linux/magic.h>
#  include <stdio.h>
#  include <string.h>
#  include <sys/statfs.h>
#  include <sys/utsname.h>
#endif

#ifdef XP_WIN
#  include <windows.h>
#endif

namespace mozilla {

// Try to map a frozen shm for writing.  Threat model: the process is
// compromised and then receives a frozen handle.
TEST(IPCSharedMemory, FreezeAndMapRW)
{
  base::SharedMemory shm;

  // Create and initialize
  ASSERT_TRUE(shm.CreateFreezeable(1));
  ASSERT_TRUE(shm.Map(1));
  auto mem = reinterpret_cast<char*>(shm.memory());
  ASSERT_TRUE(mem);
  *mem = 'A';

  // Freeze
  ASSERT_TRUE(shm.Freeze());
  ASSERT_FALSE(shm.memory());

  // Re-create as writeable
  auto handle = shm.TakeHandle();
  ASSERT_TRUE(shm.IsHandleValid(handle));
  ASSERT_FALSE(shm.IsValid());
  ASSERT_TRUE(shm.SetHandle(std::move(handle), /* read-only */ false));
  ASSERT_TRUE(shm.IsValid());

  // This should fail
  EXPECT_FALSE(shm.Map(1));
}

// Try to restore write permissions to a frozen mapping.  Threat
// model: the process has mapped frozen shm normally and then is
// compromised, or as for FreezeAndMapRW (see also the
// proof-of-concept at https://crbug.com/project-zero/1671 ).
TEST(IPCSharedMemory, FreezeAndReprotect)
{
  base::SharedMemory shm;

  // Create and initialize
  ASSERT_TRUE(shm.CreateFreezeable(1));
  ASSERT_TRUE(shm.Map(1));
  auto mem = reinterpret_cast<char*>(shm.memory());
  ASSERT_TRUE(mem);
  *mem = 'A';

  // Freeze
  ASSERT_TRUE(shm.Freeze());
  ASSERT_FALSE(shm.memory());

  // Re-map
  ASSERT_TRUE(shm.Map(1));
  mem = reinterpret_cast<char*>(shm.memory());
  ASSERT_EQ(*mem, 'A');

  // Try to alter protection; should fail
  EXPECT_FALSE(ipc::SharedMemory::SystemProtectFallible(
      mem, 1, ipc::SharedMemory::RightsReadWrite));
}

#ifndef XP_WIN
// This essentially tests whether FreezeAndReprotect would have failed
// without the freeze.  It doesn't work on Windows: VirtualProtect
// can't exceed the permissions set in MapViewOfFile regardless of the
// security status of the original handle.
TEST(IPCSharedMemory, Reprotect)
{
  base::SharedMemory shm;

  // Create and initialize
  ASSERT_TRUE(shm.CreateFreezeable(1));
  ASSERT_TRUE(shm.Map(1));
  auto mem = reinterpret_cast<char*>(shm.memory());
  ASSERT_TRUE(mem);
  *mem = 'A';

  // Re-create as read-only
  auto handle = shm.TakeHandle();
  ASSERT_TRUE(shm.IsHandleValid(handle));
  ASSERT_FALSE(shm.IsValid());
  ASSERT_TRUE(shm.SetHandle(std::move(handle), /* read-only */ true));
  ASSERT_TRUE(shm.IsValid());

  // Re-map
  ASSERT_TRUE(shm.Map(1));
  mem = reinterpret_cast<char*>(shm.memory());
  ASSERT_EQ(*mem, 'A');

  // Try to alter protection; should succeed, because not frozen
  EXPECT_TRUE(ipc::SharedMemory::SystemProtectFallible(
      mem, 1, ipc::SharedMemory::RightsReadWrite));
}
#endif

#ifdef XP_WIN
// Try to regain write permissions on a read-only handle using
// DuplicateHandle; this will succeed if the object has no DACL.
// See also https://crbug.com/338538
TEST(IPCSharedMemory, WinUnfreeze)
{
  base::SharedMemory shm;

  // Create and initialize
  ASSERT_TRUE(shm.CreateFreezeable(1));
  ASSERT_TRUE(shm.Map(1));
  auto mem = reinterpret_cast<char*>(shm.memory());
  ASSERT_TRUE(mem);
  *mem = 'A';

  // Freeze
  ASSERT_TRUE(shm.Freeze());
  ASSERT_FALSE(shm.memory());

  // Extract handle.
  auto handle = shm.TakeHandle();
  ASSERT_TRUE(shm.IsHandleValid(handle));
  ASSERT_FALSE(shm.IsValid());

  // Unfreeze.
  HANDLE newHandle = INVALID_HANDLE_VALUE;
  bool unfroze = ::DuplicateHandle(
      GetCurrentProcess(), handle.release(), GetCurrentProcess(), &newHandle,
      FILE_MAP_ALL_ACCESS, false, DUPLICATE_CLOSE_SOURCE);
  ASSERT_FALSE(unfroze);
}
#endif

// Test that a read-only copy sees changes made to the writeable
// mapping in the case that the page wasn't accessed before the copy.
TEST(IPCSharedMemory, ROCopyAndWrite)
{
  base::SharedMemory shmRW, shmRO;

  // Create and initialize
  ASSERT_TRUE(shmRW.CreateFreezeable(1));
  ASSERT_TRUE(shmRW.Map(1));
  auto memRW = reinterpret_cast<char*>(shmRW.memory());
  ASSERT_TRUE(memRW);

  // Create read-only copy
  ASSERT_TRUE(shmRW.ReadOnlyCopy(&shmRO));
  EXPECT_FALSE(shmRW.IsValid());
  ASSERT_EQ(shmRW.memory(), memRW);
  ASSERT_EQ(shmRO.max_size(), size_t(1));

  // Map read-only
  ASSERT_TRUE(shmRO.IsValid());
  ASSERT_TRUE(shmRO.Map(1));
  auto memRO = reinterpret_cast<const char*>(shmRO.memory());
  ASSERT_TRUE(memRO);
  ASSERT_NE(memRW, memRO);

  // Check
  *memRW = 'A';
  EXPECT_EQ(*memRO, 'A');
}

// Test that a read-only copy sees changes made to the writeable
// mapping in the case that the page was accessed before the copy
// (and, before that, sees the state as of when the copy was made).
TEST(IPCSharedMemory, ROCopyAndRewrite)
{
  base::SharedMemory shmRW, shmRO;

  // Create and initialize
  ASSERT_TRUE(shmRW.CreateFreezeable(1));
  ASSERT_TRUE(shmRW.Map(1));
  auto memRW = reinterpret_cast<char*>(shmRW.memory());
  ASSERT_TRUE(memRW);
  *memRW = 'A';

  // Create read-only copy
  ASSERT_TRUE(shmRW.ReadOnlyCopy(&shmRO));
  EXPECT_FALSE(shmRW.IsValid());
  ASSERT_EQ(shmRW.memory(), memRW);
  ASSERT_EQ(shmRO.max_size(), size_t(1));

  // Map read-only
  ASSERT_TRUE(shmRO.IsValid());
  ASSERT_TRUE(shmRO.Map(1));
  auto memRO = reinterpret_cast<const char*>(shmRO.memory());
  ASSERT_TRUE(memRO);
  ASSERT_NE(memRW, memRO);

  // Check
  ASSERT_EQ(*memRW, 'A');
  EXPECT_EQ(*memRO, 'A');
  *memRW = 'X';
  EXPECT_EQ(*memRO, 'X');
}

// See FreezeAndMapRW.
TEST(IPCSharedMemory, ROCopyAndMapRW)
{
  base::SharedMemory shmRW, shmRO;

  // Create and initialize
  ASSERT_TRUE(shmRW.CreateFreezeable(1));
  ASSERT_TRUE(shmRW.Map(1));
  auto memRW = reinterpret_cast<char*>(shmRW.memory());
  ASSERT_TRUE(memRW);
  *memRW = 'A';

  // Create read-only copy
  ASSERT_TRUE(shmRW.ReadOnlyCopy(&shmRO));
  ASSERT_TRUE(shmRO.IsValid());

  // Re-create as writeable
  auto handle = shmRO.TakeHandle();
  ASSERT_TRUE(shmRO.IsHandleValid(handle));
  ASSERT_FALSE(shmRO.IsValid());
  ASSERT_TRUE(shmRO.SetHandle(std::move(handle), /* read-only */ false));
  ASSERT_TRUE(shmRO.IsValid());

  // This should fail
  EXPECT_FALSE(shmRO.Map(1));
}

// See FreezeAndReprotect
TEST(IPCSharedMemory, ROCopyAndReprotect)
{
  base::SharedMemory shmRW, shmRO;

  // Create and initialize
  ASSERT_TRUE(shmRW.CreateFreezeable(1));
  ASSERT_TRUE(shmRW.Map(1));
  auto memRW = reinterpret_cast<char*>(shmRW.memory());
  ASSERT_TRUE(memRW);
  *memRW = 'A';

  // Create read-only copy
  ASSERT_TRUE(shmRW.ReadOnlyCopy(&shmRO));
  ASSERT_TRUE(shmRO.IsValid());

  // Re-map
  ASSERT_TRUE(shmRO.Map(1));
  auto memRO = reinterpret_cast<char*>(shmRO.memory());
  ASSERT_EQ(*memRO, 'A');

  // Try to alter protection; should fail
  EXPECT_FALSE(ipc::SharedMemory::SystemProtectFallible(
      memRO, 1, ipc::SharedMemory::RightsReadWrite));
}

TEST(IPCSharedMemory, IsZero)
{
  base::SharedMemory shm;

  static constexpr size_t kSize = 65536;
  ASSERT_TRUE(shm.Create(kSize));
  ASSERT_TRUE(shm.Map(kSize));

  auto* mem = reinterpret_cast<char*>(shm.memory());
  for (size_t i = 0; i < kSize; ++i) {
    ASSERT_EQ(mem[i], 0) << "offset " << i;
  }
}

#ifndef FUZZING
TEST(IPCSharedMemory, BasicIsZero)
{
  auto shm = MakeRefPtr<ipc::SharedMemoryBasic>();

  static constexpr size_t kSize = 65536;
  ASSERT_TRUE(shm->Create(kSize));
  ASSERT_TRUE(shm->Map(kSize));

  auto* mem = reinterpret_cast<char*>(shm->memory());
  for (size_t i = 0; i < kSize; ++i) {
    ASSERT_EQ(mem[i], 0) << "offset " << i;
  }
}
#endif

#if defined(XP_LINUX) && !defined(ANDROID)
// Test that memfd_create is used where expected.
//
// More precisely: if memfd_create support is expected, verify that
// shared memory isn't subject to a filesystem size limit.
TEST(IPCSharedMemory, IsMemfd)
{
  static constexpr int kMajor = 3;
  static constexpr int kMinor = 17;

  struct utsname uts;
  ASSERT_EQ(uname(&uts), 0) << strerror(errno);
  ASSERT_STREQ(uts.sysname, "Linux");
  int major, minor;
  ASSERT_EQ(sscanf(uts.release, "%d.%d", &major, &minor), 2);
  bool expectMemfd = major > kMajor || (major == kMajor && minor >= kMinor);

  base::SharedMemory shm;
  ASSERT_TRUE(shm.Create(1));
  UniqueFileHandle fd = shm.TakeHandle();
  ASSERT_TRUE(fd);

  struct statfs fs;
  ASSERT_EQ(fstatfs(fd.get(), &fs), 0) << strerror(errno);
  EXPECT_EQ(fs.f_type, TMPFS_MAGIC);
  static constexpr decltype(fs.f_blocks) kNoLimit = 0;
  if (expectMemfd) {
    EXPECT_EQ(fs.f_blocks, kNoLimit);
  } else {
    // On older kernels, we expect the memfd / no-limit test to fail.
    // (In theory it could succeed if backported memfd support exists;
    // if that ever happens, this check can be removed.)
    EXPECT_NE(fs.f_blocks, kNoLimit);
  }
}
#endif

}  // namespace mozilla