// Copyright 2011 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "chrome/browser/win/browser_util.h"

#include <windows.h>

// sddl.h must come after windows.h.
#include <winternl.h>

#include <sddl.h>

#include <algorithm>
#include <climits>
#include <memory>
#include <optional>
#include <string>
#include <utility>

#include "base/base_paths.h"
#include "base/check.h"
#include "base/files/file_path.h"
#include "base/path_service.h"
#include "base/win/scoped_handle.h"
#include "base/win/scoped_localalloc.h"

namespace browser_util {

namespace {

std::optional<std::wstring> GetNtPathFromWin32Path(const std::wstring& path) {
  base::win::ScopedHandle file(::CreateFileW(
      path.c_str(), 0, FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
      nullptr, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, nullptr));
  if (!file.is_valid()) {
    return std::nullopt;
  }

  constexpr ULONG kMaxNameSize = USHRT_MAX + sizeof(UNICODE_STRING);
  std::unique_ptr<BYTE[]> buffer = std::make_unique<BYTE[]>(kMaxNameSize);
  DWORD return_length;
  // Information class 1 is ObjectNameInformation.
  NTSTATUS status =
      ::NtQueryObject(file.get(), static_cast<OBJECT_INFORMATION_CLASS>(1),
                      buffer.get(), kMaxNameSize, &return_length);
  if (!NT_SUCCESS(status)) {
    return std::nullopt;
  }

  PUNICODE_STRING name = reinterpret_cast<PUNICODE_STRING>(buffer.get());
  return std::wstring(name->Buffer, name->Length / sizeof(name->Buffer[0]));
}

}  // namespace

bool IsBrowserAlreadyRunning() {
  static HANDLE handle = nullptr;
  base::FilePath exe_dir_path;
  // DIR_EXE is obtained from the path of FILE_EXE and, on Windows, FILE_EXE is
  // obtained from reading the PEB of the currently running process. This means
  // that even if the EXE file is moved, the DIR_EXE will still reflect the
  // original location of the EXE from when it was started. This is important as
  // IsBrowserAlreadyRunning must detect any running browser in Chrome's install
  // directory, and not in a temporary directory if it is subsequently renamed
  // or moved while running.
  if (!base::PathService::Get(base::DIR_EXE, &exe_dir_path)) {
    // If this fails, there isn't much that can be done. However, assuming that
    // browser is *not* already running is the safer action here, as it means
    // that any pending upgrade actions will occur and hopefully the issue that
    // caused this failure will be resolved by the newer version. This might
    // cause the currently running browser to be temporarily broken, but it's
    // probably broken already if this API is failing.
    return false;
  }
  std::optional<std::wstring> nt_dir_name =
      GetNtPathFromWin32Path(exe_dir_path.value());
  if (!nt_dir_name) {
    // See above for why false is returned here.
    return false;
  }
  std::replace(nt_dir_name->begin(), nt_dir_name->end(), '\\', '!');
  std::ranges::transform(*nt_dir_name, nt_dir_name->begin(), tolower);
  nt_dir_name = L"Global\\" + nt_dir_name.value();
  if (handle != NULL)
    ::CloseHandle(std::exchange(handle, nullptr));

  // For this to work for both user and system installs, we need the event to be
  // accessible to all interactive users so that we can correctly detect any
  // instance they are running. Otherwise, we can end up executing pending
  // upgrade actions while there are instances running, resulting in reliability
  // issues for one of the users.
  // Security Descriptor for the global browser running event:
  //   SYSTEM : EVENT_ALL_ACCESS
  //   Interactive User : EVENT_ALL_ACCESS
  static constexpr wchar_t kAllAccessDescriptor[] =
      L"D:P(A;;0x1F0003;;;SY)(A;;0x1F0003;;;IU)";
  SECURITY_ATTRIBUTES attributes = {sizeof(SECURITY_ATTRIBUTES), nullptr,
                                    FALSE};
  if (!::ConvertStringSecurityDescriptorToSecurityDescriptor(
          kAllAccessDescriptor, SDDL_REVISION_1,
          &attributes.lpSecurityDescriptor, nullptr)) {
    // If this fails, it usually means the security descriptor string is
    // incorrect. As a fallback, create the event with the default descriptor
    // by setting it to nullptr. This works for single user devices which is the
    // most common case for Windows.
    DPCHECK(false);
    attributes.lpSecurityDescriptor = nullptr;
  }
  base::win::ScopedLocalAlloc scoped_sd(attributes.lpSecurityDescriptor);

  handle = ::CreateEventW(&attributes, /*bManualReset=*/TRUE,
                          /*bInitialState=*/TRUE, nt_dir_name->c_str());
  int error = ::GetLastError();
  // There is another browser running if `CreateEventW` succeeded and the object
  // existed prior to the call or if `CreateEventW` failed due to access denied.
  return error == (handle ? ERROR_ALREADY_EXISTS : ERROR_ACCESS_DENIED);
}

}  // namespace browser_util