chrome/install_static/install_util.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 "chrome/install_static/install_util.h"

#include <windows.h>
#include <assert.h>
#include <algorithm>
#include <iostream>
#include <iterator>
#include <memory>
#include <sstream>

#include "chrome_elf/nt_registry/nt_registry.h"

namespace install_static {

ProcessType g_process_type = ProcessType::UNINITIALIZED;

// TODO(ananta)
// http://crbug.com/604923
// The constants defined in this file are also defined in chrome/installer and
// other places. we need to unify them.

// Chrome channel display names.
const wchar_t kChromeChannelUnknown[] = L"unknown";
const wchar_t kChromeChannelCanary[] = L"canary";
const wchar_t kChromeChannelDev[] = L"dev";
const wchar_t kChromeChannelBeta[] = L"beta";
const wchar_t kChromeChannelStable[] = L"";
const wchar_t kChromeChannelStableExplicit[] = L"stable";
const wchar_t kRegApField[] = L"ap";

#if defined(GOOGLE_CHROME_BUILD)
const wchar_t kRegPathClientState[] = L"Software\\Google\\Update\\ClientState";
const wchar_t kRegPathClientStateMedium[] =
    L"Software\\Google\\Update\\ClientStateMedium";
const wchar_t kRegPathChromePolicy[] = L"SOFTWARE\\Policies\\Google\\Chrome";
#else
const wchar_t kRegPathClientState[] =
    L"Software\\Chromium\\Update\\ClientState";
const wchar_t kRegPathClientStateMedium[] =
    L"Software\\Chromium\\Update\\ClientStateMedium";
const wchar_t kRegPathChromePolicy[] = L"SOFTWARE\\Policies\\Chromium";
#endif

const wchar_t kRegValueUsageStats[] = L"usagestats";
const wchar_t kUninstallArgumentsField[] = L"UninstallArguments";
const wchar_t kMetricsReportingEnabled[] = L"MetricsReportingEnabled";

const wchar_t kAppGuidCanary[] = L"{4ea16ac7-fd5a-47c3-875b-dbf4a2008c20}";
const wchar_t kAppGuidGoogleChrome[] =
    L"{8A69D345-D564-463c-AFF1-A69D9E530F96}";
const wchar_t kAppGuidGoogleBinaries[] =
    L"{4DC8B4CA-1BDA-483e-B5FA-D3C12E15B62D}";

const wchar_t kHeadless[] = L"CHROME_HEADLESS";
const wchar_t kShowRestart[] = L"CHROME_CRASHED";
const wchar_t kRestartInfo[] = L"CHROME_RESTART";
const wchar_t kRtlLocale[] = L"RIGHT_TO_LEFT";

const char kGpuProcess[] = "gpu-process";
const char kPpapiPluginProcess[] = "ppapi";
const char kRendererProcess[] = "renderer";
const char kUtilityProcess[] = "utility";
const char kProcessType[] = "type";
const char kCrashpadHandler[] = "crashpad-handler";

namespace {

// TODO(ananta)
// http://crbug.com/604923
// These constants are defined in the chrome/installer directory as well. We
// need to unify them.
#if defined(GOOGLE_CHROME_BUILD)
const wchar_t kSxSSuffix[] = L" SxS";
const wchar_t kGoogleChromeInstallSubDir1[] = L"Google";
const wchar_t kGoogleChromeInstallSubDir2[] = L"Chrome";
#else
const wchar_t kChromiumInstallSubDir[] = L"Chromium";
#endif  // defined(GOOGLE_CHROME_BUILD)

const wchar_t kUserDataDirname[] = L"User Data";
const wchar_t kBrowserCrashDumpMetricsSubKey[] = L"\\BrowserCrashDumpAttempts";

const wchar_t kRegPathGoogleUpdate[] = L"Software\\Google\\Update";
const wchar_t kRegGoogleUpdateVersion[] = L"version";

// Registry key to store the stats/crash sampling state of Chrome. If set to 1,
// stats and crash reports will be uploaded in line with the user's consent,
// otherwise, uploads will be disabled. It is used to sample clients, to reduce
// server load for metics and crashes. This is controlled by the
// MetricsReporting feature in chrome_metrics_services_manager_client.cc and is
// written when metrics services are started up and when consent changes.
const wchar_t kRegValueChromeStatsSample[] = L"UsageStatsInSample";

void Trace(const wchar_t* format_string, ...) {
  static const int kMaxLogBufferSize = 1024;
  static wchar_t buffer[kMaxLogBufferSize] = {};

  va_list args = {};

  va_start(args, format_string);
  vswprintf(buffer, kMaxLogBufferSize, format_string, args);
  OutputDebugStringW(buffer);
  va_end(args);
}

bool GetLanguageAndCodePageFromVersionResource(const char* version_resource,
                                               WORD* language,
                                               WORD* code_page) {
  if (!version_resource)
    return false;

  struct LanguageAndCodePage {
    WORD language;
    WORD code_page;
  };

  LanguageAndCodePage* translation_info = nullptr;
  uint32_t data_size_in_bytes = 0;
  BOOL query_result = VerQueryValueW(
      version_resource, L"\\VarFileInfo\\Translation",
      reinterpret_cast<void**>(&translation_info), &data_size_in_bytes);
  if (!query_result)
    return false;

  *language = translation_info->language;
  *code_page = translation_info->code_page;
  return true;
}

bool GetValueFromVersionResource(const char* version_resource,
                                 const std::wstring& name,
                                 std::wstring* value_str) {
  assert(value_str);
  value_str->clear();

  // TODO(ananta)
  // It may be better in the long run to enumerate the languages and code pages
  // in the version resource and return the value from the first match.
  WORD language = 0;
  WORD code_page = 0;
  if (!GetLanguageAndCodePageFromVersionResource(version_resource, &language,
                                                 &code_page)) {
    return false;
  }

  const size_t array_size = 8;
  WORD lang_codepage[array_size] = {};
  size_t i = 0;
  // Use the language and codepage
  lang_codepage[i++] = language;
  lang_codepage[i++] = code_page;
  // Use the default language and codepage from the resource.
  lang_codepage[i++] = ::GetUserDefaultLangID();
  lang_codepage[i++] = code_page;
  // Use the language from the resource and Latin codepage (most common).
  lang_codepage[i++] = language;
  lang_codepage[i++] = 1252;
  // Use the default language and Latin codepage (most common).
  lang_codepage[i++] = ::GetUserDefaultLangID();
  lang_codepage[i++] = 1252;

  static_assert((array_size % 2) == 0,
                "Language code page size should be a multiple of 2");
  assert(array_size == i);

  for (i = 0; i < array_size;) {
    wchar_t sub_block[MAX_PATH];
    WORD language = lang_codepage[i++];
    WORD code_page = lang_codepage[i++];
    _snwprintf_s(sub_block, MAX_PATH, MAX_PATH,
                 L"\\StringFileInfo\\%04hx%04hx\\%ls", language, code_page,
                 name.c_str());
    void* value = nullptr;
    uint32_t size = 0;
    BOOL r = ::VerQueryValueW(version_resource, sub_block, &value, &size);
    if (r && value) {
      value_str->assign(static_cast<wchar_t*>(value));
      return true;
    }
  }
  return false;
}

// Returns the executable path for the current process.
std::wstring GetCurrentProcessExePath() {
  wchar_t exe_path[MAX_PATH];
  if (::GetModuleFileName(nullptr, exe_path, MAX_PATH) == 0)
    return std::wstring();
  return exe_path;
}

bool RecursiveDirectoryCreate(const std::wstring& full_path) {
  // If the path exists, we've succeeded if it's a directory, failed otherwise.
  const wchar_t* full_path_str = full_path.c_str();
  DWORD file_attributes = ::GetFileAttributes(full_path_str);
  if (file_attributes != INVALID_FILE_ATTRIBUTES) {
    if ((file_attributes & FILE_ATTRIBUTE_DIRECTORY) != 0) {
      Trace(L"%hs( %ls directory exists )\n", __func__, full_path_str);
      return true;
    }
    Trace(L"%hs( %ls directory conflicts with an existing file. )\n", __func__,
          full_path_str);
    return false;
  }

  // Invariant:  Path does not exist as file or directory.

  // Attempt to create the parent recursively.  This will immediately return
  // true if it already exists, otherwise will create all required parent
  // directories starting with the highest-level missing parent.
  std::wstring parent_path;
  std::size_t pos = full_path.find_last_of(L"/\\");
  if (pos != std::wstring::npos) {
    parent_path = full_path.substr(0, pos);
    if (!RecursiveDirectoryCreate(parent_path)) {
      Trace(L"Failed to create one of the parent directories");
      return false;
    }
  }
  if (!::CreateDirectory(full_path_str, nullptr)) {
    DWORD error_code = ::GetLastError();
    if (error_code == ERROR_ALREADY_EXISTS) {
      DWORD file_attributes = ::GetFileAttributes(full_path_str);
      if ((file_attributes != INVALID_FILE_ATTRIBUTES) &&
          ((file_attributes & FILE_ATTRIBUTE_DIRECTORY) != 0)) {
        // This error code ERROR_ALREADY_EXISTS doesn't indicate whether we
        // were racing with someone creating the same directory, or a file
        // with the same path.  If the directory exists, we lost the
        // race to create the same directory.
        return true;
      } else {
        Trace(L"Failed to create directory %ls, last error is %d\n",
              full_path_str, error_code);
        return false;
      }
    }
  }
  return true;
}

std::wstring GetChromeInstallRegistryPath() {
  std::wstring registry_path = L"Software\\";
  registry_path += GetChromeInstallSubDirectory();
  return registry_path;
}

bool GetCollectStatsConsentImpl(const std::wstring& exe_path) {
  bool enabled = true;

  if (ReportingIsEnforcedByPolicy(&enabled))
    return enabled;

  bool system_install = IsSystemInstall(exe_path.c_str());
  std::wstring app_guid;

  if (IsSxSChrome(exe_path.c_str())) {
    app_guid = kAppGuidCanary;
  } else {
    app_guid = IsMultiInstall(system_install) ? kAppGuidGoogleBinaries
                                              : kAppGuidGoogleChrome;
  }

  DWORD out_value = 0;

  // If system_install, first try kRegPathClientStateMedium.
  std::wstring full_key_path(kRegPathClientStateMedium);
  full_key_path.append(1, L'\\');
  full_key_path.append(app_guid);
  if (system_install &&
      nt::QueryRegValueDWORD(nt::HKLM, nt::WOW6432, full_key_path.c_str(),
                             kRegValueUsageStats, &out_value))
    return (out_value == 1);

  // Second, try kRegPathClientState.
  full_key_path = kRegPathClientState;
  full_key_path.append(1, L'\\');
  full_key_path.append(app_guid);
  return (nt::QueryRegValueDWORD((system_install ? nt::HKLM : nt::HKCU),
                                 nt::WOW6432, full_key_path.c_str(),
                                 kRegValueUsageStats, &out_value) &&
          out_value == 1);
}

// Returns true if the |source| string matches the |pattern|. The pattern
// may contain wildcards like '?' which matches one character or a '*'
// which matches 0 or more characters.
// Please note that pattern matches the whole string. If you want to find
// something in the middle of the string then you need to specify the pattern
// as '*xyz*'.
// |source_index| is the index of the current character being matched in
// |source|.
// |pattern_index| is the index of the current pattern character in |pattern|
// which is matched with source.
bool MatchPatternImpl(const std::wstring& source,
                      const std::wstring& pattern,
                      size_t source_index,
                      size_t pattern_index) {
  if (source.empty() && pattern.empty())
    return true;

  if (source_index > source.length() || pattern_index > pattern.length())
    return false;

  // If we reached the end of both strings, then we are done.
  if ((source_index == source.length()) &&
      (pattern_index == pattern.length())) {
    return true;
  }

  // If the current character in the pattern is a '*' then make sure that
  // characters after the pattern are present in the source string. This
  // assumes that you won't have two consecutive '*' characters in the pattern.
  if ((pattern[pattern_index] == L'*') &&
      (pattern_index + 1 < pattern.length()) &&
      (source_index >= source.length())) {
    return false;
  }

  // If the pattern contains wildcard characters '?' or '.' or there is a match
  // then move ahead in both strings.
  if ((pattern[pattern_index] == L'?') ||
      (pattern[pattern_index] == source[source_index])) {
    return MatchPatternImpl(source, pattern, source_index + 1,
                            pattern_index + 1);
  }

  // If we have a '*' then there are two possibilities
  // 1. We consider current character of source.
  // 2. We ignore current character of source.
  if (pattern[pattern_index] == L'*') {
    return MatchPatternImpl(source, pattern, source_index + 1, pattern_index) ||
           MatchPatternImpl(source, pattern, source_index, pattern_index + 1);
  }
  return false;
}

// Defines the type of whitespace characters typically found in strings.
constexpr char kWhiteSpaces[] = " \t\n\r\f\v";
constexpr wchar_t kWhiteSpaces16[] = L" \t\n\r\f\v";

// Define specializations for white spaces based on the type of the string.
template <class StringType>
StringType GetWhiteSpacesForType();
template <>
std::wstring GetWhiteSpacesForType() {
  return kWhiteSpaces16;
}
template <>
std::string GetWhiteSpacesForType() {
  return kWhiteSpaces;
}

// Trim whitespaces from left & right
template <class StringType>
void TrimT(StringType* str) {
  str->erase(str->find_last_not_of(GetWhiteSpacesForType<StringType>()) + 1);
  str->erase(0, str->find_first_not_of(GetWhiteSpacesForType<StringType>()));
}

bool IsValidNumber(const std::string& str) {
  if (str.empty())
    return false;
  return std::all_of(str.begin(), str.end(), ::isdigit);
}

// Tokenizes a string based on a single character delimiter.
template <class StringType>
std::vector<StringType> TokenizeStringT(
    const StringType& str,
    typename StringType::value_type delimiter,
    bool trim_spaces) {
  std::vector<StringType> tokens;
  std::basic_istringstream<typename StringType::value_type> buffer(str);
  for (StringType token; std::getline(buffer, token, delimiter);) {
    if (trim_spaces)
      TrimT<StringType>(&token);
    tokens.push_back(token);
  }
  return tokens;
}

}  // namespace

bool IsSxSChrome(const wchar_t* exe_path) {
  return ::wcsstr(exe_path, L"Chrome SxS\\Application") != nullptr;
}

bool IsSystemInstall(const wchar_t* exe_path) {
  wchar_t program_dir[MAX_PATH] = {};
  DWORD ret = ::GetEnvironmentVariable(L"PROGRAMFILES", program_dir, MAX_PATH);
  if (ret && ret < MAX_PATH && !::wcsnicmp(exe_path, program_dir, ret)) {
    return true;
  }

  ret = ::GetEnvironmentVariable(L"PROGRAMFILES(X86)", program_dir, MAX_PATH);
  if (ret && ret < MAX_PATH && !::wcsnicmp(exe_path, program_dir, ret)) {
    return true;
  }

  return false;
}

bool IsMultiInstall(bool is_system_install) {
  std::wstring args;

  std::wstring full_key_path(kRegPathClientState);
  full_key_path.append(1, L'\\');
  full_key_path.append(kAppGuidGoogleChrome);
  if (!nt::QueryRegValueSZ((is_system_install ? nt::HKLM : nt::HKCU),
                           nt::WOW6432, full_key_path.c_str(),
                           kUninstallArgumentsField, &args))
    return false;

  return (args.find(L"--multi-install") != std::wstring::npos);
}

bool GetCollectStatsConsent() {
  return GetCollectStatsConsentImpl(GetCurrentProcessExePath());
}

bool GetCollectStatsConsentForTesting(const std::wstring& exe_path) {
  return GetCollectStatsConsentImpl(exe_path);
}

bool GetCollectStatsInSample() {
  std::wstring registry_path = GetChromeInstallRegistryPath();

  DWORD out_value = 0;
  if (!nt::QueryRegValueDWORD(nt::HKCU, nt::WOW6432, registry_path.c_str(),
                              kRegValueChromeStatsSample, &out_value)) {
    // If reading the value failed, treat it as though sampling isn't in effect,
    // implicitly meaning this install is in the sample.
    return true;
  }
  return out_value == 1;
}

bool SetCollectStatsInSample(bool in_sample) {
  std::wstring registry_path = GetChromeInstallRegistryPath();

  HANDLE key_handle = INVALID_HANDLE_VALUE;
  if (!nt::CreateRegKey(nt::HKCU, registry_path.c_str(),
                        KEY_SET_VALUE | KEY_WOW64_32KEY, &key_handle)) {
    nt::CloseRegKey(key_handle);
    return false;
  }

  return nt::SetRegValueDWORD(key_handle, kRegValueChromeStatsSample,
                              in_sample ? 1 : 0);
}

bool ReportingIsEnforcedByPolicy(bool* metrics_is_enforced_by_policy) {
  DWORD value = 0;

  // First, try HKLM.
  if (nt::QueryRegValueDWORD(nt::HKLM, nt::NONE, kRegPathChromePolicy,
                             kMetricsReportingEnabled, &value)) {
    *metrics_is_enforced_by_policy = (value != 0);
    return true;
  }

  // Second, try HKCU.
  if (nt::QueryRegValueDWORD(nt::HKCU, nt::NONE, kRegPathChromePolicy,
                             kMetricsReportingEnabled, &value)) {
    *metrics_is_enforced_by_policy = (value != 0);
    return true;
  }

  return false;
}

void InitializeProcessType() {
  assert(g_process_type == ProcessType::UNINITIALIZED);
  typedef bool (*IsSandboxedProcessFunc)();
  IsSandboxedProcessFunc is_sandboxed_process_func =
      reinterpret_cast<IsSandboxedProcessFunc>(
          ::GetProcAddress(::GetModuleHandle(nullptr), "IsSandboxedProcess"));
  if (is_sandboxed_process_func && is_sandboxed_process_func()) {
    g_process_type = ProcessType::NON_BROWSER_PROCESS;
    return;
  }

  // TODO(robertshield): Drop the command line check when we drop support for
  // enabling chrome_elf in unsandboxed processes.
  const wchar_t* command_line = GetCommandLine();
  if (command_line && ::wcsstr(command_line, L"--type")) {
    g_process_type = ProcessType::NON_BROWSER_PROCESS;
    return;
  }

  g_process_type = ProcessType::BROWSER_PROCESS;
}

bool IsNonBrowserProcess() {
  assert(g_process_type != ProcessType::UNINITIALIZED);
  return g_process_type == ProcessType::NON_BROWSER_PROCESS;
}

bool GetDefaultUserDataDirectory(std::wstring* result) {
  static const wchar_t kLocalAppData[] = L"%LOCALAPPDATA%";

  std::unique_ptr<wchar_t> user_data_dir_path;

  // This environment variable should be set on Windows 7 and up.
  // If we fail to find this variable then we default to the temporary files
  // path.
  DWORD size = ::ExpandEnvironmentStrings(kLocalAppData, nullptr, 0);
  if (size) {
    user_data_dir_path.reset(new wchar_t[size]);
    if (::ExpandEnvironmentStrings(kLocalAppData, user_data_dir_path.get(),
                                   size) != size) {
      user_data_dir_path.reset();
    }
  }
  // We failed to find the %LOCALAPPDATA% folder. Fallback to the temporary
  // files path. If we fail to find this we bail.
  if (!user_data_dir_path.get()) {
    size = ::GetTempPath(0, nullptr);
    if (!size)
      return false;
    user_data_dir_path.reset(new wchar_t[size + 1]);
    if (::GetTempPath(size + 1, user_data_dir_path.get()) != size)
      return false;
  }

  std::wstring install_sub_directory = GetChromeInstallSubDirectory();

  *result = user_data_dir_path.get();
  if ((*result)[result->length() - 1] != L'\\')
    result->append(L"\\");
  result->append(install_sub_directory);
  result->append(L"\\");
  result->append(kUserDataDirname);
  return true;
}

bool GetDefaultCrashDumpLocation(std::wstring* crash_dir) {
  // In order to be able to start crash handling very early, we do not rely on
  // chrome's PathService entries (for DIR_CRASH_DUMPS) being available on
  // Windows. See https://crbug.com/564398.
  if (!GetDefaultUserDataDirectory(crash_dir))
    return false;

  // We have to make sure the user data dir exists on first run. See
  // http://crbug.com/591504.
  if (!RecursiveDirectoryCreate(crash_dir->c_str()))
    return false;
  crash_dir->append(L"\\Crashpad");
  return true;
}

std::string GetEnvironmentString(const std::string& variable_name) {
  return UTF16ToUTF8(GetEnvironmentString16(UTF8ToUTF16(variable_name)));
}

std::wstring GetEnvironmentString16(const std::wstring& variable_name) {
  DWORD value_length =
      ::GetEnvironmentVariable(variable_name.c_str(), nullptr, 0);
  if (value_length == 0)
    return std::wstring();
  std::unique_ptr<wchar_t[]> value(new wchar_t[value_length]);
  ::GetEnvironmentVariable(variable_name.c_str(), value.get(), value_length);
  return value.get();
}

bool SetEnvironmentString(const std::string& variable_name,
                          const std::string& new_value) {
  return SetEnvironmentString16(UTF8ToUTF16(variable_name),
                                UTF8ToUTF16(new_value));
}

bool SetEnvironmentString16(const std::wstring& variable_name,
                            const std::wstring& new_value) {
  return !!SetEnvironmentVariable(variable_name.c_str(), new_value.c_str());
}

bool HasEnvironmentVariable(const std::string& variable_name) {
  return HasEnvironmentVariable16(UTF8ToUTF16(variable_name));
}

bool HasEnvironmentVariable16(const std::wstring& variable_name) {
  return !!::GetEnvironmentVariable(variable_name.c_str(), nullptr, 0);
}

bool GetExecutableVersionDetails(const std::wstring& exe_path,
                                 std::wstring* product_name,
                                 std::wstring* version,
                                 std::wstring* special_build,
                                 std::wstring* channel_name) {
  assert(product_name);
  assert(version);
  assert(special_build);
  assert(channel_name);

  // Default values in case we don't find a version resource.
  *product_name = L"Chrome";
  *version = L"0.0.0.0-devel";
  *channel_name = kChromeChannelUnknown;
  special_build->clear();

  DWORD dummy = 0;
  DWORD length = ::GetFileVersionInfoSize(exe_path.c_str(), &dummy);
  if (length) {
    std::unique_ptr<char> data(new char[length]);
    if (::GetFileVersionInfo(exe_path.c_str(), dummy, length, data.get())) {
      GetValueFromVersionResource(data.get(), L"ProductVersion", version);

      std::wstring official_build;
      GetValueFromVersionResource(data.get(), L"Official Build",
                                  &official_build);
      if (official_build != L"1")
        version->append(L"-devel");
      GetValueFromVersionResource(data.get(), L"ProductShortName",
                                  product_name);
      GetValueFromVersionResource(data.get(), L"SpecialBuild", special_build);
    }
  }
  GetChromeChannelName(!IsSystemInstall(exe_path.c_str()), true, channel_name);
  return true;
}

void GetChromeChannelName(bool is_per_user_install,
                          bool add_modifier,
                          std::wstring* channel_name) {
  channel_name->clear();
  // TODO(ananta)
  // http://crbug.com/604923
  // Unify this with the chrome/installer/util/channel_info.h/.cc.
  if (IsSxSChrome(GetCurrentProcessExePath().c_str())) {
    *channel_name = L"canary";
  } else {
    std::wstring value;
    bool channel_available = false;
    bool is_multi_install = IsMultiInstall(!is_per_user_install);
    if (is_multi_install) {
      std::wstring full_key_path(kRegPathClientState);
      full_key_path.append(1, L'\\');
      full_key_path.append(kAppGuidGoogleBinaries);
      channel_available = nt::QueryRegValueSZ(
          is_per_user_install ? nt::HKCU : nt::HKLM, nt::WOW6432,
          full_key_path.c_str(), kRegApField, &value);
    } else {
      std::wstring full_key_path(kRegPathClientState);
      full_key_path.append(1, L'\\');
      full_key_path.append(kAppGuidGoogleChrome);
      channel_available = nt::QueryRegValueSZ(
          is_per_user_install ? nt::HKCU : nt::HKLM, nt::WOW6432,
          full_key_path.c_str(), kRegApField, &value);
    }
    if (channel_available) {
      static const wchar_t kChromeChannelBetaPattern[] = L"1?1-*";
      static const wchar_t kChromeChannelBetaX64Pattern[] = L"*x64-beta*";
      static const wchar_t kChromeChannelDevPattern[] = L"2?0-d*";
      static const wchar_t kChromeChannelDevX64Pattern[] = L"*x64-dev*";

      std::transform(value.begin(), value.end(), value.begin(), ::tolower);

      // Empty channel names or those containing "stable" should be reported as
      // an empty string. Exceptions being if |add_modifier| is true and this
      // is a multi install. In that case we report the channel name as "-m".
      if (value.empty() ||
          (value.find(kChromeChannelStableExplicit) != std::wstring::npos)) {
        if (add_modifier && is_multi_install)
          channel_name->append(L"-m");
        return;
      }

      if (MatchPattern(value, kChromeChannelDevPattern) ||
          MatchPattern(value, kChromeChannelDevX64Pattern)) {
        channel_name->assign(kChromeChannelDev);
      }

      if (MatchPattern(value, kChromeChannelBetaPattern) ||
          MatchPattern(value, kChromeChannelBetaX64Pattern)) {
        channel_name->assign(kChromeChannelBeta);
      }

      if (add_modifier && is_multi_install)
        channel_name->append(L"-m");

      // If we fail to find any matching pattern in the channel name then we
      // default to empty which means stable. Not sure if this is ok.
      // TODO(ananta)
      // http://crbug.com/604923
      // Check if this is ok.
    } else {
      *channel_name = kChromeChannelUnknown;
    }
  }
}

std::string GetGoogleUpdateVersion() {
  // TODO(ananta)
  // Consider whether Chromium should connect to Google update to manage
  // updates. Should this be returning an empty string for Chromium builds?.
  std::wstring update_version;
  if (nt::QueryRegValueSZ(nt::AUTO, nt::WOW6432, kRegPathGoogleUpdate,
                          kRegGoogleUpdateVersion, &update_version))
    return UTF16ToUTF8(update_version);

  return std::string();
}

std::wstring GetChromeInstallSubDirectory() {
#if defined(GOOGLE_CHROME_BUILD)
  std::wstring result = kGoogleChromeInstallSubDir1;
  result += L"\\";
  result += kGoogleChromeInstallSubDir2;
  if (IsSxSChrome(GetCurrentProcessExePath().c_str()))
    result += kSxSSuffix;
  return result;
#else
  return std::wstring(kChromiumInstallSubDir);
#endif
}

std::wstring GetBrowserCrashDumpAttemptsRegistryPath() {
  std::wstring registry_path = GetChromeInstallRegistryPath();
  registry_path += kBrowserCrashDumpMetricsSubKey;
  return registry_path;
}

bool MatchPattern(const std::wstring& source, const std::wstring& pattern) {
  assert(pattern.find(L"**") == std::wstring::npos);
  return MatchPatternImpl(source, pattern, 0, 0);
}

std::string UTF16ToUTF8(const std::wstring& source) {
  if (source.empty() ||
      static_cast<int>(source.size()) > std::numeric_limits<int>::max()) {
    return std::string();
  }
  int size = ::WideCharToMultiByte(CP_UTF8, 0, &source[0],
                                   static_cast<int>(source.size()), nullptr, 0,
                                   nullptr, nullptr);
  std::string result(size, '\0');
  if (::WideCharToMultiByte(CP_UTF8, 0, &source[0],
                            static_cast<int>(source.size()), &result[0], size,
                            nullptr, nullptr) != size) {
    assert(false);
    return std::string();
  }
  return result;
}

std::wstring UTF8ToUTF16(const std::string& source) {
  if (source.empty() ||
      static_cast<int>(source.size()) > std::numeric_limits<int>::max()) {
    return std::wstring();
  }
  int size = ::MultiByteToWideChar(CP_UTF8, 0, &source[0],
                                   static_cast<int>(source.size()), nullptr, 0);
  std::wstring result(size, L'\0');
  if (::MultiByteToWideChar(CP_UTF8, 0, &source[0],
                            static_cast<int>(source.size()), &result[0],
                            size) != size) {
    assert(false);
    return std::wstring();
  }
  return result;
}

std::vector<std::string> TokenizeString(const std::string& str,
                                        char delimiter,
                                        bool trim_spaces) {
  return TokenizeStringT<std::string>(str, delimiter, trim_spaces);
}

std::vector<std::wstring> TokenizeString16(const std::wstring& str,
                                           wchar_t delimiter,
                                           bool trim_spaces) {
  return TokenizeStringT<std::wstring>(str, delimiter, trim_spaces);
}

bool CompareVersionStrings(const std::string& version1,
                           const std::string& version2,
                           int* result) {
  if (version1.empty() || version2.empty())
    return false;

  // Tokenize both version strings with "." as the separator. If either of
  // the returned token lists are empty then bail.
  std::vector<std::string> version1_components =
      TokenizeString(version1, '.', false);
  if (version1_components.empty())
    return false;

  std::vector<std::string> version2_components =
      TokenizeString(version2, '.', false);
  if (version2_components.empty())
    return false;

  // You may have less tokens in either string. Use the minimum of the number
  // of tokens as the initial count.
  const size_t count =
      std::min(version1_components.size(), version2_components.size());
  for (size_t i = 0; i < count; ++i) {
    // If either of the version components don't contain valid numeric digits
    // bail.
    if (!IsValidNumber(version1_components[i]) ||
        !IsValidNumber(version2_components[i])) {
      return false;
    }

    int version1_component = std::stoi(version1_components[i]);
    int version2_component = std::stoi(version2_components[i]);

    if (version1_component > version2_component) {
      *result = 1;
      return true;
    }

    if (version1_component < version2_component) {
      *result = -1;
      return true;
    }
  }

  // Handle remaining tokens. Here if we have non zero tokens remaining in the
  // version 1 list then it means that the version1 string is larger. If the
  // version 1 token list has tokens left, then if either of these tokens is
  // greater than 0 then it means that the version1 string is smaller than the
  // version2 string.
  if (version1_components.size() > version2_components.size()) {
    for (size_t i = count; i < version1_components.size(); ++i) {
      // If the version components don't contain valid numeric digits bail.
      if (!IsValidNumber(version1_components[i]))
        return false;

      if (std::stoi(version1_components[i]) > 0) {
        *result = 1;
        return true;
      }
    }
  } else if (version1_components.size() < version2_components.size()) {
    for (size_t i = count; i < version2_components.size(); ++i) {
      // If the version components don't contain valid numeric digits bail.
      if (!IsValidNumber(version2_components[i]))
        return false;

      if (std::stoi(version2_components[i]) > 0) {
        *result = -1;
        return true;
      }
    }
  }
  // Here it means that both versions are equal.
  *result = 0;
  return true;
}

std::string GetSwitchValueFromCommandLine(const std::string& command_line,
                                          const std::string& switch_name) {
  assert(!command_line.empty());
  assert(!switch_name.empty());

  std::string command_line_copy = command_line;
  // Remove leading and trailing spaces.
  TrimT<std::string>(&command_line_copy);

  // Find the switch in the command line. If we don't find the switch, return
  // an empty string.
  std::string switch_token = "--";
  switch_token += switch_name;
  switch_token += "=";
  size_t switch_offset = command_line_copy.find(switch_token);
  if (switch_offset == std::string::npos)
    return std::string();

  // The format is "--<switch name>=blah". Look for a space after the
  // "--<switch name>=" string. If we don't find a space assume that the switch
  // value ends at the end of the command line.
  size_t switch_value_start_offset = switch_offset + switch_token.length();
  if (std::string(kWhiteSpaces).find(
          command_line_copy[switch_value_start_offset]) != std::string::npos) {
    switch_value_start_offset = command_line_copy.find_first_not_of(
        GetWhiteSpacesForType<std::string>(), switch_value_start_offset);
    if (switch_value_start_offset == std::string::npos)
      return std::string();
  }
  size_t switch_value_end_offset =
      command_line_copy.find_first_of(GetWhiteSpacesForType<std::string>(),
                                      switch_value_start_offset);
  if (switch_value_end_offset == std::string::npos)
    switch_value_end_offset = command_line_copy.length();

  std::string switch_value = command_line_copy.substr(
      switch_value_start_offset,
      switch_value_end_offset - (switch_offset + switch_token.length()));
  TrimT<std::string>(&switch_value);
  return switch_value;
}

}  // namespace install_static