// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/win/registry.h"
#include <ntstatus.h>
#include <stddef.h>
#include <algorithm>
#include <iterator>
#include <memory>
#include <string>
#include <utility>
#include <vector>
#include "base/check_op.h"
#include "base/functional/callback.h"
#include "base/notreached.h"
#include "base/strings/string_util.h"
#include "base/strings/string_util_win.h"
#include "base/threading/thread_restrictions.h"
#include "base/win/object_watcher.h"
#include "base/win/scoped_handle.h"
#include "base/win/shlwapi.h"
extern "C" NTSTATUS WINAPI NtDeleteKey(IN HANDLE KeyHandle);
namespace base::win {
namespace {
// RegEnumValue() reports the number of characters from the name that were
// written to the buffer, not how many there are. This constant is the maximum
// name size, such that a buffer with this size should read any name.
constexpr DWORD MAX_REGISTRY_NAME_SIZE = 16384;
// Registry values are read as BYTE* but can have wchar_t* data whose last
// wchar_t is truncated. This function converts the reported |byte_size| to
// a size in wchar_t that can store a truncated wchar_t if necessary.
inline DWORD to_wchar_size(DWORD byte_size) {
return (byte_size + sizeof(wchar_t) - 1) / sizeof(wchar_t);
}
// Mask to pull WOW64 access flags out of REGSAM access.
constexpr REGSAM kWow64AccessMask = KEY_WOW64_32KEY | KEY_WOW64_64KEY;
constexpr DWORD kInvalidIterValue = static_cast<DWORD>(-1);
} // namespace
// Watches for modifications to a key.
class RegKey::Watcher : public ObjectWatcher::Delegate {
public:
Watcher() = default;
Watcher(const Watcher&) = delete;
Watcher& operator=(const Watcher&) = delete;
~Watcher() override = default;
bool StartWatching(HKEY key, ChangeCallback callback);
// ObjectWatcher::Delegate:
void OnObjectSignaled(HANDLE object) override {
DCHECK(watch_event_.is_valid());
DCHECK_EQ(watch_event_.get(), object);
std::move(callback_).Run();
}
private:
ScopedHandle watch_event_;
ObjectWatcher object_watcher_;
ChangeCallback callback_;
};
bool RegKey::Watcher::StartWatching(HKEY key, ChangeCallback callback) {
DCHECK(key);
DCHECK(callback_.is_null());
if (!watch_event_.is_valid()) {
watch_event_.Set(CreateEvent(nullptr, TRUE, FALSE, nullptr));
}
if (!watch_event_.is_valid()) {
return false;
}
DWORD filter = REG_NOTIFY_CHANGE_NAME | REG_NOTIFY_CHANGE_ATTRIBUTES |
REG_NOTIFY_CHANGE_LAST_SET | REG_NOTIFY_CHANGE_SECURITY |
REG_NOTIFY_THREAD_AGNOSTIC;
// Watch the registry key for a change of value.
LONG result =
RegNotifyChangeKeyValue(key, /*bWatchSubtree=*/TRUE, filter,
watch_event_.get(), /*fAsynchronous=*/TRUE);
if (result != ERROR_SUCCESS) {
watch_event_.Close();
return false;
}
callback_ = std::move(callback);
return object_watcher_.StartWatchingOnce(watch_event_.get(), this);
}
// RegKey ----------------------------------------------------------------------
RegKey::RegKey() = default;
RegKey::RegKey(HKEY key) : key_(key) {}
RegKey::RegKey(HKEY rootkey, const wchar_t* subkey, REGSAM access) {
if (rootkey) {
if (access & (KEY_SET_VALUE | KEY_CREATE_SUB_KEY | KEY_CREATE_LINK)) {
(void)Create(rootkey, subkey, access);
} else {
(void)Open(rootkey, subkey, access);
}
} else {
DCHECK(!subkey);
wow64access_ = access & kWow64AccessMask;
}
}
RegKey::RegKey(RegKey&& other) noexcept
: key_(other.key_),
wow64access_(other.wow64access_),
key_watcher_(std::move(other.key_watcher_)) {
other.key_ = nullptr;
other.wow64access_ = 0;
}
RegKey& RegKey::operator=(RegKey&& other) {
Close();
std::swap(key_, other.key_);
std::swap(wow64access_, other.wow64access_);
key_watcher_ = std::move(other.key_watcher_);
return *this;
}
RegKey::~RegKey() {
Close();
}
LONG RegKey::Create(HKEY rootkey, const wchar_t* subkey, REGSAM access) {
DWORD disposition_value;
return CreateWithDisposition(rootkey, subkey, &disposition_value, access);
}
LONG RegKey::CreateWithDisposition(HKEY rootkey,
const wchar_t* subkey,
DWORD* disposition,
REGSAM access) {
DCHECK(rootkey && subkey && access && disposition);
HKEY subhkey = nullptr;
LONG result =
RegCreateKeyEx(rootkey, subkey, 0, nullptr, REG_OPTION_NON_VOLATILE,
access, nullptr, &subhkey, disposition);
if (result == ERROR_SUCCESS) {
Close();
key_ = subhkey;
wow64access_ = access & kWow64AccessMask;
}
return result;
}
LONG RegKey::CreateKey(const wchar_t* name, REGSAM access) {
DCHECK(name && access);
if (!Valid()) {
// The parent key has not been opened or created.
return ERROR_INVALID_HANDLE;
}
// After the application has accessed an alternate registry view using one
// of the [KEY_WOW64_32KEY / KEY_WOW64_64KEY] flags, all subsequent
// operations (create, delete, or open) on child registry keys must
// explicitly use the same flag. Otherwise, there can be unexpected
// behavior.
// http://msdn.microsoft.com/en-us/library/windows/desktop/aa384129.aspx.
if ((access & kWow64AccessMask) != wow64access_) {
NOTREACHED();
}
HKEY subkey = nullptr;
LONG result = RegCreateKeyEx(key_, name, 0, nullptr, REG_OPTION_NON_VOLATILE,
access, nullptr, &subkey, nullptr);
if (result == ERROR_SUCCESS) {
Close();
key_ = subkey;
wow64access_ = access & kWow64AccessMask;
}
return result;
}
LONG RegKey::Open(HKEY rootkey, const wchar_t* subkey, REGSAM access) {
return Open(rootkey, subkey, /*options=*/0, access);
}
LONG RegKey::OpenKey(const wchar_t* relative_key_name, REGSAM access) {
DCHECK(relative_key_name && access);
if (!Valid()) {
// The parent key has not been opened or created.
return ERROR_INVALID_HANDLE;
}
// After the application has accessed an alternate registry view using one
// of the [KEY_WOW64_32KEY / KEY_WOW64_64KEY] flags, all subsequent
// operations (create, delete, or open) on child registry keys must
// explicitly use the same flag. Otherwise, there can be unexpected
// behavior.
// http://msdn.microsoft.com/en-us/library/windows/desktop/aa384129.aspx.
if ((access & kWow64AccessMask) != wow64access_) {
NOTREACHED();
}
HKEY subkey = nullptr;
LONG result = RegOpenKeyEx(key_, relative_key_name, 0, access, &subkey);
// We have to close the current opened key before replacing it with the new
// one.
if (result == ERROR_SUCCESS) {
Close();
key_ = subkey;
wow64access_ = access & kWow64AccessMask;
}
return result;
}
void RegKey::Close() {
if (key_) {
::RegCloseKey(key_);
key_ = nullptr;
wow64access_ = 0;
}
}
// TODO(wfh): Remove this and other unsafe methods. See http://crbug.com/375400
void RegKey::Set(HKEY key) {
if (key_ != key) {
Close();
key_ = key;
}
}
HKEY RegKey::Take() {
DCHECK_EQ(wow64access_, 0u);
HKEY key = key_;
key_ = nullptr;
return key;
}
bool RegKey::HasValue(const wchar_t* name) const {
return RegQueryValueEx(key_, name, nullptr, nullptr, nullptr, nullptr) ==
ERROR_SUCCESS;
}
base::expected<DWORD, LONG> RegKey::GetValueCount() const {
DWORD count = 0;
LONG result =
RegQueryInfoKey(key_, nullptr, nullptr, nullptr, nullptr, nullptr,
nullptr, &count, nullptr, nullptr, nullptr, nullptr);
if (result == ERROR_SUCCESS) {
return base::ok(count);
}
return base::unexpected(result);
}
LONG RegKey::GetValueNameAt(DWORD index, std::wstring* name) const {
wchar_t buf[256];
DWORD bufsize = std::size(buf);
LONG r = ::RegEnumValue(key_, index, buf, &bufsize, nullptr, nullptr, nullptr,
nullptr);
if (r == ERROR_SUCCESS) {
name->assign(buf, bufsize);
}
return r;
}
LONG RegKey::DeleteKey(const wchar_t* name, RecursiveDelete recursive) {
DCHECK(name);
if (!Valid()) {
return ERROR_INVALID_HANDLE;
}
// Verify the key exists before attempting delete to replicate previous
// behavior.
RegKey target_key;
LONG result = target_key.Open(key_, name, REG_OPTION_OPEN_LINK,
wow64access_ | KEY_QUERY_VALUE | DELETE);
if (result != ERROR_SUCCESS) {
return result;
}
if (recursive.value()) {
target_key.Close();
return RegDelRecurse(key_, name, wow64access_);
}
// Next, try to delete the key if it is a symbolic link.
if (auto deleted_link = target_key.DeleteIfLink(); deleted_link.has_value()) {
return deleted_link.value();
}
// It's not a symbolic link, so try to delete it without recursing.
return ::RegDeleteKeyEx(target_key.key_, L"", wow64access_, 0);
}
LONG RegKey::DeleteValue(const wchar_t* value_name) {
// `RegDeleteValue()` will return an error if `key_` is invalid.
LONG result = RegDeleteValue(key_, value_name);
return result;
}
LONG RegKey::ReadValueDW(const wchar_t* name, DWORD* out_value) const {
DCHECK(out_value);
DWORD type = REG_DWORD;
DWORD size = sizeof(DWORD);
DWORD local_value = 0;
LONG result = ReadValue(name, &local_value, &size, &type);
if (result == ERROR_SUCCESS) {
if ((type == REG_DWORD || type == REG_BINARY) && size == sizeof(DWORD)) {
*out_value = local_value;
} else {
result = ERROR_CANTREAD;
}
}
return result;
}
LONG RegKey::ReadInt64(const wchar_t* name, int64_t* out_value) const {
DCHECK(out_value);
DWORD type = REG_QWORD;
int64_t local_value = 0;
DWORD size = sizeof(local_value);
LONG result = ReadValue(name, &local_value, &size, &type);
if (result == ERROR_SUCCESS) {
if ((type == REG_QWORD || type == REG_BINARY) &&
size == sizeof(local_value)) {
*out_value = local_value;
} else {
result = ERROR_CANTREAD;
}
}
return result;
}
LONG RegKey::ReadValue(const wchar_t* name, std::wstring* out_value) const {
DCHECK(out_value);
const size_t kMaxStringLength = 1024; // This is after expansion.
// Use the one of the other forms of ReadValue if 1024 is too small for you.
wchar_t raw_value[kMaxStringLength];
DWORD type = REG_SZ, size = sizeof(raw_value);
LONG result = ReadValue(name, raw_value, &size, &type);
if (result == ERROR_SUCCESS) {
if (type == REG_SZ) {
*out_value = raw_value;
} else if (type == REG_EXPAND_SZ) {
wchar_t expanded[kMaxStringLength];
size = ExpandEnvironmentStrings(raw_value, expanded, kMaxStringLength);
// Success: returns the number of wchar_t's copied
// Fail: buffer too small, returns the size required
// Fail: other, returns 0
if (size == 0 || size > kMaxStringLength) {
result = ERROR_MORE_DATA;
} else {
*out_value = expanded;
}
} else {
// Not a string. Oops.
result = ERROR_CANTREAD;
}
}
return result;
}
LONG RegKey::ReadValue(const wchar_t* name,
void* data,
DWORD* dsize,
DWORD* dtype) const {
LONG result = RegQueryValueEx(key_, name, nullptr, dtype,
reinterpret_cast<LPBYTE>(data), dsize);
return result;
}
LONG RegKey::ReadValues(const wchar_t* name,
std::vector<std::wstring>* values) {
values->clear();
DWORD type = REG_MULTI_SZ;
DWORD size = 0;
LONG result = ReadValue(name, nullptr, &size, &type);
if (result != ERROR_SUCCESS || size == 0) {
return result;
}
if (type != REG_MULTI_SZ) {
return ERROR_CANTREAD;
}
std::vector<wchar_t> buffer(size / sizeof(wchar_t));
result = ReadValue(name, buffer.data(), &size, nullptr);
if (result != ERROR_SUCCESS || size == 0) {
return result;
}
// Parse the double-null-terminated list of strings.
// Note: This code is paranoid to not read outside of |buf|, in the case where
// it may not be properly terminated.
auto entry = buffer.cbegin();
auto buffer_end = buffer.cend();
while (entry < buffer_end && *entry != '\0') {
auto entry_end = std::find(entry, buffer_end, '\0');
values->emplace_back(entry, entry_end);
entry = entry_end + 1;
}
return 0;
}
LONG RegKey::WriteValue(const wchar_t* name, DWORD in_value) {
return WriteValue(name, &in_value, static_cast<DWORD>(sizeof(in_value)),
REG_DWORD);
}
LONG RegKey::WriteValue(const wchar_t* name, const wchar_t* in_value) {
return WriteValue(
name, in_value,
static_cast<DWORD>(sizeof(*in_value) *
(std::char_traits<wchar_t>::length(in_value) + 1)),
REG_SZ);
}
LONG RegKey::WriteValue(const wchar_t* name,
const void* data,
DWORD dsize,
DWORD dtype) {
DCHECK(data || !dsize);
LONG result =
RegSetValueEx(key_, name, 0, dtype,
reinterpret_cast<LPBYTE>(const_cast<void*>(data)), dsize);
return result;
}
bool RegKey::StartWatching(ChangeCallback callback) {
if (!key_watcher_) {
key_watcher_ = std::make_unique<Watcher>();
}
if (!key_watcher_->StartWatching(key_, std::move(callback))) {
return false;
}
return true;
}
LONG RegKey::Open(HKEY rootkey,
const wchar_t* subkey,
DWORD options,
REGSAM access) {
DCHECK(options == 0 || options == REG_OPTION_OPEN_LINK) << options;
DCHECK(rootkey && subkey && access);
HKEY subhkey = nullptr;
LONG result = RegOpenKeyEx(rootkey, subkey, options, access, &subhkey);
if (result == ERROR_SUCCESS) {
Close();
key_ = subhkey;
wow64access_ = access & kWow64AccessMask;
}
return result;
}
expected<bool, LONG> RegKey::IsLink() const {
DWORD value_type = 0;
LONG result = ::RegQueryValueEx(key_, L"SymbolicLinkValue",
/*lpReserved=*/nullptr, &value_type,
/*lpData=*/nullptr, /*lpcbData=*/nullptr);
if (result == ERROR_FILE_NOT_FOUND) {
return ok(false);
}
if (result == ERROR_SUCCESS) {
return ok(value_type == REG_LINK);
}
return unexpected(result);
}
std::optional<LONG> RegKey::DeleteIfLink() {
if (auto is_link = IsLink(); !is_link.has_value()) {
return is_link.error(); // Failed to determine if a link.
} else if (is_link.value() == false) {
return std::nullopt; // Not a link.
}
const NTSTATUS delete_result = ::NtDeleteKey(key_);
if (delete_result == STATUS_SUCCESS) {
return ERROR_SUCCESS;
}
using RtlNtStatusToDosErrorFunction = ULONG(WINAPI*)(NTSTATUS);
static const RtlNtStatusToDosErrorFunction rtl_nt_status_to_dos_error =
reinterpret_cast<RtlNtStatusToDosErrorFunction>(::GetProcAddress(
::GetModuleHandle(L"ntdll.dll"), "RtlNtStatusToDosError"));
// The most common cause of failure is the presence of subkeys, which is
// reported as `STATUS_CANNOT_DELETE` and maps to `ERROR_ACCESS_DENIED`.
return rtl_nt_status_to_dos_error
? static_cast<LONG>(rtl_nt_status_to_dos_error(delete_result))
: ERROR_ACCESS_DENIED;
}
// static
LONG RegKey::RegDelRecurse(HKEY root_key, const wchar_t* name, REGSAM access) {
// First, open the key; taking care not to traverse symbolic links.
RegKey target_key;
LONG result = target_key.Open(
root_key, name, REG_OPTION_OPEN_LINK,
access | KEY_ENUMERATE_SUB_KEYS | KEY_QUERY_VALUE | DELETE);
if (result == ERROR_FILE_NOT_FOUND) { // The key doesn't exist.
return ERROR_SUCCESS;
}
if (result != ERROR_SUCCESS) {
return result;
}
// Next, try to delete the key if it is a symbolic link.
if (auto deleted_link = target_key.DeleteIfLink(); deleted_link.has_value()) {
return deleted_link.value();
}
// It's not a symbolic link, so try to delete it without recursing.
result = ::RegDeleteKeyEx(target_key.key_, L"", access, 0);
if (result == ERROR_SUCCESS) {
return result;
}
// Enumerate the keys.
const DWORD kMaxKeyNameLength = 256; // Includes string terminator.
auto subkey_buffer = std::make_unique<wchar_t[]>(kMaxKeyNameLength);
while (true) {
DWORD key_size = kMaxKeyNameLength;
if (::RegEnumKeyEx(target_key.key_, 0, &subkey_buffer[0], &key_size,
nullptr, nullptr, nullptr, nullptr) != ERROR_SUCCESS) {
break;
}
CHECK_LT(key_size, kMaxKeyNameLength);
CHECK_EQ(subkey_buffer[key_size], L'\0');
if (RegDelRecurse(target_key.key_, &subkey_buffer[0], access) !=
ERROR_SUCCESS) {
break;
}
}
// Try again to delete the key.
return ::RegDeleteKeyEx(target_key.key_, L"", access, 0);
}
// RegistryValueIterator ------------------------------------------------------
RegistryValueIterator::RegistryValueIterator(HKEY root_key,
const wchar_t* folder_key,
REGSAM wow64access)
: name_(MAX_PATH, '\0'), value_(MAX_PATH, '\0') {
Initialize(root_key, folder_key, wow64access);
}
RegistryValueIterator::RegistryValueIterator(HKEY root_key,
const wchar_t* folder_key)
: name_(MAX_PATH, '\0'), value_(MAX_PATH, '\0') {
Initialize(root_key, folder_key, 0);
}
void RegistryValueIterator::Initialize(HKEY root_key,
const wchar_t* folder_key,
REGSAM wow64access) {
DCHECK_EQ(wow64access & ~kWow64AccessMask, static_cast<REGSAM>(0));
LONG result =
RegOpenKeyEx(root_key, folder_key, 0, KEY_READ | wow64access, &key_);
if (result != ERROR_SUCCESS) {
key_ = nullptr;
} else {
DWORD count = 0;
result =
::RegQueryInfoKey(key_, nullptr, nullptr, nullptr, nullptr, nullptr,
nullptr, &count, nullptr, nullptr, nullptr, nullptr);
if (result != ERROR_SUCCESS) {
::RegCloseKey(key_);
key_ = nullptr;
} else {
index_ = count - 1;
}
}
Read();
}
RegistryValueIterator::~RegistryValueIterator() {
if (key_)
::RegCloseKey(key_);
}
DWORD RegistryValueIterator::ValueCount() const {
DWORD count = 0;
LONG result =
::RegQueryInfoKey(key_, nullptr, nullptr, nullptr, nullptr, nullptr,
nullptr, &count, nullptr, nullptr, nullptr, nullptr);
if (result != ERROR_SUCCESS)
return 0;
return count;
}
bool RegistryValueIterator::Valid() const {
return key_ != nullptr && index_ != kInvalidIterValue;
}
void RegistryValueIterator::operator++() {
if (index_ != kInvalidIterValue)
--index_;
Read();
}
bool RegistryValueIterator::Read() {
if (Valid()) {
DWORD capacity = static_cast<DWORD>(name_.capacity());
DWORD name_size = capacity;
// |value_size_| is in bytes. Reserve the last character for a NUL.
value_size_ = static_cast<DWORD>((value_.size() - 1) * sizeof(wchar_t));
LONG result = ::RegEnumValue(
key_, index_, WriteInto(&name_, name_size), &name_size, nullptr, &type_,
reinterpret_cast<BYTE*>(value_.data()), &value_size_);
if (result == ERROR_MORE_DATA) {
// Registry key names are limited to 255 characters and fit within
// MAX_PATH (which is 260) but registry value names can use up to 16,383
// characters and the value itself is not limited
// (from http://msdn.microsoft.com/en-us/library/windows/desktop/
// ms724872(v=vs.85).aspx).
// Resize the buffers and retry if their size caused the failure.
DWORD value_size_in_wchars = to_wchar_size(value_size_);
if (value_size_in_wchars + 1 > value_.size())
value_.resize(value_size_in_wchars + 1, '\0');
value_size_ = static_cast<DWORD>((value_.size() - 1) * sizeof(wchar_t));
name_size = name_size == capacity ? MAX_REGISTRY_NAME_SIZE : capacity;
result = ::RegEnumValue(
key_, index_, WriteInto(&name_, name_size), &name_size, nullptr,
&type_, reinterpret_cast<BYTE*>(value_.data()), &value_size_);
}
if (result == ERROR_SUCCESS) {
DCHECK_LT(to_wchar_size(value_size_), value_.size());
value_[to_wchar_size(value_size_)] = '\0';
return true;
}
}
name_[0] = '\0';
value_[0] = '\0';
value_size_ = 0;
return false;
}
// RegistryKeyIterator --------------------------------------------------------
RegistryKeyIterator::RegistryKeyIterator(HKEY root_key,
const wchar_t* folder_key) {
Initialize(root_key, folder_key, 0);
}
RegistryKeyIterator::RegistryKeyIterator(HKEY root_key,
const wchar_t* folder_key,
REGSAM wow64access) {
Initialize(root_key, folder_key, wow64access);
}
RegistryKeyIterator::~RegistryKeyIterator() {
if (key_)
::RegCloseKey(key_);
}
DWORD RegistryKeyIterator::SubkeyCount() const {
DWORD count = 0;
LONG result =
::RegQueryInfoKey(key_, nullptr, nullptr, nullptr, &count, nullptr,
nullptr, nullptr, nullptr, nullptr, nullptr, nullptr);
if (result != ERROR_SUCCESS)
return 0;
return count;
}
bool RegistryKeyIterator::Valid() const {
return key_ != nullptr && index_ != kInvalidIterValue;
}
void RegistryKeyIterator::operator++() {
if (index_ != kInvalidIterValue)
--index_;
Read();
}
bool RegistryKeyIterator::Read() {
if (Valid()) {
DWORD ncount = static_cast<DWORD>(std::size(name_));
FILETIME written;
LONG r = ::RegEnumKeyEx(key_, index_, name_, &ncount, nullptr, nullptr,
nullptr, &written);
if (ERROR_SUCCESS == r)
return true;
}
name_[0] = '\0';
return false;
}
void RegistryKeyIterator::Initialize(HKEY root_key,
const wchar_t* folder_key,
REGSAM wow64access) {
DCHECK_EQ(wow64access & ~kWow64AccessMask, static_cast<REGSAM>(0));
LONG result =
RegOpenKeyEx(root_key, folder_key, 0, KEY_READ | wow64access, &key_);
if (result != ERROR_SUCCESS) {
key_ = nullptr;
} else {
DWORD count = 0;
result =
::RegQueryInfoKey(key_, nullptr, nullptr, nullptr, &count, nullptr,
nullptr, nullptr, nullptr, nullptr, nullptr, nullptr);
if (result != ERROR_SUCCESS) {
::RegCloseKey(key_);
key_ = nullptr;
} else {
index_ = count - 1;
}
}
Read();
}
} // namespace base::win
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