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- /*
- * Copyright 2011-present Facebook, Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
- #include <folly/Random.h>
- #include <array>
- #include <atomic>
- #include <mutex>
- #include <random>
- #include <folly/File.h>
- #include <folly/FileUtil.h>
- #include <folly/SingletonThreadLocal.h>
- #include <folly/ThreadLocal.h>
- #include <folly/portability/SysTime.h>
- #include <folly/portability/Unistd.h>
- #include <folly/synchronization/CallOnce.h>
- #include <glog/logging.h>
- #ifdef _MSC_VER
- #include <wincrypt.h> // @manual
- #endif
- namespace folly {
- namespace {
- void readRandomDevice(void* data, size_t size) {
- #ifdef _MSC_VER
- static folly::once_flag flag;
- static HCRYPTPROV cryptoProv;
- folly::call_once(flag, [&] {
- if (!CryptAcquireContext(
- &cryptoProv,
- nullptr,
- nullptr,
- PROV_RSA_FULL,
- CRYPT_VERIFYCONTEXT)) {
- if (GetLastError() == NTE_BAD_KEYSET) {
- // Mostly likely cause of this is that no key container
- // exists yet, so try to create one.
- PCHECK(CryptAcquireContext(
- &cryptoProv, nullptr, nullptr, PROV_RSA_FULL, CRYPT_NEWKEYSET));
- } else {
- LOG(FATAL) << "Failed to acquire the default crypto context.";
- }
- }
- });
- CHECK(size <= std::numeric_limits<DWORD>::max());
- PCHECK(CryptGenRandom(cryptoProv, (DWORD)size, (BYTE*)data));
- #else
- // Keep the random device open for the duration of the program.
- static int randomFd = ::open("/dev/urandom", O_RDONLY | O_CLOEXEC);
- PCHECK(randomFd >= 0);
- auto bytesRead = readFull(randomFd, data, size);
- PCHECK(bytesRead >= 0 && size_t(bytesRead) == size);
- #endif
- }
- class BufferedRandomDevice {
- public:
- static once_flag flag;
- static constexpr size_t kDefaultBufferSize = 128;
- static void notifyNewGlobalEpoch() {
- globalEpoch_.fetch_add(1, std::memory_order_relaxed);
- }
- explicit BufferedRandomDevice(size_t bufferSize = kDefaultBufferSize);
- void get(void* data, size_t size) {
- auto const globalEpoch = globalEpoch_.load(std::memory_order_relaxed);
- if (LIKELY(globalEpoch == epoch_ && size <= remaining())) {
- memcpy(data, ptr_, size);
- ptr_ += size;
- } else {
- getSlow(static_cast<unsigned char*>(data), size);
- }
- }
- private:
- void getSlow(unsigned char* data, size_t size);
- inline size_t remaining() const {
- return size_t(buffer_.get() + bufferSize_ - ptr_);
- }
- static std::atomic<size_t> globalEpoch_;
- size_t epoch_{size_t(-1)}; // refill on first use
- const size_t bufferSize_;
- std::unique_ptr<unsigned char[]> buffer_;
- unsigned char* ptr_;
- };
- once_flag BufferedRandomDevice::flag;
- std::atomic<size_t> BufferedRandomDevice::globalEpoch_{0};
- struct RandomTag {};
- BufferedRandomDevice::BufferedRandomDevice(size_t bufferSize)
- : bufferSize_(bufferSize),
- buffer_(new unsigned char[bufferSize]),
- ptr_(buffer_.get() + bufferSize) { // refill on first use
- call_once(flag, [this]() {
- detail::AtFork::registerHandler(
- this,
- /*prepare*/ []() { return true; },
- /*parent*/ []() {},
- /*child*/
- []() {
- // Ensure child and parent do not share same entropy pool.
- BufferedRandomDevice::notifyNewGlobalEpoch();
- });
- });
- }
- void BufferedRandomDevice::getSlow(unsigned char* data, size_t size) {
- auto const globalEpoch = globalEpoch_.load(std::memory_order_relaxed);
- if (globalEpoch != epoch_) {
- epoch_ = globalEpoch_;
- ptr_ = buffer_.get() + bufferSize_;
- }
- DCHECK_GT(size, remaining());
- if (size >= bufferSize_) {
- // Just read directly.
- readRandomDevice(data, size);
- return;
- }
- size_t copied = remaining();
- memcpy(data, ptr_, copied);
- data += copied;
- size -= copied;
- // refill
- readRandomDevice(buffer_.get(), bufferSize_);
- ptr_ = buffer_.get();
- memcpy(data, ptr_, size);
- ptr_ += size;
- }
- } // namespace
- void Random::secureRandom(void* data, size_t size) {
- using Single = SingletonThreadLocal<BufferedRandomDevice, RandomTag>;
- Single::get().get(data, size);
- }
- ThreadLocalPRNG::result_type ThreadLocalPRNG::operator()() {
- struct Wrapper {
- Random::DefaultGenerator object{Random::create()};
- };
- using Single = SingletonThreadLocal<Wrapper, RandomTag>;
- return Single::get().object();
- }
- } // namespace folly
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