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// 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/rand_util.h"
#include <windows.h>
#include <stddef.h>
#include <stdint.h>
// #define needed to link in RtlGenRandom(), a.k.a. SystemFunction036. See the
// "Community Additions" comment on MSDN here:
// http://msdn.microsoft.com/en-us/library/windows/desktop/aa387694.aspx
#define SystemFunction036 NTAPI SystemFunction036
#include <NTSecAPI.h>
#undef SystemFunction036
#include <algorithm>
#include <atomic>
#include <limits>
#include "base/check.h"
#include "base/feature_list.h"
#include "third_party/boringssl/src/include/openssl/crypto.h"
#include "third_party/boringssl/src/include/openssl/rand.h"
namespace base {
namespace internal {
namespace {
// The BoringSSl helpers are duplicated in rand_util_fuchsia.cc and
// rand_util_posix.cc.
std::atomic<bool> g_use_boringssl;
BASE_FEATURE(kUseBoringSSLForRandBytes,
"UseBoringSSLForRandBytes",
FEATURE_DISABLED_BY_DEFAULT);
} // namespace
void ConfigureBoringSSLBackedRandBytesFieldTrial() {
g_use_boringssl.store(FeatureList::IsEnabled(kUseBoringSSLForRandBytes),
std::memory_order_relaxed);
}
bool UseBoringSSLForRandBytes() {
return g_use_boringssl.load(std::memory_order_relaxed);
}
} // namespace internal
namespace {
void RandBytes(void* output, size_t output_length, bool avoid_allocation) {
if (!avoid_allocation && internal::UseBoringSSLForRandBytes()) {
// Ensure BoringSSL is initialized so it can use things like RDRAND.
CRYPTO_library_init();
// BoringSSL's RAND_bytes always returns 1. Any error aborts the program.
(void)RAND_bytes(static_cast<uint8_t*>(output), output_length);
return;
}
char* output_ptr = static_cast<char*>(output);
while (output_length > 0) {
const ULONG output_bytes_this_pass = static_cast<ULONG>(std::min(
output_length, static_cast<size_t>(std::numeric_limits<ULONG>::max())));
const bool success =
RtlGenRandom(output_ptr, output_bytes_this_pass) != FALSE;
CHECK(success);
output_length -= output_bytes_this_pass;
output_ptr += output_bytes_this_pass;
}
}
} // namespace
void RandBytes(void* output, size_t output_length) {
RandBytes(output, output_length, /*avoid_allocation=*/false);
}
namespace internal {
double RandDoubleAvoidAllocation() {
uint64_t number;
RandBytes(&number, sizeof(number), /*avoid_allocation=*/true);
// This transformation is explained in rand_util.cc.
return (number >> 11) * 0x1.0p-53;
}
} // namespace internal
} // namespace base
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