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// Copyright 2017 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 <zircon/syscalls.h>
#include <atomic>
#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_posix.cc and
// rand_util_win.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
void RandBytes(void* output, size_t output_length) {
if (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;
}
zx_cprng_draw(output, output_length);
}
namespace internal {
double RandDoubleAvoidAllocation() {
uint64_t number;
zx_cprng_draw(&number, sizeof(number));
// This transformation is explained in rand_util.cc.
return (number >> 11) * 0x1.0p-53;
}
} // namespace internal
} // namespace base
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