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95 lines
2.6 KiB
C++
95 lines
2.6 KiB
C++
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// Copyright 2012 The Chromium Authors
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "base/rand_util.h"
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#include <windows.h>
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#include <stddef.h>
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#include <stdint.h>
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// #define needed to link in RtlGenRandom(), a.k.a. SystemFunction036. See the
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// "Community Additions" comment on MSDN here:
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// http://msdn.microsoft.com/en-us/library/windows/desktop/aa387694.aspx
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#define SystemFunction036 NTAPI SystemFunction036
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#include <NTSecAPI.h>
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#undef SystemFunction036
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#include <algorithm>
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#include <atomic>
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#include <limits>
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#include "base/check.h"
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#include "base/feature_list.h"
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#include "third_party/boringssl/src/include/openssl/crypto.h"
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#include "third_party/boringssl/src/include/openssl/rand.h"
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namespace base {
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namespace internal {
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namespace {
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// The BoringSSl helpers are duplicated in rand_util_fuchsia.cc and
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// rand_util_posix.cc.
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std::atomic<bool> g_use_boringssl;
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BASE_FEATURE(kUseBoringSSLForRandBytes,
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"UseBoringSSLForRandBytes",
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FEATURE_DISABLED_BY_DEFAULT);
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} // namespace
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void ConfigureBoringSSLBackedRandBytesFieldTrial() {
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g_use_boringssl.store(FeatureList::IsEnabled(kUseBoringSSLForRandBytes),
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std::memory_order_relaxed);
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}
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bool UseBoringSSLForRandBytes() {
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return g_use_boringssl.load(std::memory_order_relaxed);
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}
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} // namespace internal
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namespace {
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void RandBytes(void* output, size_t output_length, bool avoid_allocation) {
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if (!avoid_allocation && internal::UseBoringSSLForRandBytes()) {
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// Ensure BoringSSL is initialized so it can use things like RDRAND.
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CRYPTO_library_init();
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// BoringSSL's RAND_bytes always returns 1. Any error aborts the program.
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(void)RAND_bytes(static_cast<uint8_t*>(output), output_length);
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return;
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}
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char* output_ptr = static_cast<char*>(output);
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while (output_length > 0) {
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const ULONG output_bytes_this_pass = static_cast<ULONG>(std::min(
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output_length, static_cast<size_t>(std::numeric_limits<ULONG>::max())));
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const bool success =
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RtlGenRandom(output_ptr, output_bytes_this_pass) != FALSE;
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CHECK(success);
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output_length -= output_bytes_this_pass;
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output_ptr += output_bytes_this_pass;
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}
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}
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} // namespace
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void RandBytes(void* output, size_t output_length) {
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RandBytes(output, output_length, /*avoid_allocation=*/false);
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}
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namespace internal {
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double RandDoubleAvoidAllocation() {
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uint64_t number;
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RandBytes(&number, sizeof(number), /*avoid_allocation=*/true);
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// This transformation is explained in rand_util.cc.
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return (number >> 11) * 0x1.0p-53;
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}
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} // namespace internal
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} // namespace base
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