1 // Copyright 2017 The Chromium Authors 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #include "base/rand_util.h" 6 7 #include <zircon/syscalls.h> 8 9 #include <atomic> 10 11 #include "base/containers/span.h" 12 #include "base/feature_list.h" 13 #include "third_party/boringssl/src/include/openssl/crypto.h" 14 #include "third_party/boringssl/src/include/openssl/rand.h" 15 16 namespace base { 17 18 namespace internal { 19 20 namespace { 21 22 // The BoringSSl helpers are duplicated in rand_util_posix.cc and 23 // rand_util_win.cc. 24 std::atomic<bool> g_use_boringssl; 25 26 BASE_FEATURE(kUseBoringSSLForRandBytes, 27 "UseBoringSSLForRandBytes", 28 FEATURE_DISABLED_BY_DEFAULT); 29 30 } // namespace 31 ConfigureBoringSSLBackedRandBytesFieldTrial()32void ConfigureBoringSSLBackedRandBytesFieldTrial() { 33 g_use_boringssl.store(FeatureList::IsEnabled(kUseBoringSSLForRandBytes), 34 std::memory_order_relaxed); 35 } 36 UseBoringSSLForRandBytes()37bool UseBoringSSLForRandBytes() { 38 return g_use_boringssl.load(std::memory_order_relaxed); 39 } 40 41 } // namespace internal 42 RandBytes(span<uint8_t> output)43void RandBytes(span<uint8_t> output) { 44 if (internal::UseBoringSSLForRandBytes()) { 45 // Ensure BoringSSL is initialized so it can use things like RDRAND. 46 CRYPTO_library_init(); 47 // BoringSSL's RAND_bytes always returns 1. Any error aborts the program. 48 (void)RAND_bytes(output.data(), output.size()); 49 return; 50 } 51 52 zx_cprng_draw(output.data(), output.size()); 53 } 54 RandBytes(void * output,size_t output_length)55void RandBytes(void* output, size_t output_length) { 56 RandBytes(make_span(static_cast<uint8_t*>(output), output_length)); 57 } 58 59 namespace internal { 60 RandDoubleAvoidAllocation()61double RandDoubleAvoidAllocation() { 62 uint64_t number; 63 zx_cprng_draw(&number, sizeof(number)); 64 // This transformation is explained in rand_util.cc. 65 return (number >> 11) * 0x1.0p-53; 66 } 67 68 } // namespace internal 69 70 } // namespace base 71