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/feature_list.h" 12 #include "third_party/boringssl/src/include/openssl/crypto.h" 13 #include "third_party/boringssl/src/include/openssl/rand.h" 14 15 namespace base { 16 17 namespace internal { 18 19 namespace { 20 21 // The BoringSSl helpers are duplicated in rand_util_posix.cc and 22 // rand_util_win.cc. 23 std::atomic<bool> g_use_boringssl; 24 25 BASE_FEATURE(kUseBoringSSLForRandBytes, 26 "UseBoringSSLForRandBytes", 27 FEATURE_DISABLED_BY_DEFAULT); 28 29 } // namespace 30 ConfigureBoringSSLBackedRandBytesFieldTrial()31void ConfigureBoringSSLBackedRandBytesFieldTrial() { 32 g_use_boringssl.store(FeatureList::IsEnabled(kUseBoringSSLForRandBytes), 33 std::memory_order_relaxed); 34 } 35 UseBoringSSLForRandBytes()36bool UseBoringSSLForRandBytes() { 37 return g_use_boringssl.load(std::memory_order_relaxed); 38 } 39 40 } // namespace internal 41 RandBytes(void * output,size_t output_length)42void RandBytes(void* output, size_t output_length) { 43 if (internal::UseBoringSSLForRandBytes()) { 44 // Ensure BoringSSL is initialized so it can use things like RDRAND. 45 CRYPTO_library_init(); 46 // BoringSSL's RAND_bytes always returns 1. Any error aborts the program. 47 (void)RAND_bytes(static_cast<uint8_t*>(output), output_length); 48 return; 49 } 50 51 zx_cprng_draw(output, output_length); 52 } 53 54 namespace internal { 55 RandDoubleAvoidAllocation()56double RandDoubleAvoidAllocation() { 57 uint64_t number; 58 zx_cprng_draw(&number, sizeof(number)); 59 // This transformation is explained in rand_util.cc. 60 return (number >> 11) * 0x1.0p-53; 61 } 62 63 } // namespace internal 64 65 } // namespace base 66