1 //===-- RandomNumberGenerator.cpp - Implement RNG class -------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file implements deterministic random number generation (RNG). 10 // The current implementation is NOT cryptographically secure as it uses 11 // the C++11 <random> facilities. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #include "llvm/Support/RandomNumberGenerator.h" 16 17 #include "DebugOptions.h" 18 19 #include "llvm/Support/CommandLine.h" 20 #include "llvm/Support/Debug.h" 21 #include "llvm/Support/raw_ostream.h" 22 #ifdef _WIN32 23 #include "llvm/Support/Windows/WindowsSupport.h" 24 #else 25 #include "Unix/Unix.h" 26 #endif 27 28 using namespace llvm; 29 30 #define DEBUG_TYPE "rng" 31 namespace { 32 struct CreateSeed { 33 static void *call() { 34 return new cl::opt<uint64_t>( 35 "rng-seed", cl::value_desc("seed"), cl::Hidden, 36 cl::desc("Seed for the random number generator"), cl::init(0)); 37 } 38 }; 39 } // namespace 40 static ManagedStatic<cl::opt<uint64_t>, CreateSeed> Seed; 41 void llvm::initRandomSeedOptions() { *Seed; } 42 43 RandomNumberGenerator::RandomNumberGenerator(StringRef Salt) { 44 LLVM_DEBUG(if (*Seed == 0) dbgs() 45 << "Warning! Using unseeded random number generator.\n"); 46 47 // Combine seed and salts using std::seed_seq. 48 // Data: Seed-low, Seed-high, Salt 49 // Note: std::seed_seq can only store 32-bit values, even though we 50 // are using a 64-bit RNG. This isn't a problem since the Mersenne 51 // twister constructor copies these correctly into its initial state. 52 std::vector<uint32_t> Data; 53 Data.resize(2 + Salt.size()); 54 Data[0] = *Seed; 55 Data[1] = *Seed >> 32; 56 57 llvm::copy(Salt, Data.begin() + 2); 58 59 std::seed_seq SeedSeq(Data.begin(), Data.end()); 60 Generator.seed(SeedSeq); 61 } 62 63 RandomNumberGenerator::result_type RandomNumberGenerator::operator()() { 64 return Generator(); 65 } 66 67 // Get random vector of specified size 68 std::error_code llvm::getRandomBytes(void *Buffer, size_t Size) { 69 #ifdef _WIN32 70 HCRYPTPROV hProvider; 71 if (CryptAcquireContext(&hProvider, 0, 0, PROV_RSA_FULL, 72 CRYPT_VERIFYCONTEXT | CRYPT_SILENT)) { 73 ScopedCryptContext ScopedHandle(hProvider); 74 if (CryptGenRandom(hProvider, Size, static_cast<BYTE *>(Buffer))) 75 return std::error_code(); 76 } 77 return std::error_code(GetLastError(), std::system_category()); 78 #else 79 int Fd = open("/dev/urandom", O_RDONLY); 80 if (Fd != -1) { 81 std::error_code Ret; 82 ssize_t BytesRead = read(Fd, Buffer, Size); 83 if (BytesRead == -1) 84 Ret = std::error_code(errno, std::system_category()); 85 else if (BytesRead != static_cast<ssize_t>(Size)) 86 Ret = std::error_code(EIO, std::system_category()); 87 if (close(Fd) == -1) 88 Ret = std::error_code(errno, std::system_category()); 89 90 return Ret; 91 } 92 return std::error_code(errno, std::system_category()); 93 #endif 94 } 95