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/Error.h" 22 #include "llvm/Support/ManagedStatic.h" 23 #include "llvm/Support/raw_ostream.h" 24 #ifdef _WIN32 25 #include "llvm/Support/Windows/WindowsSupport.h" 26 #else 27 #include "Unix/Unix.h" 28 #endif 29 30 using namespace llvm; 31 32 #define DEBUG_TYPE "rng" 33 namespace { 34 struct CreateSeed { 35 static void *call() { 36 return new cl::opt<uint64_t>( 37 "rng-seed", cl::value_desc("seed"), cl::Hidden, 38 cl::desc("Seed for the random number generator"), cl::init(0)); 39 } 40 }; 41 } // namespace 42 static ManagedStatic<cl::opt<uint64_t>, CreateSeed> Seed; 43 void llvm::initRandomSeedOptions() { *Seed; } 44 45 RandomNumberGenerator::RandomNumberGenerator(StringRef Salt) { 46 LLVM_DEBUG(if (*Seed == 0) dbgs() 47 << "Warning! Using unseeded random number generator.\n"); 48 49 // Combine seed and salts using std::seed_seq. 50 // Data: Seed-low, Seed-high, Salt 51 // Note: std::seed_seq can only store 32-bit values, even though we 52 // are using a 64-bit RNG. This isn't a problem since the Mersenne 53 // twister constructor copies these correctly into its initial state. 54 std::vector<uint32_t> Data; 55 Data.resize(2 + Salt.size()); 56 Data[0] = *Seed; 57 Data[1] = *Seed >> 32; 58 59 llvm::copy(Salt, Data.begin() + 2); 60 61 std::seed_seq SeedSeq(Data.begin(), Data.end()); 62 Generator.seed(SeedSeq); 63 } 64 65 RandomNumberGenerator::result_type RandomNumberGenerator::operator()() { 66 return Generator(); 67 } 68 69 // Get random vector of specified size 70 std::error_code llvm::getRandomBytes(void *Buffer, size_t Size) { 71 #ifdef _WIN32 72 HCRYPTPROV hProvider; 73 if (CryptAcquireContext(&hProvider, 0, 0, PROV_RSA_FULL, 74 CRYPT_VERIFYCONTEXT | CRYPT_SILENT)) { 75 ScopedCryptContext ScopedHandle(hProvider); 76 if (CryptGenRandom(hProvider, Size, static_cast<BYTE *>(Buffer))) 77 return std::error_code(); 78 } 79 return std::error_code(GetLastError(), std::system_category()); 80 #else 81 int Fd = open("/dev/urandom", O_RDONLY); 82 if (Fd != -1) { 83 std::error_code Ret; 84 ssize_t BytesRead = read(Fd, Buffer, Size); 85 if (BytesRead == -1) 86 Ret = errnoAsErrorCode(); 87 else if (BytesRead != static_cast<ssize_t>(Size)) 88 Ret = std::error_code(EIO, std::system_category()); 89 if (close(Fd) == -1) 90 Ret = errnoAsErrorCode(); 91 92 return Ret; 93 } 94 return errnoAsErrorCode(); 95 #endif 96 } 97