1 //===-- RandomNumberGenerator.cpp - Implement RNG class -------------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file implements deterministic random number generation (RNG). 11 // The current implementation is NOT cryptographically secure as it uses 12 // the C++11 <random> facilities. 13 // 14 //===----------------------------------------------------------------------===// 15 16 #include "llvm/Support/RandomNumberGenerator.h" 17 #include "llvm/Support/CommandLine.h" 18 #include "llvm/Support/Debug.h" 19 #include "llvm/Support/raw_ostream.h" 20 #ifdef _WIN32 21 #include "Windows/WindowsSupport.h" 22 #else 23 #include "Unix/Unix.h" 24 #endif 25 26 using namespace llvm; 27 28 #define DEBUG_TYPE "rng" 29 30 // Tracking BUG: 19665 31 // http://llvm.org/bugs/show_bug.cgi?id=19665 32 // 33 // Do not change to cl::opt<uint64_t> since this silently breaks argument parsing. 34 static cl::opt<unsigned long long> 35 Seed("rng-seed", cl::value_desc("seed"), cl::Hidden, 36 cl::desc("Seed for the random number generator"), cl::init(0)); 37 38 RandomNumberGenerator::RandomNumberGenerator(StringRef Salt) { 39 LLVM_DEBUG(if (Seed == 0) dbgs() 40 << "Warning! Using unseeded random number generator.\n"); 41 42 // Combine seed and salts using std::seed_seq. 43 // Data: Seed-low, Seed-high, Salt 44 // Note: std::seed_seq can only store 32-bit values, even though we 45 // are using a 64-bit RNG. This isn't a problem since the Mersenne 46 // twister constructor copies these correctly into its initial state. 47 std::vector<uint32_t> Data; 48 Data.resize(2 + Salt.size()); 49 Data[0] = Seed; 50 Data[1] = Seed >> 32; 51 52 std::copy(Salt.begin(), Salt.end(), Data.begin() + 2); 53 54 std::seed_seq SeedSeq(Data.begin(), Data.end()); 55 Generator.seed(SeedSeq); 56 } 57 58 RandomNumberGenerator::result_type RandomNumberGenerator::operator()() { 59 return Generator(); 60 } 61 62 // Get random vector of specified size 63 std::error_code llvm::getRandomBytes(void *Buffer, size_t Size) { 64 #ifdef _WIN32 65 HCRYPTPROV hProvider; 66 if (CryptAcquireContext(&hProvider, 0, 0, PROV_RSA_FULL, 67 CRYPT_VERIFYCONTEXT | CRYPT_SILENT)) { 68 ScopedCryptContext ScopedHandle(hProvider); 69 if (CryptGenRandom(hProvider, Size, static_cast<BYTE *>(Buffer))) 70 return std::error_code(); 71 } 72 return std::error_code(GetLastError(), std::system_category()); 73 #else 74 int Fd = open("/dev/urandom", O_RDONLY); 75 if (Fd != -1) { 76 std::error_code Ret; 77 ssize_t BytesRead = read(Fd, Buffer, Size); 78 if (BytesRead == -1) 79 Ret = std::error_code(errno, std::system_category()); 80 else if (BytesRead != static_cast<ssize_t>(Size)) 81 Ret = std::error_code(EIO, std::system_category()); 82 if (close(Fd) == -1) 83 Ret = std::error_code(errno, std::system_category()); 84 85 return Ret; 86 } 87 return std::error_code(errno, std::system_category()); 88 #endif 89 } 90