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