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