97 lines · cpp
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-exception6//7//===----------------------------------------------------------------------===//8//9// This file implements deterministic random number generation (RNG).10// The current implementation is NOT cryptographically secure as it uses11// 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 _WIN3225#include "llvm/Support/Windows/WindowsSupport.h"26#else27#include "Unix/Unix.h"28#endif29 30using namespace llvm;31 32#define DEBUG_TYPE "rng"33namespace {34struct 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} // namespace42static ManagedStatic<cl::opt<uint64_t>, CreateSeed> Seed;43void llvm::initRandomSeedOptions() { *Seed; }44 45RandomNumberGenerator::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, Salt51 // Note: std::seed_seq can only store 32-bit values, even though we52 // are using a 64-bit RNG. This isn't a problem since the Mersenne53 // 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 65RandomNumberGenerator::result_type RandomNumberGenerator::operator()() {66 return Generator();67}68 69// Get random vector of specified size70std::error_code llvm::getRandomBytes(void *Buffer, size_t Size) {71#ifdef _WIN3272 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#else81 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#endif96}97