1 //===-- RandomNumberGenerator.cpp - Implement RNG class -------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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.
14 //===----------------------------------------------------------------------===//
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"
21 #include "Windows/WindowsSupport.h"
23 #include "Unix/Unix.h"
28 #define DEBUG_TYPE "rng"
30 // Tracking BUG: 19665
31 // http://llvm.org/bugs/show_bug.cgi?id=19665
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"),
36 cl::desc("Seed for the random number generator"), cl::init(0));
38 RandomNumberGenerator::RandomNumberGenerator(StringRef Salt) {
41 dbgs() << "Warning! Using unseeded random number generator.\n"
44 // Combine seed and salts using std::seed_seq.
45 // Data: Seed-low, Seed-high, Salt
46 // Note: std::seed_seq can only store 32-bit values, even though we
47 // are using a 64-bit RNG. This isn't a problem since the Mersenne
48 // twister constructor copies these correctly into its initial state.
49 std::vector<uint32_t> Data;
50 Data.resize(2 + Salt.size());
54 std::copy(Salt.begin(), Salt.end(), Data.begin() + 2);
56 std::seed_seq SeedSeq(Data.begin(), Data.end());
57 Generator.seed(SeedSeq);
60 RandomNumberGenerator::result_type RandomNumberGenerator::operator()() {
64 // Get random vector of specified size
65 std::error_code llvm::getRandomBytes(void *Buffer, size_t Size) {
68 if (CryptAcquireContext(&hProvider, 0, 0, PROV_RSA_FULL,
69 CRYPT_VERIFYCONTEXT | CRYPT_SILENT)) {
70 ScopedCryptContext ScopedHandle(hProvider);
71 if (CryptGenRandom(hProvider, Size, static_cast<BYTE *>(Buffer)))
72 return std::error_code();
74 return std::error_code(GetLastError(), std::system_category());
76 int Fd = open("/dev/urandom", O_RDONLY);
79 ssize_t BytesRead = read(Fd, Buffer, Size);
81 Ret = std::error_code(errno, std::system_category());
82 else if (BytesRead != static_cast<ssize_t>(Size))
83 Ret = std::error_code(EIO, std::system_category());
85 Ret = std::error_code(errno, std::system_category());
89 return std::error_code(errno, std::system_category());