lib/Support/RandomNumberGenerator.cpp

   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 }