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