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
RandomNumberGenerator(StringRef Salt)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
operator ()()58 RandomNumberGenerator::result_type RandomNumberGenerator::operator()() {
59 return Generator();
60 }
61
62 // Get random vector of specified size
getRandomBytes(void * Buffer,size_t 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 }
90