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