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/Error.h"
22 #include "llvm/Support/ManagedStatic.h"
23 #include "llvm/Support/raw_ostream.h"
24 #ifdef _WIN32
25 #include "llvm/Support/Windows/WindowsSupport.h"
26 #else
27 #include "Unix/Unix.h"
28 #endif
29
30 using namespace llvm;
31
32 #define DEBUG_TYPE "rng"
33 namespace {
34 struct CreateSeed {
call__anon028ecb4d0111::CreateSeed35 static void *call() {
36 return new cl::opt<uint64_t>(
37 "rng-seed", cl::value_desc("seed"), cl::Hidden,
38 cl::desc("Seed for the random number generator"), cl::init(0));
39 }
40 };
41 } // namespace
42 static ManagedStatic<cl::opt<uint64_t>, CreateSeed> Seed;
initRandomSeedOptions()43 void llvm::initRandomSeedOptions() { *Seed; }
44
RandomNumberGenerator(StringRef Salt)45 RandomNumberGenerator::RandomNumberGenerator(StringRef Salt) {
46 LLVM_DEBUG(if (*Seed == 0) dbgs()
47 << "Warning! Using unseeded random number generator.\n");
48
49 // Combine seed and salts using std::seed_seq.
50 // Data: Seed-low, Seed-high, Salt
51 // Note: std::seed_seq can only store 32-bit values, even though we
52 // are using a 64-bit RNG. This isn't a problem since the Mersenne
53 // twister constructor copies these correctly into its initial state.
54 std::vector<uint32_t> Data;
55 Data.resize(2 + Salt.size());
56 Data[0] = *Seed;
57 Data[1] = *Seed >> 32;
58
59 llvm::copy(Salt, Data.begin() + 2);
60
61 std::seed_seq SeedSeq(Data.begin(), Data.end());
62 Generator.seed(SeedSeq);
63 }
64
operator ()()65 RandomNumberGenerator::result_type RandomNumberGenerator::operator()() {
66 return Generator();
67 }
68
69 // Get random vector of specified size
getRandomBytes(void * Buffer,size_t Size)70 std::error_code llvm::getRandomBytes(void *Buffer, size_t Size) {
71 #ifdef _WIN32
72 HCRYPTPROV hProvider;
73 if (CryptAcquireContext(&hProvider, 0, 0, PROV_RSA_FULL,
74 CRYPT_VERIFYCONTEXT | CRYPT_SILENT)) {
75 ScopedCryptContext ScopedHandle(hProvider);
76 if (CryptGenRandom(hProvider, Size, static_cast<BYTE *>(Buffer)))
77 return std::error_code();
78 }
79 return std::error_code(GetLastError(), std::system_category());
80 #else
81 int Fd = open("/dev/urandom", O_RDONLY);
82 if (Fd != -1) {
83 std::error_code Ret;
84 ssize_t BytesRead = read(Fd, Buffer, Size);
85 if (BytesRead == -1)
86 Ret = errnoAsErrorCode();
87 else if (BytesRead != static_cast<ssize_t>(Size))
88 Ret = std::error_code(EIO, std::system_category());
89 if (close(Fd) == -1)
90 Ret = errnoAsErrorCode();
91
92 return Ret;
93 }
94 return errnoAsErrorCode();
95 #endif
96 }
97