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
30using namespace llvm;
31
32#define DEBUG_TYPE "rng"
33namespace {
34struct CreateSeed {
35 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(Val: 0));
39 }
40};
41} // namespace
42static ManagedStatic<cl::opt<uint64_t>, CreateSeed> Seed;
43void llvm::initRandomSeedOptions() { *Seed; }
44
45RandomNumberGenerator::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(new_size: 2 + Salt.size());
56 Data[0] = *Seed;
57 Data[1] = *Seed >> 32;
58
59 llvm::copy(Range&: Salt, Out: Data.begin() + 2);
60
61 std::seed_seq SeedSeq(Data.begin(), Data.end());
62 Generator.seed(q&: SeedSeq);
63}
64
65RandomNumberGenerator::result_type RandomNumberGenerator::operator()() {
66 return Generator();
67}
68
69// Get random vector of specified size
70std::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(file: "/dev/urandom", O_RDONLY);
82 if (Fd != -1) {
83 std::error_code Ret;
84 ssize_t BytesRead = read(fd: Fd, buf: Buffer, nbytes: 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: Fd) == -1)
90 Ret = errnoAsErrorCode();
91
92 return Ret;
93 }
94 return errnoAsErrorCode();
95#endif
96}
97