1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
|
/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2020, Peter Elliott <pelliott@ualberta.ca>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include <AK/Assertions.h>
#include <AK/ByteBuffer.h>
#include <AK/Types.h>
#include <Kernel/Arch/i386/CPU.h>
#include <Kernel/Lock.h>
#include <Kernel/StdLib.h>
#include <LibCrypto/Cipher/AES.h>
#include <LibCrypto/Cipher/Cipher.h>
#include <LibCrypto/Hash/SHA2.h>
namespace Kernel {
template<typename CipherT, typename HashT, int KeySize>
class FortunaPRNG {
public:
constexpr static size_t pool_count = 32;
constexpr static size_t reseed_threshold = 16;
using CipherType = CipherT;
using BlockType = CipherT::BlockType;
using HashType = HashT;
using DigestType = HashT::DigestType;
FortunaPRNG()
: m_counter(ByteBuffer::create_zeroed(BlockType::block_size()))
{
}
void get_random_bytes(u8* buffer, size_t n)
{
if (m_p0_len >= reseed_threshold) {
this->reseed();
}
ASSERT(is_seeded());
// FIXME: More than 2^20 bytes cannot be generated without refreshing the key.
ASSERT(n < (1 << 20));
typename CipherType::CTRMode cipher(m_key, KeySize);
Bytes buffer_span { buffer, n };
auto counter_span = m_counter.bytes();
cipher.key_stream(buffer_span, counter_span, &counter_span);
// Extract a new key from the prng stream.
Bytes key_span = m_key.bytes();
cipher.key_stream(key_span, counter_span, &counter_span);
}
template<typename T>
void add_random_event(const T& event_data, size_t pool)
{
pool %= pool_count;
if (pool == 0) {
m_p0_len++;
}
m_pools[pool].update(reinterpret_cast<const u8*>(&event_data), sizeof(T));
}
bool is_seeded() const
{
return m_reseed_number > 0;
}
bool is_ready() const
{
return is_seeded() || m_p0_len >= reseed_threshold;
}
private:
void reseed()
{
HashType new_key;
new_key.update(m_key);
for (size_t i = 0; i < pool_count; ++i) {
if (m_reseed_number % (1 << i) == 0) {
DigestType digest = m_pools[i].digest();
new_key.update(digest.immutable_data(), digest.data_length());
}
}
DigestType digest = new_key.digest();
m_key = ByteBuffer::copy(digest.immutable_data(),
digest.data_length());
m_reseed_number++;
m_p0_len = 0;
}
ByteBuffer m_counter;
size_t m_reseed_number { 0 };
size_t m_p0_len { 0 };
ByteBuffer m_key;
HashType m_pools[pool_count];
};
class KernelRng : public Lockable<FortunaPRNG<Crypto::Cipher::AESCipher, Crypto::Hash::SHA256, 256>> {
AK_MAKE_ETERNAL;
public:
KernelRng();
static KernelRng& the();
void wait_for_entropy();
void wake_if_ready();
private:
WaitQueue m_seed_queue;
};
class EntropySource {
template<typename T>
struct Event {
u64 timestamp;
size_t source;
T event_data;
};
public:
EntropySource()
: m_source(next_source++)
{
}
template<typename T>
void add_random_event(const T& event_data)
{
// We don't lock this because on the off chance a pool is corrupted, entropy isn't lost.
Event<T> event = { read_tsc(), m_source, event_data };
KernelRng::the().resource().add_random_event(event, m_pool);
m_pool++;
KernelRng::the().wake_if_ready();
}
private:
static size_t next_source;
size_t m_pool { 0 };
size_t m_source;
Lock m_lock;
};
// NOTE: These API's are primarily about expressing intent/needs in the calling code.
// The only difference is that get_fast_random is guaranteed not to block.
void get_fast_random_bytes(u8*, size_t);
void get_good_random_bytes(u8*, size_t);
template<typename T>
inline T get_fast_random()
{
T value;
get_fast_random_bytes(reinterpret_cast<u8*>(&value), sizeof(T));
return value;
}
template<typename T>
inline T get_good_random()
{
T value;
get_good_random_bytes(reinterpret_cast<u8*>(&value), sizeof(T));
return value;
}
}
|
