ladybird/Kernel/Random.h
Hendiadyoin1 0d934fc991 Kernel::CPU: Move headers into common directory
Alot of code is shared between i386/i686/x86 and x86_64
and a lot probably will be used for compatability modes.
So we start by moving the headers into one Directory.
We will probalby be able to move some cpp files aswell.
2021-03-21 09:35:23 +01:00

216 lines
6.1 KiB
C++

/*
* 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/x86/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 = typename CipherT::BlockType;
using HashType = HashT;
using DigestType = typename HashT::DigestType;
FortunaPRNG()
: m_counter(ByteBuffer::create_zeroed(BlockType::block_size()))
{
}
bool get_random_bytes(u8* buffer, size_t n)
{
ScopedSpinLock lock(m_lock);
if (!is_ready())
return false;
if (m_p0_len >= reseed_threshold) {
this->reseed();
}
VERIFY(is_seeded());
// FIXME: More than 2^20 bytes cannot be generated without refreshing the key.
VERIFY(n < (1 << 20));
typename CipherType::CTRMode cipher(m_key, KeySize, Crypto::Cipher::Intent::Encryption);
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);
return true;
}
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));
}
[[nodiscard]] bool is_seeded() const
{
return m_reseed_number > 0;
}
[[nodiscard]] bool is_ready() const
{
VERIFY(m_lock.is_locked());
return is_seeded() || m_p0_len >= reseed_threshold;
}
SpinLock<u8>& get_lock() { return m_lock; }
private:
void reseed()
{
HashType new_key;
new_key.update(m_key);
for (size_t i = 0; i < pool_count; ++i) {
if (m_reseed_number % (1u << 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];
SpinLock<u8> m_lock;
};
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();
SpinLock<u8>& get_lock() { return resource().get_lock(); }
private:
WaitQueue m_seed_queue;
};
class EntropySource {
template<typename T>
struct Event {
u64 timestamp;
size_t source;
T event_data;
};
public:
enum class Static : size_t {
Interrupts,
MaxHardcodedSourceIndex,
};
EntropySource()
: m_source(next_source++)
{
}
EntropySource(Static hardcoded_source)
: m_source(static_cast<size_t>(hardcoded_source))
{
}
template<typename T>
void add_random_event(const T& event_data)
{
auto& kernel_rng = KernelRng::the();
ScopedSpinLock lock(kernel_rng.get_lock());
// 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 };
kernel_rng.resource().add_random_event(event, m_pool);
m_pool++;
kernel_rng.wake_if_ready();
}
private:
static size_t next_source;
size_t m_pool { 0 };
size_t m_source;
};
// 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);
bool get_good_random_bytes(u8*, size_t, bool allow_wait = true, bool fallback_to_fast = true);
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;
}
}