mirror of
https://github.com/SerenityOS/serenity
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195 lines
5.4 KiB
C++
195 lines
5.4 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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* Copyright (c) 2020, Peter Elliott <pelliott@ualberta.ca>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include <AK/Assertions.h>
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#include <AK/ByteBuffer.h>
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#include <AK/Types.h>
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#include <Kernel/Arch/i386/CPU.h>
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#include <Kernel/Lock.h>
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#include <Kernel/StdLib.h>
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#include <LibCrypto/Cipher/AES.h>
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#include <LibCrypto/Cipher/Cipher.h>
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#include <LibCrypto/Hash/SHA2.h>
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namespace Kernel {
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template<typename CipherT, typename HashT, int KeySize>
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class FortunaPRNG {
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public:
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constexpr static size_t pool_count = 32;
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constexpr static size_t reseed_threshold = 16;
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using CipherType = CipherT;
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using BlockType = CipherT::BlockType;
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using HashType = HashT;
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using DigestType = HashT::DigestType;
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FortunaPRNG()
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: m_counter(ByteBuffer::create_zeroed(BlockType::block_size()))
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{
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}
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void get_random_bytes(u8* buffer, size_t n)
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{
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if (m_p0_len >= reseed_threshold) {
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this->reseed();
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}
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ASSERT(is_seeded());
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// FIXME: More than 2^20 bytes cannot be generated without refreshing the key.
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ASSERT(n < (1 << 20));
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typename CipherType::CTRMode cipher(m_key, KeySize, Crypto::Cipher::Intent::Encryption);
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Bytes buffer_span { buffer, n };
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auto counter_span = m_counter.bytes();
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cipher.key_stream(buffer_span, counter_span, &counter_span);
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// Extract a new key from the prng stream.
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Bytes key_span = m_key.bytes();
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cipher.key_stream(key_span, counter_span, &counter_span);
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}
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template<typename T>
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void add_random_event(const T& event_data, size_t pool)
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{
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pool %= pool_count;
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if (pool == 0) {
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m_p0_len++;
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}
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m_pools[pool].update(reinterpret_cast<const u8*>(&event_data), sizeof(T));
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}
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bool is_seeded() const
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{
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return m_reseed_number > 0;
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}
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bool is_ready() const
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{
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return is_seeded() || m_p0_len >= reseed_threshold;
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}
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private:
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void reseed()
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{
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HashType new_key;
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new_key.update(m_key);
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for (size_t i = 0; i < pool_count; ++i) {
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if (m_reseed_number % (1 << i) == 0) {
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DigestType digest = m_pools[i].digest();
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new_key.update(digest.immutable_data(), digest.data_length());
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}
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}
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DigestType digest = new_key.digest();
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m_key = ByteBuffer::copy(digest.immutable_data(),
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digest.data_length());
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m_reseed_number++;
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m_p0_len = 0;
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}
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ByteBuffer m_counter;
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size_t m_reseed_number { 0 };
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size_t m_p0_len { 0 };
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ByteBuffer m_key;
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HashType m_pools[pool_count];
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};
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class KernelRng : public Lockable<FortunaPRNG<Crypto::Cipher::AESCipher, Crypto::Hash::SHA256, 256>> {
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AK_MAKE_ETERNAL;
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public:
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KernelRng();
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static KernelRng& the();
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void wait_for_entropy();
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void wake_if_ready();
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private:
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WaitQueue m_seed_queue;
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};
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class EntropySource {
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template<typename T>
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struct Event {
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u64 timestamp;
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size_t source;
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T event_data;
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};
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public:
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EntropySource()
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: m_source(next_source++)
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{
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}
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template<typename T>
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void add_random_event(const T& event_data)
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{
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// We don't lock this because on the off chance a pool is corrupted, entropy isn't lost.
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Event<T> event = { read_tsc(), m_source, event_data };
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KernelRng::the().resource().add_random_event(event, m_pool);
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m_pool++;
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KernelRng::the().wake_if_ready();
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}
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private:
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static size_t next_source;
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size_t m_pool { 0 };
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size_t m_source;
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Lock m_lock;
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};
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// NOTE: These API's are primarily about expressing intent/needs in the calling code.
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// The only difference is that get_fast_random is guaranteed not to block.
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void get_fast_random_bytes(u8*, size_t);
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void get_good_random_bytes(u8*, size_t);
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template<typename T>
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inline T get_fast_random()
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{
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T value;
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get_fast_random_bytes(reinterpret_cast<u8*>(&value), sizeof(T));
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return value;
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}
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template<typename T>
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inline T get_good_random()
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{
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T value;
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get_good_random_bytes(reinterpret_cast<u8*>(&value), sizeof(T));
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return value;
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}
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}
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