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Kernel: Replace existing random implementation with Fortuna

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Peter Elliott 2020-06-22 20:23:35 -06:00 • committed by Andreas Kling
parent f2d51f13a6
commit 0f32155fa4
3 changed files with 49 additions and 30 deletions
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26
Kernel/Random.h
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@ -1,6 +1,6 @@
/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2020, Peter Elliott <pelliott@ualberta.ca
* Copyright (c) 2020, Peter Elliott <pelliott@ualberta.ca>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@ -32,11 +32,14 @@
#include <AK/Types.h>
#include <Kernel/StdLib.h>
#include <LibCrypto/Cipher/Cipher.h>
#include <LibCrypto/Cipher/AES.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;
@ -45,7 +48,6 @@ class FortunaPRNG {
using HashType = HashT;
using DigestType = HashT::DigestType;
public:
void get_random_bytes(u8* buffer, size_t n)
{
if (m_p0_len >= reseed_threshold) {
@ -57,7 +59,7 @@ public:
// FIXME: More than 2^20 bytes cannot be generated without refreshing the key.
ASSERT(n < (1 << 20));
CipherType cipher(m_key, m_key.size());
CipherType cipher(m_key, KeySize);
size_t block_size = CipherType::BlockSizeInBits / 8;
@ -67,9 +69,10 @@ public:
// Extract a new key from the prng stream.
for (size_t i = 0; i < KeySize; i += block_size) {
for (size_t i = 0; i < KeySize/8; i += block_size) {
this->generate_block(cipher, &(m_key[i]), min(block_size, KeySize - i));
}
}
template<typename T>
@ -79,13 +82,14 @@ public:
if (pool == 0) {
m_p0_len++;
}
m_pools[pool].update(reinterpret_cast<u8*>(&event_data), sizeof(T));
m_pools[pool].update(reinterpret_cast<const u8*>(&event_data), sizeof(T));
}
private:
void generate_block(CipherType cipher, u8* buffer, size_t size)
{
BlockType input((u8*)m_counter, sizeof(m_counter));
BlockType input((u8*)&m_counter, sizeof(m_counter));
BlockType output;
cipher.encrypt_block(input, output);
m_counter++;
@ -119,6 +123,16 @@ private:
HashType m_pools[pool_count];
};
class KernelRng : public FortunaPRNG<Crypto::Cipher::AESCipher, Crypto::Hash::SHA256, 256> {
AK_MAKE_ETERNAL;
public:
static KernelRng& the();
private:
KernelRng();
};
// NOTE: These API's are primarily about expressing intent/needs in the calling code.
// We don't make any guarantees about actual fastness or goodness yet.