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/*
* Copyright (c) 2020, Ali Mohammad Pur <mpfard@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/ByteBuffer.h>
#include <AK/Span.h>
#include <AK/StdLibExtras.h>
#include <LibCrypto/Cipher/Cipher.h>
namespace Crypto {
namespace Cipher {
template<typename T>
class Mode {
public:
virtual ~Mode() { }
virtual void encrypt(ReadonlyBytes in, Bytes& out, ReadonlyBytes ivec = {}, Bytes* ivec_out = nullptr) = 0;
virtual void decrypt(ReadonlyBytes in, Bytes& out, ReadonlyBytes ivec = {}) = 0;
virtual size_t IV_length() const = 0;
const T& cipher() const { return m_cipher; }
Optional<ByteBuffer> create_aligned_buffer(size_t input_size) const
{
size_t remainder = (input_size + T::block_size()) % T::block_size();
if (remainder == 0)
return ByteBuffer::create_uninitialized(input_size);
else
return ByteBuffer::create_uninitialized(input_size + T::block_size() - remainder);
}
virtual String class_name() const = 0;
T& cipher() { return m_cipher; }
protected:
virtual void prune_padding(Bytes& data)
{
auto size = data.size();
switch (m_cipher.padding_mode()) {
case PaddingMode::CMS: {
auto maybe_padding_length = data[size - 1];
if (maybe_padding_length >= T::block_size()) {
// cannot be padding (the entire block cannot be padding)
return;
}
for (auto i = size - maybe_padding_length; i < size; ++i) {
if (data[i] != maybe_padding_length) {
// not padding, part of data
return;
}
}
data = data.slice(0, size - maybe_padding_length);
break;
}
case PaddingMode::RFC5246: {
auto maybe_padding_length = data[size - 1];
// FIXME: If we want constant-time operations, this loop should not stop
for (auto i = size - maybe_padding_length - 1; i < size; ++i) {
if (data[i] != maybe_padding_length) {
// note that this is likely invalid padding
return;
}
}
data = data.slice(0, size - maybe_padding_length - 1);
break;
}
case PaddingMode::Null: {
while (data[size - 1] == 0)
--size;
data = data.slice(0, size);
break;
}
default:
// FIXME: support other padding modes
VERIFY_NOT_REACHED();
break;
}
}
// FIXME: Somehow add a reference version of this
template<typename... Args>
Mode(Args... args)
: m_cipher(args...)
{
}
private:
T m_cipher;
};
}
}
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