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// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later
#include <algorithm>
#include <cstring>
#include "core/crypto/xts_encryption_layer.h"
namespace Core::Crypto {
constexpr u64 XTS_SECTOR_SIZE = 0x4000;
XTSEncryptionLayer::XTSEncryptionLayer(FileSys::VirtualFile base_, Key256 key_)
: EncryptionLayer(std::move(base_)), cipher(key_, Mode::XTS) {}
std::size_t XTSEncryptionLayer::Read(u8* data, std::size_t length, std::size_t offset) const {
if (length == 0)
return 0;
const auto sector_offset = offset & 0x3FFF;
if (sector_offset == 0) {
if (length % XTS_SECTOR_SIZE == 0) {
std::vector<u8> raw = base->ReadBytes(length, offset);
cipher.XTSTranscode(raw.data(), raw.size(), data, offset / XTS_SECTOR_SIZE,
XTS_SECTOR_SIZE, Op::Decrypt);
return raw.size();
}
if (length > XTS_SECTOR_SIZE) {
const auto rem = length % XTS_SECTOR_SIZE;
const auto read = length - rem;
return Read(data, read, offset) + Read(data + read, rem, offset + read);
}
std::vector<u8> buffer = base->ReadBytes(XTS_SECTOR_SIZE, offset);
if (buffer.size() < XTS_SECTOR_SIZE)
buffer.resize(XTS_SECTOR_SIZE);
cipher.XTSTranscode(buffer.data(), buffer.size(), buffer.data(), offset / XTS_SECTOR_SIZE,
XTS_SECTOR_SIZE, Op::Decrypt);
std::memcpy(data, buffer.data(), std::min(buffer.size(), length));
return std::min(buffer.size(), length);
}
// offset does not fall on block boundary (0x4000)
std::vector<u8> block = base->ReadBytes(0x4000, offset - sector_offset);
if (block.size() < XTS_SECTOR_SIZE)
block.resize(XTS_SECTOR_SIZE);
cipher.XTSTranscode(block.data(), block.size(), block.data(),
(offset - sector_offset) / XTS_SECTOR_SIZE, XTS_SECTOR_SIZE, Op::Decrypt);
const std::size_t read = XTS_SECTOR_SIZE - sector_offset;
if (length + sector_offset < XTS_SECTOR_SIZE) {
std::memcpy(data, block.data() + sector_offset, std::min<u64>(length, read));
return std::min<u64>(length, read);
}
std::memcpy(data, block.data() + sector_offset, read);
return read + Read(data + read, length - read, offset + read);
}
} // namespace Core::Crypto
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