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xts_encryption_layer: Implement XTSEncryptionLayer

This commit is contained in:
Zach Hilman 2018-08-16 17:01:32 -04:00
parent 10e5356e9a
commit c4845df3d4
3 changed files with 81 additions and 1 deletions

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@ -0,0 +1,54 @@
// Copyright 2018 yuzu emulator team
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.
#include <cstring>
#include "common/assert.h"
#include "core/crypto/xts_encryption_layer.h"
namespace Core::Crypto {
XTSEncryptionLayer::XTSEncryptionLayer(FileSys::VirtualFile base_, Key256 key_)
: EncryptionLayer(std::move(base_)), cipher(key_, Mode::XTS) {}
size_t XTSEncryptionLayer::Read(u8* data, size_t length, size_t offset) const {
if (length == 0)
return 0;
const auto sector_offset = offset & 0x3FFF;
if (sector_offset == 0) {
if (length % 0x4000 == 0) {
std::vector<u8> raw = base->ReadBytes(length, offset);
cipher.XTSTranscode(raw.data(), raw.size(), data, offset / 0x4000, 0x4000, Op::Decrypt);
return raw.size();
}
if (length > 0x4000) {
const auto rem = length % 0x4000;
const auto read = length - rem;
return Read(data, read, offset) + Read(data + read, rem, offset + read);
}
std::vector<u8> buffer = base->ReadBytes(0x4000, offset);
if (buffer.size() < 0x4000)
buffer.resize(0x4000);
cipher.XTSTranscode(buffer.data(), buffer.size(), buffer.data(), offset / 0x4000, 0x4000,
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() < 0x4000)
block.resize(0x4000);
cipher.XTSTranscode(block.data(), block.size(), block.data(), (offset - sector_offset) / 0x4000,
0x4000, Op::Decrypt);
const size_t read = 0x4000 - sector_offset;
if (length + sector_offset < 0x4000) {
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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@ -0,0 +1,26 @@
// Copyright 2018 yuzu emulator team
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.
#pragma once
#include <vector>
#include "core/crypto/aes_util.h"
#include "core/crypto/encryption_layer.h"
#include "core/crypto/key_manager.h"
namespace Core::Crypto {
// Sits on top of a VirtualFile and provides XTS-mode AES decription.
class XTSEncryptionLayer : public EncryptionLayer {
public:
XTSEncryptionLayer(FileSys::VirtualFile base, Key256 key);
size_t Read(u8* data, size_t length, size_t offset) const override;
private:
// Must be mutable as operations modify cipher contexts.
mutable AESCipher<Key256> cipher;
};
} // namespace Core::Crypto

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@ -178,7 +178,7 @@ VirtualFile NCA::Decrypt(NCASectionHeader s_header, VirtualFile in, u64 starting
return std::static_pointer_cast<VfsFile>(out); return std::static_pointer_cast<VfsFile>(out);
} }
case NCASectionCryptoType::XTS: case NCASectionCryptoType::XTS:
// TODO(DarkLordZach): Implement XTSEncryptionLayer. // TODO(DarkLordZach): Find a test case for XTS-encrypted NCAs
default: default:
LOG_ERROR(Crypto, "called with unhandled crypto type={:02X}", LOG_ERROR(Crypto, "called with unhandled crypto type={:02X}",
static_cast<u8>(s_header.raw.header.crypto_type)); static_cast<u8>(s_header.raw.header.crypto_type));