From c4845df3d4b9fc3fc19dd936af87090ffb3fbdf2 Mon Sep 17 00:00:00 2001 From: Zach Hilman Date: Thu, 16 Aug 2018 17:01:32 -0400 Subject: [PATCH] xts_encryption_layer: Implement XTSEncryptionLayer --- src/core/crypto/xts_encryption_layer.cpp | 54 ++++++++++++++++++++++++ src/core/crypto/xts_encryption_layer.h | 26 ++++++++++++ src/core/file_sys/content_archive.cpp | 2 +- 3 files changed, 81 insertions(+), 1 deletion(-) create mode 100644 src/core/crypto/xts_encryption_layer.cpp create mode 100644 src/core/crypto/xts_encryption_layer.h diff --git a/src/core/crypto/xts_encryption_layer.cpp b/src/core/crypto/xts_encryption_layer.cpp new file mode 100644 index 000000000..431099580 --- /dev/null +++ b/src/core/crypto/xts_encryption_layer.cpp @@ -0,0 +1,54 @@ +// Copyright 2018 yuzu emulator team +// Licensed under GPLv2 or any later version +// Refer to the license.txt file included. + +#include +#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 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 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 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(length, read)); + return std::min(length, read); + } + std::memcpy(data, block.data() + sector_offset, read); + return read + Read(data + read, length - read, offset + read); +} +} // namespace Core::Crypto diff --git a/src/core/crypto/xts_encryption_layer.h b/src/core/crypto/xts_encryption_layer.h new file mode 100644 index 000000000..1e1acaf4a --- /dev/null +++ b/src/core/crypto/xts_encryption_layer.h @@ -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 +#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 cipher; +}; + +} // namespace Core::Crypto diff --git a/src/core/file_sys/content_archive.cpp b/src/core/file_sys/content_archive.cpp index 47afcad9b..008e11d8c 100644 --- a/src/core/file_sys/content_archive.cpp +++ b/src/core/file_sys/content_archive.cpp @@ -178,7 +178,7 @@ VirtualFile NCA::Decrypt(NCASectionHeader s_header, VirtualFile in, u64 starting return std::static_pointer_cast(out); } case NCASectionCryptoType::XTS: - // TODO(DarkLordZach): Implement XTSEncryptionLayer. + // TODO(DarkLordZach): Find a test case for XTS-encrypted NCAs default: LOG_ERROR(Crypto, "called with unhandled crypto type={:02X}", static_cast(s_header.raw.header.crypto_type));