55 lines
1.8 KiB
C++
55 lines
1.8 KiB
C++
// Copyright 2018 yuzu emulator team
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// Licensed under GPLv2 or any later version
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// Refer to the license.txt file included.
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#include <cstring>
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#include "common/assert.h"
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#include "core/crypto/ctr_encryption_layer.h"
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namespace Core::Crypto {
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CTREncryptionLayer::CTREncryptionLayer(FileSys::VirtualFile base_, Key128 key_, size_t base_offset)
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: EncryptionLayer(std::move(base_)), base_offset(base_offset), cipher(key_, Mode::CTR),
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iv(16, 0) {}
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size_t CTREncryptionLayer::Read(u8* data, size_t length, size_t offset) const {
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if (length == 0)
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return 0;
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const auto sector_offset = offset & 0xF;
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if (sector_offset == 0) {
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UpdateIV(base_offset + offset);
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std::vector<u8> raw = base->ReadBytes(length, offset);
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cipher.Transcode(raw.data(), raw.size(), data, Op::Decrypt);
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return length;
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}
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// offset does not fall on block boundary (0x10)
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std::vector<u8> block = base->ReadBytes(0x10, offset - sector_offset);
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UpdateIV(base_offset + offset - sector_offset);
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cipher.Transcode(block.data(), block.size(), block.data(), Op::Decrypt);
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size_t read = 0x10 - sector_offset;
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if (length + sector_offset < 0x10) {
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std::memcpy(data, block.data() + sector_offset, std::min<u64>(length, read));
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return std::min<u64>(length, read);
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}
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std::memcpy(data, block.data() + sector_offset, read);
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return read + Read(data + read, length - read, offset + read);
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}
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void CTREncryptionLayer::SetIV(const std::vector<u8>& iv_) {
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const auto length = std::min(iv_.size(), iv.size());
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iv.assign(iv_.cbegin(), iv_.cbegin() + length);
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}
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void CTREncryptionLayer::UpdateIV(size_t offset) const {
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offset >>= 4;
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for (size_t i = 0; i < 8; ++i) {
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iv[16 - i - 1] = offset & 0xFF;
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offset >>= 8;
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}
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cipher.SetIV(iv);
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}
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} // namespace Core::Crypto
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