57 lines
1.9 KiB
C++
57 lines
1.9 KiB
C++
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// 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 "common/assert.h"
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#include "core/crypto/ctr_encryption_layer.h"
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namespace 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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if (raw.size() != length)
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return Read(data, raw.size(), offset);
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cipher.Transcode(raw.data(), length, 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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memcpy_s(data, length, block.data() + sector_offset, std::min<u64>(length, read));
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return read;
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}
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memcpy_s(data, length, 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(std::vector<u8> iv_) {
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const auto length = std::min<size_t>(iv_.size(), iv.size());
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for (size_t i = 0; i < length; ++i)
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iv[i] = iv_[i];
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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 Crypto
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