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-rw-r--r--src/core/crypto/ctr_encryption_layer.cpp56
1 files changed, 56 insertions, 0 deletions
diff --git a/src/core/crypto/ctr_encryption_layer.cpp b/src/core/crypto/ctr_encryption_layer.cpp
new file mode 100644
index 000000000..8799496e2
--- /dev/null
+++ b/src/core/crypto/ctr_encryption_layer.cpp
@@ -0,0 +1,56 @@
+// Copyright 2018 yuzu emulator team
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include "common/assert.h"
+#include "core/crypto/ctr_encryption_layer.h"
+
+namespace Crypto {
+CTREncryptionLayer::CTREncryptionLayer(FileSys::VirtualFile base_, Key128 key_, size_t base_offset)
+ : EncryptionLayer(std::move(base_)), base_offset(base_offset), cipher(key_, Mode::CTR),
+ iv(16, 0) {}
+
+size_t CTREncryptionLayer::Read(u8* data, size_t length, size_t offset) const {
+ if (length == 0)
+ return 0;
+
+ const auto sector_offset = offset & 0xF;
+ if (sector_offset == 0) {
+ UpdateIV(base_offset + offset);
+ std::vector<u8> raw = base->ReadBytes(length, offset);
+ if (raw.size() != length)
+ return Read(data, raw.size(), offset);
+ cipher.Transcode(raw.data(), length, data, Op::DECRYPT);
+ return length;
+ }
+
+ // offset does not fall on block boundary (0x10)
+ std::vector<u8> block = base->ReadBytes(0x10, offset - sector_offset);
+ UpdateIV(base_offset + offset - sector_offset);
+ cipher.Transcode(block.data(), block.size(), block.data(), Op::DECRYPT);
+ size_t read = 0x10 - sector_offset;
+
+ if (length + sector_offset < 0x10) {
+ memcpy_s(data, length, block.data() + sector_offset, std::min<u64>(length, read));
+ return read;
+ }
+
+ memcpy_s(data, length, block.data() + sector_offset, read);
+ return read + Read(data + read, length - read, offset + read);
+}
+
+void CTREncryptionLayer::SetIV(std::vector<u8> iv_) {
+ const auto length = std::min<size_t>(iv_.size(), iv.size());
+ for (size_t i = 0; i < length; ++i)
+ iv[i] = iv_[i];
+}
+
+void CTREncryptionLayer::UpdateIV(size_t offset) const {
+ offset >>= 4;
+ for (size_t i = 0; i < 8; ++i) {
+ iv[16 - i - 1] = offset & 0xFF;
+ offset >>= 8;
+ }
+ cipher.SetIV(iv);
+}
+} // namespace Crypto