1 files changed, 112 insertions, 0 deletions
diff --git a/src/core/file_sys/fssystem/fssystem_aes_xts_storage.cpp b/src/core/file_sys/fssystem/fssystem_aes_xts_storage.cpp
new file mode 100644
index 000000000..022424229
--- /dev/null
+++ b/src/core/file_sys/fssystem/fssystem_aes_xts_storage.cpp
@@ -0,0 +1,112 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "common/alignment.h"
+#include "common/swap.h"
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fssystem/fssystem_aes_xts_storage.h"
+#include "core/file_sys/fssystem/fssystem_pooled_buffer.h"
+#include "core/file_sys/fssystem/fssystem_utility.h"
+
+namespace FileSys {
+
+void AesXtsStorage::MakeAesXtsIv(void* dst, size_t dst_size, s64 offset, size_t block_size) {
+    ASSERT(dst != nullptr);
+    ASSERT(dst_size == IvSize);
+    ASSERT(offset >= 0);
+
+    const uintptr_t out_addr = reinterpret_cast<uintptr_t>(dst);
+
+    *reinterpret_cast<s64_be*>(out_addr + sizeof(s64)) = offset / block_size;
+}
+
+AesXtsStorage::AesXtsStorage(VirtualFile base, const void* key1, const void* key2, size_t key_size,
+                             const void* iv, size_t iv_size, size_t block_size)
+    : m_base_storage(std::move(base)), m_block_size(block_size), m_mutex() {
+    ASSERT(m_base_storage != nullptr);
+    ASSERT(key1 != nullptr);
+    ASSERT(key2 != nullptr);
+    ASSERT(iv != nullptr);
+    ASSERT(key_size == KeySize);
+    ASSERT(iv_size == IvSize);
+    ASSERT(Common::IsAligned(m_block_size, AesBlockSize));
+
+    std::memcpy(m_key.data() + 0, key1, KeySize);
+    std::memcpy(m_key.data() + 0x10, key2, KeySize);
+    std::memcpy(m_iv.data(), iv, IvSize);
+
+    m_cipher.emplace(m_key, Core::Crypto::Mode::XTS);
+}
+
+size_t AesXtsStorage::Read(u8* buffer, size_t size, size_t offset) const {
+    // Allow zero-size reads.
+    if (size == 0) {
+        return size;
+    }
+
+    // Ensure buffer is valid.
+    ASSERT(buffer != nullptr);
+
+    // We can only read at block aligned offsets.
+    ASSERT(Common::IsAligned(offset, AesBlockSize));
+    ASSERT(Common::IsAligned(size, AesBlockSize));
+
+    // Read the data.
+    m_base_storage->Read(buffer, size, offset);
+
+    // Setup the counter.
+    std::array<u8, IvSize> ctr;
+    std::memcpy(ctr.data(), m_iv.data(), IvSize);
+    AddCounter(ctr.data(), IvSize, offset / m_block_size);
+
+    // Handle any unaligned data before the start.
+    size_t processed_size = 0;
+    if ((offset % m_block_size) != 0) {
+        // Determine the size of the pre-data read.
+        const size_t skip_size =
+            static_cast<size_t>(offset - Common::AlignDown(offset, m_block_size));
+        const size_t data_size = std::min(size, m_block_size - skip_size);
+
+        // Decrypt into a pooled buffer.
+        {
+            PooledBuffer tmp_buf(m_block_size, m_block_size);
+            ASSERT(tmp_buf.GetSize() >= m_block_size);
+
+            std::memset(tmp_buf.GetBuffer(), 0, skip_size);
+            std::memcpy(tmp_buf.GetBuffer() + skip_size, buffer, data_size);
+
+            m_cipher->SetIV(ctr);
+            m_cipher->Transcode(tmp_buf.GetBuffer(), m_block_size, tmp_buf.GetBuffer(),
+                                Core::Crypto::Op::Decrypt);
+
+            std::memcpy(buffer, tmp_buf.GetBuffer() + skip_size, data_size);
+        }
+
+        AddCounter(ctr.data(), IvSize, 1);
+        processed_size += data_size;
+        ASSERT(processed_size == std::min(size, m_block_size - skip_size));
+    }
+
+    // Decrypt aligned chunks.
+    char* cur = reinterpret_cast<char*>(buffer) + processed_size;
+    size_t remaining = size - processed_size;
+    while (remaining > 0) {
+        const size_t cur_size = std::min(m_block_size, remaining);
+
+        m_cipher->SetIV(ctr);
+        m_cipher->Transcode(cur, cur_size, cur, Core::Crypto::Op::Decrypt);
+
+        remaining -= cur_size;
+        cur += cur_size;
+
+        AddCounter(ctr.data(), IvSize, 1);
+    }
+
+    return size;
+}
+
+size_t AesXtsStorage::GetSize() const {
+    return m_base_storage->GetSize();
+}
+
+} // namespace FileSys