1 files changed, 206 insertions, 0 deletions
diff --git a/src/core/file_sys/nca_patch.cpp b/src/core/file_sys/nca_patch.cpp
new file mode 100644
index 000000000..e0111bffc
--- /dev/null
+++ b/src/core/file_sys/nca_patch.cpp
@@ -0,0 +1,206 @@
+// 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/aes_util.h"
+#include "core/file_sys/nca_patch.h"
+
+namespace FileSys {
+
+BKTR::BKTR(VirtualFile base_romfs_, VirtualFile bktr_romfs_, RelocationBlock relocation_,
+           std::vector<RelocationBucket> relocation_buckets_, SubsectionBlock subsection_,
+           std::vector<SubsectionBucket> subsection_buckets_, bool is_encrypted_,
+           Core::Crypto::Key128 key_, u64 base_offset_, u64 ivfc_offset_,
+           std::array<u8, 8> section_ctr_)
+    : base_romfs(std::move(base_romfs_)), bktr_romfs(std::move(bktr_romfs_)),
+      relocation(relocation_), relocation_buckets(std::move(relocation_buckets_)),
+      subsection(subsection_), subsection_buckets(std::move(subsection_buckets_)),
+      encrypted(is_encrypted_), key(key_), base_offset(base_offset_), ivfc_offset(ivfc_offset_),
+      section_ctr(section_ctr_) {
+    for (size_t i = 0; i < relocation.number_buckets - 1; ++i) {
+        relocation_buckets[i].entries.push_back({relocation.base_offsets[i + 1], 0, 0});
+    }
+
+    for (size_t i = 0; i < subsection.number_buckets - 1; ++i) {
+        subsection_buckets[i].entries.push_back({subsection_buckets[i + 1].entries[0].address_patch,
+                                                 {0},
+                                                 subsection_buckets[i + 1].entries[0].ctr});
+    }
+
+    relocation_buckets.back().entries.push_back({relocation.size, 0, 0});
+}
+
+BKTR::~BKTR() = default;
+
+size_t BKTR::Read(u8* data, size_t length, size_t offset) const {
+    // Read out of bounds.
+    if (offset >= relocation.size)
+        return 0;
+    const auto relocation = GetRelocationEntry(offset);
+    const auto section_offset = offset - relocation.address_patch + relocation.address_source;
+    const auto bktr_read = relocation.from_patch;
+
+    const auto next_relocation = GetNextRelocationEntry(offset);
+
+    if (offset + length > next_relocation.address_patch) {
+        const u64 partition = next_relocation.address_patch - offset;
+        return Read(data, partition, offset) +
+               Read(data + partition, length - partition, offset + partition);
+    }
+
+    if (!bktr_read) {
+        ASSERT_MSG(section_offset >= ivfc_offset, "Offset calculation negative.");
+        return base_romfs->Read(data, length, section_offset - ivfc_offset);
+    }
+
+    if (!encrypted) {
+        return bktr_romfs->Read(data, length, section_offset);
+    }
+
+    const auto subsection = GetSubsectionEntry(section_offset);
+    Core::Crypto::AESCipher<Core::Crypto::Key128> cipher(key, Core::Crypto::Mode::CTR);
+
+    // Calculate AES IV
+    std::vector<u8> iv(16);
+    auto subsection_ctr = subsection.ctr;
+    auto offset_iv = section_offset + base_offset;
+    for (size_t i = 0; i < section_ctr.size(); ++i)
+        iv[i] = section_ctr[0x8 - i - 1];
+    offset_iv >>= 4;
+    for (size_t i = 0; i < sizeof(u64); ++i) {
+        iv[0xF - i] = static_cast<u8>(offset_iv & 0xFF);
+        offset_iv >>= 8;
+    }
+    for (size_t i = 0; i < sizeof(u32); ++i) {
+        iv[0x7 - i] = static_cast<u8>(subsection_ctr & 0xFF);
+        subsection_ctr >>= 8;
+    }
+    cipher.SetIV(iv);
+
+    const auto next_subsection = GetNextSubsectionEntry(section_offset);
+
+    if (section_offset + length > next_subsection.address_patch) {
+        const u64 partition = next_subsection.address_patch - section_offset;
+        return Read(data, partition, offset) +
+               Read(data + partition, length - partition, offset + partition);
+    }
+
+    const auto block_offset = section_offset & 0xF;
+    if (block_offset != 0) {
+        auto block = bktr_romfs->ReadBytes(0x10, section_offset & ~0xF);
+        cipher.Transcode(block.data(), block.size(), block.data(), Core::Crypto::Op::Decrypt);
+        if (length + block_offset < 0x10) {
+            std::memcpy(data, block.data() + block_offset, std::min(length, block.size()));
+            return std::min(length, block.size());
+        }
+
+        const auto read = 0x10 - block_offset;
+        std::memcpy(data, block.data() + block_offset, read);
+        return read + Read(data + read, length - read, offset + read);
+    }
+
+    const auto raw_read = bktr_romfs->Read(data, length, section_offset);
+    cipher.Transcode(data, raw_read, data, Core::Crypto::Op::Decrypt);
+    return raw_read;
+}
+
+template <bool Subsection, typename BlockType, typename BucketType>
+std::pair<size_t, size_t> BKTR::SearchBucketEntry(u64 offset, BlockType block,
+                                                  BucketType buckets) const {
+    if constexpr (Subsection) {
+        const auto last_bucket = buckets[block.number_buckets - 1];
+        if (offset >= last_bucket.entries[last_bucket.number_entries].address_patch)
+            return {block.number_buckets - 1, last_bucket.number_entries};
+    } else {
+        ASSERT_MSG(offset <= block.size, "Offset is out of bounds in BKTR relocation block.");
+    }
+
+    size_t bucket_id = std::count_if(block.base_offsets.begin() + 1,
+                                     block.base_offsets.begin() + block.number_buckets,
+                                     [&offset](u64 base_offset) { return base_offset <= offset; });
+
+    const auto bucket = buckets[bucket_id];
+
+    if (bucket.number_entries == 1)
+        return {bucket_id, 0};
+
+    size_t low = 0;
+    size_t mid = 0;
+    size_t high = bucket.number_entries - 1;
+    while (low <= high) {
+        mid = (low + high) / 2;
+        if (bucket.entries[mid].address_patch > offset) {
+            high = mid - 1;
+        } else {
+            if (mid == bucket.number_entries - 1 ||
+                bucket.entries[mid + 1].address_patch > offset) {
+                return {bucket_id, mid};
+            }
+
+            low = mid + 1;
+        }
+    }
+
+    UNREACHABLE_MSG("Offset could not be found in BKTR block.");
+}
+
+RelocationEntry BKTR::GetRelocationEntry(u64 offset) const {
+    const auto res = SearchBucketEntry<false>(offset, relocation, relocation_buckets);
+    return relocation_buckets[res.first].entries[res.second];
+}
+
+RelocationEntry BKTR::GetNextRelocationEntry(u64 offset) const {
+    const auto res = SearchBucketEntry<false>(offset, relocation, relocation_buckets);
+    const auto bucket = relocation_buckets[res.first];
+    if (res.second + 1 < bucket.entries.size())
+        return bucket.entries[res.second + 1];
+    return relocation_buckets[res.first + 1].entries[0];
+}
+
+SubsectionEntry BKTR::GetSubsectionEntry(u64 offset) const {
+    const auto res = SearchBucketEntry<true>(offset, subsection, subsection_buckets);
+    return subsection_buckets[res.first].entries[res.second];
+}
+
+SubsectionEntry BKTR::GetNextSubsectionEntry(u64 offset) const {
+    const auto res = SearchBucketEntry<true>(offset, subsection, subsection_buckets);
+    const auto bucket = subsection_buckets[res.first];
+    if (res.second + 1 < bucket.entries.size())
+        return bucket.entries[res.second + 1];
+    return subsection_buckets[res.first + 1].entries[0];
+}
+
+std::string BKTR::GetName() const {
+    return base_romfs->GetName();
+}
+
+size_t BKTR::GetSize() const {
+    return relocation.size;
+}
+
+bool BKTR::Resize(size_t new_size) {
+    return false;
+}
+
+std::shared_ptr<VfsDirectory> BKTR::GetContainingDirectory() const {
+    return base_romfs->GetContainingDirectory();
+}
+
+bool BKTR::IsWritable() const {
+    return false;
+}
+
+bool BKTR::IsReadable() const {
+    return true;
+}
+
+size_t BKTR::Write(const u8* data, size_t length, size_t offset) {
+    return 0;
+}
+
+bool BKTR::Rename(std::string_view name) {
+    return base_romfs->Rename(name);
+}
+
+} // namespace FileSys