Implement BKTR backing

Allows reading patched RomFs
strato-emu · Aug 12, 2023 · 494ef35 · 494ef35
1 parent b092b56
commit 494ef35
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diff --git a/app/CMakeLists.txt b/app/CMakeLists.txt
@@ -265,6 +265,9 @@ add_library(skyline SHARED
         ${source_DIR}/skyline/vfs/npdm.cpp
         ${source_DIR}/skyline/vfs/nca.cpp
         ${source_DIR}/skyline/vfs/ticket.cpp
+        ${source_DIR}/skyline/vfs/cnmt.cpp
+        ${source_DIR}/skyline/vfs/bktr.cpp
+        ${source_DIR}/skyline/vfs/patch_manager.cpp
         ${source_DIR}/skyline/services/serviceman.cpp
         ${source_DIR}/skyline/services/base_service.cpp
         ${source_DIR}/skyline/services/sm/IUserInterface.cpp

diff --git a/app/src/main/cpp/skyline/vfs/bktr.cpp b/app/src/main/cpp/skyline/vfs/bktr.cpp
@@ -0,0 +1,227 @@
+// SPDX-License-Identifier: MPL-2.0
+// Copyright © 2024 Strato Team and Contributors (https://github.com/strato-emu/)
+
+#include "bktr.h"
+#include "region_backing.h"
+
+namespace skyline::vfs {
+    template <typename BlockType, typename BucketType>
+    std::pair<u64, u64> SearchBucketEntry(u64 offset, const BlockType &block, const BucketType &buckets, bool isSubsection) {
+        if (isSubsection) {
+            const auto &lastBucket{buckets[block.numberBuckets - 1]};
+            if (offset >= lastBucket.entries[lastBucket.numberEntries].addressPatch) {
+                return {block.numberBuckets - 1, lastBucket.numberEntries};
+            }
+        }
+
+        u64 bucketId{static_cast<u64>(std::distance(block.baseOffsets.begin(),
+                                                    std::upper_bound(block.baseOffsets.begin() + 1,
+                                                                     block.baseOffsets.begin() + block.numberBuckets, offset)) - 1)};
+
+        const auto &bucket{buckets[bucketId]};
+
+        if (bucket.numberEntries == 1)
+            return {bucketId, 0};
+
+        auto entryIt{std::upper_bound(bucket.entries.begin(), bucket.entries.begin() + bucket.numberEntries, offset, [](u64 offset, const auto& entry) {
+            return offset < entry.addressPatch;
+        })};
+
+        if (entryIt != bucket.entries.begin()) {
+            u64 entryIndex{static_cast<u64>(std::distance(bucket.entries.begin(), entryIt) - 1)};
+            return {bucketId, entryIndex};
+        }
+        Logger::Error("Offset could not be found.");
+        return {0, 0};
+    }
+
+    BKTR::BKTR(std::shared_ptr<vfs::Backing> pBaseRomfs, std::shared_ptr<vfs::Backing> pBktrRomfs, RelocationBlock pRelocation,
+               std::vector<RelocationBucket> pRelocationBuckets, SubsectionBlock pSubsection,
+               std::vector<SubsectionBucket> pSubsectionBuckets, bool pIsEncrypted, std::array<u8, 16> pKey,
+               u64 pBaseOffset, u64 pIvfcOffset, std::array<u8, 8> pSectionCtr)
+               : baseRomFs(std::move(pBaseRomfs)), bktrRomFs(std::move(pBktrRomfs)),
+                 relocation(pRelocation), relocationBuckets(std::move(pRelocationBuckets)),
+                 subsection(pSubsection), subsectionBuckets(std::move(pSubsectionBuckets)),
+                 isEncrypted(pIsEncrypted), key(pKey), baseOffset(pBaseOffset), ivfcOffset(pIvfcOffset),
+                 sectionCtr(pSectionCtr) {
+
+        for (std::size_t i = 0; i < relocation.numberBuckets - 1; ++i)
+            relocationBuckets[i].entries.push_back({relocation.baseOffsets[i + 1], 0, 0});
+
+        for (std::size_t i = 0; i < subsection.numberBuckets - 1; ++i)
+            subsectionBuckets[i].entries.push_back({subsectionBuckets[i + 1].entries[0].addressPatch, {0}, subsectionBuckets[i + 1].entries[0].ctr});
+
+        relocationBuckets.back().entries.push_back({relocation.size, 0, 0});
+    }
+
+    size_t BKTR::ReadImpl(span<u8> output, size_t offset) {
+        if (offset >= relocation.size)
+            return 0;
+
+        const auto relocationEntry{GetRelocationEntry(offset)};
+        const auto sectionOffset{offset - relocationEntry.addressPatch + relocationEntry.addressSource};
+
+        const auto nextRelocation{GetNextRelocationEntry(offset)};
+
+       if (offset + output.size() > nextRelocation.addressPatch) {
+           const u64 partition{nextRelocation.addressPatch - offset};
+           span<u8> data(output.data() + partition, output.size() - partition);
+           return ReadWithPartition(data, output.size() - partition, offset + partition) + ReadWithPartition(output, partition, offset);
+       }
+
+       if (!relocationEntry.fromPatch) {
+           auto regionBacking{std::make_shared<RegionBacking>(baseRomFs, sectionOffset - ivfcOffset, output.size())};
+           return regionBacking->Read(output);
+       }
+
+        if (!isEncrypted)
+            return bktrRomFs->Read(output, sectionOffset);
+
+        const auto subsectionEntry{GetSubsectionEntry(sectionOffset)};
+
+        crypto::AesCipher cipher(key, MBEDTLS_CIPHER_AES_128_CTR);
+        cipher.SetIV(GetCipherIV(subsectionEntry, sectionOffset));
+
+        const auto nextSubsection{GetNextSubsectionEntry(sectionOffset)};
+
+        if (sectionOffset + output.size() > nextSubsection.addressPatch) {
+            const u64 partition{nextSubsection.addressPatch - sectionOffset};
+            span<u8> data(output.data() + partition, output.size() - partition);
+            return ReadWithPartition(data, output.size() - partition, offset + partition) +
+                ReadWithPartition(output, partition, offset);
+        }
+
+        const auto blockOffset{sectionOffset & 0xF};
+        if (blockOffset != 0) {
+            std::vector<u8> block(0x10);
+            auto regionBacking{std::make_shared<RegionBacking>(bktrRomFs, sectionOffset & static_cast<u32>(~0xF), 0x10)};
+            regionBacking->Read(block);
+
+            cipher.Decrypt(block.data(), block.data(), block.size());
+            if (output.size() + blockOffset < 0x10) {
+                std::memcpy(output.data(), block.data() + blockOffset, std::min(output.size(), block.size()));
+                return std::min(output.size(), block.size());
+            }
+
+            const auto read{0x10 - blockOffset};
+            std::memcpy(output.data(), block.data() + blockOffset, read);
+            span<u8> data(output.data() + read, output.size() - read);
+            return read + ReadWithPartition(data, output.size() - read, offset + read);
+        }
+
+        auto regionBacking{std::make_shared<RegionBacking>(bktrRomFs, sectionOffset, output.size())};
+        auto readSize{regionBacking->Read(output)};
+        cipher.Decrypt(output.data(), output.data(), readSize);
+        return readSize;
+    }
+
+    size_t BKTR::ReadWithPartition(span<u8> output, size_t length, size_t offset) {
+        if (offset >= relocation.size)
+            return 0;
+
+        const auto relocationEntry{GetRelocationEntry(offset)};
+        const auto sectionOffset{offset - relocationEntry.addressPatch + relocationEntry.addressSource};
+
+        const auto nextRelocation{GetNextRelocationEntry(offset)};
+
+        if (offset + length > nextRelocation.addressPatch) {
+            const u64 partition{nextRelocation.addressPatch - offset};
+            span<u8> data(output.data() + partition, length - partition);
+            return ReadWithPartition(data, length - partition, offset + partition) + ReadWithPartition(output, partition, offset);
+        }
+
+       if (!relocationEntry.fromPatch) {
+           span<u8> data(output.data(), length);
+           auto regionBacking{std::make_shared<RegionBacking>(baseRomFs, sectionOffset - ivfcOffset, length)};
+           return regionBacking->Read(data);
+       }
+
+       if (!isEncrypted)
+           return bktrRomFs->Read(output, sectionOffset);
+
+        const auto subsectionEntry{GetSubsectionEntry(sectionOffset)};
+
+        crypto::AesCipher cipher(key, MBEDTLS_CIPHER_AES_128_CTR);
+        cipher.SetIV(GetCipherIV(subsectionEntry, sectionOffset));
+
+        const auto nextSubsection{GetNextSubsectionEntry(sectionOffset)};
+
+        if (sectionOffset + length > nextSubsection.addressPatch) {
+            const u64 partition{nextSubsection.addressPatch - sectionOffset};
+            span<u8> data(output.data() + partition, length - partition);
+            return ReadWithPartition(data, length - partition, offset + partition) +
+                ReadWithPartition(output, partition, offset);
+        }
+
+        const auto blockOffset{sectionOffset & 0xF};
+        if (blockOffset != 0) {
+            std::vector<u8> block(0x10);
+            auto regionBacking{std::make_shared<RegionBacking>(bktrRomFs, sectionOffset & static_cast<u32>(~0xF), 0x10)};
+            regionBacking->Read(block);
+
+            cipher.Decrypt(block.data(), block.data(), block.size());
+            if (length + blockOffset < 0x10) {
+                std::memcpy(output.data(), block.data() + blockOffset, std::min(length, block.size()));
+                return std::min(length, block.size());
+            }
+
+            const auto read{0x10 - blockOffset};
+            std::memcpy(output.data(), block.data() + blockOffset, read);
+            span<u8> data(output.data() + read, length - read);
+            return read + ReadWithPartition(data, length - read, offset + read);
+        }
+
+        auto regionBacking{std::make_shared<RegionBacking>(bktrRomFs, sectionOffset, length)};
+        span<u8> data(output.data(), length);
+        size_t readSize{0};
+        if (length)
+            readSize = regionBacking->Read(data);
+        cipher.Decrypt(data.data(), data.data(), readSize);
+        return readSize;
+    }
+
+    SubsectionEntry BKTR::GetNextSubsectionEntry(u64 offset) {
+        const auto entry{SearchBucketEntry(offset, subsection, subsectionBuckets, true)};
+        const auto bucket{subsectionBuckets[entry.first]};
+        if (entry.second + 1 < bucket.entries.size())
+            return bucket.entries[entry.second + 1];
+        return subsectionBuckets[entry.first + 1].entries[0];
+    }
+
+    RelocationEntry BKTR::GetRelocationEntry(u64 offset) {
+        const auto entry{SearchBucketEntry(offset, relocation, relocationBuckets, false)};
+        return relocationBuckets[entry.first].entries[entry.second];
+    }
+
+    SubsectionEntry BKTR::GetSubsectionEntry(u64 offset) {
+        const auto entry{SearchBucketEntry(offset, subsection, subsectionBuckets, true)};
+        return subsectionBuckets[entry.first].entries[entry.second];
+    }
+
+    RelocationEntry BKTR::GetNextRelocationEntry(u64 offset) {
+        const auto entry{SearchBucketEntry(offset, relocation, relocationBuckets, false)};
+        const auto bucket{relocationBuckets[entry.first]};
+        if (entry.second + 1 < bucket.entries.size())
+            return bucket.entries[entry.second + 1];
+        return relocationBuckets[entry.first + 1].entries[0];
+    }
+
+    std::array<u8, 16> BKTR::GetCipherIV(SubsectionEntry subsectionEntry, u64 sectionOffset) {
+        std::array<u8, 16> iv{};
+        auto subsectionCtr{subsectionEntry.ctr};
+        auto offset_iv{sectionOffset + baseOffset};
+        for (std::size_t i = 0; i < sectionCtr.size(); ++i) {
+            iv[i] = sectionCtr[0x8 - i - 1];
+        }
+        offset_iv >>= 4;
+        for (std::size_t i = 0; i < sizeof(u64); ++i) {
+            iv[0xF - i] = static_cast<u8>(offset_iv & 0xFF);
+            offset_iv >>= 8;
+        }
+        for (std::size_t i = 0; i < sizeof(u32); ++i) {
+            iv[0x7 - i] = static_cast<u8>(subsectionCtr & 0xFF);
+            subsectionCtr >>= 8;
+        }
+        return iv;
+    }
+}
diff --git a/app/src/main/cpp/skyline/vfs/bktr.h b/app/src/main/cpp/skyline/vfs/bktr.h
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: MPL-2.0
+// Copyright © 2024 Strato Team and Contributors (https://github.com/strato-emu/)
+
+#pragma once
+
+#include "filesystem.h"
+#include "nca.h"
+
+namespace skyline::vfs {
+
+    /**
+     * @brief Allows reading patched RomFs
+     * @url https://switchbrew.org/wiki/NCA#RomFs_Patching
+     */
+    class BKTR : public Backing {
+      private:
+        std::shared_ptr<vfs::Backing> baseRomFs;
+        std::shared_ptr<vfs::Backing> bktrRomFs;
+        RelocationBlock relocation;
+        SubsectionBlock subsection;
+        std::vector<RelocationBucket> relocationBuckets;
+        std::vector<SubsectionBucket> subsectionBuckets;
+        bool isEncrypted;
+        u64 baseOffset;
+        u64 ivfcOffset;
+        std::array<u8, 8> sectionCtr;
+        std::array<u8, 16> key;
+
+        SubsectionEntry GetNextSubsectionEntry(u64 offset);
+
+        RelocationEntry GetRelocationEntry(u64 offset);
+
+        RelocationEntry GetNextRelocationEntry(u64 offset);
+
+        SubsectionEntry GetSubsectionEntry(u64 offset);
+
+        std::array<u8, 16> GetCipherIV(SubsectionEntry subsectionEntry, u64 sectionOffset);
+
+      public:
+
+        BKTR(std::shared_ptr<vfs::Backing> pBaseRomfs, std::shared_ptr<vfs::Backing> pBktrRomfs, RelocationBlock pRelocation,
+             std::vector<RelocationBucket> pRelocationBuckets, SubsectionBlock pSubsection,
+             std::vector<SubsectionBucket> pSubsectionBuckets, bool pIsEncrypted, std::array<u8, 16> pKey,
+             u64 pBaseOffset, u64 pIvfcOffset, std::array<u8, 8> pSectionCtr);
+
+        size_t ReadImpl(span<u8> output, size_t offset) override;
+        size_t ReadWithPartition(span<u8> output, size_t length, size_t offset);
+    };
+}