nod/lib/DiscIONFS.cpp

#include "nod/IDiscIO.hpp"
#include "nod/IFileIO.hpp"
#include "nod/Util.hpp"
#include "nod/aes.hpp"

#include <logvisor/logvisor.hpp>

#include <array>

namespace nod {

/*
 * NFS is the image format used to distribute Wii VC games for the Wii U.
 * It is an LBA format similar to WBFS but adds its own encryption layer.
 * It logically stores a standard Wii disc image with partitions.
 */

class DiscIONFS : public IDiscIO {
  struct DiscIONFSShared {
    std::vector<std::unique_ptr<IFileIO>> files;

    struct NFSHead {
      uint32_t magic; // EGGS
      uint32_t version;
      uint32_t unknown[2]; // Signature, UUID?
      uint32_t lbaRangeCount;
      struct {
        uint32_t startBlock;
        uint32_t numBlocks;
      } lbaRanges[61];
      uint32_t endMagic; // SGGE
    } nfsHead;

    uint8_t key[16];

    uint32_t calculateNumFiles() const {
      uint32_t totalBlockCount = 0;
      for (uint32_t i = 0; i < nfsHead.lbaRangeCount; ++i)
        totalBlockCount += nfsHead.lbaRanges[i].numBlocks;
      return (uint64_t(totalBlockCount) * uint64_t(0x8000) +
              (uint64_t(0x200) + uint64_t(0xF9FFFFF))) / uint64_t(0xFA00000);
    }

    struct FBO {
      uint32_t file, block, lblock, offset;
    };

    FBO logicalToFBO(uint64_t offset) const {
      auto blockAndRemBytes = std::lldiv(offset, 0x8000); /* 32768 bytes per block */
      uint32_t block = UINT32_MAX;
      for (uint32_t i = 0, physicalBlock = 0; i < nfsHead.lbaRangeCount; ++i) {
        const auto& range = nfsHead.lbaRanges[i];
        if (blockAndRemBytes.quot >= range.startBlock && blockAndRemBytes.quot - range.startBlock < range.numBlocks) {
          block = physicalBlock + (blockAndRemBytes.quot - range.startBlock);
          break;
        }
        physicalBlock += range.numBlocks;
      }
      /* This offset has no physical mapping, read zeroes */
      if (block == UINT32_MAX)
        return {UINT32_MAX, UINT32_MAX, UINT32_MAX, UINT32_MAX};
      auto fileAndRemBlocks = std::lldiv(block, 8000); /* 8000 blocks per file */
      return {uint32_t(fileAndRemBlocks.quot), uint32_t(fileAndRemBlocks.rem),
              uint32_t(blockAndRemBytes.quot), uint32_t(blockAndRemBytes.rem)};
    }

    DiscIONFSShared(SystemStringView fpin, bool& err) {
      /* Validate file path format */
      using SignedSize = std::make_signed<SystemString::size_type>::type;
      const auto dotPos = SignedSize(fpin.rfind('.'));
      const auto slashPos = SignedSize(fpin.find_last_of("/\\"));
      if (fpin.size() <= 4 || dotPos == -1 || dotPos <= slashPos ||
          fpin.compare(slashPos + 1, 4, "hif_") ||
          fpin.compare(dotPos, fpin.size() - dotPos, ".nfs")) {
        LogModule.report(logvisor::Error,
                         fmt("'{}' must begin with 'hif_' and end with '.nfs' to be accepted as an NFS image"), fpin);
        err = true;
        return;
      }

      /* Load key file */
      const SystemString dir(fpin.begin(), fpin.begin() + slashPos + 1);
      auto keyFile = NewFileIO(dir + "../code/htk.bin")->beginReadStream();
      if (!keyFile)
        keyFile = NewFileIO(dir + "htk.bin")->beginReadStream();
      if (!keyFile) {
        LogModule.report(logvisor::Error, fmt("Unable to open '{}../code/htk.bin' or '{}htk.bin'"), dir, dir);
        err = true;
        return;
      }
      if (keyFile->read(key, 16) != 16) {
        LogModule.report(logvisor::Error, fmt("Unable to read from '{}../code/htk.bin' or '{}htk.bin'"), dir, dir);
        err = true;
        return;
      }

      /* Load header from first file */
      const SystemString firstPath = fmt::format(fmt("{}hif_{:06}.nfs"), dir, 0);
      files.push_back(NewFileIO(firstPath));
      auto rs = files.back()->beginReadStream();
      if (!rs) {
        LogModule.report(logvisor::Error, fmt("'{}' does not exist"), firstPath);
        err = true;
        return;
      }
      if (rs->read(&nfsHead, 0x200) != 0x200) {
        LogModule.report(logvisor::Error, fmt("Unable to read header from '{}'"), firstPath);
        err = true;
        return;
      }
      if (std::memcmp(&nfsHead.magic, "EGGS", 4)) {
        LogModule.report(logvisor::Error, fmt("Invalid magic in '{}'"), firstPath);
        err = true;
        return;
      }
      nfsHead.lbaRangeCount = SBig(nfsHead.lbaRangeCount);
      for (uint32_t i = 0; i < nfsHead.lbaRangeCount; ++i) {
        auto& range = nfsHead.lbaRanges[i];
        range.startBlock = SBig(range.startBlock);
        range.numBlocks = SBig(range.numBlocks);
      }

      /* Ensure remaining files exist */
      const uint32_t numFiles = calculateNumFiles();
      files.reserve(numFiles);
      for (uint32_t i = 1; i < numFiles; ++i) {
        SystemString path = fmt::format(fmt("{}hif_{:06}.nfs"), dir, i);
        files.push_back(NewFileIO(path));
        if (!files.back()->exists()) {
          LogModule.report(logvisor::Error, fmt("'{}' does not exist"), path);
          err = true;
          return;
        }
      }
    }
  };
  std::shared_ptr<DiscIONFSShared> m_shared;

public:
  DiscIONFS(SystemStringView fpin, bool& err) : m_shared(std::make_shared<DiscIONFSShared>(fpin, err)) {}

  class ReadStream : public IReadStream {
    friend class DiscIONFS;
    std::shared_ptr<DiscIONFSShared> m_shared;
    std::unique_ptr<IReadStream> m_rs;
    std::unique_ptr<IAES> m_aes;

    /* Physical address - all UINT32_MAX indicates logical zero block */
    DiscIONFSShared::FBO m_physAddr;

    /* Logical address */
    uint64_t m_offset;

    /* Active file stream and its offset as set in the system.
     * Block is typically one ahead of the presently decrypted block. */
    uint32_t m_curFile = UINT32_MAX;
    uint32_t m_curBlock = UINT32_MAX;

    ReadStream(std::shared_ptr<DiscIONFSShared> shared, uint64_t offset, bool& err)
    : m_shared(std::move(shared)), m_aes(NewAES()),
      m_physAddr({UINT32_MAX, UINT32_MAX, UINT32_MAX, UINT32_MAX}), m_offset(offset) {
      m_aes->setKey(m_shared->key);
      setNewLogicalAddr(offset);
    }

    uint8_t m_encBuf[0x8000] = {};
    uint8_t m_decBuf[0x8000] = {};

    void setCurFile(uint32_t curFile) {
      if (curFile >= m_shared->files.size()) {
        LogModule.report(logvisor::Error, fmt("Out of bounds NFS file access"));
        return;
      }
      m_curFile = curFile;
      m_curBlock = UINT32_MAX;
      m_rs = m_shared->files[m_curFile]->beginReadStream();
    }

    void setCurBlock(uint32_t curBlock) {
      m_curBlock = curBlock;
      m_rs->seek(m_curBlock * 0x8000 + 0x200);
    }

    void setNewPhysicalAddr(DiscIONFSShared::FBO physAddr) {
      /* If we're just changing the offset, nothing else needs to be done */
      if (m_physAddr.file == physAddr.file && m_physAddr.block == physAddr.block) {
        m_physAddr.offset = physAddr.offset;
        return;
      }
      m_physAddr = physAddr;

      /* Set logical zero block */
      if (m_physAddr.file == UINT32_MAX) {
        memset(m_decBuf, 0, 0x8000);
        return;
      }

      /* Make necessary file and block current with system */
      if (m_physAddr.file != m_curFile)
        setCurFile(m_physAddr.file);
      if (m_physAddr.block != m_curBlock)
        setCurBlock(m_physAddr.block);

      /* Read block, handling 0x200 overlap case */
      if (m_physAddr.block == 7999) {
        m_rs->read(m_encBuf, 0x7E00);
        setCurFile(m_curFile + 1);
        m_rs->read(m_encBuf + 0x7E00, 0x200);
        m_curBlock = 0;
      } else {
        m_rs->read(m_encBuf, 0x8000);
        ++m_curBlock;
      }

      /* Decrypt */
      const uint32_t ivBuf[] = {0, 0, 0, SBig(m_physAddr.lblock)};
      m_aes->decrypt((const uint8_t*)ivBuf, m_encBuf, m_decBuf, 0x8000);
    }

    void setNewLogicalAddr(uint64_t addr) {
      setNewPhysicalAddr(m_shared->logicalToFBO(m_offset));
    }

  public:
    uint64_t read(void* buf, uint64_t length) override {
      uint64_t rem = length;
      uint8_t* dst = (uint8_t*)buf;

      /* Perform reads on block boundaries */
      while (rem) {
        uint64_t readSize = rem;
        uint32_t blockOffset = (m_physAddr.offset == UINT32_MAX) ? 0 : m_physAddr.offset;
        if (readSize + blockOffset > 0x8000)
          readSize = 0x8000 - blockOffset;

        memmove(dst, m_decBuf + blockOffset, readSize);
        dst += readSize;
        rem -= readSize;
        m_offset += readSize;
        setNewLogicalAddr(m_offset);
      }

      return dst - (uint8_t*)buf;
    }
    uint64_t position() const override { return m_offset; }
    void seek(int64_t offset, int whence) override {
      if (whence == SEEK_SET)
        m_offset = offset;
      else if (whence == SEEK_CUR)
        m_offset += offset;
      else
        return;
      setNewLogicalAddr(m_offset);
    }
  };

  std::unique_ptr<IReadStream> beginReadStream(uint64_t offset) const override {
    bool err = false;
    auto ret = std::unique_ptr<IReadStream>(new ReadStream(m_shared, offset, err));

    if (err)
      return {};

    return ret;
  }

  std::unique_ptr<IWriteStream> beginWriteStream(uint64_t offset) const override { return {}; }

  bool hasWiiCrypto() const override { return false; }
};

std::unique_ptr<IDiscIO> NewDiscIONFS(SystemStringView path) {
  bool err = false;
  auto ret = std::make_unique<DiscIONFS>(path, err);
  if (err)
    return {};
  return ret;
}

}