VirtualBox Disk Image: JavaScript parsing library

A native VirtualBox file format Images for testing can be downloaded from

  • https://www.osboxes.org/virtualbox-images/
  • https://virtualboxes.org/images/
  • https://virtualboximages.com/ or you can convert images of other formats.

Application

["VirtualBox", "QEMU", "VMWare Workstation"]

File extension

vdi

KS implementation details

License: GPL-3.0-or-later

References

This page hosts a formal specification of VirtualBox Disk Image using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.

Usage

Runtime library

All parsing code for JavaScript generated by Kaitai Struct depends on the JavaScript runtime library. You have to install it before you can parse data.

The JavaScript runtime library is available at npm:

npm install kaitai-struct

Code

See the usage examples in the JavaScript notes.

Parse structure from an ArrayBuffer:

var arrayBuffer = ...;
var data = new Vdi(new KaitaiStream(arrayBuffer));

After that, one can get various attributes from the structure by accessing fields or properties like:

data.blocksMap // => block_index = offset_in_virtual_disk / block_size actual_data_offset = blocks_map[block_index]*block_size+metadata_size+offset_in_block
The blocks_map will take up blocks_in_image_max * sizeof(uint32_t) bytes; since the blocks_map is read and written in a single operation, its size needs to be limited to INT_MAX; furthermore, when opening an image, the blocks_map size is rounded up to be aligned on BDRV_SECTOR_SIZE. Therefore this should satisfy the following: blocks_in_image_max * sizeof(uint32_t) + BDRV_SECTOR_SIZE == INT_MAX + 1 (INT_MAX + 1 is the first value not representable as an int) This guarantees that any value below or equal to the constant will, when multiplied by sizeof(uint32_t) and rounded up to a BDRV_SECTOR_SIZE boundary, still be below or equal to INT_MAX.

JavaScript source code to parse VirtualBox Disk Image

Vdi.js

// This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild

(function (root, factory) {
  if (typeof define === 'function' && define.amd) {
    define(['kaitai-struct/KaitaiStream'], factory);
  } else if (typeof module === 'object' && module.exports) {
    module.exports = factory(require('kaitai-struct/KaitaiStream'));
  } else {
    root.Vdi = factory(root.KaitaiStream);
  }
}(this, function (KaitaiStream) {
/**
 * A native VirtualBox file format
 * Images for testing can be downloaded from
 *  * https://www.osboxes.org/virtualbox-images/
 *  * https://virtualboxes.org/images/
 *  * https://virtualboximages.com/
 * or you can convert images of other formats.
 * @see {@link https://github.com/qemu/qemu/blob/master/block/vdi.c|Source}
 */

var Vdi = (function() {
  Vdi.ImageType = Object.freeze({
    DYNAMIC: 1,
    STATIC: 2,
    UNDO: 3,
    DIFF: 4,

    1: "DYNAMIC",
    2: "STATIC",
    3: "UNDO",
    4: "DIFF",
  });

  function Vdi(_io, _parent, _root) {
    this._io = _io;
    this._parent = _parent;
    this._root = _root || this;

    this._read();
  }
  Vdi.prototype._read = function() {
    this.header = new Header(this._io, this, this._root);
  }

  var Header = Vdi.Header = (function() {
    function Header(_io, _parent, _root) {
      this._io = _io;
      this._parent = _parent;
      this._root = _root || this;

      this._read();
    }
    Header.prototype._read = function() {
      this.text = KaitaiStream.bytesToStr(this._io.readBytes(64), "utf-8");
      this.signature = this._io.readBytes(4);
      if (!((KaitaiStream.byteArrayCompare(this.signature, [127, 16, 218, 190]) == 0))) {
        throw new KaitaiStream.ValidationNotEqualError([127, 16, 218, 190], this.signature, this._io, "/types/header/seq/1");
      }
      this.version = new Version(this._io, this, this._root);
      if (this.subheaderSizeIsDynamic) {
        this.headerSizeOptional = this._io.readU4le();
      }
      this._raw_headerMain = this._io.readBytes(this.headerSize);
      var _io__raw_headerMain = new KaitaiStream(this._raw_headerMain);
      this.headerMain = new HeaderMain(_io__raw_headerMain, this, this._root);
    }

    var Uuid = Header.Uuid = (function() {
      function Uuid(_io, _parent, _root) {
        this._io = _io;
        this._parent = _parent;
        this._root = _root || this;

        this._read();
      }
      Uuid.prototype._read = function() {
        this.uuid = this._io.readBytes(16);
      }

      return Uuid;
    })();

    var Version = Header.Version = (function() {
      function Version(_io, _parent, _root) {
        this._io = _io;
        this._parent = _parent;
        this._root = _root || this;

        this._read();
      }
      Version.prototype._read = function() {
        this.major = this._io.readU2le();
        this.minor = this._io.readU2le();
      }

      return Version;
    })();

    var HeaderMain = Header.HeaderMain = (function() {
      function HeaderMain(_io, _parent, _root) {
        this._io = _io;
        this._parent = _parent;
        this._root = _root || this;

        this._read();
      }
      HeaderMain.prototype._read = function() {
        this.imageType = this._io.readU4le();
        this.imageFlags = new Flags(this._io, this, this._root);
        this.description = KaitaiStream.bytesToStr(this._io.readBytes(256), "utf-8");
        if (this._parent.version.major >= 1) {
          this.blocksMapOffset = this._io.readU4le();
        }
        if (this._parent.version.major >= 1) {
          this.offsetData = this._io.readU4le();
        }
        this.geometry = new Geometry(this._io, this, this._root);
        if (this._parent.version.major >= 1) {
          this.reserved1 = this._io.readU4le();
        }
        this.diskSize = this._io.readU8le();
        this.blockDataSize = this._io.readU4le();
        if (this._parent.version.major >= 1) {
          this.blockMetadataSize = this._io.readU4le();
        }
        this.blocksInImage = this._io.readU4le();
        this.blocksAllocated = this._io.readU4le();
        this.uuidImage = new Uuid(this._io, this, this._root);
        this.uuidLastSnap = new Uuid(this._io, this, this._root);
        this.uuidLink = new Uuid(this._io, this, this._root);
        if (this._parent.version.major >= 1) {
          this.uuidParent = new Uuid(this._io, this, this._root);
        }
        if ( ((this._parent.version.major >= 1) && ((this._io.pos + 16) <= this._io.size)) ) {
          this.lchcGeometry = new Geometry(this._io, this, this._root);
        }
      }

      var Geometry = HeaderMain.Geometry = (function() {
        function Geometry(_io, _parent, _root) {
          this._io = _io;
          this._parent = _parent;
          this._root = _root || this;

          this._read();
        }
        Geometry.prototype._read = function() {
          this.cylinders = this._io.readU4le();
          this.heads = this._io.readU4le();
          this.sectors = this._io.readU4le();
          this.sectorSize = this._io.readU4le();
        }

        return Geometry;
      })();

      var Flags = HeaderMain.Flags = (function() {
        function Flags(_io, _parent, _root) {
          this._io = _io;
          this._parent = _parent;
          this._root = _root || this;

          this._read();
        }
        Flags.prototype._read = function() {
          this.reserved0 = this._io.readBitsIntBe(15);
          this.zeroExpand = this._io.readBitsIntBe(1) != 0;
          this.reserved1 = this._io.readBitsIntBe(6);
          this.diff = this._io.readBitsIntBe(1) != 0;
          this.fixed = this._io.readBitsIntBe(1) != 0;
          this.reserved2 = this._io.readBitsIntBe(8);
        }

        return Flags;
      })();

      /**
       * Size of block (bytes).
       */

      return HeaderMain;
    })();
    Object.defineProperty(Header.prototype, 'headerSize', {
      get: function() {
        if (this._m_headerSize !== undefined)
          return this._m_headerSize;
        this._m_headerSize = (this.subheaderSizeIsDynamic ? this.headerSizeOptional : 336);
        return this._m_headerSize;
      }
    });
    Object.defineProperty(Header.prototype, 'blocksMapOffset', {
      get: function() {
        if (this._m_blocksMapOffset !== undefined)
          return this._m_blocksMapOffset;
        this._m_blocksMapOffset = this.headerMain.blocksMapOffset;
        return this._m_blocksMapOffset;
      }
    });
    Object.defineProperty(Header.prototype, 'subheaderSizeIsDynamic', {
      get: function() {
        if (this._m_subheaderSizeIsDynamic !== undefined)
          return this._m_subheaderSizeIsDynamic;
        this._m_subheaderSizeIsDynamic = this.version.major >= 1;
        return this._m_subheaderSizeIsDynamic;
      }
    });
    Object.defineProperty(Header.prototype, 'blocksOffset', {
      get: function() {
        if (this._m_blocksOffset !== undefined)
          return this._m_blocksOffset;
        this._m_blocksOffset = this.headerMain.offsetData;
        return this._m_blocksOffset;
      }
    });
    Object.defineProperty(Header.prototype, 'blockSize', {
      get: function() {
        if (this._m_blockSize !== undefined)
          return this._m_blockSize;
        this._m_blockSize = (this.headerMain.blockMetadataSize + this.headerMain.blockDataSize);
        return this._m_blockSize;
      }
    });
    Object.defineProperty(Header.prototype, 'blocksMapSize', {
      get: function() {
        if (this._m_blocksMapSize !== undefined)
          return this._m_blocksMapSize;
        this._m_blocksMapSize = (Math.floor((((this.headerMain.blocksInImage * 4) + this.headerMain.geometry.sectorSize) - 1) / this.headerMain.geometry.sectorSize) * this.headerMain.geometry.sectorSize);
        return this._m_blocksMapSize;
      }
    });

    return Header;
  })();

  var BlocksMap = Vdi.BlocksMap = (function() {
    function BlocksMap(_io, _parent, _root) {
      this._io = _io;
      this._parent = _parent;
      this._root = _root || this;

      this._read();
    }
    BlocksMap.prototype._read = function() {
      this.index = new Array(this._root.header.headerMain.blocksInImage);
      for (var i = 0; i < this._root.header.headerMain.blocksInImage; i++) {
        this.index[i] = new BlockIndex(this._io, this, this._root);
      }
    }

    var BlockIndex = BlocksMap.BlockIndex = (function() {
      function BlockIndex(_io, _parent, _root) {
        this._io = _io;
        this._parent = _parent;
        this._root = _root || this;

        this._read();
      }
      BlockIndex.prototype._read = function() {
        this.index = this._io.readU4le();
      }
      Object.defineProperty(BlockIndex.prototype, 'isAllocated', {
        get: function() {
          if (this._m_isAllocated !== undefined)
            return this._m_isAllocated;
          this._m_isAllocated = this.index < this._root.blockDiscarded;
          return this._m_isAllocated;
        }
      });
      Object.defineProperty(BlockIndex.prototype, 'block', {
        get: function() {
          if (this._m_block !== undefined)
            return this._m_block;
          if (this.isAllocated) {
            this._m_block = this._root.disk.blocks[this.index];
          }
          return this._m_block;
        }
      });

      return BlockIndex;
    })();

    return BlocksMap;
  })();

  var Disk = Vdi.Disk = (function() {
    function Disk(_io, _parent, _root) {
      this._io = _io;
      this._parent = _parent;
      this._root = _root || this;

      this._read();
    }
    Disk.prototype._read = function() {
      this.blocks = new Array(this._root.header.headerMain.blocksInImage);
      for (var i = 0; i < this._root.header.headerMain.blocksInImage; i++) {
        this.blocks[i] = new Block(this._io, this, this._root);
      }
    }

    var Block = Disk.Block = (function() {
      function Block(_io, _parent, _root) {
        this._io = _io;
        this._parent = _parent;
        this._root = _root || this;

        this._read();
      }
      Block.prototype._read = function() {
        this.metadata = this._io.readBytes(this._root.header.headerMain.blockMetadataSize);
        this._raw_data = [];
        this.data = [];
        var i = 0;
        while (!this._io.isEof()) {
          this._raw_data.push(this._io.readBytes(this._root.header.headerMain.blockDataSize));
          var _io__raw_data = new KaitaiStream(this._raw_data[this._raw_data.length - 1]);
          this.data.push(new Sector(_io__raw_data, this, this._root));
          i++;
        }
      }

      var Sector = Block.Sector = (function() {
        function Sector(_io, _parent, _root) {
          this._io = _io;
          this._parent = _parent;
          this._root = _root || this;

          this._read();
        }
        Sector.prototype._read = function() {
          this.data = this._io.readBytes(this._root.header.headerMain.geometry.sectorSize);
        }

        return Sector;
      })();

      return Block;
    })();

    return Disk;
  })();
  Object.defineProperty(Vdi.prototype, 'blockDiscarded', {
    get: function() {
      if (this._m_blockDiscarded !== undefined)
        return this._m_blockDiscarded;
      this._m_blockDiscarded = 4294967294;
      return this._m_blockDiscarded;
    }
  });
  Object.defineProperty(Vdi.prototype, 'blockUnallocated', {
    get: function() {
      if (this._m_blockUnallocated !== undefined)
        return this._m_blockUnallocated;
      this._m_blockUnallocated = 4294967295;
      return this._m_blockUnallocated;
    }
  });

  /**
   * block_index = offset_in_virtual_disk / block_size actual_data_offset = blocks_map[block_index]*block_size+metadata_size+offset_in_block
   * The blocks_map will take up blocks_in_image_max * sizeof(uint32_t) bytes; since the blocks_map is read and written in a single operation, its size needs to be limited to INT_MAX; furthermore, when opening an image, the blocks_map size is rounded up to be aligned on BDRV_SECTOR_SIZE. Therefore this should satisfy the following: blocks_in_image_max * sizeof(uint32_t) + BDRV_SECTOR_SIZE == INT_MAX + 1 (INT_MAX + 1 is the first value not representable as an int) This guarantees that any value below or equal to the constant will, when multiplied by sizeof(uint32_t) and rounded up to a BDRV_SECTOR_SIZE boundary, still be below or equal to INT_MAX.
   */
  Object.defineProperty(Vdi.prototype, 'blocksMap', {
    get: function() {
      if (this._m_blocksMap !== undefined)
        return this._m_blocksMap;
      var _pos = this._io.pos;
      this._io.seek(this.header.blocksMapOffset);
      this._raw__m_blocksMap = this._io.readBytes(this.header.blocksMapSize);
      var _io__raw__m_blocksMap = new KaitaiStream(this._raw__m_blocksMap);
      this._m_blocksMap = new BlocksMap(_io__raw__m_blocksMap, this, this._root);
      this._io.seek(_pos);
      return this._m_blocksMap;
    }
  });
  Object.defineProperty(Vdi.prototype, 'disk', {
    get: function() {
      if (this._m_disk !== undefined)
        return this._m_disk;
      var _pos = this._io.pos;
      this._io.seek(this.header.blocksOffset);
      this._m_disk = new Disk(this._io, this, this._root);
      this._io.seek(_pos);
      return this._m_disk;
    }
  });

  return Vdi;
})();
return Vdi;
}));