Android Boot Image: JavaScript parsing library

File extension

img

KS implementation details

License: CC0-1.0

This page hosts a formal specification of Android Boot 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 AndroidImg(new KaitaiStream(arrayBuffer));

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

data.base // => base loading address

JavaScript source code to parse Android Boot Image

AndroidImg.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.AndroidImg = factory(root.KaitaiStream);
  }
}(this, function (KaitaiStream) {
/**
 * @see {@link https://source.android.com/devices/bootloader/boot-image-header|Source}
 */

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

    this._read();
  }
  AndroidImg.prototype._read = function() {
    this.magic = this._io.readBytes(8);
    if (!((KaitaiStream.byteArrayCompare(this.magic, [65, 78, 68, 82, 79, 73, 68, 33]) == 0))) {
      throw new KaitaiStream.ValidationNotEqualError([65, 78, 68, 82, 79, 73, 68, 33], this.magic, this._io, "/seq/0");
    }
    this.kernel = new Load(this._io, this, this._root);
    this.ramdisk = new Load(this._io, this, this._root);
    this.second = new Load(this._io, this, this._root);
    this.tagsLoad = this._io.readU4le();
    this.pageSize = this._io.readU4le();
    this.headerVersion = this._io.readU4le();
    this.osVersion = new OsVersion(this._io, this, this._root);
    this.name = KaitaiStream.bytesToStr(KaitaiStream.bytesTerminate(this._io.readBytes(16), 0, false), "ASCII");
    this.cmdline = KaitaiStream.bytesToStr(KaitaiStream.bytesTerminate(this._io.readBytes(512), 0, false), "ASCII");
    this.sha = this._io.readBytes(32);
    this.extraCmdline = KaitaiStream.bytesToStr(KaitaiStream.bytesTerminate(this._io.readBytes(1024), 0, false), "ASCII");
    if (this.headerVersion > 0) {
      this.recoveryDtbo = new SizeOffset(this._io, this, this._root);
    }
    if (this.headerVersion > 0) {
      this.bootHeaderSize = this._io.readU4le();
    }
    if (this.headerVersion > 1) {
      this.dtb = new LoadLong(this._io, this, this._root);
    }
  }

  var Load = AndroidImg.Load = (function() {
    function Load(_io, _parent, _root) {
      this._io = _io;
      this._parent = _parent;
      this._root = _root || this;

      this._read();
    }
    Load.prototype._read = function() {
      this.size = this._io.readU4le();
      this.addr = this._io.readU4le();
    }

    return Load;
  })();

  var LoadLong = AndroidImg.LoadLong = (function() {
    function LoadLong(_io, _parent, _root) {
      this._io = _io;
      this._parent = _parent;
      this._root = _root || this;

      this._read();
    }
    LoadLong.prototype._read = function() {
      this.size = this._io.readU4le();
      this.addr = this._io.readU8le();
    }

    return LoadLong;
  })();

  var SizeOffset = AndroidImg.SizeOffset = (function() {
    function SizeOffset(_io, _parent, _root) {
      this._io = _io;
      this._parent = _parent;
      this._root = _root || this;

      this._read();
    }
    SizeOffset.prototype._read = function() {
      this.size = this._io.readU4le();
      this.offset = this._io.readU8le();
    }

    return SizeOffset;
  })();

  var OsVersion = AndroidImg.OsVersion = (function() {
    function OsVersion(_io, _parent, _root) {
      this._io = _io;
      this._parent = _parent;
      this._root = _root || this;

      this._read();
    }
    OsVersion.prototype._read = function() {
      this.version = this._io.readU4le();
    }
    Object.defineProperty(OsVersion.prototype, 'month', {
      get: function() {
        if (this._m_month !== undefined)
          return this._m_month;
        this._m_month = (this.version & 15);
        return this._m_month;
      }
    });
    Object.defineProperty(OsVersion.prototype, 'patch', {
      get: function() {
        if (this._m_patch !== undefined)
          return this._m_patch;
        this._m_patch = ((this.version >>> 11) & 127);
        return this._m_patch;
      }
    });
    Object.defineProperty(OsVersion.prototype, 'year', {
      get: function() {
        if (this._m_year !== undefined)
          return this._m_year;
        this._m_year = (((this.version >>> 4) & 127) + 2000);
        return this._m_year;
      }
    });
    Object.defineProperty(OsVersion.prototype, 'major', {
      get: function() {
        if (this._m_major !== undefined)
          return this._m_major;
        this._m_major = ((this.version >>> 25) & 127);
        return this._m_major;
      }
    });
    Object.defineProperty(OsVersion.prototype, 'minor', {
      get: function() {
        if (this._m_minor !== undefined)
          return this._m_minor;
        this._m_minor = ((this.version >>> 18) & 127);
        return this._m_minor;
      }
    });

    return OsVersion;
  })();
  Object.defineProperty(AndroidImg.prototype, 'kernelImg', {
    get: function() {
      if (this._m_kernelImg !== undefined)
        return this._m_kernelImg;
      var _pos = this._io.pos;
      this._io.seek(this.pageSize);
      this._m_kernelImg = this._io.readBytes(this.kernel.size);
      this._io.seek(_pos);
      return this._m_kernelImg;
    }
  });

  /**
   * tags offset from base
   */
  Object.defineProperty(AndroidImg.prototype, 'tagsOffset', {
    get: function() {
      if (this._m_tagsOffset !== undefined)
        return this._m_tagsOffset;
      this._m_tagsOffset = (this.tagsLoad - this.base);
      return this._m_tagsOffset;
    }
  });

  /**
   * ramdisk offset from base
   */
  Object.defineProperty(AndroidImg.prototype, 'ramdiskOffset', {
    get: function() {
      if (this._m_ramdiskOffset !== undefined)
        return this._m_ramdiskOffset;
      this._m_ramdiskOffset = (this.ramdisk.addr > 0 ? (this.ramdisk.addr - this.base) : 0);
      return this._m_ramdiskOffset;
    }
  });

  /**
   * 2nd bootloader offset from base
   */
  Object.defineProperty(AndroidImg.prototype, 'secondOffset', {
    get: function() {
      if (this._m_secondOffset !== undefined)
        return this._m_secondOffset;
      this._m_secondOffset = (this.second.addr > 0 ? (this.second.addr - this.base) : 0);
      return this._m_secondOffset;
    }
  });

  /**
   * kernel offset from base
   */
  Object.defineProperty(AndroidImg.prototype, 'kernelOffset', {
    get: function() {
      if (this._m_kernelOffset !== undefined)
        return this._m_kernelOffset;
      this._m_kernelOffset = (this.kernel.addr - this.base);
      return this._m_kernelOffset;
    }
  });

  /**
   * dtb offset from base
   */
  Object.defineProperty(AndroidImg.prototype, 'dtbOffset', {
    get: function() {
      if (this._m_dtbOffset !== undefined)
        return this._m_dtbOffset;
      if (this.headerVersion > 1) {
        this._m_dtbOffset = (this.dtb.addr > 0 ? (this.dtb.addr - this.base) : 0);
      }
      return this._m_dtbOffset;
    }
  });
  Object.defineProperty(AndroidImg.prototype, 'dtbImg', {
    get: function() {
      if (this._m_dtbImg !== undefined)
        return this._m_dtbImg;
      if ( ((this.headerVersion > 1) && (this.dtb.size > 0)) ) {
        var _pos = this._io.pos;
        this._io.seek((Math.floor(((((((this.pageSize + this.kernel.size) + this.ramdisk.size) + this.second.size) + this.recoveryDtbo.size) + this.pageSize) - 1) / this.pageSize) * this.pageSize));
        this._m_dtbImg = this._io.readBytes(this.dtb.size);
        this._io.seek(_pos);
      }
      return this._m_dtbImg;
    }
  });
  Object.defineProperty(AndroidImg.prototype, 'ramdiskImg', {
    get: function() {
      if (this._m_ramdiskImg !== undefined)
        return this._m_ramdiskImg;
      if (this.ramdisk.size > 0) {
        var _pos = this._io.pos;
        this._io.seek((Math.floor((((this.pageSize + this.kernel.size) + this.pageSize) - 1) / this.pageSize) * this.pageSize));
        this._m_ramdiskImg = this._io.readBytes(this.ramdisk.size);
        this._io.seek(_pos);
      }
      return this._m_ramdiskImg;
    }
  });
  Object.defineProperty(AndroidImg.prototype, 'recoveryDtboImg', {
    get: function() {
      if (this._m_recoveryDtboImg !== undefined)
        return this._m_recoveryDtboImg;
      if ( ((this.headerVersion > 0) && (this.recoveryDtbo.size > 0)) ) {
        var _pos = this._io.pos;
        this._io.seek(this.recoveryDtbo.offset);
        this._m_recoveryDtboImg = this._io.readBytes(this.recoveryDtbo.size);
        this._io.seek(_pos);
      }
      return this._m_recoveryDtboImg;
    }
  });
  Object.defineProperty(AndroidImg.prototype, 'secondImg', {
    get: function() {
      if (this._m_secondImg !== undefined)
        return this._m_secondImg;
      if (this.second.size > 0) {
        var _pos = this._io.pos;
        this._io.seek((Math.floor(((((this.pageSize + this.kernel.size) + this.ramdisk.size) + this.pageSize) - 1) / this.pageSize) * this.pageSize));
        this._m_secondImg = this._io.readBytes(this.second.size);
        this._io.seek(_pos);
      }
      return this._m_secondImg;
    }
  });

  /**
   * base loading address
   */
  Object.defineProperty(AndroidImg.prototype, 'base', {
    get: function() {
      if (this._m_base !== undefined)
        return this._m_base;
      this._m_base = (this.kernel.addr - 32768);
      return this._m_base;
    }
  });

  return AndroidImg;
})();
return AndroidImg;
}));