Broadcom devices .trx firmware packaging: JavaScript parsing library

.trx file format is widely used for distribution of firmware updates for Broadcom devices. The most well-known are ASUS routers.

Fundamentally, it includes a footer which acts as a safeguard against installing a firmware package on a wrong hardware model or version, and a header which list numerous partitions packaged inside a single .trx file.

trx files not necessarily contain all these headers.

File extension

trx

KS implementation details

License: GPL-2.0-or-later
Minimal Kaitai Struct required: 0.9

This page hosts a formal specification of Broadcom devices .trx firmware packaging 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 BroadcomTrx(new KaitaiStream(arrayBuffer));

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

data.header // => get header

JavaScript source code to parse Broadcom devices .trx firmware packaging

BroadcomTrx.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.BroadcomTrx = factory(root.KaitaiStream);
  }
}(this, function (KaitaiStream) {
/**
 * .trx file format is widely used for distribution of firmware
 * updates for Broadcom devices. The most well-known are ASUS routers.
 * 
 * Fundamentally, it includes a footer which acts as a safeguard
 * against installing a firmware package on a wrong hardware model or
 * version, and a header which list numerous partitions packaged inside
 * a single .trx file.
 * 
 * trx files not necessarily contain all these headers.
 * @see {@link https://github.com/openwrt/openwrt/blob/3f5619f/tools/firmware-utils/src/trx.c|Source}
 * @see {@link https://web.archive.org/web/20190127154419/https://openwrt.org/docs/techref/header|Source}
 * @see {@link https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/mtd/partitions/brcm,trx.txt|Source}
 */

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

    this._read();
  }
  BroadcomTrx.prototype._read = function() {
  }

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

      this._read();
    }
    Revision.prototype._read = function() {
      this.major = this._io.readU1();
      this.minor = this._io.readU1();
    }

    return Revision;
  })();

  var Version = BroadcomTrx.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.readU1();
      this.minor = this._io.readU1();
      this.patch = this._io.readU1();
      this.tweak = this._io.readU1();
    }

    return Version;
  })();

  /**
   * A safeguard against installation of firmware to an incompatible device
   */

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

      this._read();
    }
    Tail.prototype._read = function() {
      this.version = new Version(this._io, this, this._root);
      this.productId = KaitaiStream.bytesToStr(KaitaiStream.bytesTerminate(this._io.readBytes(12), 0, false), "utf-8");
      this.compHw = new Array(4);
      for (var i = 0; i < 4; i++) {
        this.compHw[i] = new HwCompInfo(this._io, this, this._root);
      }
      this.reserved = this._io.readBytes(32);
    }

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

        this._read();
      }
      HwCompInfo.prototype._read = function() {
        this.min = new Revision(this._io, this, this._root);
        this.max = new Revision(this._io, this, this._root);
      }

      return HwCompInfo;
    })();

    /**
     * 1.9.2.7 by default
     */

    /**
     * 0.02 - 2.99
     */

    return Tail;
  })();

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

      this._read();
    }
    Header.prototype._read = function() {
      this.magic = this._io.readBytes(4);
      if (!((KaitaiStream.byteArrayCompare(this.magic, [72, 68, 82, 48]) == 0))) {
        throw new KaitaiStream.ValidationNotEqualError([72, 68, 82, 48], this.magic, this._io, "/types/header/seq/0");
      }
      this.len = this._io.readU4le();
      this.crc32 = this._io.readU4le();
      this.version = this._io.readU2le();
      this.flags = new Flags(this._io, this, this._root);
      this.partitions = []
      var i = 0;
      do {
        var _ = new Partition(this._io, this, this._root, i);
        this.partitions.push(_);
        i++;
      } while (!( ((i >= 4) || (!(_.isPresent))) ));
    }

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

        this._read();
      }
      Partition.prototype._read = function() {
        this.ofsBody = this._io.readU4le();
      }
      Object.defineProperty(Partition.prototype, 'isPresent', {
        get: function() {
          if (this._m_isPresent !== undefined)
            return this._m_isPresent;
          this._m_isPresent = this.ofsBody != 0;
          return this._m_isPresent;
        }
      });
      Object.defineProperty(Partition.prototype, 'isLast', {
        get: function() {
          if (this._m_isLast !== undefined)
            return this._m_isLast;
          if (this.isPresent) {
            this._m_isLast =  ((this.idx == (this._parent.partitions.length - 1)) || (!(this._parent.partitions[(this.idx + 1)].isPresent))) ;
          }
          return this._m_isLast;
        }
      });
      Object.defineProperty(Partition.prototype, 'lenBody', {
        get: function() {
          if (this._m_lenBody !== undefined)
            return this._m_lenBody;
          if (this.isPresent) {
            this._m_lenBody = (this.isLast ? (this._root._io.size - this.ofsBody) : this._parent.partitions[(this.idx + 1)].ofsBody);
          }
          return this._m_lenBody;
        }
      });
      Object.defineProperty(Partition.prototype, 'body', {
        get: function() {
          if (this._m_body !== undefined)
            return this._m_body;
          if (this.isPresent) {
            var io = this._root._io;
            var _pos = io.pos;
            io.seek(this.ofsBody);
            this._m_body = io.readBytes(this.lenBody);
            io.seek(_pos);
          }
          return this._m_body;
        }
      });

      return Partition;
    })();

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

        this._read();
      }
      Flags.prototype._read = function() {
        this.flags = new Array(16);
        for (var i = 0; i < 16; i++) {
          this.flags[i] = this._io.readBitsIntLe(1) != 0;
        }
      }

      return Flags;
    })();

    /**
     * Length of file including header
     */

    /**
     * CRC from `version` (??? todo: see the original and disambiguate) to end of file
     */

    /**
     * Offsets of partitions from start of header
     */

    return Header;
  })();
  Object.defineProperty(BroadcomTrx.prototype, 'header', {
    get: function() {
      if (this._m_header !== undefined)
        return this._m_header;
      var _pos = this._io.pos;
      this._io.seek(0);
      this._m_header = new Header(this._io, this, this._root);
      this._io.seek(_pos);
      return this._m_header;
    }
  });
  Object.defineProperty(BroadcomTrx.prototype, 'tail', {
    get: function() {
      if (this._m_tail !== undefined)
        return this._m_tail;
      var _pos = this._io.pos;
      this._io.seek((this._io.size - 64));
      this._m_tail = new Tail(this._io, this, this._root);
      this._io.seek(_pos);
      return this._m_tail;
    }
  });

  return BroadcomTrx;
})();
return BroadcomTrx;
}));