DNS (Domain Name Service) packet: JavaScript parsing library

(No support for Auth-Name + Add-Name for simplicity)

KS implementation details

License: CC0-1.0

References

This page hosts a formal specification of DNS (Domain Name Service) packet 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 DnsPacket(new KaitaiStream(arrayBuffer));

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

data.transactionId // => ID to keep track of request/responces

JavaScript source code to parse DNS (Domain Name Service) packet

DnsPacket.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.DnsPacket = factory(root.KaitaiStream);
  }
}(this, function (KaitaiStream) {
/**
 * (No support for Auth-Name + Add-Name for simplicity)
 */

var DnsPacket = (function() {
  DnsPacket.ClassType = Object.freeze({
    IN_CLASS: 1,
    CS: 2,
    CH: 3,
    HS: 4,

    1: "IN_CLASS",
    2: "CS",
    3: "CH",
    4: "HS",
  });

  DnsPacket.TypeType = Object.freeze({
    A: 1,
    NS: 2,
    MD: 3,
    MF: 4,
    CNAME: 5,
    SOA: 6,
    MB: 7,
    MG: 8,
    MR: 9,
    NULL: 10,
    WKS: 11,
    PTR: 12,
    HINFO: 13,
    MINFO: 14,
    MX: 15,
    TXT: 16,
    AAAA: 28,
    SRV: 33,

    1: "A",
    2: "NS",
    3: "MD",
    4: "MF",
    5: "CNAME",
    6: "SOA",
    7: "MB",
    8: "MG",
    9: "MR",
    10: "NULL",
    11: "WKS",
    12: "PTR",
    13: "HINFO",
    14: "MINFO",
    15: "MX",
    16: "TXT",
    28: "AAAA",
    33: "SRV",
  });

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

    this._read();
  }
  DnsPacket.prototype._read = function() {
    this.transactionId = this._io.readU2be();
    this.flags = new PacketFlags(this._io, this, this._root);
    if (this.flags.isOpcodeValid) {
      this.qdcount = this._io.readU2be();
    }
    if (this.flags.isOpcodeValid) {
      this.ancount = this._io.readU2be();
    }
    if (this.flags.isOpcodeValid) {
      this.nscount = this._io.readU2be();
    }
    if (this.flags.isOpcodeValid) {
      this.arcount = this._io.readU2be();
    }
    if (this.flags.isOpcodeValid) {
      this.queries = new Array(this.qdcount);
      for (var i = 0; i < this.qdcount; i++) {
        this.queries[i] = new Query(this._io, this, this._root);
      }
    }
    if (this.flags.isOpcodeValid) {
      this.answers = new Array(this.ancount);
      for (var i = 0; i < this.ancount; i++) {
        this.answers[i] = new Answer(this._io, this, this._root);
      }
    }
    if (this.flags.isOpcodeValid) {
      this.authorities = new Array(this.nscount);
      for (var i = 0; i < this.nscount; i++) {
        this.authorities[i] = new Answer(this._io, this, this._root);
      }
    }
    if (this.flags.isOpcodeValid) {
      this.additionals = new Array(this.arcount);
      for (var i = 0; i < this.arcount; i++) {
        this.additionals[i] = new Answer(this._io, this, this._root);
      }
    }
  }

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

      this._read();
    }
    MxInfo.prototype._read = function() {
      this.preference = this._io.readU2be();
      this.mx = new DomainName(this._io, this, this._root);
    }

    return MxInfo;
  })();

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

      this._read();
    }
    PointerStruct.prototype._read = function() {
      this.value = this._io.readU1();
    }
    Object.defineProperty(PointerStruct.prototype, 'contents', {
      get: function() {
        if (this._m_contents !== undefined)
          return this._m_contents;
        var io = this._root._io;
        var _pos = io.pos;
        io.seek((this.value + ((this._parent.length - 192) << 8)));
        this._m_contents = new DomainName(io, this, this._root);
        io.seek(_pos);
        return this._m_contents;
      }
    });

    /**
     * Read one byte, then offset to that position, read one domain-name and return
     */

    return PointerStruct;
  })();

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

      this._read();
    }
    Label.prototype._read = function() {
      this.length = this._io.readU1();
      if (this.isPointer) {
        this.pointer = new PointerStruct(this._io, this, this._root);
      }
      if (!(this.isPointer)) {
        this.name = KaitaiStream.bytesToStr(this._io.readBytes(this.length), "utf-8");
      }
    }
    Object.defineProperty(Label.prototype, 'isPointer', {
      get: function() {
        if (this._m_isPointer !== undefined)
          return this._m_isPointer;
        this._m_isPointer = this.length >= 192;
        return this._m_isPointer;
      }
    });

    /**
     * RFC1035 4.1.4: If the first two bits are raised it's a pointer-offset to a previously defined name
     */

    /**
     * Otherwise its a string the length of the length value
     */

    return Label;
  })();

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

      this._read();
    }
    Query.prototype._read = function() {
      this.name = new DomainName(this._io, this, this._root);
      this.type = this._io.readU2be();
      this.queryClass = this._io.readU2be();
    }

    return Query;
  })();

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

      this._read();
    }
    DomainName.prototype._read = function() {
      this.name = []
      var i = 0;
      do {
        var _ = new Label(this._io, this, this._root);
        this.name.push(_);
        i++;
      } while (!( ((_.length == 0) || (_.length >= 192)) ));
    }

    /**
     * Repeat until the length is 0 or it is a pointer (bit-hack to get around lack of OR operator)
     */

    return DomainName;
  })();

  var AddressV6 = DnsPacket.AddressV6 = (function() {
    function AddressV6(_io, _parent, _root) {
      this._io = _io;
      this._parent = _parent;
      this._root = _root || this;

      this._read();
    }
    AddressV6.prototype._read = function() {
      this.ipV6 = this._io.readBytes(16);
    }

    return AddressV6;
  })();

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

      this._read();
    }
    Service.prototype._read = function() {
      this.priority = this._io.readU2be();
      this.weight = this._io.readU2be();
      this.port = this._io.readU2be();
      this.target = new DomainName(this._io, this, this._root);
    }

    return Service;
  })();

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

      this._read();
    }
    Txt.prototype._read = function() {
      this.length = this._io.readU1();
      this.text = KaitaiStream.bytesToStr(this._io.readBytes(this.length), "utf-8");
    }

    return Txt;
  })();

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

      this._read();
    }
    TxtBody.prototype._read = function() {
      this.data = [];
      var i = 0;
      while (!this._io.isEof()) {
        this.data.push(new Txt(this._io, this, this._root));
        i++;
      }
    }

    return TxtBody;
  })();

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

      this._read();
    }
    Address.prototype._read = function() {
      this.ip = this._io.readBytes(4);
    }

    return Address;
  })();

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

      this._read();
    }
    Answer.prototype._read = function() {
      this.name = new DomainName(this._io, this, this._root);
      this.type = this._io.readU2be();
      this.answerClass = this._io.readU2be();
      this.ttl = this._io.readS4be();
      this.rdlength = this._io.readU2be();
      switch (this.type) {
      case DnsPacket.TypeType.SRV:
        this._raw_payload = this._io.readBytes(this.rdlength);
        var _io__raw_payload = new KaitaiStream(this._raw_payload);
        this.payload = new Service(_io__raw_payload, this, this._root);
        break;
      case DnsPacket.TypeType.A:
        this._raw_payload = this._io.readBytes(this.rdlength);
        var _io__raw_payload = new KaitaiStream(this._raw_payload);
        this.payload = new Address(_io__raw_payload, this, this._root);
        break;
      case DnsPacket.TypeType.CNAME:
        this._raw_payload = this._io.readBytes(this.rdlength);
        var _io__raw_payload = new KaitaiStream(this._raw_payload);
        this.payload = new DomainName(_io__raw_payload, this, this._root);
        break;
      case DnsPacket.TypeType.NS:
        this._raw_payload = this._io.readBytes(this.rdlength);
        var _io__raw_payload = new KaitaiStream(this._raw_payload);
        this.payload = new DomainName(_io__raw_payload, this, this._root);
        break;
      case DnsPacket.TypeType.SOA:
        this._raw_payload = this._io.readBytes(this.rdlength);
        var _io__raw_payload = new KaitaiStream(this._raw_payload);
        this.payload = new AuthorityInfo(_io__raw_payload, this, this._root);
        break;
      case DnsPacket.TypeType.MX:
        this._raw_payload = this._io.readBytes(this.rdlength);
        var _io__raw_payload = new KaitaiStream(this._raw_payload);
        this.payload = new MxInfo(_io__raw_payload, this, this._root);
        break;
      case DnsPacket.TypeType.TXT:
        this._raw_payload = this._io.readBytes(this.rdlength);
        var _io__raw_payload = new KaitaiStream(this._raw_payload);
        this.payload = new TxtBody(_io__raw_payload, this, this._root);
        break;
      case DnsPacket.TypeType.PTR:
        this._raw_payload = this._io.readBytes(this.rdlength);
        var _io__raw_payload = new KaitaiStream(this._raw_payload);
        this.payload = new DomainName(_io__raw_payload, this, this._root);
        break;
      case DnsPacket.TypeType.AAAA:
        this._raw_payload = this._io.readBytes(this.rdlength);
        var _io__raw_payload = new KaitaiStream(this._raw_payload);
        this.payload = new AddressV6(_io__raw_payload, this, this._root);
        break;
      default:
        this.payload = this._io.readBytes(this.rdlength);
        break;
      }
    }

    /**
     * Time to live (in seconds)
     */

    /**
     * Length in octets of the following payload
     */

    return Answer;
  })();

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

      this._read();
    }
    PacketFlags.prototype._read = function() {
      this.flag = this._io.readU2be();
    }
    Object.defineProperty(PacketFlags.prototype, 'qr', {
      get: function() {
        if (this._m_qr !== undefined)
          return this._m_qr;
        this._m_qr = ((this.flag & 32768) >>> 15);
        return this._m_qr;
      }
    });
    Object.defineProperty(PacketFlags.prototype, 'ra', {
      get: function() {
        if (this._m_ra !== undefined)
          return this._m_ra;
        this._m_ra = ((this.flag & 128) >>> 7);
        return this._m_ra;
      }
    });
    Object.defineProperty(PacketFlags.prototype, 'tc', {
      get: function() {
        if (this._m_tc !== undefined)
          return this._m_tc;
        this._m_tc = ((this.flag & 512) >>> 9);
        return this._m_tc;
      }
    });
    Object.defineProperty(PacketFlags.prototype, 'isOpcodeValid', {
      get: function() {
        if (this._m_isOpcodeValid !== undefined)
          return this._m_isOpcodeValid;
        this._m_isOpcodeValid =  ((this.opcode == 0) || (this.opcode == 1) || (this.opcode == 2)) ;
        return this._m_isOpcodeValid;
      }
    });
    Object.defineProperty(PacketFlags.prototype, 'rcode', {
      get: function() {
        if (this._m_rcode !== undefined)
          return this._m_rcode;
        this._m_rcode = ((this.flag & 15) >>> 0);
        return this._m_rcode;
      }
    });
    Object.defineProperty(PacketFlags.prototype, 'opcode', {
      get: function() {
        if (this._m_opcode !== undefined)
          return this._m_opcode;
        this._m_opcode = ((this.flag & 30720) >>> 11);
        return this._m_opcode;
      }
    });
    Object.defineProperty(PacketFlags.prototype, 'aa', {
      get: function() {
        if (this._m_aa !== undefined)
          return this._m_aa;
        this._m_aa = ((this.flag & 1024) >>> 10);
        return this._m_aa;
      }
    });
    Object.defineProperty(PacketFlags.prototype, 'z', {
      get: function() {
        if (this._m_z !== undefined)
          return this._m_z;
        this._m_z = ((this.flag & 64) >>> 6);
        return this._m_z;
      }
    });
    Object.defineProperty(PacketFlags.prototype, 'rd', {
      get: function() {
        if (this._m_rd !== undefined)
          return this._m_rd;
        this._m_rd = ((this.flag & 256) >>> 8);
        return this._m_rd;
      }
    });
    Object.defineProperty(PacketFlags.prototype, 'cd', {
      get: function() {
        if (this._m_cd !== undefined)
          return this._m_cd;
        this._m_cd = ((this.flag & 16) >>> 4);
        return this._m_cd;
      }
    });
    Object.defineProperty(PacketFlags.prototype, 'ad', {
      get: function() {
        if (this._m_ad !== undefined)
          return this._m_ad;
        this._m_ad = ((this.flag & 32) >>> 5);
        return this._m_ad;
      }
    });

    return PacketFlags;
  })();

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

      this._read();
    }
    AuthorityInfo.prototype._read = function() {
      this.primaryNs = new DomainName(this._io, this, this._root);
      this.resoponsibleMailbox = new DomainName(this._io, this, this._root);
      this.serial = this._io.readU4be();
      this.refreshInterval = this._io.readU4be();
      this.retryInterval = this._io.readU4be();
      this.expireLimit = this._io.readU4be();
      this.minTtl = this._io.readU4be();
    }

    return AuthorityInfo;
  })();

  /**
   * ID to keep track of request/responces
   */

  /**
   * How many questions are there
   */

  /**
   * Number of resource records answering the question
   */

  /**
   * Number of resource records pointing toward an authority
   */

  /**
   * Number of resource records holding additional information
   */

  return DnsPacket;
})();
return DnsPacket;
}));