dns-suite.js/pure-parser.js

'use strict';

var pdns = module.exports;

var classes = exports.DNS_CLASSES || require('./dns.classes.js').DNS_CLASSES;
var types = exports.DNS_TYPES || require('./dns.types.js').DNS_TYPES;

// Order http://www.zytrax.com/books/dns/ch15/

pdns.unpackHeader = function (i) {
  // i is one element from a Uint16Array (as a 16-bit unsigned integer)

  var header = {
    id:     0                   // added here to preserve console.log order

  , qr:     (i & 0x8000) >> 15  // Query Response (0 is question, 1 is response)
  , opcode: (i & 0x7800) >> 11  // 0 is question
  , aa:     (i &  0x400) >> 10  // Authoritative Answer (response-only)
  , tc:     (i &  0x200) >>  9  // TrunCated - expect another packet with same (?) id
  , rd:     (i &  0x100) >>  8  // Recursion Desired

  , ra:     (i &   0x80) >>  7
  , res1:   (i &   0x40) >>  6  // z
  , res2:   (i &   0x20) >>  5  // ad
  , res3:   (i &   0x10) >>  4  // cd
  , rcode:  (i &    0xF)        // Error Code (response-only)
  };

  return header;
};

pdns.unpackQname = function (ui8, ptr, q) {
  return pdns._unpackQname(ui8, ptr, q || {
    name: ''
  , type: 0
  , typeName: ''
  , class: 0
  , className: ''
  , byteLength: 0
  , labels: []
  , cpcount: 0
  });
};

pdns._unpackQname = function (ui8, ptr, q) {
  if (q.cpcount > 25) {
    throw new Error("compression pointer loop detected (over 25 pointers seems like a loop)");
  }

  var total = ptr;
  var i;

  var len;
  var label = [];

  do {
    label.length = 0;
    len = ui8[total];
    if (0xc0 === len) {
      var cpptr = ui8[total + 1];

      // we're not coming back!
      ptr = cpptr;
      q.cpcount += 1;
      q.byteLength += 2; // cp and len
      return pdns.unpackQname(ui8, ptr, q);
    }
    //str.length = 0; // fast empty array
    if (ui8.byteLength - total < len) {
      throw new Error(
        "Expected a string of length " + len
          + " but packet itself has " + (ui8.byteLength - total) + " bytes remaining"
      );
    }
    for (i = 0; i < len; i += 1) {
      total += 1;
      // TODO check url-allowable characters
      label.push(String.fromCharCode(ui8[total]));
    }
    if (label.length) {
      q.labels.push(label.join(''));
    }
    total += 1;
    //console.log('total', total, ui8[total], String.fromCharCode(ui8[total]));
  } while (len);

  //str.pop(); // remove trailing '.'

  q.name = q.labels.join('.');
  if (0 === q.cpcount) {
    q.byteLength = total - ptr;
  }

  return q;
};

pdns.unpack = function (ab) {
  if (ab.buffer) {
    ab = ab.buffer;
  }

  // SANITY Check
  if (ab.byteLength < 12) {
    throw new Error(
      "A DNS header has a minimum length of 12 bytes but this packet has only " + ab.byteLength + "bytes."
    );
  }

  // DO: new Uint8Array(arrayBuffer);
  // DO NOT: Uint8Array.from(arrayBuffer); // WILL NOT WORK

  // DO: new DataView(arrayBuffer).getUint16(7);
  // DO NOT: arrayBuffer.slice();
  //
  // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer
  // https://developer.mozilla.org/en-US/docs/Web/API/ArrayBufferView
  // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array
  // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/slice

  // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView
  var dv = new DataView(ab);
  var id = dv.getUint16(0);
  var header = pdns.unpackHeader(dv.getUint16(2));
  var qdcount = dv.getUint16(4);  // query count
  var ancount = dv.getUint16(6);  // answer count
  var nscount = dv.getUint16(8);  // authority count
  var arcount = dv.getUint16(10); // additional count
  var total = 12;
  var i;
  var rec;
  var ui8 = new Uint8Array(ab);

  // TODO move to pdns.unpackQuestion to make testable
  function unpackQuestion(ab, dv, ui8, total) {
    var ototal = total;
    var q = pdns.unpackQname(ui8, total);
    //console.log('unpackQuestion QNAME:');
    //console.log(q);
    total += q.byteLength;

    



    if (ab.byteLength - total < 4) {
      // console.error(str.join(''));
      throw new Error(
        "Expected a 2-byte QTYPE and 2-byte QCLASS following " + total + "-byte QNAME"
          + " but packet itself has " + (ab.byteLength - total) + " bytes remaining"
      );
    }

    q.type = dv.getUint16(total);
    total += 2;
    q.class = dv.getUint16(total);
    total += 2;
    q.byteLength = total - ototal;

    q.className = classes[q.class];
    q.typeName = types[q.type];
 
    return q;
  }

  function unpackAnswer(ab, dv, ui8, total) {
    var ototal = total;
    var q = pdns.unpackQname(ui8, total);
    //console.log('unpackAnswer QNAME:');
    //console.log(q);
    total += q.byteLength;
    q.className = classes[q.class];
    q.typeName = types[q.type];

    if (ab.byteLength - total < 10) {
      // console.error(str.join(''));
      throw new Error(
        "Expected a 2-byte QTYPE, 2-byte QCLASS, 4-byte TTL, and 2-byte RDLENGTH following " + total + "-byte QNAME"
          + " but packet itself has " + (ab.byteLength - total) + " bytes remaining"
      );
    }

    q.type = dv.getUint16(total);
    total += 2;
    q.class = dv.getUint16(total);
    total += 2;
    q.ttl = dv.getUint32(total);
    total += 4;
    q.rdlength = dv.getUint16(total);
    total += 2;

    q.className = classes[q.class];
    q.typeName = types[q.type];
 

    // TODO actually parse RDATA
    q.rdata = new Uint8Array(ab).slice(total, total + q.rdlength);
    console.log('q.rdata', q.rdata.byteLength, 'bytes:');
    console.log(q.rdata);
    //q.rdata = Array.prototype.slice.apply(q.rdata);

    total += q.rdlength;

    q.byteLength = total - ototal;
    return q;
  }

  header.id = id;

  console.log('qdcount', qdcount);
  header.questions = [];
  for (i = 0; i < qdcount; i += 1) {
    rec = unpackQuestion(ab, dv, ui8, total);
    total += rec.byteLength;
    header.questions.push(rec);
  }

  console.log('ancount', ancount);
  header.answers = [];
  for (i = 0; i < ancount; i += 1) {
    rec = unpackAnswer(ab, dv, ui8, total);
    total += rec.byteLength;
    header.answers.push(rec);
  }

  console.log('nscount', nscount);
  header.authority = [];
  for (i = 0; i < nscount; i += 1) {
    rec = unpackAnswer(ab, dv, ui8, total);
    total += rec.byteLength;
    header.authority.push(rec);
  }

  console.log('arcount', arcount);
  header.additional = [];
  for (i = 0; i < arcount; i += 1) {
    rec = unpackAnswer(ab, dv, ui8, total);
    total += rec.byteLength;
    header.additional.push(rec);
  }

  if (ab.byteLength !== total) {
    throw new Error(
      "Parsed " + total + " bytes, but packet is " + ab.byteLength + " bytes."
    );
  }
  header.byteLength = total;
  return header;
};
pdns.unpackRdata = require('./dns.rdata.parse.js').DNS_RDATA_PARSE;