jshaver/dns-header-parser
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Done with basic parser.

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This commit is contained in:
John Shaver 2017-09-25 15:22:52 -07:00
parent e59a0b2943
commit 10600256d8
2 changed files with 72 additions and 29 deletions
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9
index.htm Normal file
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@ -0,0 +1,9 @@
<html>
<head>
<script type="text/javascript" src="index.js"></script>
</head>
<body>
Check the console logs...
</body>
</head>
</html>

86
index.js
View file

@ -4,51 +4,85 @@ if(typeof(atob) === 'undefined') {
(function(){ (function(){
'use strict'; 'use strict';
var encodedPacket = "1MOyoQIABAAAAAAAAAAAAAAABAABAAAAKPfFWWMZCwBRAAAAUQAAAExg3kp+6eSzGAoxpggARQAAQ66CQABAEXgXCgAAEAoAAAG90gA1AC+qDJSEAQAAAQAAAAAAAAphc3NldHMtY2RuBmdpdGh1YgNjb20AAAEAAQ==" var UDP_HEADER_LENGTH = 8;
var OPCODES = ["QUERY", "IQUERY", "STATUS"]
//tcpdump file
//var encodedPacket = "1MOyoQIABAAAAAAAAAAAAAAABAABAAAAKPfFWWMZCwBRAAAAUQAAAExg3kp+6eSzGAoxpggARQAAQ66CQABAEXgXCgAAEAoAAAG90gA1AC+qDJSEAQAAAQAAAAAAAAphc3NldHMtY2RuBmdpdGh1YgNjb20AAAEAAQ=="
var encodedPacket = "RQAAQ66CQABAEXgXCgAAEAoAAAG90gA1AC+qDJSEAQAAAQAAAAAAAAphc3NldHMtY2RuBmdpdGh1YgNjb20AAAEAAQ=="
//convert to binary string to create ArrayBuffer //convert to binary string to create ArrayBuffer
var packet = atob(encodedPacket); var packet = atob(encodedPacket);
console.log("tcpdump length:", packet.length); console.log("IP length:", packet.length);
//The first 40 bytes are the tcpdump header
packet = packet.slice(40);
console.log("UDP length:", packet.length);
//We now have the raw UDP packet!
var buffer = new ArrayBuffer(packet.length); var buffer = new ArrayBuffer(packet.length);
var view = new DataView(buffer) var ipView = new DataView(buffer)
for(var i = 0; i < packet.length; ++i) { for(var i = 0; i < packet.length; ++i) {
view.setUint8(i, packet.charCodeAt(i), true); ipView.setUint8(i, packet.charCodeAt(i), true);
} }
for(i = 0; i < packet.length; ++i) { //We now can work with the raw IP packet!
}
console.log("Result:", parseDNSHeader(view)); //Get the IP header length
//Parse DNS Header (given the UDP payload) console.log("Full packet: ", view2HexString(ipView));
var ipHeaderLength = (ipView.getUint8(0, false) & 0x0F) * 4;
//Now we can ignore the IP header/UDP header and cut straight to the payload
var dnsView = new DataView(buffer, ipHeaderLength + UDP_HEADER_LENGTH);
console.log("\nPacket payload(DNS packet): ", view2HexString(dnsView));
console.log("\nResult:", parseDNSHeader(dnsView));
//Parse DNS Header (given the IP payload)
function parseDNSHeader(view) { function parseDNSHeader(view) {
return {
MessageID: getHId(view) //message ID is the first Byte
var headers = {
messageID: view.getUint16(0, false)
}; };
//flags are the 3rd-4th bytes
var flags = view.getUint16(2, false);
headers.qr = (flags & 32768) >>> 15;
headers.opcode = (flags & 30720) >>> 11;
headers.aa = (flags & 1024) >>> 10;
headers.tc = (flags & 512) >>> 9;
headers.rd = (flags & 256) >>> 8;
headers.ra = (flags & 128) >>> 7;
headers.rcode = flags & 15;
headers.qdcount = view.getUint16(4, false);
headers.ancount = view.getUint16(6, false);
headers.nscount = view.getUint16(8, false);
headers.arcount = view.getUint16(10, false);
return headers;
} }
function getHId(view) {
return view.getUint16(0, false)
}
function getQR(view) {
function view2HexString(view) {
var hexString = "";
for(var i = 0; i < view.byteLength; i += 2) {
hexString += leftPad(view.getUint8(i).toString(16));
if(i + 1 >= view.byteLength) break;
hexString += leftPad(view.getUint8(i+1).toString(16));
hexString += " ";
}
return hexString;
} }
function getOPCode(view) {
} function leftPad(str) {
function getAA(view) { return str.length == 1 ? 0 + str : str;
}
function getTC(view) {
} }