CyberChef/src/core/operations/ParseIPv4Header.mjs

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2018-05-16 22:51:51 +02:00
/**
* @author n1474335 [n1474335@gmail.com]
* @copyright Crown Copyright 2016
* @license Apache-2.0
*/
import Operation from "../Operation";
import Utils from "../Utils";
import {fromHex, toHex} from "../lib/Hex.mjs";
import {ipv4ToStr, protocolLookup, calculateTCPIPChecksum} from "../lib/Ip.mjs";
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/**
* Parse IPv4 header operation
*/
class ParseIPv4Header extends Operation {
/**
* ParseIPv4Header constructor
*/
constructor() {
super();
this.name = "Parse IPv4 header";
this.module = "JSBN";
this.description = "Given an IPv4 header, this operations parses and displays each field in an easily readable format.";
this.inputType = "string";
this.outputType = "html";
this.args = [
{
"name": "Input format",
"type": "option",
"value": ["Hex", "Raw"]
}
];
}
/**
* @param {string} input
* @param {Object[]} args
* @returns {html}
*/
run(input, args) {
const format = args[0];
let output;
if (format === "Hex") {
input = fromHex(input);
} else if (format === "Raw") {
input = Utils.strToByteArray(input);
} else {
return "Unrecognised input format.";
}
let ihl = input[0] & 0x0f;
const dscp = (input[1] >>> 2) & 0x3f,
ecn = input[1] & 0x03,
length = input[2] << 8 | input[3],
identification = input[4] << 8 | input[5],
flags = (input[6] >>> 5) & 0x07,
fragOffset = (input[6] & 0x1f) << 8 | input[7],
ttl = input[8],
protocol = input[9],
checksum = input[10] << 8 | input[11],
srcIP = input[12] << 24 | input[13] << 16 | input[14] << 8 | input[15],
dstIP = input[16] << 24 | input[17] << 16 | input[18] << 8 | input[19],
checksumHeader = input.slice(0, 10).concat([0, 0]).concat(input.slice(12, 20));
let version = (input[0] >>> 4) & 0x0f,
options = [];
// Version
if (version !== 4) {
version = version + " (Error: for IPv4 headers, this should always be set to 4)";
}
// IHL
if (ihl < 5) {
ihl = ihl + " (Error: this should always be at least 5)";
} else if (ihl > 5) {
// sort out options...
const optionsLen = ihl * 4 - 20;
options = input.slice(20, optionsLen + 20);
}
// Protocol
const protocolInfo = protocolLookup[protocol] || {keyword: "", protocol: ""};
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// Checksum
const correctChecksum = calculateTCPIPChecksum(checksumHeader),
givenChecksum = Utils.hex(checksum);
let checksumResult;
if (correctChecksum === givenChecksum) {
checksumResult = givenChecksum + " (correct)";
} else {
checksumResult = givenChecksum + " (incorrect, should be " + correctChecksum + ")";
}
output = "<table class='table table-hover table-condensed table-bordered table-nonfluid'><tr><th>Field</th><th>Value</th></tr>" +
"<tr><td>Version</td><td>" + version + "</td></tr>" +
"<tr><td>Internet Header Length (IHL)</td><td>" + ihl + " (" + (ihl * 4) + " bytes)</td></tr>" +
"<tr><td>Differentiated Services Code Point (DSCP)</td><td>" + dscp + "</td></tr>" +
"<tr><td>Explicit Congestion Notification (ECN)</td><td>" + ecn + "</td></tr>" +
"<tr><td>Total length</td><td>" + length + " bytes" +
"\n IP header: " + (ihl * 4) + " bytes" +
"\n Data: " + (length - ihl * 4) + " bytes</td></tr>" +
"<tr><td>Identification</td><td>0x" + Utils.hex(identification) + " (" + identification + ")</td></tr>" +
"<tr><td>Flags</td><td>0x" + Utils.hex(flags, 2) +
"\n Reserved bit:" + (flags >> 2) + " (must be 0)" +
"\n Don't fragment:" + (flags >> 1 & 1) +
"\n More fragments:" + (flags & 1) + "</td></tr>" +
"<tr><td>Fragment offset</td><td>" + fragOffset + "</td></tr>" +
"<tr><td>Time-To-Live</td><td>" + ttl + "</td></tr>" +
"<tr><td>Protocol</td><td>" + protocol + ", " + protocolInfo.protocol + " (" + protocolInfo.keyword + ")</td></tr>" +
"<tr><td>Header checksum</td><td>" + checksumResult + "</td></tr>" +
"<tr><td>Source IP address</td><td>" + ipv4ToStr(srcIP) + "</td></tr>" +
"<tr><td>Destination IP address</td><td>" + ipv4ToStr(dstIP) + "</td></tr>";
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if (ihl > 5) {
output += "<tr><td>Options</td><td>" + toHex(options) + "</td></tr>";
}
return output + "</table>";
}
}
export default ParseIPv4Header;