From c17e89767415dd72bae3e70ee4f00e29d47dab5e Mon Sep 17 00:00:00 2001
From: Callum Fraser <callum@callumfraser.me>
Date: Wed, 16 May 2018 21:51:51 +0100
Subject: [PATCH] Ported the ParseIPv4Header operation.

---
 src/core/operations/ParseIPv4Header.mjs | 127 ++++++++++++++++++++++++
 1 file changed, 127 insertions(+)
 create mode 100644 src/core/operations/ParseIPv4Header.mjs

diff --git a/src/core/operations/ParseIPv4Header.mjs b/src/core/operations/ParseIPv4Header.mjs
new file mode 100644
index 00000000..d88d6f60
--- /dev/null
+++ b/src/core/operations/ParseIPv4Header.mjs
@@ -0,0 +1,127 @@
+/**
+ * @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";
+import {_ipv4ToStr, _protocolLookup, calculateTCPIPChecksum} from "../lib/Ip";
+
+/**
+ * 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: ""};
+
+        // 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>";
+
+        if (ihl > 5) {
+            output += "<tr><td>Options</td><td>" + toHex(options) + "</td></tr>";
+        }
+
+        return output + "</table>";
+    }
+
+}
+
+export default ParseIPv4Header;