Add Strip IPv4 header operation

src/core/config/Categories.json

@@ -234,6 +234,7 @@
             "Parse IP range",
             "Parse IPv6 address",
             "Parse IPv4 header",
+            "Strip IPv4 header",
             "Parse TCP",
             "Parse UDP",
             "Parse SSH Host Key",

src/core/operations/StripIPv4Header.mjs

@@ -0,0 +1,57 @@
+/**
+ * @author c65722 []
+ * @copyright Crown Copyright 2024
+ * @license Apache-2.0
+ */
+
+import Operation from "../Operation.mjs";
+import OperationError from "../errors/OperationError.mjs";
+import Stream from "../lib/Stream.mjs";
+
+/**
+ * Strip IPv4 header operation
+ */
+class StripIPv4Header extends Operation {
+
+    /**
+     * StripIPv4Header constructor
+     */
+    constructor() {
+        super();
+
+        this.name = "Strip IPv4 header";
+        this.module = "Default";
+        this.description = "Strips the IPv4 header from an IPv4 packet, outputting the payload.";
+        this.infoURL = "https://wikipedia.org/wiki/IPv4";
+        this.inputType = "ArrayBuffer";
+        this.outputType = "ArrayBuffer";
+        this.args = [];
+    }
+
+    /**
+     * @param {ArrayBuffer} input
+     * @param {Object[]} args
+     * @returns {ArrayBuffer}
+     */
+    run(input, args) {
+        const MIN_HEADER_LEN = 20;
+
+        const s = new Stream(new Uint8Array(input));
+        if (s.length < MIN_HEADER_LEN) {
+            throw new OperationError("Input length is less than minimum IPv4 header length");
+        }
+
+        const ihl = s.readInt(1) & 0x0f;
+        const dataOffsetBytes = ihl * 4;
+        if (s.length < dataOffsetBytes) {
+            throw new OperationError("Input length is less than IHL");
+        }
+
+        s.moveTo(dataOffsetBytes);
+
+        return s.getBytes().buffer;
+    }
+
+}
+
+export default StripIPv4Header;

tests/operations/index.mjs

@@ -142,6 +142,7 @@ import "./tests/SIGABA.mjs";
 import "./tests/SM4.mjs";
 // import "./tests/SplitColourChannels.mjs"; // Cannot test operations that use the File type yet
 import "./tests/StrUtils.mjs";
+import "./tests/StripIPv4Header.mjs";
 import "./tests/Subsection.mjs";
 import "./tests/SwapCase.mjs";
 import "./tests/SymmetricDifference.mjs";

tests/operations/tests/StripIPv4Header.mjs

@@ -0,0 +1,126 @@
+/**
+ * Strip IPv4 header tests.
+ *
+ * @author c65722 []
+ * @copyright Crown Copyright 2024
+ * @license Apache-2.0
+ */
+
+import TestRegister from "../../lib/TestRegister.mjs";
+
+TestRegister.addTests([
+    {
+        name: "Strip IPv4 header: No options, No payload",
+        input: "450000140005400080060000c0a80001c0a80002",
+        expectedOutput: "",
+        recipeConfig: [
+            {
+                op: "From Hex",
+                args: ["None"]
+            },
+            {
+                op: "Strip IPv4 header",
+                args: [],
+            },
+            {
+                op: "To Hex",
+                args: ["None", 0]
+            }
+        ]
+    },
+    {
+        name: "Strip IPv4 header: No options, Payload",
+        input: "450000140005400080060000c0a80001c0a80002ffffffffffffffff",
+        expectedOutput: "ffffffffffffffff",
+        recipeConfig: [
+            {
+                op: "From Hex",
+                args: ["None"]
+            },
+            {
+                op: "Strip IPv4 header",
+                args: [],
+            },
+            {
+                op: "To Hex",
+                args: ["None", 0]
+            }
+        ]
+    },
+    {
+        name: "Strip IPv4 header: Options, No payload",
+        input: "460000140005400080060000c0a80001c0a8000207000000",
+        expectedOutput: "",
+        recipeConfig: [
+            {
+                op: "From Hex",
+                args: ["None"]
+            },
+            {
+                op: "Strip IPv4 header",
+                args: [],
+            },
+            {
+                op: "To Hex",
+                args: ["None", 0]
+            }
+        ]
+    },
+    {
+        name: "Strip IPv4 header: Options, Payload",
+        input: "460000140005400080060000c0a80001c0a8000207000000ffffffffffffffff",
+        expectedOutput: "ffffffffffffffff",
+        recipeConfig: [
+            {
+                op: "From Hex",
+                args: ["None"]
+            },
+            {
+                op: "Strip IPv4 header",
+                args: [],
+            },
+            {
+                op: "To Hex",
+                args: ["None", 0]
+            }
+        ]
+    },
+    {
+        name: "Strip IPv4 header: Input length lesss than minimum header length",
+        input: "450000140005400080060000c0a80001c0a800",
+        expectedOutput: "Input length is less than minimum IPv4 header length",
+        recipeConfig: [
+            {
+                op: "From Hex",
+                args: ["None"]
+            },
+            {
+                op: "Strip IPv4 header",
+                args: [],
+            },
+            {
+                op: "To Hex",
+                args: ["None", 0]
+            }
+        ]
+    },
+    {
+        name: "Strip IPv4 header: Input length less than IHL",
+        input: "460000140005400080060000c0a80001c0a80000",
+        expectedOutput: "Input length is less than IHL",
+        recipeConfig: [
+            {
+                op: "From Hex",
+                args: ["None"]
+            },
+            {
+                op: "Strip IPv4 header",
+                args: [],
+            },
+            {
+                op: "To Hex",
+                args: ["None", 0]
+            }
+        ]
+    }
+]);