Create WebSocketDecode.mjs

src/core/operations/WebSocketDecode.mjs

@@ -0,0 +1,116 @@
+/**
+ * @author cod [sysenter.dev@gmail.com]
+ * @copyright Crown Copyright 2024
+ * @license Apache-2.0
+ */
+
+import Operation from "../Operation.mjs";
+import OperationError from "../errors/OperationError.mjs";
+import { WEBSOCKET_OPCODE } from "../lib/WebSocket.mjs";
+
+/** WebSocket */
+class WebSocketDecode extends Operation {
+
+    /**
+     * Default constructor
+     */
+    constructor() {
+        super();
+
+        this.name = "WebSocket Decode";
+        this.module = "Code";
+        this.description = "Converts a WebSocket encoded to JSON. WebSocket is computer communitions protocol, providing simultaneous two-way communication channels";
+        this.infoURL = "https://wikipedia.org/wiki/WebSocket";
+        this.inputType = "ArrayBuffer";
+        this.outputType = "JSON";
+        this.args = [];
+    }
+
+        /**
+     * @param {ArrayBuffer} input
+     * @param {Object[]} args
+     * @returns {JSON}
+     */
+    run(input, args) {
+        try {
+            let pos = 0;
+            const buf = Buffer.from(new Uint8Array(input));
+
+            if (buf.length < 2) {
+                throw new OperationError("Expected size: 2 bytes");
+            }
+
+            let b0 = buf[0];
+            let b1 = buf[1];
+
+            const fin = (b0 & 0x80) === 0x80 ? true : false;
+            const opcode = WEBSOCKET_OPCODE[b0 & 0x7f];
+            let payloadLength = (b1 & 0x7f);
+
+            pos = 2;
+            const mask = (b1 & 0x80) === 0x80 ? true : false;
+            const mask_size = (mask) ? 4 : 0;
+
+            if (payloadLength < 126) {
+                /** payload is less of 126 bytes */
+                if (buf.length < (pos + payloadLength + mask_size))
+                    throw new OperationError(`Expected size: ${(pos + payloadLength + mask_size)}`);
+            } else if (payloadLength == 126) {
+                /** payload is 2 bytes */
+                pos += 2;
+                payloadLength = buf.readUInt16BE(2);
+
+                if (buf.length < (pos + payloadLength + mask_size))
+                    throw new OperationError(`Expected size: ${(pos + payloadLength + mask_size)}`);
+
+            } else if (payloadLength == 127) {
+                pos += 8;
+                payloadLength = buf.readUInt64BE(2);
+
+                if (buf.length < (pos + payloadLength + mask_size))
+                    throw new OperationError(`Expected size: ${(pos + payloadLength + mask_size)}`);
+            }
+
+            let maskBytes = Buffer.alloc(4);
+
+            if (mask) {
+                maskBytes[0] = buf[pos];
+                maskBytes[1] = buf[pos+1];
+                maskBytes[2] = buf[pos+2];
+                maskBytes[3] = buf[pos+3];
+                pos += 4;
+            }
+
+            let payload = buf.slice(pos, buf.length);
+
+            if (mask) {
+                for(var i = 0; i < payload.length; i++) {
+                    payload[i] = payload[i] ^ maskBytes[i % 4];
+                }
+            }
+
+            let content;
+
+            if ((b0 & 1) === 1) {
+                content = payload.toString();
+            } else {
+                content = payload.toString('hex');
+            }
+
+            const ws = {
+                fin: fin,
+                opcode: opcode,
+                mask_present: mask,
+                mask: maskBytes.toString('hex'),
+                payloadLength: payloadLength,
+                payload: content
+            };
+
+            return ws;
+        } catch (err) {
+            throw new OperationError(`Could not decode WebSocket to JSON: ${err}`);
+        }
+    }
+}
+
+export default WebSocketDecode;