CyberChef/src/core/operations/YARARules.mjs

/**
 * @author Matt C [matt@artemisbot.uk]
 * @copyright Crown Copyright 2019
 * @license Apache-2.0
 */

import Operation from "../Operation.mjs";
import OperationError from "../errors/OperationError.mjs";
import Yara from "libyara-wasm";
import { isWorkerEnvironment } from "../Utils.mjs";

/**
 * YARA Rules operation
 */
class YARARules extends Operation {

    /**
     * YARARules constructor
     */
    constructor() {
        super();

        this.name = "YARA Rules";
        this.module = "Yara";
        this.description = "YARA is a tool developed at VirusTotal, primarily aimed at helping malware researchers to identify and classify malware samples. It matches based on rules specified by the user containing textual or binary patterns and a boolean expression. For help on writing rules, see the <a href='https://yara.readthedocs.io/en/latest/writingrules.html'>YARA documentation.</a>";
        this.infoURL = "https://wikipedia.org/wiki/YARA";
        this.inputType = "ArrayBuffer";
        this.outputType = "string";
        this.args = [
            {
                name: "Rules",
                type: "text",
                value: "",
                rows: 5
            },
            {
                name: "Show strings",
                type: "boolean",
                value: false
            },
            {
                name: "Show string lengths",
                type: "boolean",
                value: false
            },
            {
                name: "Show metadata",
                type: "boolean",
                value: false
            },
            {
                name: "Show counts",
                type: "boolean",
                value: true
            }
        ];
    }

    /**
     * @param {string} input
     * @param {Object[]} args
     * @returns {string}
     */
    run(input, args) {
        if (isWorkerEnvironment())
            self.sendStatusMessage("Instantiating YARA...");
        const [rules, showStrings, showLengths, showMeta, showCounts] = args;
        return new Promise((resolve, reject) => {
            Yara().then(yara => {
                if (isWorkerEnvironment()) self.sendStatusMessage("Converting data for YARA.");
                let matchString = "";

                const inpArr = new Uint8Array(input); // Turns out embind knows that JS uint8array <==> C++ std::string

                if (isWorkerEnvironment()) self.sendStatusMessage("Running YARA matching.");

                const resp = yara.run(inpArr, rules);

                if (isWorkerEnvironment()) self.sendStatusMessage("Processing data.");

                if (resp.compileErrors.size() > 0) {
                    for (let i = 0; i < resp.compileErrors.size(); i++) {
                        const compileError = resp.compileErrors.get(i);
                        if (!compileError.warning) {
                            reject(new OperationError(`Error on line ${compileError.lineNumber}: ${compileError.message}`));
                        } else {
                            matchString += `Warning on line ${compileError.lineNumber}: ${compileError.message}`;
                        }
                    }
                }
                const matchedRules = resp.matchedRules;
                for (let i = 0; i < matchedRules.size(); i++) {
                    const rule = matchedRules.get(i);
                    const matches = rule.resolvedMatches;
                    let meta = "";
                    if (showMeta && rule.metadata.size() > 0) {
                        meta += " [";
                        for (let j = 0; j < rule.metadata.size(); j++) {
                            meta += `${rule.metadata.get(j).identifier}: ${rule.metadata.get(j).data}, `;
                        }
                        meta = meta.slice(0, -2) + "]";
                    }
                    const countString = showCounts ? `${matches.size()} time${matches.size() > 1 ? "s" : ""}` : "";
                    if (matches.size() === 0 || !(showStrings || showLengths)) {
                        matchString += `Input matches rule "${rule.ruleName}"${meta}${countString.length > 0 ? ` ${countString}`: ""}.\n`;
                    } else {
                        matchString += `Rule "${rule.ruleName}"${meta} matches (${countString}):\n`;
                        for (let j = 0; j < matches.size(); j++) {
                            const match = matches.get(j);
                            if (showStrings || showLengths) {
                                matchString += `Pos ${match.location}, ${showLengths ? `length ${match.matchLength}, ` : ""}identifier ${match.stringIdentifier}${showStrings ? `, data: "${match.data}"` : ""}\n`;
                            }
                        }
                    }
                }
                resolve(matchString);
            });
        });
    }

}

export default YARARules;