openrosa-xpath-evaluator/src/digest.js

Wrapper for browsers' XPath evaluator with added support for OpenRosa extensions.

/**
 * XForms 1.1 digest() function.
 * @see https://www.w3.org/TR/xforms/#fn-digest
 *
 * This implementation depends on the node-forge module, and will throw an Error
 * at runtime if the module is not available.
 */
module.exports = (message, algo, encoding) => {
    let forge;
    try {
        // eslint-disable-next-line global-require
        forge = require('node-forge');
    } catch (err) {
        throw new Error(
            `Cannot find module 'node-forge'; this is required to use the digest() function.`
        );
    }

    message = message.v;
    algo = algo && algo.v && algo.v.toLowerCase();
    encoding = (encoding && encoding.v && encoding.v.toLowerCase()) || 'base64';
    if (!algo || !/^(md5|sha-1|sha-256|sha-384|sha-512)$/.test(algo)) {
        throw new Error('Invalid algo.');
    }
    if (!/^(base64|hex)$/.test(encoding)) {
        throw new Error('Invalid encoding.');
    }
    const md = forge.md[algo.replace('-', '')].create();
    md.update(message);
    const hashBuffer = md.digest();
    if (!encoding || encoding === 'base64') {
        return forge.util.encode64(hashBuffer.bytes());
    }
    return md.digest().toHex();
};