fritzbox-api/src/digestAuthBuilder.mjs

Straightforward, lightweight and extendable Node.js library to communicate with FRITZ!Box devices

// Copyright (c) 2026, Thorsten A. Weintz. All rights reserved.
// Licensed under the MIT license. See LICENSE in the project root for license information.

import HashUtil from './hashUtil.mjs';

/**
 * Helper class for handling HTTP Digest Authentication.
 * Provides parsing and header generation utilities.
 */
class DigestAuthHelper {

    /**
     * Parses a Digest authentication header string into an object.
     *
     * @param {string} header Raw Digest header string.
     * @returns {Object<string, string>} Key-value pairs extracted from the header.
     */
    static parseDigest(header) {
        const parts = {};

        header.replace(/(\w+)=("([^"]*)"|[^,]*)/g, (_, k, v, v2) => {
            parts[k] = v2 ?? v.replace(/"/g, '');
        });

        return parts;
    }

    /**
     * Builds a Digest Authorization header for an HTTP request.
     *
     * @param {Object} param0 Authentication parameters.
     * @param {string} param0.username Username for authentication.
     * @param {string} param0.password Password for authentication.
     * @param {string} param0.method HTTP method (e.g., GET, POST).
     * @param {string} param0.uri Request URI.
     * @param {Object} digestData Parsed digest challenge data from server.
     * @param {string} digestData.realm Authentication realm.
     * @param {string} digestData.nonce Server-provided nonce.
     * @param {string} digestData.qop Quality of protection (e.g., auth).
     * @returns {string} Digest Authorization header value.
     */
    static buildDigestAuthHeader({ username, password, method, uri }, digestData) {
        const md5 = HashUtil.md5;

        const cnonce = HashUtil.randomHex(8);
        const nc = '00000001';

        const qopRaw = digestData.qop?.replace(/"/g, '');
        const qop = qopRaw === 'auth' ? 'auth' : null;

        const HA1 = md5(`${username}:${digestData.realm}:${password}`);
        const HA2 = md5(`${method}:${uri}`);

        const response = qop
            ? md5(`${HA1}:${digestData.nonce}:${nc}:${cnonce}:${qop}:${HA2}`)
            : md5(`${HA1}:${digestData.nonce}:${HA2}`);

        let header =
            `Digest username="${username}", ` +
            `realm="${digestData.realm}", ` +
            `nonce="${digestData.nonce}", ` +
            `uri="${uri}"`;

        if (qop) {
            header +=
                `, qop=${qop}` +
                `, nc=${nc}` +
                `, cnonce="${cnonce}"`;
        }

        header += `, response="${response}"`;

        return header;
    }
}

/**
 * Exports @see DigestAuthHelper as default class.
 */
export default DigestAuthHelper;