Function buildDNSQuery

script.js:723–764

(hostname)

}

function buildDNSQuery(hostname) {
    const normalizedHost = (() => {
        const trimmed = hostname.trim().replace(/\.$/, '');
        try { return new URL(`http://${trimmed}`).hostname; }
        catch { return trimmed; }
    })();

    const labels = normalizedHost.split('.').filter(Boolean);
    if (labels.length === 0) throw new Error('Invalid hostname for DNS query');

    const header = new Uint8Array(12);
    if (typeof crypto !== 'undefined' && crypto.getRandomValues) {
        crypto.getRandomValues(header.subarray(0, 2));
    } else {
        const txid = Math.floor(Math.random() * 0xffff);
        header[0] = (txid >> 8) & 0xff;
        header[1] = txid & 0xff;
    }
    header[2] = 0x01;
    header[5] = 0x01;

    const qnameParts = [];
    labels.forEach(label => {
        const bytes = Array.from(label).map(char => {
            const code = char.charCodeAt(0);
            if (code > 0x7f) throw new Error('Hostname must be ASCII/punycode encoded');
            return code;
        });
        if (bytes.length === 0 || bytes.length > 63) throw new Error('Invalid label length in hostname');
        qnameParts.push(bytes.length, ...bytes);
    });
    const qname = new Uint8Array(qnameParts.length + 1);
    qname.set(qnameParts);

    const typeAndClass = new Uint8Array([0x00, 0x01, 0x00, 0x01]);
    const query = new Uint8Array(header.length + qname.length + typeAndClass.length);
    let offset = 0;
    query.set(header, offset); offset += header.length;
    query.set(qname, offset); offset += qname.length;
    query.set(typeAndClass, offset);
    return query;
}

function encodeDnsQueryBase64Url(query) {
    const binary = Array.from(query, byte => String.fromCharCode(byte)).join('');