81 lines
2.6 KiB
JavaScript
81 lines
2.6 KiB
JavaScript
const dns = require('dns'),
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Logger = require('./Logger'),
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util = require('util'),
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dnsLookupAsync = util.promisify(dns.lookup),
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dnsResolveAsync = util.promisify(dns.resolve),
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punycode = require('punycode');
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class DnsResolver {
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/**
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* @param {Logger} logger
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*/
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constructor(logger) {
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this.logger = logger;
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}
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isIp(host) {
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return !!host.match(/\d+\.\d+\.\d+\.\d+/);
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}
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/**
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* Response port will only be present if srv record was involved.
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* @param {string} host
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* @param {number} ipFamily
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* @param {string=} srvRecordPrefix
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* @returns {Promise<{address:string, port:number=}>}
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*/
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async resolve(host, ipFamily, srvRecordPrefix) {
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this.logger.debug("DNS Lookup: " + host);
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if(this.isIp(host)) {
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this.logger.debug("Raw IP Address: " + host);
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return {address: host};
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}
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const asciiForm = punycode.toASCII(host);
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if (asciiForm !== host) {
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this.logger.debug("Encoded punycode: " + host + " -> " + asciiForm);
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host = asciiForm;
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}
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if (srvRecordPrefix) {
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this.logger.debug("SRV Resolve: " + srvRecordPrefix + '.' + host);
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let records;
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try {
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records = await dnsResolveAsync(srvRecordPrefix + '.' + host, 'SRV');
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if (records.length >= 1) {
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this.logger.debug("Found SRV Records: ", records);
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const record = records[0];
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const srvPort = record.port;
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const srvHost = record.name;
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if (srvHost === host) {
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throw new Error('Loop in DNS SRV records');
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}
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return {
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port: srvPort,
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...await this.resolve(srvHost, ipFamily, srvRecordPrefix)
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};
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}
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this.logger.debug("No SRV Record");
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} catch (e) {
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this.logger.debug(e);
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}
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}
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this.logger.debug("Standard Resolve: " + host);
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const dnsResult = await dnsLookupAsync(host, ipFamily);
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// For some reason, this sometimes returns a string address rather than an object.
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// I haven't been able to reproduce, but it's been reported on the issue tracker.
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let address;
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if (typeof dnsResult === 'string') {
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address = dnsResult;
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} else {
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address = dnsResult.address;
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}
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this.logger.debug("Found address: " + address);
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return {address: address};
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}
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}
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module.exports = DnsResolver;
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