91 lines
3.0 KiB
JavaScript
91 lines
3.0 KiB
JavaScript
const dns = require("dns");
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const express = require("express");
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const isValidDomain = require("is-valid-domain");
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const host = process.env.DNSLINK_API_HOSTNAME || "0.0.0.0";
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const port = Number(process.env.DNSLINK_API_PORT) || 3100;
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const server = express();
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const dnslinkNamespace = "skynet-ns";
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const sponsorNamespace = "skynet-sponsor-key";
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const dnslinkRegExp = new RegExp(`^dnslink=/${dnslinkNamespace}/.+$`);
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const sponsorRegExp = new RegExp(`^${sponsorNamespace}=[a-zA-Z0-9]+$`);
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const dnslinkSkylinkRegExp = new RegExp(`^dnslink=/${dnslinkNamespace}/([a-zA-Z0-9_-]{46}|[a-z0-9]{55})`);
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const hint = `valid example: dnslink=/${dnslinkNamespace}/3ACpC9Umme41zlWUgMQh1fw0sNwgWwyfDDhRQ9Sppz9hjQ`;
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server.get("/dnslink/:name", async (req, res) => {
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const success = (response) => res.json(response);
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const failure = (message) => res.status(400).send(message);
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if (!isValidDomain(req.params.name)) {
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return failure(`"${req.params.name}" is not a valid domain`);
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}
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const lookup = `_dnslink.${req.params.name}`;
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dns.resolveTxt(lookup, (error, addresses) => {
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if (error) {
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if (error.code === "ENOTFOUND") {
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return failure(`ENOTFOUND: ${lookup} TXT record doesn't exist`);
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}
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if (error.code === "ENODATA") {
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return failure(`ENODATA: ${lookup} dns lookup returned no data`);
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}
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return failure(`Failed to fetch ${lookup} TXT record: ${error.message}`);
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}
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if (addresses.length === 0) {
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return failure(`No TXT record found for ${lookup}`);
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}
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const records = addresses.flat();
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const dnslinks = records.filter((record) => dnslinkRegExp.test(record));
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if (dnslinks.length === 0) {
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return failure(`TXT records for ${lookup} found but none of them contained valid skynet dnslink - ${hint}`);
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}
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if (dnslinks.length > 1) {
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return failure(`Multiple TXT records with valid skynet dnslink found for ${lookup}, only one allowed`);
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}
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const [dnslink] = dnslinks;
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const matchSkylink = dnslink.match(dnslinkSkylinkRegExp);
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if (!matchSkylink) {
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return failure(`TXT record with skynet dnslink for ${lookup} contains invalid skylink - ${hint}`);
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}
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const skylink = matchSkylink[1];
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// check if _dnslink records contain skynet-sponsor-key entries
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const sponsors = records.filter((record) => sponsorRegExp.test(record));
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if (sponsors.length > 1) {
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return failure(`Multiple TXT records with valid sponsor key found for ${lookup}, only one allowed`);
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}
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if (sponsors.length === 1) {
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// extract just the key part from the record
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const sponsor = sponsors[0].substring(sponsors[0].indexOf("=") + 1);
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console.log(`${req.params.name} => ${skylink} | sponsor: ${sponsor}`);
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return success({ skylink, sponsor });
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}
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console.log(`${req.params.name} => ${skylink}`);
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return success({ skylink });
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});
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});
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server.listen(port, host, (error) => {
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if (error) throw error;
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console.info(`Server listening at http://${host}:${port}`);
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});
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