From c8583c96fb1baa0e0bab83297ff0cb0096c06fcc Mon Sep 17 00:00:00 2001 From: Simon Rogers Date: Tue, 3 Apr 2018 16:03:01 +0200 Subject: [PATCH] Updates for improved mDNS support and DNS-SD --- bin/digd.js | 141 ++++++++++++++++++++++++++++++++++++---------- lib/digd.js | 29 +++++++--- lib/store.json.js | 23 +++++++- lib/udpd.js | 15 +++-- 4 files changed, 166 insertions(+), 42 deletions(-) diff --git a/bin/digd.js b/bin/digd.js index 8f90164..ad1f434 100755 --- a/bin/digd.js +++ b/bin/digd.js @@ -31,6 +31,7 @@ cli.parse({ , 'address': [ false, 'ip address(es) to listen on (defaults to 0.0.0.0,::0)', 'string' ] , 'port': [ 'p', 'port (defaults to 53 for dns and 5353 for mdns)', 'int' ] , 'nameserver': [ false, 'the nameserver(s) to use for recursive lookups (defaults to ' + defaultNameservers.join(',') + ')', 'string' ] +, 'send': [ false, 'send query and response messages to the parent process', 'boolean', false ] //, 'serve': [ 's', 'path to json file with array of responses to issue for given queries', 'string' ] //, 'type': [ 't', 'type (defaults to ANY for dns and PTR for mdns)', 'string' ] //, 'query': [ 'q', 'a superfluous explicit option to set the query as a command line flag' ] @@ -90,35 +91,61 @@ cli.main(function (args, cli) { if (!('timeout' in cli)) { cli.timeout = 3000; } + cli.norecurse = true; } else { if (!cli.port) { cli.port = cli.p = 53; } } + cli.send = cli.send && (typeof process.send === 'function'); + function sendMsg(msg) { + if (cli.send) + process.send(msg); + } + var engine; var path = require('path'); var engineOpts = { filepath: path.resolve(cli.input) }; var dnsd = {}; dnsd.onMessage = function (nb, cb) { - var byteOffset = nb._dnsByteOffset || nb.byteOffset; - var queryAb = nb.buffer.slice(byteOffset, byteOffset + nb.byteLength); var query; var count; + var byteLength = 0; + if (typeof nb === 'object') { + byteLength = nb.byteLength; + var byteOffset = nb._dnsByteOffset || nb.byteOffset; + var queryAb = nb.buffer.slice(byteOffset, byteOffset + nb.byteLength); - try { - query = dnsjs.DNSPacket.parse(queryAb); - } catch(e) { - // TODO log bad queries (?) - console.error("Could not parse DNS query, ignoring."); - console.error(e); try { - hexdump = require('hexdump.js').hexdump; - console.error(hexdump(queryAb)); - console.error(''); + query = dnsjs.DNSPacket.parse(queryAb); } catch(e) { - // ignore + // TODO log bad queries (?) + console.error("Could not parse DNS query, ignoring."); + console.error(e); + try { + hexdump = require('hexdump.js').hexdump; + console.error(hexdump(queryAb)); + console.error(''); + } catch(e) { + // ignore + } + return; } + } else { + // Special mDNS only startup query to advertise DNS-SD records + query = { + header: { id: 0, qr: 0, opcode: 0, aa: 1, tc: 0, rd: 0, ra: 0, rcode: 0 } + , question: [{ name: nb, type: 12, typeName: 'PTR', class: 1, className: 'IN', unicastResponse: false }] + , answer: [] + , authority: [] + , additional: [] + , dns_sd_startup: true + }; + } + + if (cli.mdns && query.header.qr) { + console.log('Ignoring mDNS answer loopback'); return; } @@ -154,19 +181,20 @@ cli.main(function (args, cli) { printer(q); } if (query.answer.length) { - console.error('[ERROR] Query contains an answer section:'); + if (!cli.mdns) + console.log('[ERROR] Query contains an answer section:'); console.log(';; ANSWER SECTION:'); query.answer.forEach(print); } if (query.authority.length) { console.log(''); - console.error('[ERROR] Query contains an authority section:'); + console.log('[ERROR] Query contains an authority section:'); console.log(';; AUTHORITY SECTION:'); query.authority.forEach(print); } if (query.additional.length) { console.log(''); - console.error('[ERROR] Query contains an additional section:'); + console.log('[ERROR] Query contains an additional section:'); console.log(';; ADDITIONAL SECTION:'); query.additional.forEach(print); } @@ -179,6 +207,7 @@ cli.main(function (args, cli) { common.writeQuery(cli, query, queryAb); //common.writeResponse(opts, query, nb, packet); } + sendMsg({query: query}); function sendEmptyResponse(query, rcode) { // rcode @@ -189,7 +218,7 @@ cli.main(function (args, cli) { var newAb; var emptyResp = { header: { - id: query.header.id // require('crypto').randomBytes(2).readUInt16BE(0) + id: query.header.id || require('crypto').randomBytes(2).readUInt16BE(0) , qr: 1 , opcode: 0 , aa: 0 // TODO it may be authoritative @@ -213,22 +242,44 @@ cli.main(function (args, cli) { }); }); - try { - newAb = dnsjs.DNSPacket.write(emptyResp); - } catch(e) { - console.error("Could not write empty DNS response"); - console.error(e); - console.error(emptyResp); - cb(e, null, '[DEV] response sent (empty)'); - return; - } + if (!cli.mdns) { // no empty response for mDNS + try { + newAb = dnsjs.DNSPacket.write(emptyResp); + } catch(e) { + console.error("Could not write empty DNS response"); + console.error(e); + console.error(emptyResp); + cb(e, null, '[DEV] response sent (empty)'); + return; + } - cb(null, newAb, '[DEV] response sent (empty)'); + cb(null, newAb, '[DEV] response sent (empty)'); + } } function sendResponse(newPacket) { + if (cli.mdns && !query.question[0].unicastResponse) { + newPacket.question = []; + } + var newAb; + if (cli.mdns) { + let answers = []; + newPacket.answer.forEach(a => { + // Don't send response if it is already in known answers in query + if (query.answer.find(q => { return q.data === a.data; })) { + console.log('Not sending local response for', a.data, '- already known'); + } else { + answers.push(a); + } + }); + if (!answers.length) + return; + + newPacket.answer = answers; + } + try { newAb = dnsjs.DNSPacket.write(newPacket); } catch(e) { @@ -239,7 +290,26 @@ cli.main(function (args, cli) { return; } - cb(null, newAb, '[DEV] response sent (local query)'); + if (cli.mdns) { + // mDNS requires id in response header to be 0. Force it here as DNSPacket.write doesn't know about mDNS + newAb.writeUInt16LE(0, 0); + newPacket.header.id = 0; + } + + if (cli.mdns && !query.question[0].unicastResponse) { + // mDNS requires a random delay between 20 and 120ms to avoid collisions + setTimeout(() => { + cb(null, newAb, '[DEV] response sent (local query)', query.question[0].unicastResponse||false) + sendMsg({local: newPacket}); + if (query.dns_sd_startup && query.question[0].name === '_services._dns-sd._udp.local') + newPacket.answer.forEach(a => dnsd.onMessage(a.data, cb)); // advertise the records referenced by the startup _services query + }, 20 + (100.0 * Math.random()) >> 0 + ); + + } else { + cb(null, newAb, '[DEV] response sent (local query)', query.question[0].unicastResponse||false); + sendMsg({local: newPacket}); + } } function recurse() { @@ -259,7 +329,7 @@ cli.main(function (args, cli) { var newResponse = { header: { - id: query.header.id // require('crypto').randomBytes(2).readUInt16BE(0) + id: query.header.id || require('crypto').randomBytes(2).readUInt16BE(0) , qr: 0 , opcode: 0 , aa: 0 // query.header.aa ? 1 : 0 // NA? not sure what this would do @@ -297,6 +367,7 @@ cli.main(function (args, cli) { } cb(null, newAb, '[DEV] response sent'); + sendMsg({recurse: newResponse}); } } @@ -306,6 +377,7 @@ cli.main(function (args, cli) { } , onMessage: function (packet) { // yay! recursion was available after all! + newResponse.header.qr = 1; newResponse.header.ra = 1; newResponse.header.rcode = NOERROR; @@ -392,7 +464,16 @@ cli.main(function (args, cli) { respondWithResults(e); return; } - require('../lib/digd.js').query(engine, query, respondWithResults); + if (cli.mdns) { + // mdns allows multiple questions - should coalesce results... + query.question.forEach(q => { + let singleQ = query; + singleQ.question = [q]; + require('../lib/digd.js').query(engine, singleQ, respondWithResults); + }) + } else { + require('../lib/digd.js').query(engine, query, respondWithResults); + } }; cli.defaultNameservers = defaultNameservers; @@ -407,6 +488,8 @@ cli.main(function (args, cli) { console.log('index, defaultNameservers', index, cli.defaultNameservers); } } + + sendMsg({ready: 'digd.js v' + pkg.version}); }); if (cli.tcp /* TODO v1.3 !cli.notcp */) { require('../lib/tcpd.js').create(cli, dnsd); diff --git a/lib/digd.js b/lib/digd.js index 63c797b..91ae499 100644 --- a/lib/digd.js +++ b/lib/digd.js @@ -7,6 +7,7 @@ module.exports.ask = function (query, cb) { */ var NOERROR = 0; +var SERVFAIL = 2; var NXDOMAIN = 3; var REFUSED = 5; @@ -242,7 +243,7 @@ module.exports.query = function (engine, query, cb) { var results = { header: { - id: query.header.id // same as request + id: query.header.id || require('crypto').randomBytes(2).readUInt16BE(0) // same as request if not mDNS , qr: 1 , opcode: 0 // pretty much always 0 QUERY , aa: 1 // TODO right now we assume that if we have the record, we're authoritative @@ -289,10 +290,10 @@ module.exports.query = function (engine, query, cb) { console.log('[SOA] looking for', qnames, 'and proudly serving', err, myDomains); if (err) { cb(err); return; } - // this should result in a REFUSED status + // this should result in a SERVFAIL status if (!myDomains.length) { - // REFUSED will have no records, so we could still recursion, if enabled - results.header.rcode = REFUSED; + // SERVFAIL will have no records, so we could still recursion, if enabled + results.header.rcode = SERVFAIL; cb(null, results); return; } @@ -392,9 +393,14 @@ module.exports.query = function (engine, query, cb) { hasA = hasA || ('A' === r.type || 'A' === r.typeName || 'AAAA' === r.type || 'AAAA' === r.typeName); - return passCnames || ((r.type && r.type === query.question[0].type) - || (r.type && r.type === query.question[0].typeName) - || (r.typeName && r.typeName === query.question[0].typeName) + const isDNS_SD_Record = ('SRV' === r.type) || ('TXT' === r.type); + + return passCnames || ( + (r.type && r.type === query.question[0].type) || + (r.type && r.type === query.question[0].typeName) || + (r.typeName && r.typeName === query.question[0].typeName) || + (('A' === r.type) && (('PTR' === query.question[0].typeName) || ('SRV' === query.question[0].typeName))) || + isDNS_SD_Record ); }); @@ -407,6 +413,15 @@ module.exports.query = function (engine, query, cb) { } } + // DNS-SD requires selected matching records to be put into additional records - rfc6763 12.1, 12.2 + myRecords = myRecords.filter(function (r) { + if (query.question[0].name !== r.name) { + results.additional.push(dbToResourceRecord(r)); + return false; + } else + return true; + }); + if (myRecords.length) { myRecords.forEach(function (r) { results.answer.push(dbToResourceRecord(r)); diff --git a/lib/store.json.js b/lib/store.json.js index 672ebcb..602f255 100644 --- a/lib/store.json.js +++ b/lib/store.json.js @@ -369,7 +369,8 @@ module.exports.create = function (opts) { }); } , get: function (query, cb) { - var myRecords = db.records.slice(0).filter(function (r) { + const localRecords = db.records.slice(0); + var myRecords = localRecords.filter(function (r) { if ('string' !== typeof r.name) { return false; @@ -383,6 +384,26 @@ module.exports.create = function (opts) { } } }); + + // DNS-SD requires selected matching records to be put into additional records - rfc6763 12.1, 12.2 + myRecords.slice(0).forEach(r => { + if ('PTR' === r.type) { + localRecords.forEach(l => { + if ((l.name === r.data) && (('SRV' === l.type) || ('TXT' === l.type))) + myRecords.push(l); + }); + } + }); + + myRecords.slice(0).forEach(r => { + if ('SRV' === r.type) { + localRecords.forEach(l => { + if ((l.name === r.target) && (('A' === l.type) || ('AAAA' === l.type))) + myRecords.push(l); + }); + } + }); + process.nextTick(function () { cb(null, myRecords); }); diff --git a/lib/udpd.js b/lib/udpd.js index f969ec2..6aecef8 100644 --- a/lib/udpd.js +++ b/lib/udpd.js @@ -32,11 +32,12 @@ module.exports.create = function (cli, dnsd) { //console.log('[DEBUG] got a UDP message', nb.length); //console.log(nb.toString('hex')); - dnsd.onMessage(nb, function (err, newAb, dbgmsg) { + dnsd.onMessage(nb, function (err, newAb, dbgmsg, unicastResponse) { // TODO send legit error message - if (err) { server.send(Buffer.from([0x00]), rinfo.port, rinfo.address); return; } - server.send(newAb, rinfo.port, rinfo.address, function () { - console.log('[dnsd.onMessage] ' + dbgmsg, rinfo.port, rinfo.address); + const address = cli.mdns && !unicastResponse ? '224.0.0.251' : rinfo.address; + if (err) { server.send(Buffer.from([0x00]), rinfo.port, address); return; } + server.send(newAb, rinfo.port, address, function () { + console.log('[dnsd.onMessage] ' + dbgmsg, rinfo.port, address); }); }); }; @@ -46,13 +47,17 @@ module.exports.create = function (cli, dnsd) { var server = this; if (cli.mdns || '224.0.0.251' === cli.nameserver) { - server.setBroadcast(true); server.addMembership(cli.nameserver); } console.log(''); console.log('Bound and Listening:'); console.log(server.address().address + '#' + server.address().port + ' (' + server.type + ')'); + + if (cli.mdns) { + // special startup case to advertise local dns-sd records + handlers.onMessage('_services._dns-sd._udp.local', { address: '224.0.0.251', port: 5353 }); + } }; server.on('error', handlers.onError);