WIP dns server

2017-09-25 18:14:27 -06:00 · 2017-09-25 18:14:27 -06:00 · fcaafbf8b9
parent 083df5755b
commit fcaafbf8b9
4 changed files with 106 additions and 32 deletions
--- a/bin/digd.js
+++ b/bin/digd.js
@ -4,10 +4,10 @@ var cli = require('cli');
 var dig = require('../dns-request');
 var dgram = require('dgram');
 var dnsjs = require('dns-suite');
-var hexdump = require('hexdump.js').hexdump;
 var crypto = require('crypto');
 var common = require('../common');
 var defaultNameservers = require('dns').getServers();
+var hexdump;

 cli.parse({
 //  'b': [ false, 'set source IP address (defaults to 0.0.0.0)', 'string' ]
@ -81,18 +81,37 @@ cli.main(function (args, cli) {

  handlers.onMessage = function (nb, rinfo) {
    var queryAb = nb.buffer.slice(nb.byteOffset, nb.byteOffset + nb.byteLength);
-    var query = dnsjs.DNSPacket.parse(queryAb);
-    var newQuery;
+    var query;
    var count;

+    try {
+      query = dnsjs.DNSPacket.parse(queryAb);
+    } catch(e) {
+      // TODO log bad queries (?)
+      console.error("Could not parse DNS query, ignoring.");
+      try {
+        hexdump = require('hexdump.js').hexdump;
+        console.error(hexdump(queryAb));
+        console.error('');
+      } catch(e) {
+        // ignore
+      }
+      return;
+    }
+
    if (cli.debug) {
      console.log('');
      console.log('DNS Question:');
      console.log('');
      console.log(query);
      console.log('');
-      console.log(hexdump(queryAb));
-      console.log('');
+      try {
+        hexdump = require('hexdump.js').hexdump;
+        console.log(hexdump(queryAb));
+        console.log('');
+      } catch(e) {
+        // ignore
+      }
    }

    dig.logQuestion(query);
@ -138,17 +157,18 @@ cli.main(function (args, cli) {
      //common.writeResponse(opts, query, nb, packet);
    }

-    function sendEmptyResponse(query) {
-      var newQuery = {
+    function sendEmptyResponse(query, nx) {
+      var newAb;
+      var emptyResp = {
        header: {
          id: query.header.id // require('crypto').randomBytes(2).readUInt16BE(0)
        , qr: 1
        , opcode: 0
-        , aa: 0     // TODO maybe
+        , aa: 0     // TODO it may be authoritative
        , tc: 0
        , rd: query.header.rd
-        , ra: cli.norecurse ? 0 : 1
-        , rcode: 0  // no error
+        , ra: cli.norecurse ? 0 : 1 // TODO is this bit dependent on the rd bit?
+        , rcode: nx ? 3 : 0 // no error
        }
      , question: []
      , answer: []
@ -156,7 +176,7 @@ cli.main(function (args, cli) {
      , additional: []
      };
      query.question.forEach(function (q) {
-        newQuery.question.push({
+        emptyResp.question.push({
          name: q.name
        , type: q.type
        , typeName: q.typeName
@ -164,26 +184,52 @@ cli.main(function (args, cli) {
        , className: q.className
        });
      });
-      server.send(dnsjs.DNSPacket.write(newQuery), rinfo.port, rinfo.address, function () {
-        console.log('[DEV] response sent');
+
+      try {
+        newAb = dnsjs.DNSPacket.write(emptyResp);
+      } catch(e) {
+        console.error("Could not write DNS response");
+        console.error(emptyResp);
+        return;
+      }
+
+      server.send(newAb, rinfo.port, rinfo.address, function () {
+        console.log('[DEV] response sent (empty)');
+      });
+    }
+
+    function sendResponse(newPacket) {
+      var newAb;
+
+      try {
+        newAb = dnsjs.DNSPacket.write(newPacket);
+      } catch(e) {
+        console.error("Could not write DNS response");
+        console.error(newPacket);
+        return;
+      }
+
+      server.send(newAb, rinfo.port, rinfo.address, function () {
+        console.log('[DEV] response sent (local query)');
      });
    }

    function recurse() {
      if (!query.header.rd) {
        console.log("[Could not answer. Sent empty response.]");
-        sendEmptyResponse(query);
+        sendEmptyResponse(query, true);
        return;
      }

      if (cli.norecurse) {
        console.log("[Could not answer. Sent empty response.]");
-        sendEmptyResponse(query);
+        sendEmptyResponse(query, true);
        return;
      }

-      // ANY, A, AAAA, CNAME, MX, NAPTR, NS, PTR, SOA, SRV, TXT
-      newQuery = {
+      // TODO newQuery
+
+      var newResponse = {
        header: {
          id: query.header.id // require('crypto').randomBytes(2).readUInt16BE(0)
        , qr: 0
@ -200,7 +246,7 @@ cli.main(function (args, cli) {
      , additional: []
      };
      query.question.forEach(function (q) {
-        newQuery.question.push({
+        newResponse.question.push({
          name: q.name
        , type: q.type
        , typeName: q.typeName
@ -209,9 +255,19 @@ cli.main(function (args, cli) {
        });

        function updateCount() {
+          var newAb;
          count -= 1;
+
          if (!count) {
-            server.send(dnsjs.DNSPacket.write(newQuery), rinfo.port, rinfo.address, function () {
+            try {
+              newAb = dnsjs.DNSPacket.write(newResponse);
+            } catch(e) {
+              console.error("Could not write DNS response");
+              console.error(newResponse);
+              return;
+            }
+
+            server.send(newAb, rinfo.port, rinfo.address, function () {
              console.log('[DEV] response sent');
            });
          }
@ -225,29 +281,32 @@ cli.main(function (args, cli) {

            (packet.answer||[]).forEach(function (a) {
              // TODO copy each relevant property
-              console.log('ans', a);
-              newQuery.answer.push(a);
+              console.log('ans', JSON.stringify(a, null, 2));
+              newResponse.answer.push(a);
            });
            (packet.authority||[]).forEach(function (a) {
              // TODO copy each relevant property
-              console.log('auth', a);
-              newQuery.authority.push(a);
+              console.log('auth', JSON.stringify(a, null, 2));
+              newResponse.authority.push(a);
            });
            (packet.additional||[]).forEach(function (a) {
              // TODO copy each relevant property
-              console.log('add', a);
-              newQuery.additional.push(a);
+              console.log('add', JSON.stringify(a, null, 2));
+              newResponse.additional.push(a);
            });

            updateCount();

          }
        , onListening: function () {}
-        , onSent: function (res) {
+        , onSent: function (/*res*/) {
+            /*
            if (cli.debug) {
              console.log('');
              console.log('request sent to', res.nameserver);
            }
+            */
+            console.log('[DEV] response sent (recurse)');
          }
        , onTimeout: function (res) {
            console.log(";; [" + q.name + "] connection timed out; no servers could be reached");
@ -276,7 +335,11 @@ cli.main(function (args, cli) {
    }

    // TODO get local answer first, if available
-    recurse();
+    require('../dns-store').query(query, function (err, resp) {
+      if (err) { recurse(); return; }
+
+      sendResponse(resp);
+    });

  };

--- a/common.js
+++ b/common.js
@ -27,11 +27,10 @@ module.exports = {
  , 'PTR': function (q) {
      console.log(';' + q.name + '.', q.ttl, q.className, q.typeName, q.data);
    }
-  /*
  , 'SOA': function (q) {
-      console.log(';' + q.name + '.', q.ttl, q.className, q.typeName, q.data);
+      // no ';' in authority section?
+      console.log('' + q.name + '.', q.ttl, q.className, q.typeName, q.name_server, q.email_addr, q.sn, q.ref, q.ret, q.ex, q.nx);
    }
-  */
  , 'SRV': function (q) {
      console.log(';' + q.name + '.', q.ttl, q.className, q.typeName, q.priority + ' ' + q.weight + ' ' + q.port + ' ' + q.target);
    }
--- a/dns-store.js
+++ b/dns-store.js
@ -0,0 +1,10 @@
+(function () {
+'use strict';
+
+module.exports.query = function (query, cb) {
+  process.nextTick(function () {
+    cb(new Error('No local lookup method for DNS records defined.'));
+  });
+};
+
+}());
--- a/package.json
+++ b/package.json
@ -40,7 +40,9 @@
  "homepage": "https://git.daplie.com/Daplie/dig.js",
  "dependencies": {
    "cli": "^1.0.1",
-    "dns-suite": "git+https://git@git.daplie.com/Daplie/dns-suite#v1.1.0",
-    "hexdump.js": "^1.0.2"
+    "dns-suite": "git+https://git@git.daplie.com/Daplie/dns-suite#v1.1.0"
+  },
+  "optionalDependencies": {
+    "hexdump.js": "git+https://git@git.daplie.com/Daplie/hexdump.js#master"
  }
 }