dns: handle array holes in setServers()

This commit adds better handling of exceptional array formats passed to dns.setServers(). Prior to this commit, the input array was validated using map(), which preserves holes, allowing them to be passed to c-ares, crashing Node. This commit replaces map() with forEach(), which skips holes. Fixes: #8538 PR-URL: #8567 Reviewed-By: Ilkka Myller <[email protected]> Reviewed-By: Luigi Pinca <[email protected]> Reviewed-By: James M Snell <[email protected]>
nodejs · Oct 11, 2016 · 4e8c037 · 4e8c037
1 parent e8f1cf1
commit 4e8c037
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Showing 2 changed files with 32 additions and 4 deletions.
diff --git a/lib/dns.js b/lib/dns.js
@@ -286,25 +286,26 @@ exports.setServers = function(servers) {
   // cache the original servers because in the event of an error setting the
   // servers cares won't have any servers available for resolution
   const orig = cares.getServers();
+  const newSet = [];
 
-  const newSet = servers.map((serv) => {
+  servers.forEach((serv) => {
     var ipVersion = isIP(serv);
     if (ipVersion !== 0)
-      return [ipVersion, serv];
+      return newSet.push([ipVersion, serv]);
 
     const match = serv.match(/\[(.*)\](:\d+)?/);
     // we have an IPv6 in brackets
     if (match) {
       ipVersion = isIP(match[1]);
       if (ipVersion !== 0)
-        return [ipVersion, match[1]];
+        return newSet.push([ipVersion, match[1]]);
     }
 
     const s = serv.split(/:\d+$/)[0];
     ipVersion = isIP(s);
 
     if (ipVersion !== 0)
-      return [ipVersion, s];
+      return newSet.push([ipVersion, s]);
 
     throw new Error(`IP address is not properly formatted: ${serv}`);
   });

diff --git a/test/parallel/test-dns.js b/test/parallel/test-dns.js
@@ -7,6 +7,33 @@ const dns = require('dns');
 var existing = dns.getServers();
 assert(existing.length);
 
+// Verify that setServers() handles arrays with holes and other oddities
+assert.doesNotThrow(() => {
+  const servers = [];
+
+  servers[0] = '127.0.0.1';
+  servers[2] = '0.0.0.0';
+  dns.setServers(servers);
+});
+
+assert.doesNotThrow(() => {
+  const servers = ['127.0.0.1', '192.168.1.1'];
+
+  servers[3] = '127.1.0.1';
+  servers[4] = '127.1.0.1';
+  servers[5] = '127.1.1.1';
+
+  Object.defineProperty(servers, 2, {
+    enumerable: true,
+    get: () => {
+      servers.length = 3;
+      return '0.0.0.0';
+    }
+  });
+
+  dns.setServers(servers);
+});
+
 function noop() {}
 
 var goog = [