dns: validate both addresses before applying them in setLocalAddress

src/cares_wrap.cc

@@ -2332,16 +2332,16 @@ void SetLocalAddress(const FunctionCallbackInfo<Value>& args) {
   // to 0 (any).
 
   if (uv_inet_pton(AF_INET, *ip0, &addr0) == 0) {
-    ares_set_local_ip4(channel->cares_channel(), nbytes::ReadUint32BE(addr0));
     type0 = 4;
   } else if (uv_inet_pton(AF_INET6, *ip0, &addr0) == 0) {
-    ares_set_local_ip6(channel->cares_channel(), addr0);
     type0 = 6;
   } else {
     THROW_ERR_INVALID_ARG_VALUE(env, "Invalid IP address.");
     return;
   }
 
+  // Validate the second argument before applying anything, so that a call
+  // that throws leaves the channel unchanged.
   if (!args[1]->IsUndefined()) {
     CHECK(args[1]->IsString());
     node::Utf8Value ip1(isolate, args[1]);
@@ -2350,29 +2350,27 @@ void SetLocalAddress(const FunctionCallbackInfo<Value>& args) {
       if (type0 == 4) {
         THROW_ERR_INVALID_ARG_VALUE(env, "Cannot specify two IPv4 addresses.");
         return;
-      } else {
-        ares_set_local_ip4(channel->cares_channel(),
-                           nbytes::ReadUint32BE(addr1));
       }
     } else if (uv_inet_pton(AF_INET6, *ip1, &addr1) == 0) {
       if (type0 == 6) {
         THROW_ERR_INVALID_ARG_VALUE(env, "Cannot specify two IPv6 addresses.");
         return;
-      } else {
-        ares_set_local_ip6(channel->cares_channel(), addr1);
       }
     } else {
       THROW_ERR_INVALID_ARG_VALUE(env, "Invalid IP address.");
       return;
     }
   } else {
     // No second arg specified
-    if (type0 == 4) {
-      memset(&addr1, 0, sizeof(addr1));
-      ares_set_local_ip6(channel->cares_channel(), addr1);
-    } else {
-      ares_set_local_ip4(channel->cares_channel(), 0);
-    }
+    memset(&addr1, 0, sizeof(addr1));
+  }
+
+  if (type0 == 4) {
+    ares_set_local_ip4(channel->cares_channel(), nbytes::ReadUint32BE(addr0));
+    ares_set_local_ip6(channel->cares_channel(), addr1);
+  } else {
+    ares_set_local_ip6(channel->cares_channel(), addr0);
+    ares_set_local_ip4(channel->cares_channel(), nbytes::ReadUint32BE(addr1));
   }
 }
 

test/parallel/test-dns-setlocaladdress-rejected.js

@@ -0,0 +1,45 @@
+'use strict';
+const common = require('../common');
+
+// Verifies that a call to resolver.setLocalAddress() that throws leaves the
+// previously configured local address in place.
+
+// Binding to 127.0.0.0/8 addresses other than 127.0.0.1 works out of the box
+// on Linux only.
+if (!common.isLinux)
+  common.skip('requires the whole 127.0.0.0/8 range on the loopback interface');
+
+const assert = require('assert');
+const dgram = require('dgram');
+const { Resolver } = require('dns');
+
+const resolver = new Resolver({ timeout: 1000, tries: 1 });
+const server = dgram.createSocket('udp4');
+
+server.on('message', common.mustCall((msg, rinfo) => {
+  assert.strictEqual(rinfo.address, '127.0.0.2');
+  server.close();
+  resolver.cancel();
+}));
+
+server.bind(0, '127.0.0.1', common.mustCall(() => {
+  resolver.setServers([`127.0.0.1:${server.address().port}`]);
+  resolver.setLocalAddress('127.0.0.2');
+
+  assert.throws(() => {
+    resolver.setLocalAddress('127.0.0.3', '127.0.0.4');
+  }, {
+    code: 'ERR_INVALID_ARG_VALUE',
+    message: 'Cannot specify two IPv4 addresses.',
+  });
+  assert.throws(() => {
+    resolver.setLocalAddress('127.0.0.5', 'bad');
+  }, {
+    code: 'ERR_INVALID_ARG_VALUE',
+    message: 'Invalid IP address.',
+  });
+
+  resolver.resolve4('example.test', common.mustCall((err) => {
+    assert.strictEqual(err.code, 'ECANCELLED');
+  }));
+}));