dns: fix TTL value for AAAA replies to resolveAny()

We were previously reading from the wrong offset, namely
the one into the final results array, not the one for the
AAAA results itself, which could have lead to reading
uninitialized or out-of-bounds data.

Also, adjust the test accordingly; TTL values are not
modified by c-ares, but are only exposed for a subset
of all DNS record types.

PR-URL: #25187
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Khaidi Chu <[email protected]>
Reviewed-By: Ben Noordhuis <[email protected]>
Reviewed-By: Ruben Bridgewater <[email protected]>

Author: addaleax

src/cares_wrap.cc

@@ -1263,14 +1263,16 @@ class QueryAnyWrap: public QueryWrap {
     }
 
     CHECK_EQ(aaaa_count, naddr6ttls);
+    CHECK_EQ(ret->Length(), a_count + aaaa_count);
     for (uint32_t i = a_count; i < ret->Length(); i++) {
       Local<Object> obj = Object::New(env()->isolate());
       obj->Set(context,
                env()->address_string(),
                ret->Get(context, i).ToLocalChecked()).FromJust();
       obj->Set(context,
                env()->ttl_string(),
-               Integer::New(env()->isolate(), addr6ttls[i].ttl)).FromJust();
+               Integer::New(env()->isolate(), addr6ttls[i - a_count].ttl))
+          .FromJust();
       obj->Set(context,
                env()->type_string(),
                env()->dns_aaaa_string()).FromJust();

test/parallel/test-dns-resolveany.js

@@ -53,8 +53,13 @@ server.bind(0, common.mustCall(async () => {
 }));
 
 function validateResults(res) {
-  // Compare copies with ttl removed, c-ares fiddles with that value.
-  assert.deepStrictEqual(
-    res.map((r) => Object.assign({}, r, { ttl: null })),
-    answers.map((r) => Object.assign({}, r, { ttl: null })));
+  // TTL values are only provided for A and AAAA entries.
+  assert.deepStrictEqual(res.map(maybeRedactTTL), answers.map(maybeRedactTTL));
+}
+
+function maybeRedactTTL(r) {
+  const ret = { ...r };
+  if (!['A', 'AAAA'].includes(r.type))
+    delete ret.ttl;
+  return ret;
 }