dns: improve setServers() errors and performance

Issue 1: make invalid setServers yield uniform error

Behavior:
dns.setServers throws a null pointer dereference on some inputs.
Expected behavior was the more pleasant
  TypeError [ERR_INVALID_IP_ADDRESS] ...

Root cause(s?):
- Dereferencing the result of a regex match without confirming
  that there was a match.
- assuming the capture of an optional group (?)

Solution:
Confirm the match, and handle a missing port cleanly.

Tests: I added tests for various unusual inputs.

Issue 2: revise quadratic regex in setServers

Problem:
The IPv6 regex was quadratic.
On long malicious input the event loop could block.

The security team did not deem it a security risk,
but said a PR was welcome.

Solution:
Revise the regex to a linear-complexity version.

Tests:
I added REDOS tests to the "oddities" section.

Fixes: https://github.com/nodejs/node/issues/20441
Fixes: https://github.com/nodejs/node/issues/20443

PR-URL: https://github.com/nodejs/node/pull/20445
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/test/parallel/test-dns.js b/test/parallel/test-dns.js
index fb648544b9..f50b9464f1 100644
--- a/test/parallel/test-dns.js
+++ b/test/parallel/test-dns.js
@@ -62,6 +62,31 @@ assert(existing.length > 0);
   ]);
 }
 
+{
+  // Various invalidities, all of which should throw a clean error.
+  const invalidServers = [
+    ' ',
+    '\n',
+    '\0',
+    '1'.repeat(3 * 4),
+    // Check for REDOS issues.
+    ':'.repeat(100000),
+    '['.repeat(100000),
+    '['.repeat(100000) + ']'.repeat(100000) + 'a'
+  ];
+  invalidServers.forEach((serv) => {
+    assert.throws(
+      () => {
+        dns.setServers([serv]);
+      },
+      {
+        name: 'TypeError [ERR_INVALID_IP_ADDRESS]',
+        code: 'ERR_INVALID_IP_ADDRESS'
+      }
+    );
+  });
+}
+
 const goog = [
   '8.8.8.8',
   '8.8.4.4',