tls: introduce client 'session' event

OpenSSL has supported async notification of sessions and tickets since
1.1.0 using SSL_CTX_sess_set_new_cb(), for all versions of TLS. Using
the async API is optional for TLS1.2 and below, but for TLS1.3 it will
be mandatory. Future-proof applications should start to use async
notification immediately. In the future, for TLS1.3, applications that
don't use the async API will silently, but gracefully, fail to resume
sessions and instead do a full handshake.

See: https://wiki.openssl.org/index.php/TLS1.3#Sessions

PR-URL: https://github.com/nodejs/node/pull/25831
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Fedor Indutny <fedor.indutny@gmail.com>

1 files changed, 9 insertions, 1 deletions

diff --git a/test/parallel/test-tls-async-cb-after-socket-end.js b/test/parallel/test-tls-async-cb-after-socket-end.js
index 6ca38461fd..5c812c8f04 100644
--- a/test/parallel/test-tls-async-cb-after-socket-end.js
+++ b/test/parallel/test-tls-async-cb-after-socket-end.js
@@ -6,9 +6,15 @@ const fixtures = require('../common/fixtures');
 const SSL_OP_NO_TICKET = require('crypto').constants.SSL_OP_NO_TICKET;
 const tls = require('tls');
 
-// Check tls async callback after socket ends
+// Check that TLS1.2 session resumption callbacks don't explode when made after
+// the tls socket is destroyed. Disable TLS ticket support to force the legacy
+// session resumption mechanism to be used.
+
+// TLS1.2 is the last protocol version to support TLS sessions, after that the
+// new and resume session events will never be emitted on the server.
 
 const options = {
+  maxVersion: 'TLSv1.2',
   secureOptions: SSL_OP_NO_TICKET,
   key: fixtures.readSync('test_key.pem'),
   cert: fixtures.readSync('test_cert.pem')
@@ -25,6 +31,8 @@ server.on('newSession', common.mustCall((key, session, done) => {
 
 server.on('resumeSession', common.mustCall((id, cb) => {
   sessionCb = cb;
+  // Destroy the client and then call the session cb, to check that the cb
+  // doesn't explode when called after the handle has been destroyed.
   next();
 }));