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, 5 insertions, 1 deletions

diff --git a/src/node_crypto.cc b/src/node_crypto.cc
index 9715e8b776..228dd0d16d 100644
--- a/src/node_crypto.cc
+++ b/src/node_crypto.cc
@@ -512,6 +512,7 @@ void SecureContext::Init(const FunctionCallbackInfo<Value>& args) {
 
   // SSL session cache configuration
   SSL_CTX_set_session_cache_mode(sc->ctx_.get(),
+                                 SSL_SESS_CACHE_CLIENT |
                                  SSL_SESS_CACHE_SERVER |
                                  SSL_SESS_CACHE_NO_INTERNAL |
                                  SSL_SESS_CACHE_NO_AUTO_CLEAR);
@@ -1540,7 +1541,10 @@ int SSLWrap<Base>::NewSessionCallback(SSL* s, SSL_SESSION* sess) {
       reinterpret_cast<const char*>(session_id_data),
       session_id_length).ToLocalChecked();
   Local<Value> argv[] = { session_id, session };
-  w->awaiting_new_session_ = true;
+  // On servers, we pause the handshake until callback of 'newSession', which
+  // calls NewSessionDoneCb(). On clients, there is no callback to wait for.
+  if (w->is_server())
+    w->awaiting_new_session_ = true;
   w->MakeCallback(env->onnewsession_string(), arraysize(argv), argv);
 
   return 0;