tls: add getter and setter for session ticket number.

doc/api/tls.md

@@ -629,6 +629,30 @@ Existing or currently pending server connections will use the previous keys.
 
 See [Session Resumption][] for more information.
 
+### `server.getNumTickets()`
+<!-- YAML
+added: CHANGEME
+-->
+
+* Returns: {number} A number of session tickets.
+
+Returns the number of session tickets that are sent to the client after
+a full handshake.
+
+See [SSL_CTX_get_num_tickets][] for more information.
+
+### `server.setNumTickets(numTickets)`
+<!-- YAML
+added: CHANGEME
+-->
+
+* `numTickets` {number} A number of session tickets.
+
+Sets the number of session tickets that are sent to the client after
+a full handshake.
+
+See [SSL_CTX_set_num_tickets][] for more information.
+
 ## Class: `tls.TLSSocket`
 <!-- YAML
 added: v0.11.4
@@ -1628,6 +1652,8 @@ changes:
     **Default:** none, see `minVersion`.
   * `sessionIdContext` {string} Opaque identifier used by servers to ensure
     session state is not shared between applications. Unused by clients.
+  * `numTickets` {number} The number of session tickets that will be sent to the
+    client after a full handshake. **Default:** `2`.
 
 [`tls.createServer()`][] sets the default value of the `honorCipherOrder` option
 to `true`, other APIs that create secure contexts leave it unset.
@@ -2005,3 +2031,5 @@ where `secureSocket` has the same API as `pair.cleartext`.
 [specific attacks affecting larger AES key sizes]: https://www.schneier.com/blog/archives/2009/07/another_new_aes.html
 [RFC 4279]: https://tools.ietf.org/html/rfc4279
 [RFC 4086]: https://tools.ietf.org/html/rfc4086
+[SSL_CTX_get_num_tickets]: https://www.openssl.org/docs/manmaster/man3/SSL_CTX_get_num_tickets.html
+[SSL_CTX_set_num_tickets]: https://www.openssl.org/docs/manmaster/man3/SSL_CTX_set_num_tickets.html

lib/_tls_common.js

@@ -294,6 +294,10 @@ exports.createSecureContext = function createSecureContext(options) {
                                    options.clientCertEngine);
   }
 
+  if (options.numTickets) {
+    c.context.setNumTickets(options.numTickets);
+  }
+
   return c;
 };
 

lib/_tls_wrap.js

@@ -1315,6 +1315,9 @@ Server.prototype.setSecureContext = function(options) {
                                   .slice(0, 32);
   }
 
+  if (options.numTickets)
+    this.numTickets = options.numTickets;
+
   this._sharedCreds = tls.createSecureContext({
     pfx: this.pfx,
     key: this.key,
@@ -1332,7 +1335,8 @@ Server.prototype.setSecureContext = function(options) {
     secureOptions: this.secureOptions,
     honorCipherOrder: this.honorCipherOrder,
     crl: this.crl,
-    sessionIdContext: this.sessionIdContext
+    sessionIdContext: this.sessionIdContext,
+    numTickets: this.numTickets
   });
 
   if (this.sessionTimeout)
@@ -1366,6 +1370,14 @@ Server.prototype.setTicketKeys = function setTicketKeys(keys) {
   this._sharedCreds.context.setTicketKeys(keys);
 };
 
+Server.prototype.getNumTickets = function getNumTickets() {
+  return this._sharedCreds.context.getNumTickets();
+};
+
+
+Server.prototype.setNumTickets = function setNumTickets(numTickets) {
+  this._sharedCreds.context.setNumTickets(numTickets);
+};
 
 Server.prototype.setOptions = deprecate(function(options) {
   this.requestCert = options.requestCert === true;

src/node_crypto.cc

@@ -492,6 +492,8 @@ void SecureContext::Initialize(Environment* env, Local<Object> target) {
   env->SetProtoMethod(t, "enableTicketKeyCallback", EnableTicketKeyCallback);
   env->SetProtoMethodNoSideEffect(t, "getCertificate", GetCertificate<true>);
   env->SetProtoMethodNoSideEffect(t, "getIssuer", GetCertificate<false>);
+  env->SetProtoMethodNoSideEffect(t, "getNumTickets", GetNumTickets);
+  env->SetProtoMethod(t, "setNumTickets", SetNumTickets);
 
 #define SET_INTEGER_CONSTANTS(name, value)                                     \
     t->Set(FIXED_ONE_BYTE_STRING(env->isolate(), name),                        \
@@ -1558,6 +1560,32 @@ void SecureContext::SetTicketKeys(const FunctionCallbackInfo<Value>& args) {
 }
 
 
+void SecureContext::GetNumTickets(const FunctionCallbackInfo<Value>& args) {
+  SecureContext* sc;
+  ASSIGN_OR_RETURN_UNWRAP(&sc, args.Holder());
+
+  CHECK_EQ(args.Length(), 0);
+
+  uint32_t numTickets = SSL_CTX_get_num_tickets(sc->ctx_.get());
+  args.GetReturnValue().Set(static_cast<uint32_t>(numTickets));
+}
+
+
+void SecureContext::SetNumTickets(const FunctionCallbackInfo<Value>& args) {
+  SecureContext* sc;
+  ASSIGN_OR_RETURN_UNWRAP(&sc, args.Holder());
+
+  if (args.Length() != 1 || !args[0]->IsUint32()) {
+    return THROW_ERR_INVALID_ARG_TYPE(
+        sc->env(), "Number of tickets must be an unsigned 32-bit integer");
+  }
+
+  uint32_t numTickets = args[0].As<Uint32>()->Value();
+
+  CHECK(SSL_CTX_set_num_tickets(sc->ctx_.get(), numTickets));
+}
+
+
 void SecureContext::SetFreeListLength(const FunctionCallbackInfo<Value>& args) {
 }
 

src/node_crypto.h

@@ -155,6 +155,8 @@ class SecureContext final : public BaseObject {
 #endif  // !OPENSSL_NO_ENGINE
   static void GetTicketKeys(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void SetTicketKeys(const v8::FunctionCallbackInfo<v8::Value>& args);
+  static void GetNumTickets(const v8::FunctionCallbackInfo<v8::Value>& args);
+  static void SetNumTickets(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void SetFreeListLength(
       const v8::FunctionCallbackInfo<v8::Value>& args);
   static void EnableTicketKeyCallback(

test/parallel/test-tls-num-tickets.js

@@ -0,0 +1,40 @@
+'use strict';
+const common = require('../common');
+if (!common.hasCrypto)
+  common.skip('missing crypto');
+const fixtures = require('../common/fixtures');
+
+const assert = require('assert');
+const tls = require('tls');
+
+const server = tls.createServer({
+  key: fixtures.readKey('agent1-key.pem'),
+  cert: fixtures.readKey('agent1-cert.pem'),
+});
+
+const expectedNumTickets = 1;
+// 2 is the deafult value set by OpenSSL.
+assert.strictEqual(server.getNumTickets(), 2);
+// Change the number of sent session tickets.
+server.setNumTickets(expectedNumTickets);
+// Ensure that it has indeed been changed.
+assert.strictEqual(server.getNumTickets(), expectedNumTickets);
+// Ensure that an error is thrown when attempting to set the number of tickets
+// to a negative number.
+assert.throws(
+  () => server.setNumTickets(-1),
+  {
+    code: 'ERR_INVALID_ARG_TYPE',
+    message: 'Number of tickets must be an unsigned 32-bit integer'
+  }
+);
+
+// Ensure that an error is thrown when attempting to set the number of tickets
+// to Mongolian throat singing.
+assert.throws(
+  () => server.setNumTickets('HURRMMMM'),
+  {
+    code: 'ERR_INVALID_ARG_TYPE',
+    message: 'Number of tickets must be an unsigned 32-bit integer'
+  }
+);