tls: add getProtocol() to TLS sockets

This commit adds a new method for TLS sockets that returns the
negotiated protocol version.

PR-URL: #4995
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/tls.markdown

@@ -494,6 +494,24 @@ Example:
 If the peer does not provide a certificate, it returns `null` or an empty
 object.
 
+### tlsSocket.getProtocol()
+
+Returns a string containing the negotiated SSL/TLS protocol version of the
+current connection. `'unknown'` will be returned for connected sockets that have
+not completed the handshaking process. `null` will be returned for server
+sockets or disconnected client sockets.
+
+Examples:
+```
+'SSLv3'
+'TLSv1'
+'TLSv1.1'
+'TLSv1.2'
+'unknown'
+```
+
+See https://www.openssl.org/docs/manmaster/ssl/SSL_get_version.html for more
+information.
 
 ### tlsSocket.getSession()
 

lib/_tls_wrap.js

@@ -664,6 +664,13 @@ TLSSocket.prototype.getEphemeralKeyInfo = function() {
   return null;
 };
 
+TLSSocket.prototype.getProtocol = function() {
+  if (this._handle)
+    return this._handle.getProtocol();
+
+  return null;
+};
+
 // TODO: support anonymous (nocert) and PSK
 
 

src/node_crypto.cc

@@ -1203,6 +1203,7 @@ void SSLWrap<Base>::AddMethods(Environment* env, Local<FunctionTemplate> t) {
   env->SetProtoMethod(t, "setOCSPResponse", SetOCSPResponse);
   env->SetProtoMethod(t, "requestOCSP", RequestOCSP);
   env->SetProtoMethod(t, "getEphemeralKeyInfo", GetEphemeralKeyInfo);
+  env->SetProtoMethod(t, "getProtocol", GetProtocol);
 
 #ifdef SSL_set_max_send_fragment
   env->SetProtoMethod(t, "setMaxSendFragment", SetMaxSendFragment);
@@ -1965,6 +1966,15 @@ void SSLWrap<Base>::GetCurrentCipher(const FunctionCallbackInfo<Value>& args) {
 }
 
 
+template <class Base>
+void SSLWrap<Base>::GetProtocol(const FunctionCallbackInfo<Value>& args) {
+  Base* w = Unwrap<Base>(args.Holder());
+
+  const char* tls_version = SSL_get_version(w->ssl_);
+  args.GetReturnValue().Set(OneByteString(args.GetIsolate(), tls_version));
+}
+
+
 #ifdef OPENSSL_NPN_NEGOTIATED
 template <class Base>
 int SSLWrap<Base>::AdvertiseNextProtoCallback(SSL* s,

src/node_crypto.h

@@ -248,6 +248,7 @@ class SSLWrap {
   static void RequestOCSP(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void GetEphemeralKeyInfo(
       const v8::FunctionCallbackInfo<v8::Value>& args);
+  static void GetProtocol(const v8::FunctionCallbackInfo<v8::Value>& args);
 
 #ifdef SSL_set_max_send_fragment
   static void SetMaxSendFragment(

test/parallel/test-tls-getprotocol.js

@@ -0,0 +1,43 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+
+if (!common.hasCrypto) {
+  console.log('1..0 # Skipped: missing crypto');
+  return;
+}
+
+const tls = require('tls');
+const fs = require('fs');
+
+const clientConfigs = [
+  { secureProtocol: 'TLSv1_method', version: 'TLSv1' },
+  { secureProtocol: 'TLSv1_1_method', version: 'TLSv1.1' },
+  { secureProtocol: 'TLSv1_2_method', version: 'TLSv1.2' }
+];
+
+const serverConfig = {
+  key: fs.readFileSync(common.fixturesDir + '/keys/agent2-key.pem'),
+  cert: fs.readFileSync(common.fixturesDir + '/keys/agent2-cert.pem')
+};
+
+const server = tls.createServer(serverConfig, common.mustCall(function() {
+
+}, clientConfigs.length)).listen(common.PORT, common.localhostIPv4, function() {
+  let connected = 0;
+  clientConfigs.forEach(function(v) {
+    tls.connect({
+      host: common.localhostIPv4,
+      port: common.PORT,
+      rejectUnauthorized: false,
+      secureProtocol: v.secureProtocol
+    }, common.mustCall(function() {
+      assert.strictEqual(this.getProtocol(), v.version);
+      this.on('end', common.mustCall(function() {
+        assert.strictEqual(this.getProtocol(), null);
+      })).end();
+      if (++connected === clientConfigs.length)
+        server.close();
+    }));
+  });
+});