tls: add TLSSocket.getEphemeralKeyInfo()

Returns an object representing a type, name and size of an ephemeral
key exchange(PFS) in a client connection.

This api is only supported not on a server connection but on a
client. When it is called on a server connection or its key exchange
is not ephemeral, an empty object is returned.

doc/api/tls.markdown

@@ -743,6 +743,19 @@ See SSL_CIPHER_get_name() and SSL_CIPHER_get_version() in
 http://www.openssl.org/docs/ssl/ssl.html#DEALING_WITH_CIPHERS for more
 information.
 
+### tlsSocket.getEphemeralKeyInfo()
+
+Returns an object representing a type, name and size of parameter of
+an ephemeral key exchange in [Perfect forward Secrecy][] on a client
+connection. It returns an empty object when the key exchange is not
+ephemeral. As it is only supported on a client socket, it returns null
+if this is called on a server socket. The type of 'DH' and 'ECDH' are
+supported. The name property is only available in 'ECDH'.
+
+Example:
+
+    { type: 'ECDH', name: 'prime256v1', size: 256 }
+
 ### tlsSocket.renegotiate(options, callback)
 
 Initiate TLS renegotiation process. The `options` may contain the following
@@ -820,6 +833,7 @@ The numeric representation of the local port.
 [net.Server.address()]: net.html#net_server_address
 ['secureConnect']: #tls_event_secureconnect
 [secureConnection]: #tls_event_secureconnection
+[Perfect Forward Secrecy]: #tls_perfect_forward_secrecy
 [Stream]: stream.html#stream_stream
 [SSL_METHODS]: http://www.openssl.org/docs/ssl/ssl.html#DEALING_WITH_PROTOCOL_METHODS
 [tls.Server]: #tls_class_tls_server

lib/_tls_wrap.js

@@ -573,6 +573,13 @@ TLSSocket.prototype.getCipher = function(err) {
   }
 };
 
+TLSSocket.prototype.getEphemeralKeyInfo = function() {
+  if (this._handle)
+    return this._handle.getEphemeralKeyInfo();
+
+  return null;
+};
+
 // TODO: support anonymous (nocert) and PSK
 
 

src/node_crypto.cc

@@ -1003,6 +1003,7 @@ void SSLWrap<Base>::AddMethods(Environment* env, Handle<FunctionTemplate> t) {
   env->SetProtoMethod(t, "newSessionDone", NewSessionDone);
   env->SetProtoMethod(t, "setOCSPResponse", SetOCSPResponse);
   env->SetProtoMethod(t, "requestOCSP", RequestOCSP);
+  env->SetProtoMethod(t, "getEphemeralKeyInfo", GetEphemeralKeyInfo);
 
 #ifdef SSL_set_max_send_fragment
   env->SetProtoMethod(t, "setMaxSendFragment", SetMaxSendFragment);
@@ -1608,6 +1609,50 @@ void SSLWrap<Base>::RequestOCSP(
 }
 
 
+template <class Base>
+void SSLWrap<Base>::GetEphemeralKeyInfo(
+    const v8::FunctionCallbackInfo<v8::Value>& args) {
+  Base* w = Unwrap<Base>(args.Holder());
+  Environment* env = Environment::GetCurrent(args);
+
+  CHECK_NE(w->ssl_, nullptr);
+
+  // tmp key is available on only client
+  if (w->is_server())
+    return args.GetReturnValue().SetNull();
+
+  Local<Object> info = Object::New(env->isolate());
+
+  EVP_PKEY* key;
+
+  if (SSL_get_server_tmp_key(w->ssl_, &key)) {
+    switch (EVP_PKEY_id(key)) {
+      case EVP_PKEY_DH:
+        info->Set(env->type_string(),
+                  FIXED_ONE_BYTE_STRING(env->isolate(), "DH"));
+        info->Set(env->size_string(),
+                  Integer::New(env->isolate(), EVP_PKEY_bits(key)));
+        break;
+      case EVP_PKEY_EC:
+        {
+          EC_KEY* ec = EVP_PKEY_get1_EC_KEY(key);
+          int nid = EC_GROUP_get_curve_name(EC_KEY_get0_group(ec));
+          EC_KEY_free(ec);
+          info->Set(env->type_string(),
+                    FIXED_ONE_BYTE_STRING(env->isolate(), "ECDH"));
+          info->Set(env->name_string(),
+                    OneByteString(args.GetIsolate(), OBJ_nid2sn(nid)));
+          info->Set(env->size_string(),
+                    Integer::New(env->isolate(), EVP_PKEY_bits(key)));
+        }
+    }
+    EVP_PKEY_free(key);
+  }
+
+  return args.GetReturnValue().Set(info);
+}
+
+
 #ifdef SSL_set_max_send_fragment
 template <class Base>
 void SSLWrap<Base>::SetMaxSendFragment(

src/node_crypto.h

@@ -215,6 +215,8 @@ class SSLWrap {
   static void NewSessionDone(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void SetOCSPResponse(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void RequestOCSP(const v8::FunctionCallbackInfo<v8::Value>& args);
+  static void GetEphemeralKeyInfo(
+      const v8::FunctionCallbackInfo<v8::Value>& args);
 
 #ifdef SSL_set_max_send_fragment
   static void SetMaxSendFragment(

test/parallel/test-tls-client-getephemeralkeyinfo.js

@@ -0,0 +1,98 @@
+'use strict';
+var common = require('../common');
+var assert = require('assert');
+
+if (!common.hasCrypto) {
+  console.log('1..0 # Skipped: missing crypto');
+  process.exit();
+}
+var tls = require('tls');
+
+var fs = require('fs');
+var key =  fs.readFileSync(common.fixturesDir + '/keys/agent2-key.pem');
+var cert = fs.readFileSync(common.fixturesDir + '/keys/agent2-cert.pem');
+
+var ntests = 0;
+var nsuccess = 0;
+
+function loadDHParam(n) {
+  var path = common.fixturesDir;
+  if (n !== 'error') path += '/keys';
+  return fs.readFileSync(path + '/dh' + n + '.pem');
+}
+
+var cipherlist = {
+  'NOT_PFS': 'AES128-SHA256',
+  'DH': 'DHE-RSA-AES128-GCM-SHA256',
+  'ECDH': 'ECDHE-RSA-AES128-GCM-SHA256'
+};
+
+function test(size, type, name, next) {
+  var cipher = type ? cipherlist[type] : cipherlist['NOT_PFS'];
+
+  if (name) tls.DEFAULT_ECDH_CURVE = name;
+
+  var options = {
+    key: key,
+    cert: cert,
+    ciphers: cipher
+  };
+
+  if (type === 'DH') options.dhparam = loadDHParam(size);
+
+  var server = tls.createServer(options, function(conn) {
+    assert.strictEqual(conn.getEphemeralKeyInfo(), null);
+    conn.end();
+  });
+
+  server.on('close', function(err) {
+    assert(!err);
+    if (next) next();
+  });
+
+  server.listen(common.PORT, '127.0.0.1', function() {
+    var client = tls.connect({
+      port: common.PORT,
+      rejectUnauthorized: false
+    }, function() {
+      var ekeyinfo = client.getEphemeralKeyInfo();
+      assert.strictEqual(ekeyinfo.type, type);
+      assert.strictEqual(ekeyinfo.size, size);
+      assert.strictEqual(ekeyinfo.name, name);
+      nsuccess++;
+      server.close();
+    });
+  });
+}
+
+function testNOT_PFS() {
+  test(undefined, undefined, undefined, testDHE1024);
+  ntests++;
+}
+
+function testDHE1024() {
+  test(1024, 'DH', undefined, testDHE2048);
+  ntests++;
+}
+
+function testDHE2048() {
+  test(2048, 'DH', undefined, testECDHE256);
+  ntests++;
+}
+
+function testECDHE256() {
+  test(256, 'ECDH', tls.DEFAULT_ECDH_CURVE, testECDHE512);
+  ntests++;
+}
+
+function testECDHE512() {
+  test(521, 'ECDH', 'secp521r1', null);
+  ntests++;
+}
+
+testNOT_PFS();
+
+process.on('exit', function() {
+  assert.equal(ntests, nsuccess);
+  assert.equal(ntests, 5);
+});