tls: expose Finished messages in TLSSocket

Exposes SSL_get_finished and SSL_get_peer_finished routines in OpenSSL
as tlsSocket.getFinished and tlsSocket.getPeerFinished, respectively.

PR-URL: #19102
Fixes: #19055
Refs: XRPLF/rippled#2413
Reviewed-By: Fedor Indutny <fedor.indutny@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/tls.md

@@ -584,6 +584,23 @@ if called on a server socket. The supported types are `'DH'` and `'ECDH'`. The
 
 For Example: `{ type: 'ECDH', name: 'prime256v1', size: 256 }`
 
+### tlsSocket.getFinished()
+<!-- YAML
+added: REPLACEME
+-->
+
+* Returns: {Buffer|undefined} The latest `Finished` message that has been
+sent to the socket as part of a SSL/TLS handshake, or `undefined` if
+no `Finished` message has been sent yet.
+
+As the `Finished` messages are message digests of the complete handshake
+(with a total of 192 bits for TLS 1.0 and more for SSL 3.0), they can
+be used for external authentication procedures when the authentication
+provided by SSL/TLS is not desired or is not enough.
+
+Corresponds to the `SSL_get_finished` routine in OpenSSL and may be used
+to implement the `tls-unique` channel binding from [RFC 5929][].
+
 ### tlsSocket.getPeerCertificate([detailed])
 <!-- YAML
 added: v0.11.4
@@ -627,6 +644,23 @@ For example:
 
 If the peer does not provide a certificate, an empty object will be returned.
 
+### tlsSocket.getPeerFinished()
+<!-- YAML
+added: REPLACEME
+-->
+
+* Returns: {Buffer|undefined} The latest `Finished` message that is expected
+or has actually been received from the socket as part of a SSL/TLS handshake,
+or `undefined` if there is no `Finished` message so far.
+
+As the `Finished` messages are message digests of the complete handshake
+(with a total of 192 bits for TLS 1.0 and more for SSL 3.0), they can
+be used for external authentication procedures when the authentication
+provided by SSL/TLS is not desired or is not enough.
+
+Corresponds to the `SSL_get_peer_finished` routine in OpenSSL and may be used
+to implement the `tls-unique` channel binding from [RFC 5929][].
+
 ### tlsSocket.getProtocol()
 <!-- YAML
 added: v5.7.0
@@ -1359,3 +1393,4 @@ where `secure_socket` 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
 [tls.Server]: #tls_class_tls_server
 [`dns.lookup()`]: dns.html#dns_dns_lookup_hostname_options_callback
+[RFC 5929]: https://tools.ietf.org/html/rfc5929

lib/_tls_wrap.js

@@ -680,6 +680,16 @@ TLSSocket.prototype.getPeerCertificate = function(detailed) {
   return null;
 };
 
+TLSSocket.prototype.getFinished = function() {
+  if (this._handle)
+    return this._handle.getFinished();
+};
+
+TLSSocket.prototype.getPeerFinished = function() {
+  if (this._handle)
+    return this._handle.getPeerFinished();
+};
+
 TLSSocket.prototype.getSession = function() {
   if (this._handle) {
     return this._handle.getSession();

src/node_crypto.cc

@@ -1497,6 +1497,8 @@ void SSLWrap<Base>::AddMethods(Environment* env, Local<FunctionTemplate> t) {
   HandleScope scope(env->isolate());
 
   env->SetProtoMethod(t, "getPeerCertificate", GetPeerCertificate);
+  env->SetProtoMethod(t, "getFinished", GetFinished);
+  env->SetProtoMethod(t, "getPeerFinished", GetPeerFinished);
   env->SetProtoMethod(t, "getSession", GetSession);
   env->SetProtoMethod(t, "setSession", SetSession);
   env->SetProtoMethod(t, "loadSession", LoadSession);
@@ -1985,6 +1987,52 @@ void SSLWrap<Base>::GetPeerCertificate(
 }
 
 
+template <class Base>
+void SSLWrap<Base>::GetFinished(const FunctionCallbackInfo<Value>& args) {
+  Environment* env = Environment::GetCurrent(args);
+
+  Base* w;
+  ASSIGN_OR_RETURN_UNWRAP(&w, args.Holder());
+
+  // We cannot just pass nullptr to SSL_get_finished()
+  // because it would further be propagated to memcpy(),
+  // where the standard requirements as described in ISO/IEC 9899:2011
+  // sections 7.21.2.1, 7.21.1.2, and 7.1.4, would be violated.
+  // Thus, we use a dummy byte.
+  char dummy[1];
+  size_t len = SSL_get_finished(w->ssl_, dummy, sizeof dummy);
+  if (len == 0)
+    return;
+
+  char* buf = Malloc(len);
+  CHECK_EQ(len, SSL_get_finished(w->ssl_, buf, len));
+  args.GetReturnValue().Set(Buffer::New(env, buf, len).ToLocalChecked());
+}
+
+
+template <class Base>
+void SSLWrap<Base>::GetPeerFinished(const FunctionCallbackInfo<Value>& args) {
+  Environment* env = Environment::GetCurrent(args);
+
+  Base* w;
+  ASSIGN_OR_RETURN_UNWRAP(&w, args.Holder());
+
+  // We cannot just pass nullptr to SSL_get_peer_finished()
+  // because it would further be propagated to memcpy(),
+  // where the standard requirements as described in ISO/IEC 9899:2011
+  // sections 7.21.2.1, 7.21.1.2, and 7.1.4, would be violated.
+  // Thus, we use a dummy byte.
+  char dummy[1];
+  size_t len = SSL_get_peer_finished(w->ssl_, dummy, sizeof dummy);
+  if (len == 0)
+    return;
+
+  char* buf = Malloc(len);
+  CHECK_EQ(len, SSL_get_peer_finished(w->ssl_, buf, len));
+  args.GetReturnValue().Set(Buffer::New(env, buf, len).ToLocalChecked());
+}
+
+
 template <class Base>
 void SSLWrap<Base>::GetSession(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);

src/node_crypto.h

@@ -270,6 +270,8 @@ class SSLWrap {
 
   static void GetPeerCertificate(
       const v8::FunctionCallbackInfo<v8::Value>& args);
+  static void GetFinished(const v8::FunctionCallbackInfo<v8::Value>& args);
+  static void GetPeerFinished(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void GetSession(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void SetSession(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void LoadSession(const v8::FunctionCallbackInfo<v8::Value>& args);

test/parallel/test-tls-finished.js

@@ -0,0 +1,66 @@
+'use strict';
+
+const common = require('../common');
+const fixtures = require('../common/fixtures');
+
+if (!common.hasCrypto)
+  common.skip('missing crypto');
+
+// This test ensures that tlsSocket.getFinished() and
+// tlsSocket.getPeerFinished() return undefined before
+// secure connection is established, and return non-empty
+// Buffer objects with Finished messages afterwards, also
+// verifying alice.getFinished() == bob.getPeerFinished()
+// and alice.getPeerFinished() == bob.getFinished().
+
+const assert = require('assert');
+const tls = require('tls');
+
+const msg = {};
+const pem = (n) => fixtures.readKey(`${n}.pem`);
+const server = tls.createServer({
+  key: pem('agent1-key'),
+  cert: pem('agent1-cert')
+}, common.mustCall((alice) => {
+  msg.server = {
+    alice: alice.getFinished(),
+    bob: alice.getPeerFinished()
+  };
+  server.close();
+}));
+
+server.listen(0, common.mustCall(() => {
+  const bob = tls.connect({
+    port: server.address().port,
+    rejectUnauthorized: false
+  }, common.mustCall(() => {
+    msg.client = {
+      alice: bob.getPeerFinished(),
+      bob: bob.getFinished()
+    };
+    bob.end();
+  }));
+
+  msg.before = {
+    alice: bob.getPeerFinished(),
+    bob: bob.getFinished()
+  };
+}));
+
+process.on('exit', () => {
+  assert.strictEqual(undefined, msg.before.alice);
+  assert.strictEqual(undefined, msg.before.bob);
+
+  assert(Buffer.isBuffer(msg.server.alice));
+  assert(Buffer.isBuffer(msg.server.bob));
+  assert(Buffer.isBuffer(msg.client.alice));
+  assert(Buffer.isBuffer(msg.client.bob));
+
+  assert(msg.server.alice.length > 0);
+  assert(msg.server.bob.length > 0);
+  assert(msg.client.alice.length > 0);
+  assert(msg.client.bob.length > 0);
+
+  assert(msg.server.alice.equals(msg.client.alice));
+  assert(msg.server.bob.equals(msg.client.bob));
+});