tls: fix bugs of double TLS

Fixs two issues in `TLSWrap`, one of them is reported in
nodejs#30896.

1. `TLSWrap` has exactly one `StreamListener`, however,
that `StreamListener` can be replaced. We have not been
rigorous enough here: if an active write has not been
finished before the transition, the finish callback of it
will be wrongly fired the successor `StreamListener`.

2. A `TLSWrap` does not allow more than one active write,
as checked in the assertion about current_write in
`TLSWrap::DoWrite()`.

However, when users make use of an existing `tls.TLSSocket`
to establish double TLS, by
either
  tls.connect({socket: tlssock})
or
  tlsServer.emit('connection', tlssock)
we have both of the user provided `tls.TLSSocket`, tlssock and
a brand new created `TLSWrap` writing to the `TLSWrap` bound to
tlssock, which easily violates the constranint because two writers
have no idea of each other.

The design of the fix is:
when a `TLSWrap` is created on top of a user provided socket,
do not send any data to the socket until all existing writes
of the socket are done and ensure registered callbacks of
those writes can be fired.

Author: ywave620

lib/_tls_wrap.js

@@ -545,25 +545,36 @@ function TLSSocket(socket, opts) {
   this[kPendingSession] = null;
 
   let wrap;
-  if ((socket instanceof net.Socket && socket._handle) || !socket) {
-    // 1. connected socket
-    // 2. no socket, one will be created with net.Socket().connect
-    wrap = socket;
+  let handle;
+  let wrapHasActiveWriteFromPrevOwner;
+
+  if (socket) {
+    if (socket instanceof net.Socket && socket._handle) {
+      // 1. connected socket
+      wrap = socket;
+    } else {
+      // 2. socket has no handle so it is js not c++
+      // 3. unconnected sockets are wrapped
+      // TLS expects to interact from C++ with a net.Socket that has a C++ stream
+      // handle, but a JS stream doesn't have one. Wrap it up to make it look like
+      // a socket.
+      wrap = new JSStreamSocket(socket);
+    }
+
+    handle = wrap._handle;
+    wrapHasActiveWriteFromPrevOwner = wrap.writableLength > 0;
   } else {
-    // 3. socket has no handle so it is js not c++
-    // 4. unconnected sockets are wrapped
-    // TLS expects to interact from C++ with a net.Socket that has a C++ stream
-    // handle, but a JS stream doesn't have one. Wrap it up to make it look like
-    // a socket.
-    wrap = new JSStreamSocket(socket);
+    // 4. no socket, one will be created with net.Socket().connect
+    wrap = null;
+    wrapHasActiveWriteFromPrevOwner = false;
   }
 
   // Just a documented property to make secure sockets
   // distinguishable from regular ones.
   this.encrypted = true;
 
   ReflectApply(net.Socket, this, [{
-    handle: this._wrapHandle(wrap),
+    handle: this._wrapHandle(wrap, handle, wrapHasActiveWriteFromPrevOwner),
     allowHalfOpen: socket ? socket.allowHalfOpen : tlsOptions.allowHalfOpen,
     pauseOnCreate: tlsOptions.pauseOnConnect,
     manualStart: true,
@@ -582,6 +593,22 @@ function TLSSocket(socket, opts) {
   if (enableTrace && this._handle)
     this._handle.enableTrace();
 
+  if (wrapHasActiveWriteFromPrevOwner) {
+    // `wrap` is a streams.Writable in JS. This empty write will be queued
+    // and hence finish after all existing writes, which is the timing
+    // we want to start to send any tls data to `wrap`.
+    const that = this;
+    wrap.write('', (err) => {
+      if (err) {
+        debug('error got before writing any tls data to the underlying stream');
+        that.destroy(err);
+        return;
+      }
+
+      that._handle.writesIssuedByPrevListenerDone();
+    });
+  }
+
   // Read on next tick so the caller has a chance to setup listeners
   process.nextTick(initRead, this, socket);
 }
@@ -642,11 +669,14 @@ TLSSocket.prototype.disableRenegotiation = function disableRenegotiation() {
   this[kDisableRenegotiation] = true;
 };
 
-TLSSocket.prototype._wrapHandle = function(wrap, handle) {
-  if (!handle && wrap) {
-    handle = wrap._handle;
-  }
-
+/**
+ *
+ * @param {null|net.Socket} wrap
+ * @param {null|object} handle
+ * @param {boolean} wrapHasActiveWriteFromPrevOwner
+ * @returns {object}
+ */
+TLSSocket.prototype._wrapHandle = function(wrap, handle, wrapHasActiveWriteFromPrevOwner) {
   const options = this._tlsOptions;
   if (!handle) {
     handle = options.pipe ?
@@ -663,7 +693,10 @@ TLSSocket.prototype._wrapHandle = function(wrap, handle) {
   if (!(context.context instanceof NativeSecureContext)) {
     throw new ERR_TLS_INVALID_CONTEXT('context');
   }
-  const res = tls_wrap.wrap(handle, context.context, !!options.isServer);
+
+  const res = tls_wrap.wrap(handle, context.context,
+                            !!options.isServer,
+                            wrapHasActiveWriteFromPrevOwner);
   res._parent = handle;  // C++ "wrap" object: TCPWrap, JSStream, ...
   res._parentWrap = wrap;  // JS object: net.Socket, JSStreamSocket, ...
   res._secureContext = context;
@@ -680,7 +713,7 @@ TLSSocket.prototype[kReinitializeHandle] = function reinitializeHandle(handle) {
   const originalServername = this.ssl ? this._handle.getServername() : null;
   const originalSession = this.ssl ? this._handle.getSession() : null;
 
-  this.handle = this._wrapHandle(null, handle);
+  this.handle = this._wrapHandle(null, handle, false);
   this.ssl = this._handle;
 
   net.Socket.prototype[kReinitializeHandle].call(this, this.handle);

src/crypto/crypto_tls.cc

@@ -357,12 +357,15 @@ TLSWrap::TLSWrap(Environment* env,
                  Local<Object> obj,
                  Kind kind,
                  StreamBase* stream,
-                 SecureContext* sc)
+                 SecureContext* sc,
+                 bool stream_has_active_write)
     : AsyncWrap(env, obj, AsyncWrap::PROVIDER_TLSWRAP),
       StreamBase(env),
       env_(env),
       kind_(kind),
-      sc_(sc) {
+      sc_(sc),
+      has_active_write_issued_by_prev_listener_(
+        stream_has_active_write) {
   MakeWeak();
   CHECK(sc_);
   ssl_ = sc_->CreateSSL();
@@ -472,10 +475,11 @@ void TLSWrap::InitSSL() {
 void TLSWrap::Wrap(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
 
-  CHECK_EQ(args.Length(), 3);
+  CHECK_EQ(args.Length(), 4);
   CHECK(args[0]->IsObject());
   CHECK(args[1]->IsObject());
   CHECK(args[2]->IsBoolean());
+  CHECK(args[3]->IsBoolean());
 
   Local<Object> sc = args[1].As<Object>();
   Kind kind = args[2]->IsTrue() ? Kind::kServer : Kind::kClient;
@@ -490,7 +494,8 @@ void TLSWrap::Wrap(const FunctionCallbackInfo<Value>& args) {
     return;
   }
 
-  TLSWrap* res = new TLSWrap(env, obj, kind, stream, Unwrap<SecureContext>(sc));
+  TLSWrap* res = new TLSWrap(env, obj, kind, stream, Unwrap<SecureContext>(sc),
+    args[3]->IsTrue() /* stream_has_active_write */);
 
   args.GetReturnValue().Set(res->object());
 }
@@ -596,6 +601,12 @@ void TLSWrap::EncOut() {
     return;
   }
 
+  if (UNLIKELY(has_active_write_issued_by_prev_listener_)) {
+    Debug(this, "Returning from EncOut(), "
+      "has_active_write_issued_by_prev_listener_ is true");
+    return;
+  }
+
   // Split-off queue
   if (established_ && current_write_) {
     Debug(this, "EncOut() write is scheduled");
@@ -666,6 +677,15 @@ void TLSWrap::EncOut() {
 
 void TLSWrap::OnStreamAfterWrite(WriteWrap* req_wrap, int status) {
   Debug(this, "OnStreamAfterWrite(status = %d)", status);
+
+  if (UNLIKELY(has_active_write_issued_by_prev_listener_)) {
+    Debug(this, "Notify write finish to the previous_listener_");
+    CHECK_EQ(write_size_, 0);  // we must have restrained writes
+
+    previous_listener_->OnStreamAfterWrite(req_wrap, status);
+    return;
+  }
+
   if (current_empty_write_) {
     Debug(this, "Had empty write");
     BaseObjectPtr<AsyncWrap> current_empty_write =
@@ -2021,6 +2041,16 @@ void TLSWrap::GetALPNNegotiatedProto(const FunctionCallbackInfo<Value>& args) {
   args.GetReturnValue().Set(result);
 }
 
+void TLSWrap::WritesIssuedByPrevListenerDone(
+  const FunctionCallbackInfo<Value>& args) {
+  TLSWrap* w;
+  ASSIGN_OR_RETURN_UNWRAP(&w, args.Holder());
+
+  Debug(w, "WritesIssuedByPrevListenerDone is called");
+  w->has_active_write_issued_by_prev_listener_ = false;
+  w->EncOut();  // resume all of our restrained writes
+}
+
 void TLSWrap::Cycle() {
   // Prevent recursion
   if (++cycle_depth_ > 1)
@@ -2098,6 +2128,8 @@ void TLSWrap::Initialize(
   SetProtoMethod(isolate, t, "setSession", SetSession);
   SetProtoMethod(isolate, t, "setVerifyMode", SetVerifyMode);
   SetProtoMethod(isolate, t, "start", Start);
+  SetProtoMethod(isolate, t, "writesIssuedByPrevListenerDone",
+    WritesIssuedByPrevListenerDone);
 
   SetProtoMethodNoSideEffect(
       isolate, t, "exportKeyingMaterial", ExportKeyingMaterial);
@@ -2180,6 +2212,7 @@ void TLSWrap::RegisterExternalReferences(ExternalReferenceRegistry* registry) {
   registry->Register(GetSharedSigalgs);
   registry->Register(GetTLSTicket);
   registry->Register(VerifyError);
+  registry->Register(WritesIssuedByPrevListenerDone);
 
 #ifdef SSL_set_max_send_fragment
   registry->Register(SetMaxSendFragment);

src/crypto/crypto_tls.h

@@ -136,7 +136,8 @@ class TLSWrap : public AsyncWrap,
           v8::Local<v8::Object> obj,
           Kind kind,
           StreamBase* stream,
-          SecureContext* sc);
+          SecureContext* sc,
+          bool stream_has_active_write);
 
   static void SSLInfoCallback(const SSL* ssl_, int where, int ret);
   void InitSSL();
@@ -217,6 +218,8 @@ class TLSWrap : public AsyncWrap,
   static void Start(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void VerifyError(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void Wrap(const v8::FunctionCallbackInfo<v8::Value>& args);
+  static void WritesIssuedByPrevListenerDone(
+    const v8::FunctionCallbackInfo<v8::Value>& args);
 
 #ifdef SSL_set_max_send_fragment
   static void SetMaxSendFragment(
@@ -284,6 +287,8 @@ class TLSWrap : public AsyncWrap,
 
   BIOPointer bio_trace_;
 
+  bool has_active_write_issued_by_prev_listener_ = false;
+
  public:
   std::vector<unsigned char> alpn_protos_;  // Accessed by SelectALPNCallback.
   bool alpn_callback_enabled_ = false;      // Accessed by SelectALPNCallback.

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

@@ -0,0 +1,58 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+if (!common.hasCrypto) common.skip('missing crypto');
+const fixtures = require('../common/fixtures');
+const tls = require('tls');
+
+// In reality, this can be a HTTP CONNECT message, signaling the incoming
+// data is TLS encrypted
+const HEAD = 'XXXX';
+
+const subserver = tls.createServer({
+  key: fixtures.readKey('agent1-key.pem'),
+  cert: fixtures.readKey('agent1-cert.pem'),
+})
+  .on('secureConnection', common.mustCall(() => {
+    process.exit(0);
+  }));
+
+const server = tls.createServer({
+  key: fixtures.readKey('agent1-key.pem'),
+  cert: fixtures.readKey('agent1-cert.pem'),
+})
+  .listen(client)
+  .on('secureConnection', (serverTlsSock) => {
+    serverTlsSock.on('data', (chunk) => {
+      assert.strictEqual(chunk.toString(), HEAD);
+      subserver.emit('connection', serverTlsSock);
+    });
+  });
+
+function client() {
+  const down = tls.connect({
+    host: '127.0.0.1',
+    port: server.address().port,
+    rejectUnauthorized: false
+  }).on('secureConnect', () => {
+    down.write(HEAD, common.mustSucceed());
+
+    // Sending tls data on a client TLSSocket with an active write led to a crash:
+    //
+    //  node[16862]: ../src/crypto/crypto_tls.cc:963:virtual int node::crypto::TLSWrap::DoWrite(node::WriteWrap*,
+    //    uv_buf_t*, size_t, uv_stream_t*): Assertion `!current_write_' failed.
+    //  1: 0xb090e0 node::Abort() [node]
+    //  2: 0xb0915e  [node]
+    //  3: 0xca8413 node::crypto::TLSWrap::DoWrite(node::WriteWrap*, uv_buf_t*, unsigned long, uv_stream_s*) [node]
+    //  4: 0xcaa549 node::StreamBase::Write(uv_buf_t*, unsigned long, uv_stream_s*, v8::Local<v8::Object>) [node]
+    //  5: 0xca88d7 node::crypto::TLSWrap::EncOut() [node]
+    //  6: 0xd3df3e  [node]
+    //  7: 0xd3f35f v8::internal::Builtin_HandleApiCall(int, unsigned long*, v8::internal::Isolate*) [node]
+    //  8: 0x15d9ef9  [node]
+    // Aborted
+    tls.connect({
+      socket: down,
+      rejectUnauthorized: false
+    });
+  });
+}