Backported CORE-5780: Server hangs when client tries to send too long…

… DB encryption key(s)

src/remote/server/server.cpp

@@ -145,9 +145,15 @@ class NetworkCallback : public VersionedIface<ICryptKeyCallbackImpl<NetworkCallb
 	{
 		if (l > length)
 			l = length;
-		memcpy(d, data, l);
 
-		wake = true;
+		if (data)
+		{
+			memcpy(d, data, l);
+			wake = true;
+		}
+		else
+			stop();
+
 		sem.release();
 	}
 
@@ -198,7 +204,7 @@ class CryptKeyCallback : public VersionedIface<ICryptKeyCallbackImpl<CryptKeyCal
 		loadClientKey();
 		unsigned rc = keyCallback ?
 			keyCallback->callback(dataLength, data, bufferLength, buffer) :
-			// use legacy behavior if holders to do wish to accept keys from client
+			// use legacy behavior if holders do wish to accept keys from client
 			networkCallback.callback(dataLength, data, bufferLength, buffer);
 
 		return rc;
@@ -6131,7 +6137,8 @@ SSHORT rem_port::asyncReceive(PACKET* asyncPacket, const UCHAR* buffer, SSHORT d
 		return 0;
 	}
 
-	switch (xdr_peek_long(&port_async_receive->port_receive, buffer, dataSize))
+	SLONG original_op = xdr_peek_long(&port_async_receive->port_receive, buffer, dataSize);
+	switch (original_op)
 	{
 	case op_cancel:
 	case op_abort_aux_connection:
@@ -6165,14 +6172,16 @@ SSHORT rem_port::asyncReceive(PACKET* asyncPacket, const UCHAR* buffer, SSHORT d
 		break;
 	case op_abort_aux_connection:
 		if (port_async && (port_async->port_flags & PORT_connecting))
-		{
 			port_async->abort_aux_connection();
-		}
 		break;
 	case op_crypt_key_callback:
 		port_server_crypt_callback->wakeup(asyncPacket->p_cc.p_cc_data.cstr_length,
 			asyncPacket->p_cc.p_cc_data.cstr_address);
 		break;
+	case op_partial:
+		if (original_op == op_crypt_key_callback)
+			port_server_crypt_callback->wakeup(0, NULL);
+		break;
 	default:
 		fb_assert(false);
 		return 0;