Introduction to secGear

Overview

With the rapid development of cloud computing, more and more enterprises deploy computing services on the cloud. The security of user data on the third-party cloud infrastructure is facing great challenges. Confidential computing is a technology that uses hardware-based trusted execution environments (TEEs) to protect confidentiality and integrity of data in use. It relies on the bottom-layer hardware to build the minimum trust dependency, which removes the OS, hypervisor, infrastructure, system administrator, and service provider from the trusted entity list as unauthorized entities to reduce potential risks. There are various confidential computing technologies (such as Intel SGX, Arm TrustZone, and RSIC-V Keystone) and software development kits (SDKs) in the industry and the application ecosystem of different TEEs are isolated from each other, which brings high development and maintenance costs to confidential computing application developers. To help developers quickly build confidential computing solutions that protect data security on the cloud, openEuler launches the unified confidential computing programming framework secGear.

Architecture

The architecture of secGear consists of three layers that form the foundation of openEuler confidential computing software.

• Base layer: The unified layer of the confidential computing SDK provides APIs for different TEEs, enabling different architectures to share the same set of source code.
• Middleware layer: The general component layer provides confidential computing software for users to quickly build confidential computing solutions.
• Server layer: The confidential computing service layer runs dedicated solutions for typical situations.

Key Features

Switchless

Pain Points

After a conventional application is reconstructed using confidential computing, the rich execution environment (REE) logic frequently invokes the TEE logic or the REE frequently exchanges large data blocks with the TEE. Each call between the REE and TEE requires context switching among the REE user mode, REE kernel mode, driver, TEE kernel mode, and TEE user mode. When large blocks of data are exchanged during the call, multiple memory copies are generated. In addition, the interaction performance between the REE and TEE deteriorates due to factors such as the size limit of underlying data blocks, which severely affects the implementation of confidential computing applications.

Solution

Switchless is a technology that uses shared memory to reduce the number of context switches and data copies between the REE and TEE to optimize the interaction performance.

How to Use

1. Enable switchless when creating an enclave.

The configuration items of switchless are described as follows:

typedef struct {
 uint32_t num_uworkers;
 uint32_t num_tworkers;
 uint32_t switchless_calls_pool_size;
 uint32_t retries_before_fallback;
 uint32_t retries_before_sleep;
 uint32_t parameter_num;
 uint32_t workers_policy;
 uint32_t rollback_to_common;
} cc_sl_config_t;

2. Add the transition_using_threads flag when defining the API in the enclave description language (EDL) file.

enclave {
    include "secgear_urts.h"
    from "secgear_tstdc.edl" import *;
    from "secgear_tswitchless.edl" import *;
    trusted {
        public int get_string([out, size=32]char *buf);
        public int get_string_switchless([out, size=32]char *buf) transition_using_threads;
    };
};

Secure Channel

Pain Points

When requesting the confidential computing service on the cloud, the data owner needs to upload the data to be processed to the TEE on the cloud for processing. Because the TEE is not connected to the network, the data needs to be transferred to the REE over the network in plaintext and then transferred to the TEE from the REE. The data plaintext is exposed in the REE memory, which poses security risks.

Solution

A secure channel is a technology that combines confidential computing remote attestation to implement secure key negotiation between the data owner and the TEE on the cloud. It negotiates a sessionkey owned only by the data owner and the TEE on the cloud. Then the sessionkey is used to encrypt user data transferred over the network. After receiving the ciphertext data, the REE transfers the data to the TEE for decryption and processing.

How to Use

The secure channel is provided as a library and consists of the client, host, and enclave, which are icalled by the client, server client application (CA), and server trusted application (TA) of the service program respectively.

APIs

Precautions

A secure channel encapsulates only the key negotiation process and encryption and decryption APIs, but does not establish any network connection. The negotiation process reuses the network connection of the service. The network connection between the client and server is established and maintained by the service. The message sending hook function and network connection pointer are transferred during the initialization of the secure channel on the client and the server. For details, see secure channel examples.

Acronyms and Abbreviations