Use SSL/TLS to strengthen MQTT communication security

In previous articles , we explored authentication and access control mechanisms. Next, we will introduce the important role of Transport Layer Security (TLS) in improving the security of MQTT communication. This article will focus on TLS and how it guarantees the integrity, confidentiality, and authenticity of MQTT communications.

concept explanation

Before we get started, let's go over a few key concepts.

• Handshake: The TLS handshake is a process that establishes a secure connection between a client and a server. During this process, the client and server exchange information to determine the parameters of the secure connection, such as encryption algorithms, session keys, and authentication methods.
• Cipher suite: A cipher suite is a security scheme that combines encryption, hashing, and key exchange algorithms to secure a connection. TLS supports multiple cipher suites, and the client and server can negotiate to select a cipher suite during the handshake.
• Certificate: A certificate is a digital file used to prove the identity of a server or client. A certificate contains the public key of the server or client and is signed by a trusted certificate authority (CA).
• Session: A session is a communication between a client and a server. During a session, the client and server exchange data over a secure connection. Sessions can be terminated by the client or the server.

TLS overview

TLS is an encryption protocol designed to provide secure communications over the Internet. TLS can protect sensitive data such as passwords, credit card information, and personal information from being accessed or intercepted by unauthorized persons. TLS is widely used in network applications, e-mail, instant messaging and other application scenarios that require secure communication on the Internet.

TLS provides security through encryption, data integrity assurance, and authentication.

• Encryption: TLS encrypts data transmitted between the client and server using an encryption algorithm to ensure that its contents cannot be read by unauthorized users.
• Data integrity: TLS uses data integrity checking mechanisms, such as hashing algorithms, to ensure that data has not been tampered with or damaged during transmission.
• Authentication: Through the use of certificates and public key infrastructure, TLS ensures that the client communicates with the intended server and avoids communicating with an imposter.

TLS utilizes a combination of public-key and symmetric-key cryptography to achieve these security features.

A client and server need to perform a handshake before establishing a secure connection. During the handshake, the client and server send information to each other to determine secure connection parameters such as encryption algorithms, session keys, and authentication methods. TLS can use a variety of cipher suites, and the client and server negotiate to choose a cipher suite during the handshake. A certificate is a digital file used to prove the identity of a server or client. A certificate contains the server's or client's public key and is signed by a trusted CA. A trust relationship is established between the client and the server through a public key infrastructure (PKI).

Why is TLS critical to MQTT security?

For MQTT security, TLS plays an important role. It can guarantee the confidentiality, integrity and non-repudiation of MQTT messages. It can prevent sensitive data from being acquired, tampered with and intercepted by unauthorized users, and establish a secure and trusted communication channel between MQTT clients and Broker.

TLS protects confidentiality by encrypting data between MQTT clients and brokers. Without TLS, MQTT messages are sent in the clear, meaning anyone with network access can intercept and read the data. Using TLS can encrypt the content of the message, which cannot be accessed without authorization.

TLS provides data integrity protection. It prevents MQTT messages from being tampered with or destroyed during transmission. Each message is digitally signed over TLS, ensuring that it has not been altered in transit without authorization. If any unauthorized changes occur, the integrity check will fail, indicating that the data has been tampered with.

TLS implements the authentication function to ensure that the MQTT client and the Broker can authenticate each other. Clients can use SSL/TLS certificates to check whether they have established a connection with a legally authorized Broker. This prevents malicious entities from impersonating the Broker and establishes a trust relationship between the client and the MQTT infrastructure.

TLS provides the property of non-repudiation. By using digital signatures, TLS prevents senders from denying the transmission of their messages. A digital signature confirms the authenticity and origin of a message, so it can be proven that a particular client sent a particular message.

Finally, TLS also protects MQTT communications from eavesdropping attacks, where an attacker intercepts and listens to MQTT messages. It also prevents man-in-the-middle attacks, where attackers try to intercept and tamper with messages passed between clients and brokers.

TLS authentication method

one-way authentication

One-way authentication is the simplest authentication method in TLS. In one-way authentication, the server presents a digital certificate to the client, and the client checks the certificate to make sure it is valid and signed by a trusted CA. If the certificate is verified, the client can establish a secure connection with the server. When there is no need to authenticate the client, one-way authentication can meet the needs.

two-way authentication

Mutual authentication, or mTLS, is a more secure form of authentication in TLS. In mutual authentication, the client and server authenticate each other. The client presents the digital certificate to the server, and the server checks the certificate to make sure it is valid and signed by a trusted CA. The server also presents the digital certificate to the client, who checks the certificate to make sure it is valid and signed by a trusted CA. If both certificates are verified, the client and server can establish a secure connection. Two-way authentication is used when it is necessary to verify the identity of both the client and the server.

PSK authentication

Pre-Shared Key (PSK) is a method of authenticating clients and servers using a shared secret. The client and server agree on a key before connecting. During the handshake, the client and server use this key to identify each other. PSK can be used when public key cryptography cannot be used. This method is less secure than other methods because the same key is used for each connection.

Encryption without certificate

Certificateless cryptography utilizes key agreements, such as Diffie-Hellman, to have the client and server generate a shared secret. In this way, they can establish a secure communication channel between each other. This shared secret is not transmitted over the network, making it difficult to intercept or eavesdrop. At the same time, certificateless cryptography simplifies the implementation and management of TLS by eliminating the need to rely on trusted third parties to issue and manage digital certificates. However, the main limitation of this approach is that it requires both client and server to have the same key agreement parameters, which can pose challenges in some cases. Furthermore, due to the limited popularity of certificateless cryptography in TLS implementations, its applicability in practice may be somewhat limited.

Choose the Appropriate Authentication Method

The choice of authentication method is very important to ensure the security of TLS. When choosing an authentication method, consider security requirements, implementation complexity, and resource constraints.

• One-way authentication is suitable for situations where the identity of the client is not important.
• Two-way authentication requires both the client and the server to authenticate.
• PSK is an alternative when public key cryptography cannot be used, but is less secure than public key cryptography.
• Certificateless encryption is an effective solution when digital certificates cannot be obtained or trusted.
• Using a private key per device is especially useful when devices in the network have different security needs, or when the security of the entire network depends on the security of each device.

When selecting an authentication method, a thorough needs and risk analysis should be performed in order to make an informed decision.

Best Practices

When implementing TLS, careful planning and execution are required to ensure the security of communications. Here are some best practices for implementing TLS:

• Use latest version of TLS: Select the latest version of the TLS protocol to use the most secure encryption and hashing algorithms.
• Use a strong cipher suite: Choose a strong cipher suite to ensure high-strength encryption and data integrity.
• Use a trusted certificate: Use a digital certificate signed by a trusted CA to verify the identity of the server or client.
• Implement certificate revocation: Establish a certificate revocation mechanism for revoking compromised or expired certificates.
• Monitor certificate expiration: Monitor digital certificate expiration to ensure timely renewal.
• Secure Key Management: Create a secure key management system to manage keys used for authentication.
• Regularly update and patch software: The software used for the TLS implementation is regularly updated and patched to address any known vulnerabilities.

epilogue

TLS gives us a way to communicate securely on the Internet. TLS security can be enhanced by assigning unique keys to each device and choosing an appropriate authentication method. By following the implementation best practices provided in this article, you can take full advantage of the capabilities of TLS and build a more secure IoT platform.

EMQX supports one-way/two-way authentication of X509 certificates. You can enable SSL/TLS for all protocols supported by EMQX, and you can also enable SSL/TLS for the HTTP API provided by EMQX. The HTTP API provided by EMQX can also be set to use TLS.

For more information about EMQX, please check out our documentation , GitHub , Slack and forums .

Copyright statement: This article is original by EMQ, please indicate the source for reprinting.

Original link: https://www.emqx.com/zh/blog/fortifying-mqtt-communication-security-with-ssl-tls