TLS protects traffic at the transport layer so you can wrap a number of higher-level plain-text protocols in TLS to secure them.

It is an update to the Secure Sockets Layer ( SSL) protocol that preceded it, and often people still refer to both collectively as “SSL” or use the terms “SSL” and “TLS” interchangeably.

Transport Layer Security ( TLS) is a protocol you can use to protect network communications from eavesdropping and other types of attacks.

I hope you are already familiar with SSL and TLS.

We will use openssl to create the required certificates and verify the mutual TLS authentication. In this article we will explore Mutual Transport Layer Security (MTLS) and we will use a client and server setup to quickly validate mTLS authentication.

7.2 Create Certificate Signing Request (CSR).

6.2 Generate Certificate Signing Request (CSR).

Why should we use mutual authentication (MTLS)? Note that since the server does not respond with a ServerHello at all, the protocol version is not yet chosen, and SSL 3.0 is still, at least conceptually, a possibility at that early point of the handshake. The command-line tool openssl s_client can send an SNI with an explicit -servername option.Īs explained, SSL 3.0 and all TLS versions are quite similar and use the same record format (at least in the early stage of the handshake) so OpenSSL tends to reuse the same functions.

SNI is needed by some servers because they host several SSL-enabled sites on the same IP address, and need that parameter to know which certificate they should use. As points out, this is due to a lack of SNI: this is an extension by which the client documents in its ClientHello message the name of the target server. In your case, things did not even reach that point: the server responded with a fatal alert 40 ('handshake_failure', see the standard). If the client wants to do TLS 1.2 only, then he must announce 'up to TLS 1.2' in its ClientHello, and also close the connection if the server responds with a message that says anything else than 'let's do TLS 1.2'.

Your client does not tell 'let's use TLS 1.2' it says 'I know up to TLS 1.2'.Ī client may have its own extra requirements, but there is no room to state them in the ClientHello message. In SSL/TLS, the client does not request a specific protocol version the client announces the maximum protocol version that it supports, and then the server chooses the protocol version that will be used.

Openssl test tls 1.2 with cert