If the specified protocol is not supported on the server, you will receive an error similar to: “ SSL routines:tls_construct_client_hello:no protocols available“ To verify the protocol, view the SSL-Session section of the console output.
To disable TLSv1.3, use the -no_tls1_3 flag: openssl s_client -connect :443 -no_tls1_3 Alternatively, to disable the use of a specific SSL/TLS protocol version, the following flags are supported: -no_ssl2, -no_ssl3, -no_tls1, -no_tls1_1, -no_tls1_2, and -no_tls1_3.įor the case of, TLSv1.3 is supported. Other supported SSL and TLS version flags include -tls1_2, tls1_1, tls1, ssl2, and ssl3. For example, to test TLS 1.3 with openssl s_client, run the following: openssl s_client -connect :443 -tls1_3 To specify the TLS version in the connection for testing various protocols, add the appropriate TLS/SSL flag to the command. Here is a screenshot of the beginning of an example output from the above command: The server’s public key bit length is also returned. The end entity server certificate will be the only certificate printed in PEM format.ĭetails about the SSL handshake, its verification, and the TLS version and cipher will be returned. The information will include the servers certificate chain, printed as subject and issuer. Use the openssl s_client -connect flag to display diagnostic information about the SSL connection to the server. openssl s_client examples openssl s_client connect openssl s_client -connect :443 If you are testing the performance of your SSL connections, read our article on the openssl s_time utility. This utility will help uncover errors and misconfigurations. Testing SSL configuration on servers is a critical function that should be routine in your organization or systems. The post strives to walk you through various examples of testing SSL connections with different ciphers, TLS versions, and SSL server certificate analysis. The s_client command from OpenSSL is a helpful test client for troubleshooting remote SSL or TLS connections.
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