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openssl s_client

OpenSSL command to create TLS client connections. More information:

  • Display the start and expiry dates for a domain's certificate:

openssl s_client -connect {{host}}:{{port}} 2>/dev/null | openssl x509 -noout -dates

  • Display the certificate presented by an SSL/TLS server:

openssl s_client -connect {{host}}:{{port}} </dev/null

  • Set the Server Name Indicator (SNI) when connecting to the SSL/TLS server:

openssl s_client -connect {{host}}:{{port}} -servername {{hostname}}

  • Display the complete certificate chain of an HTTPS server:

openssl s_client -connect {{host}}:443 -showcerts </dev/null