openssl s_client is not a particularly great tool for this, but it can be done. For more information, see OpenSSL s_client commands man page in the OpenSSL toolkit. A group of ciphers can also be passed. You will get output like below as reply: To create a full circle, we’ll make sure our s_server is actually working by accessing it via openssl s_client: joris@beanie ~ $ openssl s_client -connect localhost:44330 CONNECTED(00000003) depth=0 C = NL, ST = Utrecht, L = Utrecht, O = Company, OU = Unit, CN = localhos t The handshake still passes OK because the extension appears to be non-essential (or at least considered to be such by openssl) and you get the connected TLS tunnel. Don’t worry about this unless you need it because some application requires a PKCS12 file or you’re given one that you need to get stuff out of. First, making the HTTP request, and second, extracting your content from the response. # openssl s_client -connect server:443 -CAfile cert.pem. SNI is a TLS extension that supports one host or IP address to serve multiple hostnames so that host and IP no longer have to be one to one. openssl s_client -starttls smtp -connect example.com:25 openssl s_client -starttls smtp -connect example.com:465 openssl s_client -starttls smtp -connect example.com:587. The following table includes some commonly used s_client commands. # openssl x509 -in cert.pem -out rootcert.crt. openssl s_client -connect ldap-host:636 -showcerts. openssl s_client-connect www. Let's break this down into two parts. example. If it is to check the SSL certificate (which is why I came across your question), it still doesn't work with s_client as Magnus pointed out 7 years ago. Hence in your test the openssl s_client command advertises that is supports NPN but the server turns a blind eye onto ot. See man psql.. To connect to an SSL HTTP server the command: openssl s_client -connect servername:443 would typically be used (https uses port 443). If the connection succeeds then an HTTP command can be given such as "GET /" to retrieve a web page. If it is to interact with the database, any decent client will do.psql can be called with the sslmode=require option. You didn't specify why you wanted to use s_client.. The hardest part here is that s_client closes the connection when its stdin gets closed. Convert a root certificate to a form that can be published on a web site for downloading by a browser. Use the -servername switch to enable SNI in s_client. Making the HTTP request. As soon as you connect to the server, run: ehlo example.com. openssl s_client sni openssl s_client -connect example.com:443 -servername example.com. openssl s_client -cipher ECDHE-RSA-AES256-SHA:ECDHE-RSA-AES256-GCM-SHA384 \ -connect example.com:443 The above list specifies two specific ciphers. TLS/SSL and crypto library. Contribute to openssl/openssl development by creating an account on GitHub. Extract a certificate from a server. $ openssl s_client -connect www.feistyduck.com:443 -servername www.feistyduck.com In order to specify the server name, OpenSSL needs to use a feature of the newer handshake format (the feature is called Server Name Indication [SNI]), and that will force it to abandon the old format. Think of it like a zip file for keys & certificates, which includes options to password protect etc. Accessing the s_server via openssl s_client. To view a complete list of s_client commands in the command line, enter openssl -?. S_Client closes the connection when its stdin gets closed an HTTP command can be published a... The sslmode=require option for more information, see openssl s_client is not a particularly great for. -Servername switch to enable sni in s_client openssl s_client password soon as you connect to the server run... 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