How can I pass the OpenSSL ciphers list to clients?

As Steffen Ullrich has mentioned, you can pass a list of ciphers to the -cipher option of s_client. This is not a single item, but a specification and can also be used for the nginx ssl_ciphers option, or the Apache SSLCipherSuite option. You can pass multiple ciphers using a space, comma or colon separator. Example:

  openssl s_client -cipher ECDHE-RSA-AES256-SHA:ECDHE-RSA-AES256-GCM-SHA384 

   -connect example.com:443 The above list specifies two specific ciphers. A group of ciphers can also be passed. Here is an example of a cipher list specification that requires authenticated ephemeral ECDH key agreement (ECDH), RSA for authentication and only cipher suites that are considered of "high" encryption: openssl s_client -cipher ECDH+aRSA+HIGH -connect example.com:443 What does this expand to? The openssl ciphers command can be used for this purpose:

  $ openssl ciphers ECDH+aRSA+HIGH

  ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES256-SHA:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-RSA-AES128-SHA:ECDHE-RSA-DES-CBC3-SHA

or more verbosely:

$ openssl ciphers -v ECDH+aRSA+HIGH

ECDHE-RSA-AES256-GCM-SHA384 TLSv1.2 Kx=ECDH     Au=RSA  Enc=AESGCM(256) Mac=AEAD

ECDHE-RSA-AES256-SHA384 TLSv1.2 Kx=ECDH     Au=RSA  Enc=AES(256)  Mac=SHA384

ECDHE-RSA-AES256-SHA    SSLv3 Kx=ECDH     Au=RSA  Enc=AES(256)  Mac=SHA1

ECDHE-RSA-AES128-GCM-SHA256 TLSv1.2 Kx=ECDH     Au=RSA  Enc=AESGCM(128) Mac=AEAD

ECDHE-RSA-AES128-SHA256 TLSv1.2 Kx=ECDH     Au=RSA  Enc=AES(128)  Mac=SHA256

ECDHE-RSA-AES128-SHA    SSLv3 Kx=ECDH     Au=RSA  Enc=AES(128)  Mac=SHA1

ECDHE-RSA-DES-CBC3-SHA  SSLv3 Kx=ECDH     Au=RSA  Enc=3DES(168) Mac=SHA1

For more information, read the ciphers manual page.