OpenSSL Configuration

xCAT does not ship OpenSSL RPMS nor does it statically link to any OpenSSL libraries. Communication between the xCAT client and daemon utilizes OpenSSL and the administrator can configure SSL_version and SSL_cipher that should be used by xCAT daemons.

The configuration is stored in the xCAT site table using the site.xcatsslversion and site.xcatsslciphers variables.

Configuration

By default, xCAT ships with TLSv1 configured. The current highest SSL version that can be supported is TLSv1.2.

• For rhels7.x and sles12.x and higher:

  chtab key=xcatsslversion site.value=TLSv12
  

• For ubuntu 14.x and higher:

  chtab key=xcatsslversion site.value=TLSv1_2
  

• For AIX 7.1.3.x:

  chtab key=xcatsslversion site.value=TLSv1_2
  

If running > TLSv1, it is possible to disable insecure ciphers. Here’s an example of one possible configuration:

"xcatsslciphers","kDH:kEDH:kRSA:!SSLv3:!SSLv2:!aNULL:!eNULL:!MEDIUM:!LOW:!MD5:!EXPORT:!CAMELLIA:!ECDH",,

After making any changes to these configuration values, xcatd must be restarted:

service restart xcatd

If any mistakes have been made and communiation is lost to xCAT, use XCATBYPASS to fix/remove the bad configuration:

XCATBYPASS=1 tabedit site

Validation

Use the openssl command to validate the SSL configuration is valid and expected.

• To check whether TLSv1 is supported by xcatd:

  openssl s_client -connect 127.0.0.1:3001 -tls1
  

• To check if SSLv3 is disabled on xcatd:

  openssl s_client -connect localhost:3001 -ssl3
  

  You should get a reponse similar to:

  70367087597568:error:14094410:SSL routines:SSL3_READ_BYTES:sslv3 alert handshake failure:s3_pkt.c:1259:SSL alert number 40
  70367087597568:error:1409E0E5:SSL routines:SSL3_WRITE_BYTES:ssl handshake failure:s3_pkt.c:598: