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 the 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 attributes.

Configuration

site.xcatsslversion is the SSL_version option used by xcatd and passed to IO::Socket::SSL->start_SSL(). See https://metacpan.org/pod/IO::Socket::SSL for more information. By default, xCAT ships with an empty value for site.xcatsslversion. In this case, xcatd will use SSLv23:!SSLv2:!SSLv3:!TLSv1 internally.

Here is an example of changing site.xcatsslversion to a different value, TLSv1_2, for example.

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 communication is lost to xCAT, use XCATBYPASS to fix 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 response 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: