SMT 11: Procedure to change the CA Certificate's Signature Algorithm from SHA1 to SHA256

  • 7021475
  • 19-Sep-2017
  • 19-Sep-2017

Environment

SUSE Linux Enterprise Server 11
Subscription Management Tool 11

Situation

For internal secuity reasons or policy, the standard SHA1 Signature Algorithm of the SMT CA Certificate must be changed to SHA256.

Resolution

IMPORTANT: the following procedure will remove and recreate the CA Certificate, hence all the Client systems already registered against the SMT must be re-registered to get the new certificate, it is a mandatory step.

First, verify and be sure that your current CA Certificate's Signature Algorithm is SHA1:

# openssl x509 -in /var/lib/CAM/YaST_Default_CA/cacert.pem -text

You will have to see a line like this: "Signature Algorithm: sha1"

To change it to SHA256, edit the following file with the editor of your preference:

/var/lib/CAM/openssl.cnf.tmpl

Inside the file you will find multiple times the following configuration option:

default_md=sha1

Change all the above lines for:

default_md=sha256

Once finished, save the file and exit the editor.

And finally, you will have to delete the old CA certificate and create a new one with SHA256, by following all the steps of this TID:

NOTE: Do not deviate from the steps of the TID, follow it by the letter, using all the names for the Certificates and the SMT FQDN as described in it.

https://www.suse.com/support/kb/doc/?id=7006024

And again, because you are recreating the CA certificate, you will have to re-create the Server certificate too (as explained in the above TID) and also de-register and re-register all the Client systems to get the new certificates.

Cause

The Yast ca_mgm module has as default sha1, but the OpenSSL version in SLES 11 already has sha256 and needs to be changed manually.

19 September 2017 - Ariel Barrettino, initial publishing.

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