Server Authentication with Certificates

Certificates Stored in File
Certificates Stored in SAF

Tectia Server for IBM z/OS includes two implementations of certificate authentication. One is based on keys and X.509 certificates in files and software cryptography. This is the same implementation that is available in Tectia products on other platforms. The other implementation is based on keys and certificates managed by the z/OS System Authorization Facility (SAF) and cryptographic operations handled by the z/OS Integrated Cryptographic Service Facility (ICSF).

The two implementations can be combined or used separately. The Tectia validation can use trusted keys stored in file or in SAF, or the SAF validation can be used alone.

SAF Validation

ICSF is the interface to hardware cryptographic devices. Tectia Server for IBM z/OS benefits from the higher security and performance that these devices provide for keys and certificates managed by SAF.

Tectia Server for IBM z/OS also supports SAF keys that do not use hardware crypto devices, the so-called NON-ICSF keys. For these keys, the cryptographic operations are performed in software.

The interface to SAF in Tectia Server for IBM z/OS is implemented with a Tectia External Key Provider. The External Key Providers are configured with specification strings in a configuration file or on a command line.

Tectia Server for IBM z/OS validates public keys by matching them against trusted keys stored in the file system.

SAF does a limited form of certificate checking that only determines which SAF user is the owner of the certificate. SAF does not check the contents of the certificate, such as the validity period, or check for certificate revocation. Instead of revoking a certificate the site can reduce the user's access rights in SAF.

A trusted key provider must be configured if SAF certificate checking is to be used.

To enable SAF checking of remote Secure Shell servers, their certificates can be entered into SAF as SITE keys and placed on a key ring for the trusted key provider.

Tectia Certificate Validation

The Tectia Certificate Validator does a full validation of the certificate and can be configured to use external PKI services such as LDAP servers that store revocation information.

When a trusted key provider is configured, the Tectia validator takes its trusted CA certificates from SAF, otherwise they are read from files.

Tectia Server for IBM z/OS can be configured to support either public-key or certificate authentication. With certificate authentication, the private key and certificate can be stored either in SAF or in file.

It is also possible to configure the server to use a key from SAF and use only the public key extracted from the certificate for authentication.

If a SAF key is configured but the key cannot be found or ICSF is required but not available, the server will issue an error message and will not start up.