Title

The Ubuntu operating system, for PKI-based authentication, must validate certificates by constructing a certification path (which includes status information) to an accepted trust anchor. (Cat II impact)

Discussion

Without path validation, an informed trust decision by the relying party cannot be made when presented with any certificate not already explicitly trusted. A trust anchor is an authoritative entity represented via a public key and associated data. It is used in the context of public key infrastructures, X.509 digital certificates, and DNSSEC. When there is a chain of trust, usually the top entity to be trusted becomes the trust anchor; it can be, for example, a Certification Authority (CA). A certification path starts with the subject certificate and proceeds through a number of intermediate certificates up to a trusted root certificate, typically issued by a trusted CA. This requirement verifies that a certification path to an accepted trust anchor is used for certificate validation and that the path includes status information. Path validation is necessary for a relying party to make an informed trust decision when presented with any certificate not already explicitly trusted. Status information for certification paths includes certificate revocation lists or online certificate status protocol responses. Validation of the certificate status information is out of scope for this requirement. Satisfies: SRG-OS-000066-GPOS-00034, SRG-OS-000384-GPOS-00167

Check Content

Verify the Ubuntu operating system, for PKI-based authentication, had valid certificates by constructing a certification path (which includes status information) to an accepted trust anchor. Check which pkcs11 module is being used via the "use_pkcs11_module" in "/etc/pam_pkcs11/pam_pkcs11.conf" and then ensure "ca" is enabled in "cert_policy" with the following command: # sudo grep cert_policy /etc/pam_pkcs11/pam_pkcs11.conf cert_policy = ca,signature,ocsp_on; If "cert_policy" is not set to "ca", has a value of "none", or the line is commented out, this is a finding.

Fix Text

Configure the Ubuntu operating system, for PKI-based authentication, to validate certificates by constructing a certification path (which includes status information) to an accepted trust anchor. Determine which pkcs11 module is being used via the "use_pkcs11_module" in "/etc/pam_pkcs11/pam_pkcs11.conf" and ensure "ca" is enabled in "cert_policy". Add or update the "cert_policy" to ensure "ca" is enabled: cert_policy = ca,signature,ocsp_on;

Additional Identifiers

Rule ID: SV-215164r610931_rule

Vulnerability ID: V-215164

Group Title: SRG-OS-000066-GPOS-00034

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.