From Domain Name System (DNS) Security Requirements Guide
Part of SRG-APP-000516-DNS-000114
Associated with: CCI-000366
The use of CNAME records for exercises, tests, or zone-spanning aliases should be temporary (e.g., to facilitate a migration). When a host name is an alias for a record in another zone, an adversary has two points of attack: the zone in which the alias is defined and the zone authoritative for the alias's canonical name. This configuration also reduces the speed of client resolution because it requires a second lookup after obtaining the canonical name. Furthermore, in the case of an authoritative name server, this information is promulgated throughout the enterprise to caching servers and thus compounds the vulnerability.
Review the DNS server's hosted zones and respective records. Within the zone statement will be a file option that will display the name of the zone file. The record type column will display CNAME. This is usually the third or fourth field in a record depending on whether the TTL value is utilized. Without a TTL value, the CNAME type will be in the third field; otherwise, it will display as the fourth field. Review the zone files and the DNS zone record documentation to confirm that there are no CNAME records older than 6 months. The exceptions are glue records supporting zone delegations, CNAME records supporting a system migration, or CNAME records that point to third party Content Delivery Networks (CDN) or cloud computing platforms. In the case of third-party CDNs or cloud offerings, an approved mission need must be demonstrated (AO approval of use of a commercial cloud offering would satisfy this requirement). If there are zone-spanning CNAME records older than 6 months and the CNAME records resolves to anything other than fully qualified domain name for glue records supporting zone delegations, CNAME records supporting a system migration, or CNAME records that point to third-party Content Delivery Networks (CDN) or cloud computing platforms with a AO-approved and documented mission need, this is a finding.
Remove any zone-spanning CNAME records that have been active for more than six months.
Lavender hyperlinks in small type off to the right (of CSS
class id, if you view the page source) point to
globally unique URIs for each document and item. Copy the
link location and paste anywhere you need to talk
unambiguously about these things.
You can obtain data about documents and items in other
formats. Simply provide an HTTP header Accept:
text/turtle or
Accept: application/rdf+xml.
Powered by sagemincer