Title

Permissions assigned to the dnssec-keygen keys used with the BIND 9.x implementation must enforce read-only access to the key owner and deny access to all other users. (Cat II impact)

Discussion

To enable zone transfer (requests and responses) through authenticated messages, it is necessary to generate a key for every pair of name servers. The key also can be used for securing other transactions such as dynamic updates, DNS queries, and responses. The binary key string that is generated by most key generation utilities used with DNSSEC is Base64 encoded. A TSIG is a string used to generate the message authentication hash stored in a TSIG RR and used to authenticate an entire DNS message. Weak permissions could allow an adversary to modify the file(s), thus defeating the security objective.

Check Content

With the assistance of the DNS administrator, identify all dnssec-keygen key files that reside on the BIND 9.x server. An example dnssec-keygen key file will look like the following: Kns1.example.com_ns2.example.com.+161+28823.key OR Kns1.example.com_ns2.example.com.+161+28823.private For each key file identified, verify that the key file is owned by "named" and permissions are set to 400: # ls -al -r-------- 1 named named 77 Jul 1 15:00 Kns1.example.com_ns2.example.com+161+28823.key If the key files are not owned by “named”, this is a finding. If the key files are more permissive than 400, this is a finding.

Fix Text

Change the permissions of the dnssec-keygen key files: # chmod 400 <key_file>

Additional Identifiers

Rule ID: SV-272388r1124010_rule

Vulnerability ID: V-272388

Group Title: SRG-APP-000516-DNS-000086

Expert Comments

CCIs tied to check.

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