Title

The key file used by a BIND 9.x server must be owned by the account under which the name server software is run. (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 can also 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. TSIG is a string used to generate the message authentication hash stored in a TSIG RR and used to authenticate an entire DNS message.

Check Content

Verify permissions assigned to the TSIG keys enforce read-write access to the key owner and deny access to group or system users. With the assistance of the DNS administrator, determine the location of the TSIG keys used by the BIND 9.x implementation: # ls -al <TSIG_Key_Location> -rw-------. 1 named named 76 May 10 20:35 tsig-example.key If the key files are more permissive than 600, this is a finding.

Fix Text

Change the permissions of the TSIG key files: # chmod 600 <TSIG_key_file>

Additional Identifiers

Rule ID: SV-272374r1082245_rule

Vulnerability ID: V-272374

Group Title: SRG-APP-000176-DNS-000018

Expert Comments

CCIs tied to check.

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