Title

On the BIND 9.x server the private key corresponding to the zone signing key (ZSK), stored on name servers accepting dynamic updates, must be group owned by root. (Cat II impact)

Discussion

The private keys in the key signing key (KSK) and ZSK key pairs must be protected from unauthorized access. If possible, the private keys should be stored offline (with respect to the internet-facing, DNSSEC-aware name server) in a physically secure, nonnetwork-accessible machine along with the zone file primary copy. This strategy is not feasible in situations in which the DNSSEC-aware name server has to support dynamic updates. To support dynamic update transactions, the DNSSEC-aware name server (which usually is a primary authoritative name server) has to have both the zone file primary copy and the private key corresponding to the zone-signing key (ZSK-private) online to immediately update the signatures for the updated RRsets. The private key corresponding to the key-signing key (KSK-private) can still be kept offline.

Check Content

Note: This check only verifies for ZSK key file ownership. Permissions for key files are required under BIND-9X-001132 and BIND-9X-001142. For each signed zone file, identify the ZSK "key id" number: # cat <signed_zone_file> | grep -i "zsk" ZSK; alg = ECDSAP256SHA256; key id = 22335 Using the ZSK "key id", verify the private ZSK. Kexample.com.+008+22335.private Verify that the private ZSK is owned by root: # ls -l <ZSK_key_file> -r------- 1 root root 1776 Jul 3 17:56 Kexample.com.+008+22335.private If the key file is not group owned by root, this is a finding.

Fix Text

Change the group ownership of the ZSK private key to the root group account. # chgrp root <key_file>

Additional Identifiers

Rule ID: SV-272391r1068271_rule

Vulnerability ID: V-272391

Group Title: SRG-APP-000516-DNS-000111

Expert Comments

CCIs tied to check.

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