The BIND 9.x server validity period for the RRSIGs covering the DS RR for zones delegated children must be no less than two days and no more than one week.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-72475	BIND-9X-001311	SV-87099r1_rule		Medium

Description
The best way for a zone administrator to minimize the impact of a key compromise is by limiting the validity period of RRSIGs in the zone and in the parent zone. This strategy limits the time during which an attacker can take advantage of a compromised key to forge responses. An attacker that has compromised a ZSK can use that key only during the KSK's signature validity interval. An attacker that has compromised a KSK can use that key for only as long as the signature interval of the RRSIG covering the DS RR in the delegating parent. These validity periods should be short, which will require frequent re-signing. To prevent the impact of a compromised KSK, a delegating parent should set the signature validity period for RRSIGs covering DS RRs in the range of a few days to 1 week. This re-signing does not require frequent rollover of the parent's ZSK, but scheduled ZSK rollover should still be performed at regular intervals.

Description

The best way for a zone administrator to minimize the impact of a key compromise is by limiting the validity period of RRSIGs in the zone and in the parent zone. This strategy limits the time during which an attacker can take advantage of a compromised key to forge responses. An attacker that has compromised a ZSK can use that key only during the KSK's signature validity interval. An attacker that has compromised a KSK can use that key for only as long as the signature interval of the RRSIG covering the DS RR in the delegating parent. These validity periods should be short, which will require frequent re-signing. To prevent the impact of a compromised KSK, a delegating parent should set the signature validity period for RRSIGs covering DS RRs in the range of a few days to 1 week. This re-signing does not require frequent rollover of the parent's ZSK, but scheduled ZSK rollover should still be performed at regular intervals.

STIG	Date
BIND 9.x Security Technical Implementation Guide	2018-01-02

Details

Check Text ( C-72677r1_chk )
With the assistance of the DNS Administrator, identify the RRSIGs that cover the DS resource records for each child zone. Each record will list an expiration and inception date, the difference of which will provide the validity period. The dates are listed in the following format: YYYYMMDDHHMMSS For each RRSIG identified, verify that the validity period is no less than two days and is no longer than seven days. If the validity period is outside of the specified range, this is a finding.

Check Text ( C-72677r1_chk )

With the assistance of the DNS Administrator, identify the RRSIGs that cover the DS resource records for each child zone.

Each record will list an expiration and inception date, the difference of which will provide the validity period.

The dates are listed in the following format:

YYYYMMDDHHMMSS

For each RRSIG identified, verify that the validity period is no less than two days and is no longer than seven days.

If the validity period is outside of the specified range, this is a finding.

Fix Text (F-78831r1_fix)
Resign the child zone files and have the zone administrator provide updated DS resource records for the child zone.