TMA-BIND-3.1

Ignore Erroneous or Unwanted Queries

MediumLevel 1Automatedbind

Description

BIND can be configured to ignore requests originating from specified network segments. This is accomplished by implementing the blackhole option in named.conf. It is recommended that this feature be implemented to ignore requests that originate outside of expected network segments. The audit requires a non-empty blackhole address list in the global options. The audit parses the effective configuration printed by named-checkconf -p (all include files resolved) from /etc/named.conf (RHEL; chroot /var/named/chroot is detected) or /etc/bind/named.conf (Debian/Ubuntu).

How it is checked

Audit method: Shell command

shell

if [ -f /var/named/chroot/etc/named.conf ]; then out=$(named-checkconf -t /var/named/chroot -p /etc/named.conf 2>/dev/null) || exit 1
else conf=/etc/named.conf; [ -f "$conf" ] || conf=/etc/bind/named.conf
  out=$(named-checkconf -p "$conf" 2>/dev/null) || exit 1; fi
flat=$(printf '%s\n' "$out" | tr '\t\n' '  ' | tr -s ' ')
opts=$(printf '%s\n' "$out" | awk '/^options[ \t]*\{/{f=1} f{print} f&&/^\};/{exit}' | tr '\t\n' '  ' | tr -s ' ')
printf '%s\n' "$opts" | grep -Eq '[{; ]blackhole \{ *[^} ]' && echo compliant || echo 'no blackhole list in options'

Expected output: compliant

How it is fixed

Fix method: Guidance or infrastructure patch

Add a blackhole option for multicast and link local addresses, and all private RFC 1918 addresses that are not being used. blackhole { // Private RFC 1918 addresses 10/8; 192.168/16; 172.16/12; // Multicast 224/8; // Link Local 169.254/16; };

Properties

Operating systems: Any
Tags: binddnsaccess-control
Reference: CIS ISC BIND DNS Server 9.11 Benchmark v1.0.0 - 3.1 Ignore Erroneous or Unwanted Queries

Check this host

Run this on a machine you are allowed to audit. The scan is read-only.

shell

tmaegis scan --target bind