Cis Bind9 V301 3 3

CIS 3.3 — Restrict Query Origins

Profile Applicability

• Level 1 - Authoritative Name Server
• Level 1 - Caching Only Name Server

Description

BIND can be configured to restrict access to its query services based on source IP address. It is recommended that the allow-query option be used to restrict access to only the networks authorized to use the name server. For an external authoritative only name server, the authorized networks may include all networks, however for internal authoritative or caching name servers the authorized networks should be explicitly configured.

Rationale

Using allow-query in conjunction with an ACL of trusted networks will reduce the risk of unauthorized access to name services content. Additionally, the exposure of vulnerabilities present in BIND's query handlers is reduced by this configuration as requests with an untrusted source will be rejected before the request is fully parsed by named. Keep in mind however, that the source IP addresses can be easily spoofed, and the firewall and network architecture also needs to protect internal name servers from external spoofed requests.

Impact

Not Applicable

Audit Procedure

Verify that the BIND configuration files contain a global allow-query option with only the predefined ACL localhost and an ACL of the explicitly authorized networks. For an external authoritative only name server, the authorized networks may be the ACL any which represents any IPv4 or IPV6 host, but for caching and internal name servers, the authorized_networks should be an ACL with an explicit list of networks. The name of the ACL does not have to be authorized_networks.

$ grep allow-query $CONFIG_FILES
    allow-query     { localhost; authorized_networks };

For an external authoritative only name server:

$ grep allow-query $CONFIG_FILES
    allow-query     { any };

Remediation

For remediation:

• Create an ACL for the authorized trusted networks in the named.conf file.

acl authorized_networks { 10.10.32.0/24; 10.10.34.0/24; . . . };

• Add the allow-query statement to the global options of the named.conf file with the localhost ACL and the authorized trusted networks ACL.

allow-query     { localhost; authorized_networks };

Default Value

The default package install allows queries only from localhost.

References

Not Applicable

CIS Controls

MITRE ATT&CK Mappings

Profile

• Level 1 - Authoritative Name Server
• Level 1 - Caching Only Name Server