Cis Bind V100 4 2

CIS 4.2 — Include Cryptographic Key Files

Profile Applicability

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

Description

Do not place keys directly in the BIND named.conf, but use separate configuration files for the keys and include them into the named.conf file, in order to protect the keys from unintentional disclosure.

Rationale

Although the keys may be placed directly in the named.conf file, putting it in a separate file will limit the number of times it needs to be viewed, and make it independent of viewing and changes to the main configuration file.

Impact

Not specified in the PDF.

Audit Procedure

Use the grep command below to search the named.conf file to ensure it doesn't have any secret keys placed in the file.

# grep -C 3 secret /etc/named.conf

key host1-host2.cisecurity.org {
    algorithm hmac-sha256;
    secret "1R3DP9D81/yWXjqf3hlg2beRpti1883JnZ3s7RVb1HU=";
};

Remediation

Move each key definition statement from the named.conf file into its own key file. It is recommended to name both the key and the key file after the two hosts that will be sharing the secret key, in order to avoid confusion. Then include the key files with include statements in the named.conf. An example is shown below with the key definition statement moved to a separate key file, however it is also accepted for only the secret statement to be moved to another file.

# grep -C 1 include /etc/named.conf

// Include the key file used for the host1 and host2 TSIG comms
include "/etc/private/host1-host2.cisecurity.org.key";

# cat /var/named/chroot/etc/private/host1-host2.cisecurity.org.key
key host1-host2.cisecurity.org {
 algorithm hmac-sha256;
 secret "1R3DP9D81/yWXjqf3hlg2beRpti1883JnZ3s7RVb1HU=";
};

Default Value

During a default install an rndc key is generated in a separate file /etc/rndc.key and included in the named.conf.

References

Not specified in the PDF.

CIS Controls

MITRE ATT&CK Mappings

Profile

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