Title

The BIND 9.x server digital signature algorithm used for DNSSEC-enabled zones must be FIPS-compatible. (Cat II impact)

Discussion

The choice of digital signature algorithm will be based on recommended algorithms in well-known standards. NIST's Digital Signature Standard (DSS) [FIPS186] provides three algorithm choices: - Digital Signature Algorithm (DSA). - RSA. - Elliptic Curve DSA (ECDSA). Of these three algorithms, RSA and DSA are more widely available and are considered candidates of choice for DNSSEC. In terms of performance, both RSA and DSA have comparable signature generation speeds, but DSA is much slower for signature verification. Hence, RSA is the recommended algorithm as far as this guideline is concerned. RSA with SHA-1 is currently the only cryptographic algorithm mandated to be implemented with DNSSEC, although other algorithm suites (i.e., RSA/SHA-256, ECDSA) are also specified. It can be expected that name servers and clients will be able to use the RSA algorithm at a minimum. It is suggested that at least one ZSK for a zone use the RSA algorithm. NIST's Secure Hash Standard (SHS) (FIPS 180-3) specifies SHA-1, SHA-224, SHA-256, SHA-384, and SHA-512 as approved hash algorithms to be used as part of the algorithm suite for generating digital signatures using the digital signature algorithms in NIST's DSS[FIPS186]. It is expected that there will be support for Elliptic Curve Cryptography in the DNSSEC. The migration path for USG DNSSEC operation will be to ECDSA (or similar) from RSA/SHA-1 and RSA/SHA-256 before September 30th, 2015.

Check Content

Verify that the DNSSEC and TSIG keys used by the BIND 9.x implementation are FIPS 180-3 compliant. If the server is in a classified network, the DNSSEC portion of the requirement is Not Applicable. DNSSEC KEYS: Inspect the "named.conf" file and identify all of the DNSSEC signed zone files: zone "example.com" { file "signed_zone_file"; }; For each signed zone file identified, inspect the file for the "DNSKEY" records: 86400 DNSKEY 257 3 8 ( <KEY HASH> ) ; KSK; 86400 DNSKEY 256 3 8 ( <KEY HASH> ) ; ZSK; The fifth field in the above example identifies what algorithm was used to create the DNSKEY. If the fifth field the KSK DNSKEY is less than "8" (SHA256), this is a finding. If the algorithm used to create the ZSK is less than "8" (SHA256), this is a finding. TSIG KEYS: Inspect the "named.conf" file and identify all of the TSIG key statements: key tsig_example. { algorithm hmac-SHA256; include "tsig-example.key"; }; If each key statement does not use "hmac-SHA256" or a stronger algorithm, this is a finding.

Fix Text

Create new DNSSEC and TSIG keys using a FIPS 180-3 approved cryptographic algorithm that meets or exceeds the strength of SHA256.

Additional Identifiers

Rule ID: SV-272409r1069909_rule

Vulnerability ID: V-272409

Group Title: SRG-APP-000516-DNS-000090

Expert Comments

CCIs tied to check.

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