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Delve deep into DNSSEC

Posted by Men & Mice on 3/28/14 8:49 AM

By Mr. Carsten Strotmann, one of Men & Mice experts.

BIND 9.10 is the new version of the BIND 9 DNS server from ISC (not to be confused with BIND 10, which is a different DNS server product). We will report in a series of articles about the new features in BIND 9.10. The first beta version of BIND 9.10 was released this week and can be found at ftp://ftp.isc.org/isc/bind9/9.10.0b1/.

BIND 9.10 contains a new command-line tool to test DNSSEC installations. The tool is called delve and it works very much like the well-known dig, but with special DNSSEC validation powers.

delve checks the DNSSEC validation chain using the same code that is used by the BIND 9 DNS server itself. Compared with the DNSSEC testing function in dig +sigchase, delve is much closer to what really happens inside a DNS server.

1.1 A simple lookup

Without extra arguments, delve will query the local DNS server (taken from /etc/resolv.conf) for an IPv4-Address record at the given domain name. It tries to validate the answer received, prints the result of the validation, the requested data and the RRSIG Record (DNSSEC signature) used to verify the data.

1.2 pretty-printing

As with dig, resource record types and network classes can be given in almost any order on the commandline. The switch +multi (for multiline) enables pretty printing; human readable output that is neatly formatted for a 78 column screen.

and IPv6

1.3 tracing DNSSEC validation

delve comes with a set of trace switches that can help troubleshoot DNSSEC validation issues. The first switch, +rtrace, prints the extra DNS lookups delve performs to validate the answer:

In this example, in addition to the MX-Record (Mail-Exchanger) Record, the DNSKEY record (DNSSEC public key) and the DS record (Delegation signer) for dnsworkshop.org, as well as the DNSKEY and DS records for ORG and the DNSKEY for the root-zone "." have been requested. The trust-anchor for the Internet Root-Zone is compiled into delve and acts as the starting trust anchor for the validation.

The switch +mtrace prints the content of any additional DNS records that have been fetched for validation.

+vtrace prints out the DNSSEC chain of validation:

delve is a very useful tool, not only for BIND 9 admins, but for everyone who needs to troubleshoot and fix DNS- and DNSSEC related issues.

Topics: IPv6, DNSSEC, BIND 9

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