I was interested in how a recursive DNS server resolves DNS queries in detail. That is, not only the mere AAAA or A record, but also DNSSEC keys and signatures, the authority and additional section when testing with
dig , and so on. For this I made two simple DNS queries to my recursive DNS server which resulted in more than 100 DNS packets at all. Wow.
In the following I am publishing a downloadable pcap so that you can analyse it by yourself. Furthermore I am showing some listings and screenshots to get an idea of the DNS resolution process.
Continue reading Single DNS Query – Hundreds of Packets
In my last blogpost I showed how to perform a DNSSEC KSK rollover. I did it quite slowly and carefully. This time I am looking into an emergency rollover of the KSK. That is: What to do if your KSK is compromised and you must replace it IMMEDIATELY.
I am listing the procedures and commands I used to replace the KSK of my delegated subdomain
dyn.weberdns.de with BIND. And as you might already suggest it, I am showing DNSViz graphs after every step since it greatly reveals the current DNSKEYs etc.
Continue reading DNSSEC KSK Emergency Rollover
Probably the most crucial part in a DNSSEC environment is the maintenance of the key-signing key, the KSK. You should rollover this key on a regular basis, though not that often as the zone signing keys, the ZSKs. I am doing a KSK rollover every 2 years.
In the following I will describe the two existing methods for a KSK rollover along with a step-by-step guide how I performed such a rollover for my zone “weberdns.de”. Of course again with many graphics from DNSViz (with “redundant edges”) that easily reveal the keys and signatures at a glance.
Note that this blogpost is NOT about the Root Zone KSK Rollover
that appears in 2017/2018. It is merely about your OWN zone
that is secured via DNSSEC.
Continue reading DNSSEC KSK Key Rollover
If you are already familiar with DNSSEC this is quite easy: How to sign a delegated subdomain zone. For the sake of completeness I am showing how to generate and use the appropriate DS record in order to preserve the chain of trust for DNSSEC.
Continue reading Signing a Delegated Subdomain
What is the biggest problem of PGP? The key distribution. This is well-known and not new at all. What is new is the OPENPGPKEY DNS resource record that delivers PGP public keys for mail addresses. If signed and verified with DNSSEC a mail sender can get the correct public key for his recipient. This solves both key distribution problems: 1) the delivery of the public key and 2) the authenticity of the key itself, i.e., that you’re using the correct key to encrypt a mail.
The “DNS-Based Authentication of Named Entities (DANE) Bindings for OpenPGP” is specified in the experimental RFC 7929. Let’s have a look on how you can add your public key into the zone file of your DNS server.
Continue reading PGP Key Distribution via DNSSEC: OPENPGPKEY
I know that BIND correctly changes the serial numbers of zones when it is enabled with inline signing and auto-dnssec. However, I got confused one more time as I looked on some of my SOA records. So, just for the record, here is an example how the serial numbers increase while the admin has not changed anything manually on the zone files.
Continue reading BIND Inline-Signing Serial Numbers Cruncher
One important maintenance requirement for DNSSEC is the key rollover of the zone signing key (ZSK). With this procedure a new public/private key pair is used for signing the resource records, of course without any problems for the end user, i.e., no falsified signatures, etc.
In fact it is really simply to rollover the ZSK with BIND. It is almost one single CLI command to generate a new key with certain time ranges. BIND will use the correct keys at the appropriate time automatically. Here we go:
Continue reading DNSSEC ZSK Key Rollover
This is really cool. After DNSSEC is used to sign a complete zone, SSH connections can be authenticated via checking the SSH fingerprint against the SSHFP resource record on the DNS server. With this way, administrators will never get the well-known “The authenticity of host ‘xyz’ can’t be established.” message again. Here we go:
Continue reading SSHFP: Authenticate SSH Fingerprints via DNSSEC
DNS-based Authentication of Named Entities (DANE) is a great feature that uses the advantages of a DNSSEC signed zone in order to tell the client which TLS certificate he has to expect when connecting to a secure destination over HTTPS or SMTPS. Via a secure channel (DNSSEC) the client can request the public key of the server. This means, that a Man-in-the-Middle attack (MITM) with a spoofed certificate would be exposed directly, i.e., is not possible anymore. Furthermore, the trust to certificate authorities (CAs) is not needed anymore.
In this blog post I will show how to use DANE and its DNS records within an authoritative DNS server to provide enhanced security features for the public.
Continue reading How to use DANE/TLSA
To solve the chicken-or-egg problem for DNSSEC from the other side, let’s use an authoritative DNS server (BIND) for signing DNS zones. This tutorial describes how to generate the keys and configure the “Berkeley Internet Name Domain” (BIND) server in order to automatically sign zones. I am not explaining many details of DNSSEC at all, but only the configuration and verification steps for a concrete BIND server.
It is really easy to tell BIND to do the inline signing. With this option enabled, the admin can still configure the static database for his zone files without any relation to DNSSEC. Everything with signing and maintaining is fully done by BIND without any user interaction. Great.
Continue reading DNSSEC Signing w/ BIND
If you are searching for a DNSSEC validating DNS server, you can use BIND to do that. In fact, with a current version of BIND, e.g. version 9.10, the dnssec-validation is enabled by default. If you are already using BIND as a recursive or forwarding/caching server, you’re almost done. If not, this is a very basic installation guide for BIND with DNSSEC validation enabled and some notes on how to test it.
Continue reading BIND DNSSEC Validation
This is a basic tutorial on how to install BIND, the Berkeley Internet Name Domain server, on a Ubuntu server in order to run it as an authoritative DNS server. It differs from other tutorials because I am using three servers (one as a hidden primary and two secondaries as the public accessible ones), as well as some security such as denying recursive lookups and public zone transfers, as well as using TSIG for authenticating internal zone transfers. That is, this post is not an absolute beginner’s guide.
Continue reading Basic BIND Installation
I am using the DNS Proxy on a Palo Alto Networks firewall for some user subnets. Besides the default/primary DNS server, it can be configured with proxy rules (also called conditional forwarding) which I am using for reverse DNS lookups, i.e., PTR records, that are answered by a BIND DNS server. While it is easy and well-known to configure the legacy IP (IPv4) reverse records, the IPv6 ones are slightly more difficult. Fortunately, there are some good tools on the Internet to help reversing IPv6 addresses.
Continue reading Palo Alto DNS Proxy Rule for Reverse DNS