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Verifying delphinusdns signed zones

March 6th, 2020

I just wrote a little in the handbook regarding verifying what dddctl sign produces. It's often a good idea to take this step in order to unearth any unintended bugs. Thanks!

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Default key creating algorithm has been changed

March 4th, 2020

I have changed the default key creating algorithm to alg 13 from alg 8, in the -current code. Alg 13 is ECDSAP256SHA256. This is generally recommended in IRC #dns. It will not affect 1.4.x release which still uses alg 8.

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What am I currently working on?

March 3rd, 2020

I have some uncommitted code to allow the double-signature method for rollovers.This should allow algorithm rollovers eventually. I was stuck trying to make this work though. My main source of dns programming advice was able to help me out again interpreting RFC 4034 right. It turns out in the scenario of introducing a different sized key (3072 bits vs. 1024 bits) I was not sorting the RR's right in canonical mode. The problem lies in my interpretation of RFC 4034, section 3.1.8.1 where the signature is produced by going over the RRset. In my code (not changed yet) I ordered around the wire format of RR(i), but instead the ordering is done first around the RDATA instead. Thanks goes to Habbie once again! Since algorithm rollovers aren't supported in Delphinusdnsd 1.4.x I don't feel I need to backport changes here. But we'll likely see a different sorting algorithm for 1.5.0.

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Monthly DNSSEC maintenance

March 3rd, 2020

When you do a dig for "+dnssec delphinusdns.org A" you will see something like this:

; <<>> dig 9.10.8-P1 <<>> +dnssec delphinusdns.org
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 53016
;; flags: qr rd ra ad; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags: do; udp: 4096
;; QUESTION SECTION:
;delphinusdns.org.              IN      A

;; ANSWER SECTION:
delphinusdns.org.       86385   IN      A       85.10.199.4
delphinusdns.org.       86385   IN      RRSIG   A 10 2 86400 \
20200502072347 20200218072347 64280 delphinusdns.org. ...
I have added a ... in place of the signature in the RRSIG record. What I'm most concerned with is the signature expire fields and the signature inception fields.
20200502072347 20200218072347
Those two. If a DNSSEC zone goes beyond the date of the "signature expiration" the zone is marked as expired thus bogus and remote recursive nameservers may reply with SERVFAIL. Obviously one doesn't want that so there must be a timely maintenance to up the signature expiration. I do this semi-automatically with a script and some typing (the tab expansion in the shell is great help here). I call this "re-signing the zone".

It is done with dddctl sign command and dddctl will take the current time and go back 2 weeks in order to create a small overlap. This is needed to prevent unsynched clocks to always recognize the window between inception and expiration. The new inception was 18th of February and is exactly 2 weeks in the past. The new expiration is roughly 2 months in the future (by default in delphinusdns) so this zone has ample time (after a month perhaps) to do a zone re-sign. Re-signs are easy, you take the previous keys and just resign the zone (with a new SOA serial value so that the replicants can pick up the change).

In the past while being the only sysadmin at an operation I discouraged the use of DNSSEC because of this. With just one sysadmin there is no backup, and if you fall sick for over 1 month time the business will suffer. So either automate this and hope that the automation never ever fails or don't do DNSSEC and open your domain to forgeries (as DNSSEC has cryptographic integrity). It's a choice one must make, and it isn't easy. DNSSEC really requires two hostmasters who know what they're doing, to have a backup when the other falls sick or is unavailable for whatever reason.

BTW you can't use re-signing to do key rollovers, they have to be done seperately. See the handbook for how to do this.

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Split Horizon DNS

February 20th, 2020

Earlier today I was approached on split-horizon dns and whether I can implement something like this. The short answer is no, but you can still do split horizon DNS with delphinusdnsd with pf. It requires setting up 2 or 3 delphinusdnsd bound on several interfaces including localhost on their own port. With pf rules you would then do an rdr-to 127.0.0.1 port X where X is the delphinusdnsd that it should speak to. You would have the same setup on both replicant and master and they would axfr on their own unique axfr port. A large list of IP's can be assembled from this website (iana.org).

The reason I'm hesitant on bringing back split horizon to delphinusdnsd is that it doesn't really fit well with AXFR, it's a mess there. The hack that I explained it the first paragraph keeps it on a boundary though and could be done well. Debugging split horizon dns is a pain too, but I think with regions configured in all running delphinusdnsd's you can have an overview of which delphinusdnsd was hit. You just gotta watch the logs closely and follow up to complaints. Good luck!

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Delphinusdnsd is probably not 2038 safe

February 14th, 2020

Happy Valentines day. Delphinusdnsd is programmed on OpenBSD which is Y2038 safe, but the ports may break on January 19th, 2038 or after. I don't know what will happen actually. I'll keep an eye on this. 2035 is likely the last year when I will work on this code, perhaps there will be more light, then.

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Delphinusdnsd 1.4.1 released

February 4th, 2020

This is a fix for Linux platform. From the commit log on the STABLE_1.4 branch:

This is the first STABLE_1_4 commit leading to release 1.4.1, changes:

-replace linux's TAILQ macros with libbsd's
-replace TAILQ_FOREACH for linux with libbsd's TAILQ_FOREACH_SAFE
-increase buffer buf in struct tcpentry by 1 more byte to prevent possible
 overflow
-change lookup_zone to take another argument to indicate size of buffer
-remove length variable in tcploop to squelch warning
-replace a casting pointer with an unpack16() in tcploop
-fix formatting of serial log in raxfr.c (this fixes my output in linux).

This effort fixes formatting and crashes on Linux/arm and fixes a general
off-by-one (not sure if it's exploitable).
Hope this will be OK, the downloads are available all I have left to do is signify the SHA256.sig file (will be done shortly). Enjoy.

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Self Interview: An Open Source Project after 2005 AD

January 31st, 2020

What tools did I use? What experience did I have to have?
When I started writing wildcarddnsd/delphinusdnsd I had 10 years of experience with the UN*X Operating System. I had a lot of sysadmin experience and some C programming experience. I started in 2005 (it was autumn) originally the source code was checked in at sourceforge I believe. I personally felt I was "ready" to lay down this code.

UNIX tools I used to write and debug delphinusdnsd

  • vi - to enter the code from scratch (lots of fun!)
  • tcpdump - to debug answers that delphinusdnsd gives
  • hexdump - to debug dddctl's signing functions
  • less/more - to paginate outputs and to look at zonefiles and code
  • gdb - to debug crashes
  • irssi - to share my enjoyment of writing on a DNS server on IRC and to get support from people who have already done so.
  • BSD - what I started using to write delphinusdnsd, up to this day
  • Linux - what I ported delphinusdnsd to, up to this day
  • make - to execute the makefiles which executed the compiler, assembler and linker.
  • dig - used mostly to query the server
  • drill - used on FreeBSD instead of dig
  • ldns-tools - helped a lot finding problems with the DNSSEC code
  • Other DNS servers (BIND,nsd) - to compare their output from mine.

Literature used
Countless books about DNS, Unix network programming and YACC guided me along the way, 10 years experience with UN*X OS's in 2005 started me on this journey.

It's 2020 now, why did I decide to keep doing this?
I have put 15 years under my belt with this, I intend to do another 15 (god willing). It is a lot of fun steering my own project.

If I could turn back time would I do it again?
Yes.

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Why was 1.3.0 an oddball release?

January 31st, 2020

1.3.0 was an oddball release because I applied to funding from the federal german government in a program called Prototypefund.de, shifting the release date early by half a year. I didn't get selected with delphinusdnsd. Meaning, I paid out of my own pocket to work on version 1.4.0 and 1.4.1 (January 2019 through February 2020). In 2018 between summer and christmas I had another project (OpenBSD powerpc64 port which ultimately failed) while waiting on the selection results of prototypefund. All releases before 1.3.0 were also constructed from my spare time as I could find it. I'm glad 1.4.X is out and I'm looking forward to programming on 1.5.0 (expected to be released in late December). Someone I met is working on an OpenBSD port for me and I'm looking forward to featuring him on the Credits section of the delphinusdns.org site once the work is committed at OpenBSD. The porting work is no easy feat and I'm glad someone is doing this for me.

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Delphinusdnsd 1.4.1 to be released in February

January 26th, 2020

I believe the fixes I made to delphinusdnsd (on linux) were good. I'm going to backport the code to the STABLE_1_4 branch soon and then tag it RELEASE_1_4_1. I'm gonna run the code as it is now for another week on the particular Linux computer that had problems throughout december and early january and if I don't see any more crashes then it's a done deal. Sorry for inconveniences. This I believe did not affect BSD versions of this code, only Linux although and off-by-one was fixed (I think), that should have impact on all platforms.

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