Centroid.EU Blog

(this blog is mostly encrypted - adults only)

Nominum's statements

September 23rd, 2009

As some of you may know I'm the author of the Wildcard DNS server. I read the following words from Nominum: "Open Source DNS a Recipe for Problems". And I have to disagree to this somewhat. But when looking at my own meagre DNS server, there is a few areas of concern. First, my server wasn't meant to be put on the Internet when I first wrote it close to four years ago, but it's functionality allowed it to be run as an authoritative nameserver. I have been serving the centroid.eu zone with it and continually studying the logs of it and I'm happy to report that my server was never killed from remote, I never had to restart the server. I'm surprised that it works out to be fairly stable.

Wildcard DNS was and is a research project and while I'm at it I'm sharing the source of it. Whoever wants to use it should know the license. The license (BSD license) protects me as the author of the program from being sued by someone who may get damaged by using this DNS server. There is some risk using this software, but I personally am pretty happy. Writing a DNS server isn't easy, but when you do you learn a lot. How the DNS protocol is utterly broken (by using 16 bit ID's), for example. Nominum can't get around the 16 bit ID problem, it's a protocol problem.

So anyhow, I'm in the process of adding new functionality to Wildcard DNS that no other open source nameserver has, and I'm looking forward in seeing it run and experiment with it. When it turns out to work pretty well the functionality can be put into other nameservers at their will.

If you ask me Nominum just wants a bigger chunk of the monopoly that BIND used to have and now are on a warpath to be the dominant dns server. Good for them, and good luck.

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Happy Equinox

September 22nd, 2009

Today is the equinox. The sun sets at the North Pole and rises at the South Pole. Also night should be as long as day.

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Random Hackepedia

September 19th, 2009

A process covers the entire address space for the size of a pointer (32 bit in 32 bit architectures, 64 bit for 64 bit architectures). Since virtual memory is being used not all areas of a process has real memory assigned to it and only some parts (access to parts that have no memory results in a SIGSEGV signal and the process is killed)...

To read more about heap, click on link.

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Equinox in a few days

September 17th, 2009

The last equinox of this year is in a few days, 5.

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Random Hackepedia

September 12th, 2009

A Firewall is part of an Operating System's networking stack that allows one to create policies for network traffic, and permit or deny that traffic accordingly...

To read more about firewalls , click on the link.

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Planet of the Users (OpenBSD song)

September 8th, 2009

Today the new OpenBSD song came out for OpenBSD 4.6. The song is inspired by the movie "Planet of the Apes", where in the future Puffy flies to our planet in a timemachine. As he lands he sees a world that is evil. People have their arms surgically removed at birth and have a screen before their eyes to see, probably to take them out of their misery. Personal robots do all tasks that arms would have done. Puffy gets caught after someone identifies him as a hacker, but then escapes after turning the warden fish's display off (who by the way sees him as a woman in a bikini).

The story reminds me of a brainstorm I had in my old apartment where people get their limbs removed in order to program for a slave driver. Can't run away if you got no legs.

Puffy says "stop this future", and I agree, we don't need limbless people that would otherwise have healthy limbs. Down with slavery!

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Identifying OS by TTL

September 7th, 2009

By default BSD and Linux systems have a TTL of 64. Windows systems have a default TTL of 128. Given that information one can with some certainty say what OS did a DNS lookup on a wildcarddns DNS server. It requires logging turned on and evaluating the log with AWK.

Here is a small shell script:

grep wild /var/log/all | grep ttl | grep -v "ttl=0" | 
awk '{split($14,a,  "="); split(a[2], b, ")"); print b[1]; }'|\
sort | uniq -c |  \
awk 'BEGIN { printf("DNS lookups per operating system\n"); } {if ($2 > 64) { if 
($2 > 128) hash["unknown"] += $1; else hash["windows"] += $1;} else hash["unix"]
 += $1; } END { for (i in hash) { printf("%10-s - %s lookups\n", i, hash[i]);} }
'

The output looks somewhat like this:

DNS lookups per operating system
unknown    - 11 lookups
windows    - 90 lookups
unix       - 242 lookups

Unknown OS is anything over a TTL of 128 (probably with a default ttl of 255).

Here are some TTL's of default systems:

setebos$ uname -a
OpenBSD setebos.solarscale.de 4.5 GENERIC#0 i386
setebos$ sysctl -a | grep ttl 
net.inet.ip.ttl=64

# uname -a
SunOS sycorax 5.10 Generic_137138-09 i86pc i386 i86pc
# ndd /dev/ip ip_def_ttl
255
# ndd /dev/udp udp_ipv4_ttl
255

[pjp@uranus ~]$ uname -a
Linux uranus.centroid.eu 2.6.18-92.1.13.el5 #1 SMP  ... cut
[pjp@uranus ~]$ cat /proc/sys/net/ipv4/ip_default_ttl
64

So unknown can be changed to solaris.

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Schneier's new crypto book

September 5th, 2009

Bruce Schneier announces a new book called "cryptography engineering" which is a sequel to "practical cryptography". I think I'm gonna buy this new book since I have another book of his called "applied cryptography" and it was a nice to have.

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Random Hackepedia

September 5th, 2009

A system call is an API for a userland process to communicate with the kernel to request data or services outside of it's protected memory...

To read more about system calls go to hackepedia.

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Wildcarddns feature

August 31st, 2009

I've improved the code on wildcarddnsd so that it grabs the incoming ttl and displays it in the logs. Eventually I want to make it so that the dns server closest to an IP will reply. This requires some coding with sockets between two or more wildcarddns servers and allowing it to get the TTL is just a small step. How long it'll be before done I don't know, don't get your hopes up too high on it, unless you want to do some work and contribute.

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