Centroid.EU Blog

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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Random Hackepedia

August 28th, 2009

One major change I've noticed in Solaris 10 is that admintool is gone...

To read more about Solaris 10 go here

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It's donation time again

August 24th, 2009

A small amount goes to MARC mailing list archive for their superb archiving services, I use MARC regularely.

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The IPv4 Address Report

August 22nd, 2009

I came across this webpage called the IPv4 Address report. It predicts when we will run out of IPv4 space. At the time of this writing it was 694 days and I noticed over a couple of weeks that this number can grow or shrink as the prediction passes over time.

Running out of IPv4 space is hardly the end of the world. It just means that IPv6 will be a must have rather than a nice-to-have. This blog already is mirrored on ipv6 space at ipv6.solarscale.de . (you can only reach it if you have IPv6 configured).

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Random Hackepedia

August 21st, 2009

Encryption is the art of obfuscating information so that a third party cannot read its contents...

Read on, here.

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