blog.foosion.org

Hiding information steganographically

Posted by bene - 04/12/08 at 12:12:59 am

I just found this nice Unix tool to hide sensible data in your multimedia files like JPEG images: steghide

It attaches the secret in compressed+encrypted form and even adds a checksum

The usage is quite simple:

# steghide embed -cf hidden.jpg -ef secret.txt
# steghide extract -sf hidden.jpg

Iotop

Posted by bene - 30/06/08 at 11:06:55 pm

One of the drawbacks of top is that it often can’t help to spot processes which push up system load so high.
High system loads are often caused by very I/O intensive tasks.
And as I/O intensive needn’t mean CPU intensive, those tasks may not even show up in top.

This is where Iotop comes into play. It is just a python script which evaluates the per-task disk I/O accounting statistics exported by the Linux kernel (2.6.20+).

This is what you need to enable in your kernel configuration:

General setup
[*] Export task/process statistics through netlink (EXPERIMENTAL)
[ ]   Enable per-task delay accounting (EXPERIMENTAL)
[*]   Enable extended accounting over taskstats (EXPERIMENTAL)
[*]     Enable per-task storage I/O accounting (EXPERIMENTAL)

Now THAT feels ever more like home…

Posted by Nils - 18/06/08 at 06:06:22 am

Firefox 3 is finally ready to download (though all servers are at the moment more or less overwhelmed, due to the worldrecord attempt).

Since it’s first release it integrates very well into the various systems because someone at Mozilla (after all) had the look & feel in mind. I think thats a big achievement though I stilled wished a support for the various password managers like the keychain or the kde wallet would have made it into the final release.

To top it all off, the UI gets even more “mac” with Aroonax’s GrApple Theme from takebacktheweb.org. (Which is an awesome domainname by the way )

So folks, have a nice day and light a candle, hoping for people around the world to finally abandon this so called “internet explorer” and get their copy of web-freedom.

word!

Songbird

Posted by micele - 17/06/08 at 11:06:21 am

Did anyone try Songbird? As a Linux user I’m always in search of a good audio player. Of course there is Amarok and of course there is Audacious but in my eyes there is not much in between. Amarok is quite large and didn’t really work out at all on my 600MHz P3. On the other hand Audacious is quite tiny but not made for handling large music archives like, .. let’s say.. mine
More accidentally I discovered a new audio player called Songbird. It somehow uses mozillas xul and seems to be a good compromise. To be honest, I didn’t test it too much so far. This might relate to my love-hate relationship to some other media player. Obviously the design is somehow inspired by this specific product
The current version 0.6 is still alpha, so please be patient. Maybe at some day it becomes a real alternative to the mentioned audio players. At least I already love it for it’s logo

Linux kernel 2.6.25.6

Posted by bene - 09/06/08 at 09:06:15 pm

Chris Wright just pushed version 2.6.25.6 to the current stable kernel tree.

It’s definitely worth to check it out: There are 50 commits since 2.6.25.5, many of them backports of bugfixes in 2.6.26-rcx…

Happy compiling

Colored Manpages

Posted by micele - 05/06/08 at 10:06:16 pm

Manpages are a very appropriate instrument for documentation on linux und unix based systems. Unfortunately manpages have been invented in times of monochrome displays. Todays colored displays offer much more clearness and readability. Unfortunately manpages don’t - at least not by default…
I really tried hard to give my linux manpages more readability and finally - it worked. There are a lot of different (and also difficult) approaches. In my eyes the most easiest way is to simply add some less capabilities (less is used as the default man page browser) to enforce coloring. This can be done by using your favorite shell .rc for setting those capabilities. In my case i just added

export LESS_TERMCAP_mb=$'\E[01;31m'
export LESS_TERMCAP_md=$'\E[01;31m'
export LESS_TERMCAP_me=$'\E[0m'
export LESS_TERMCAP_se=$'\E[0m'
export LESS_TERMCAP_so=$'\E[01;44;33m'
export LESS_TERMCAP_ue=$'\E[0m'
export LESS_TERMCAP_us=$'\E[01;32m'

to my .zshrc. The result is quite satisfying and looks like this:

I really fell in love with man pages again. Ok, I confess: I sometimes really care about appearance

Update: While gentoo has some problems with the mentioned method it even works fine for mac.

Pimp my ext3

Posted by micele - 03/04/08 at 03:04:09 pm

Auf heise open findet man seit zwei Wochen einen Artikel über Ext3, dem Standard Dateisystem unter Linux.
Auf insgesamt 10 Seiten setzt sich Autor Dr. Oliver Diedrich ausführlich mit den Interna des Dateisystem auseinander und erläutert an welchen Stellen Potential zum Tunen gegeben ist.
Ein lesenswerter Artikel.

Meet the GIMP

Posted by bene - 09/03/08 at 02:03:53 pm

Rolf Steinort published a very nice series of video podcasts about GIMP – 35 episodes so far!

If you ever wanted to edit pictures on Linux but got stuck at the unusual user interface, you should definitely watch the tutorials.

Episode 001: Preparing an image for the web

libnotify over ssh

Posted by bene - 15/02/08 at 09:02:36 pm

libnotify is a nice desktop notification framework, very similar to Growl. It’s basically a client-server architecture: the desktop implements a notification-daemon where the clients send notifications to (via D-Bus).

In my case it’s notification-daemon-xfce and on the client side primarily galarm and pidgin (using a patched pidgin-libnotify plugin).

With notify-send you can also create your own notification. I wrote a little zsh wrapper function to get a notification when the command terminates:

# run some command and notify about the result via the notification-daemon
function run () {
$@
local error=$?
if [[ $error -eq 0 ]]; then
notify-send “`hostname -s` | terminated:” “$1 $2″ -i finish -t 0
else
notify-send “`hostname -s` | aborted:” “$1 $2″ -u critical -i undo -t 0
fi
return $error
}

The usage is quite simple:
# run sudo update-eix

All of this is nice but I decided to need notification of remote events as well.
I hate to wait or poll till a command on my server terminates, instead the server should notify me.
Additionally I run a WeeChat IRC-client 24/7 in screen and want a notification for (private) IRC messages.

Accomplishing my requirements is a tough task, but after some research I found this nice idea of Jared Quinn: libnotify-with-irssi-over-ssh.
The trick is to tunnel the notification through the terminal using the print pipe.

I adapted his scripts and patched them to fit my needs:

My favorite terminal is rxvt-unicode so the .Xdefaults entry looks a bit different:
URxvt.print-pipe: ~/scripts/unmarshal.pl
My unmarshal script collects the content of the pipe and sends the notification to the daemon:
unmarshal.pl (html)

…the WeeChat plugin (based on growl-notify):

remote-notification.pl (html)

…and finally the drop-in replacement for notify-send:

notify-send (html)

If notify-send is placed in /usr/local/bin/ on the remote host, you can just type something like run sudo updatedb and get a notification to the desk.

Root exploit for Linux 2.6.24.1

Posted by micele - 11/02/08 at 12:02:34 pm

It’s time for a new local root exploit on the linux kernel. Two exploits have been reported. Both are based on leaky dealing with pointers regarding the function vmsplice, brought in by kernel release 2.6.17. For this reason one of the exploits works for all kernel versions from 2.6.17 to 2.6.24.1. Kernel Bug Tracker says:

Both exploits cause kernel Oops or (randomly) give root privilegies to the user.

A new kernel version 2.6.24.2 has been released and the regarding changelog reports a kind of fix. But comments like

But we also must check whether we can access the actual memory region pointed to by the struct iovec to fix the access checks properly.

still don’t sound like 100% fixed and reliable…