Vasilis Mavroudis and IT stuff...

sh, bash, dash and Ubuntu

Vasilis Mavroudis — Wed, 17 Apr 2013 17:28:58 +0000

Hi!
I wanted to install a quite old package in my ubuntu computer using the .sh file I downloaded from their website. So, I tried typing in terminal:

sudo ./package_name.sh

and I got:

/bin/sh: 0: Can’t open ./package_name.sh

Briliant! Since you are here, you are probably looking for a fix.

The problem stems from the fact that Ubuntu uses dash as the default shell and your script is written with another shell in mind. The most usual is bash (sh).

So type in a terminal window:

sudo bash ./package_name.sh

This will force ubuntu to run the script using bash.

Enjoy!
Vasilis

PSAD Quick Fix

Vasilis Mavroudis — Fri, 04 Jan 2013 13:01:45 +0000

I like psad. I use it often and I find the email reports really handy.

Here is an issue I faced in Ubuntu and the solution:

Instead of the reports I received an email with the following contents:

[-] You may just need to add a default logging rule to the /sbin/iptables
‘filter’ ‘INPUT’ chain on oxide-server. For more information,
see the file “FW_HELP” in the psad sources directory or visit:

http://www.cipherdyne.org/psad/docs/fwconfig.html

[-] You may just need to add a default logging rule to the /sbin/ip6tables
‘filter’ ‘INPUT’ chain on oxide-server. For more information,
see the file “FW_HELP” in the psad sources directory or visit:

http://www.cipherdyne.org/psad/docs/fwconfig.html

I found on the web several people with the same problem, so here is what worked for me:

Enable ufw logging. Type in console as root: ufw logging on
Type as root:
iptables -A INPUT -j LOG
iptables -A FORWARD -j LOG
ip6tables -A INPUT -j LOG
ip6tables -A FORWARD -j LOG
Open /etc/ufw/before.rules and type before the COMMIT directive:
-A INPUT -j LOG
-A FORWARD -j LOG
Open /etc/ufw/before6.rules and type before the COMMIT directive:
-A INPUT -j LOG
-A FORWARD -j LOG
Restart ufw by typing as root:
ufw disable
ufw enable
Test if it worked:
psad –fw-analyze

I know that some parts appear to do very similar things but for a strange reason it worked only after the exact above procedure.

Hope it helps!
Vasilis

SWikipedia: S (named ess spelled ‘es’- in compound words; plural esses, forms/script: ) is the nineteenth (19th) letter in the ISO basic Latin alphabet. →

Image resize & JPG to PDF

Vasilis Mavroudis — Fri, 21 Dec 2012 09:55:04 +0000

I am preparing some applications and I needed to scan several documents and upload them online in PDF format. The problem is that there is an upload limit of 3MB per PDF document. Since I like to have my files well organized and maintain digital records for everything I always use the maximum resolution (600dpi) when scanning. This, of course, results in 5-6 MB images.

So, I had to resize multiple JPG documents and then combine them in 6-7 pdf files.

The tools I found extremely handy for this purpose were:

FastStone Photo Resizer: For resizing multiple files in a fraction of their original size. Worked like a charm! (http://www.faststone.org/FSResizerDetail.htm)
FM JPG To PDF Free: For combining the images to a single PDF. Pay close attention (as always?) when installing the application and uncheck the installation of unnecessary features like “Babylon search”, unless you really like them. (http://www.fm-pdf.com/FM-JPG-To-PDF-Converter-Free-Setup.exe)

From this point the procedure was easy an it was more drag n’ drop.

Let me know if you are aware of better alternatives!

Have fun!
Vasilis

P.S.: Maybe next time I should try using a loseless image format, like PNG, instead of JPG.

I’m back!

Vasilis Mavroudis — Sat, 20 Oct 2012 12:43:05 +0000

Hi everyone!

I am back from Germany where I worked as an intern in Deutsche Bank.

It was a delightful experience and I am more than happy I accepted the offer!
I presented my thesis about two weeks ago and I am currently working on other things.

The last 8-9 months I have been experimenting with OpenWRT and other alternative OSes for embedded devices and I have some nice projects in mind! Stay tuned for more!

Best wishes,
Vasilis

Bash script for webpage changes monitoring

Vasilis Mavroudis — Thu, 26 Jan 2012 13:22:36 +0000

I wrote a simple bash script for monitoring changes in a webpage. I was able to find a couple or more such scripts on the web but non of those worked for https websites with non-valid cerfificates. So here is one that does:

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#!/bin/bash

while true; do

if [[ -f new_page.html ]]; then
mv new_page.html old_page.html
fi
wget --tries=45 --wait=10 $1 -O new_page.html --no-check-certificate > /dev/null 2>&1
diff ./new_page.html ./old_page.html > /dev/null
if [[ $? -ne 0 ]]; then
echo "The webpage has changed!"
date
# mpg123 -q /home/user/latin_rhythm_guitar.mp3
firefox $1
else
echo "No change"
date
fi
# sleep some time
sleep 1800
done

The line mpg123 -q /home/user/latin_rhythm_guitar.mp3 is commented out. If you choose to play a song each time a change in the webpage occurs change the filename and un-comment.

Part of the source code is from the script found here.

Netgear DG834PN external antenna mod

Vasilis Mavroudis — Sun, 13 Nov 2011 22:00:09 +0000

I am a happy owner of the DG834PN router from Netgear.
It is a little old but I am satisfied from its speed and wifi coverage.

However, I always felt I had to hack this router. The router by default does not support an external antenna. This is fine, since it covers every corner of my appartment. But I had to add an external anntenna connector anyway…

So here it is:

I bought male-female rp-sma cable and cut it in the middle.

I soldered the female part on the internal antenna circuit and used some tape to keep the cable from moving.

Here is the first soldering point:

…and the other one:
*Your can use your multimeter to search for soldering points.

Drilled a hole on the backpanel and glued the connector.

Closed the router case carefully and connected it to power!
Everything works fine! (I need to clean that desk.)

I do not have a way to measure if the signal was improved inside the house, since it was maximum anyway. But I will try around the house and keep you updated!

ZAProxy & a common question

Vasilis Mavroudis — Sat, 05 Nov 2011 09:55:06 +0000

One of my favourite tools for penetration testing is ZAProxy or ZAP.
In case you haven’t heard about it you can find more information and download it here.

In this post I will publish an answer Psiinon (the project lead) gave in the ZAP mailing list. I decided to publish this because I was asked the same thing many times, especially from new ZAP users.

Question:
Is there any danger when scanning with ZAP against a live website (e.g. create/delete/update/corrupt data)?

Answer: (Psiinon)

I usually try to explain it this way:

Proxying (and therefore passive scanning) requests via ZAP is completely safe and legal, it just allows you to see whats going on.

Spidering is a bit more dangerous. Is could cause problems depending on how your application works (and we should make the ‘no post’ option visible!).

Active scanning is dangerous and depending on your app may create/modify/delete data.

So the only really safe thing is proxying and passive scanning, the other 2 could cause problems and could be considered illegal if you perform them on apps you dont have permission to test.

I have wondered about adding a ‘safe’ mode to ZAP which will only allow you to do safe things. Thoughts anyone? I know its not something pentesters would use;)

Hope that helps,

Psiinon

I did searched a bit in the ZAP FAQ or wiki but I was not able to find it. Hope it helps!

Best regards,
Vasilis

embedded systems wiki

Vasilis Mavroudis — Thu, 15 Sep 2011 17:01:07 +0000

Hi! Sorry for the long absense…
I got back from Denmark but I won’t say much on it instead I am going to post some photos in the next days.

Today I was looking for interesting embedded systems websites and I came towards this wiki: elinux.org . It is filled with information and guides on embedded systems hacking and much more!

I hope you enjoy it!

Ubuntu Studio

Vasilis Mavroudis — Tue, 19 Jul 2011 13:22:14 +0000

This is not a review or something similar. I simply came across it today and thought it would be great to share with you.
Even though I am an every day linux user and more or less familiar with what is going on with linux, the community continues to surprise me! I present you Ubuntu Studio.

From Ubuntu Studio website:

Ubuntu Studio is a multimedia editing/creation flavor of Ubuntu. It’s built for the GNU/Linux audio, video, and graphic enthusiast or professional.

Our aim is to make it more accessible for new users to get into the tools that GNU/Linux has to offer for multimedia creation and production. We also want to spotlight what’s out there, and show users tools they might not know to exist.

One important detail that I would like to add is that Ubuntu Studio uses real-time kernel which is really important for music producers.

The disto’s website is: http://ubuntustudio.org/
Here is a nice Wiki on the project with plenty of information.

I am going to spare some time installing and testing this ubuntu variant.

Hope you enjoy it,
Vasilis

Javascript snippet to recover hidden password from browser

Vasilis Mavroudis — Thu, 23 Jun 2011 21:46:53 +0000

I ‘ll leave this here, for future use…

Steps:
1. Open your browser and use the autocomplete feature but do not press submit.
2. Copy the snippet below to your address bar and press enter

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javascript:(function(){var s,F,j,f,i;s="";F=document.forms;
for(j=0;j<F.length;++j){f=F[j];for(i=0;i<f.length;++i){if(f[i].type.toLowerCase()=="password")s+=f[i].value+"\n";}}
if(s)alert("Password is:\n\n"+s);else alert("No passwords");})();

3. An alert box, with your password will appear.