Suramya's Blog : Welcome to my crazy life…

February 7, 2018

Hacking the Brainwaves Cyber Security CTF Hackathon 2018

Earlier this year I took part in the Brainwaves Cyber Security Hackathon 2018 with Disha Agarwala and it was a great experience. We both learnt a lot from the hackathon and in this post I will talk about how we approached the problems and some of our learning’s from the session.

Questions we had to answer/solve in the Hackathon:

  • Find the Webserver’s version and the Operating system on the box
  • Find what processes are running on the server?
  • What fuzzy port is the SSH server running on?
  • Discover the site architecture and layout.
  • Describe the major vulnerability in the home page of the given website based on OWASP TOP 1. Portal Url: https://socgen-ctf.0x10.info
  • Gain access to member area and admin area through blind sql, or session management.
  • Dump all user account from member area. [SQLi]
  • [Broken Validation] Demonstrate how you can modify the limit in order management.
  • [Open Redirect] Redirect site/page to hackerearth.com
  • List any other common bug came across while on the site
    • After logging into the member area, perform the following functions:
    • Find the master hash & crack it
    • Dump all user’s
    • Find the email ID and password of saved users

Information Gathering:

In order to find the services running on the server, the first thing we had to do was find the IP/hostname of the actual server hosting the site which was a bit tricky because the URL provided is protected by CloudFlare. So, any scans of socgen-ctf.0x10.info took us to the CloudFlare proxy server instead of the actual server which was a problem.

We figured this out by trying to access the IP address that socgen-ctf.0x10.info translated to in the browser.

suramya@gallifrey:~$ host socgen-ctf.0x10.info 
socgen-ctf.0x10.info has address 104.28.15.64 

Since the site homepage didn’t do anything except display text that refreshed every 15 seconds we needed to find other pages in the site to give us an a attack surface. We checked to see if the site had a robots.txt (It tells web crawlers not to index certain directories). These directories are usually ones that have sensitive data and in this case the file existed with the following contents:

# robots.txt
Sitemap: http://socgen-ctf.0x10.info/sitemap.xml
User-agent: *
Disallow: images
Disallow: /common/
Disallow: /cgi-bin/

The images directory didn’t have any interesting files in it but the /common/ directory on the other hand had a file named embed.php in it which basically ran a PHP Info dump. This dump has a lot of information that can be used to attack the site but the main item we found here was the IP address of the actual server where the services were running (38.109.218.93).

Using this information we were able to initiate a nmap scan to get the services running on the site. The nmap command that gave us all the information we needed was:

nmap -sV -O -sS -T4 -p 1-65535 -v 38.109.218.93

This gave us the following result set after a really really long run time:

PORT     STATE    SERVICE       VERSION
23/tcp   filtered telnet
25/tcp   open     smtp?
80/tcp   open     http          This is not* a web server, look for ssh banner
81/tcp   open     http          nginx 1.4.6 (Ubuntu)
82/tcp   open     http          nginx 1.4.6 (Ubuntu)
137/tcp  filtered netbios-ns
138/tcp  filtered netbios-dgm
139/tcp  filtered netbios-ssn
445/tcp  filtered microsoft-ds
497/tcp  filtered retrospect
1024/tcp open     kdm?
1720/tcp open     h323q931?
2220/tcp open     ssh           OpenSSH 6.6.1p1 Ubuntu 2ubuntu2.8 (Ubuntu Linux; protocol 2.0)
2376/tcp open     ssl/docker?
3380/tcp open     sns-channels?
3389/tcp open     ms-wbt-server xrdp
5060/tcp filtered sip
5554/tcp filtered sgi-esphttp
8000/tcp open     http          nginx 1.4.6 (Ubuntu)
8080/tcp open     http          Jetty 9.4.z-SNAPSHOT
8086/tcp open     http          nginx 1.10.3 (Ubuntu)
9090/tcp open     http          Transmission BitTorrent management httpd (unauthorized)
9996/tcp filtered palace-5
19733/tcp filtered unknown
25222/tcp filtered unknown
30316/tcp filtered unknown
33389/tcp open     ms-wbt-server xrdp
33465/tcp filtered unknown
34532/tcp filtered unknown
35761/tcp filtered unknown
35812/tcp filtered unknown
35951/tcp filtered unknown
37679/tcp filtered unknown
38289/tcp filtered unknown
38405/tcp filtered unknown
38995/tcp filtered unknown
40314/tcp filtered unknown
44194/tcp filtered unknown
47808/tcp filtered bacnet

For some reason the results from the nmap scan varied so we had to run the scan multiple times to get all the services on the host. This was possibility because the server was setup to make automated scanning more difficult.

Once we identified the port where the SSH server was running on (2220) we were able to connect to the port and that gave us the exact OS Details of the server. We did already know that the server was running Ubuntu along with the kernel version from the PHP Info dump but this gave us the exact version.

Discovering Site architecture:

Since we had to discover the URL to the members & admin area before we could attack it, we used dirb which is a Web Content Scanner to get the list ofall the public directories/files on the site. This gave us the URL’s to several interesting files and directories. One of the files identified by dirb was https://socgen-ctf.0x10.info/sitemap.xml. When we visited the link it gave us a list of other URL’s on the site of interest (we had to replace the hostname to socgen-ctf.0x10.info) including the members area (http://socgen-ctf.0x10.info/members.php?p=login) and siteadmin (http://socgen-ctf.0x10.info/siteadmin).

After a long and fruitless effort to use SQL Injection on the siteadmin area we started to explore the other files/URL’s identified by dirb. This gave us a whole bunch of files/data that seem to be left over from other hackathons so we ignored them.

SQL Injection

The main site https://socgen-ctf.0x10.info/index.php?p=. appeared to be vulnerable to SQL at the first glance because when we visit https://socgen-ctf.0x10.info/index.php?p=.’ (note the trailing single quote) it reloads the page. This meant that we could write queries to it however since it didn’t display a true or false on the page a SQL injection wasn’t easily possible. (We could have tried a blind injection but that would require a lot of effort for a non-guaranteed result.

As we explored the remaining URL’s in sitemap.xml one of the links (https://socgen-ctf.0x10.info/embedframe.php) was interesting as it appeared to give a dump of data being read from the site DB. Opening the site while watching the Developer Toolbar for network traffic identified a URL that appeared to be vulnerable to SQL injection (https://socgen-ctf.0x10.info/ajax.php?cid=&p=view_channel&id=28) and once we tested the url we found that the variable id was indeed vulnerable to injection.

We used blind sql to gain access by executing true and false statements and see that it returns different results for true(displays ‘1’ on the webpage) and false (displays 0) . We checked whether a UNION query runs on the site which it did and using other queries we identified the DB backend to be a mysql database (5.xx.xxx version). Then we found out the table name (members) which was an easy guess since the website had an add customer field. After identifying the number of columns in the table we got stuck because any statements to list the available tables or extract data were failing with an error about inconsistent column numbers.

Finally, we ran sqlmap which is an open source tool for automating SQL injection. It took us a few tries to get the software running because initially any attempt to scan the site was rejected with a 403 error message. Turns out that the connections were being rejected because the site didn’t like the useragent the software was sending by default and adding a flag to randomize the useragent resolved the permission denied issue.

Once the scan ran successfully we tried to get access to the MySQL usertable but that failed because the user we were authenticating as to the MySQL server didn’t have access to the table required.

sqlmap -u 'https://socgen-ctf.0x10.info/ajax.php?cid=&p=view_channel&id=28' --random-agent -p id --passwords

So, then we tried getting an interactive shell and an OOB shell both of which failed. We finally ran the command to do a full dump of everything that the system allowed us to export using SQL injection via SQLMap. This included the DB schema, table schema’s and a dump of every table on the database server which the mysql user had access to. The command we used is the following:

sqlmap -u 'https://socgen-ctf.0x10.info/ajax.php?cid=&p=view_channel&id=28' --random-agent -p id  --all --threads 3

This gave us a full dump of all the tables and the software was helpful enough to identify password hashes when they existed in the table and offered to attempt decryption as well. In this case the password was encrypted with a basic unsalted MD5 hash which was cracked quite easily. Giving us the password for the first two accounts in the database (admin & demo).

Looking at the rest of the entries in the users table we noticed that they all had funny values in the email address field, instead of a regular email address we had entries that looked like the following:

,,,"0000-00-00 00:00:[email protected]509a6f75849b",1
,1,RU,

As we had no clue what this was about the first thing we attempted was to access the
https://socgen-ctf.0x10.info/cdn-cgi/l/email-protection URL. This URL gave us a message that told us that the email addresses in the DB were obfuscated by CloudFlare to protect them from Bots. A quick Google search gave us a 21 line python script which we tweaked to convert all the hash to email address and passwords. (The code is listed below for reference)

#! /usr/bin/env python 
# -*- coding: utf-8 -*- 
# vim:fenc=utf-8 
# 
# Copyright © 2016 xl7dev  
# Distributed under terms of the MIT license. 

""" 

""" 
import sys 
import re 
fp = sys.argv[1] 
def deCFEmail(): 
   r = int(fp[:2],16) 
   email = ''.join([chr(int(fp[i:i+2], 16) ^ r) for i in range(2, len(fp), 2)]) 
   print email 
if __name__ == "__main__":                                                                                                                                                                       
   deCFEmail() 

This gave us the email addresses and passwords for all the users on the site. Since the accounts appeared to be created by SQL injection a bunch of them didn’t have any passwords but the remaining were valid accounts for the most part and we verified a couple by logging in manually with the credentials.

OWASP TOP 10 Vulnerability

To find the vulnerabilities in the home page we tried various manual techniques at first but drew a blank so we decided to use the owasp-zap. This tool allows you to automatically scan for vulnerabilities in a given URL along with a whole other stuff.

At first the scan failed because of the same issue as earlier with the user-agent. This time we took a different approach to resolve the issue by configuring owasp-zap as a proxy server and configuring Firefox traffic to use this proxy server for all traffic. This gave us the site in the software and we were then able to trigger both an active scan and spider scan of the site.

This gave us detailed reports that highlighted various issues in the site which we submitted.

Redirecting HomePage

The redirection of the home page was quite simple. We tried inserting a customer name with javascript tags in it and were able to do so successfully. So we inserted the following into the DB and the system automatically redirected the page when the Customer list section was accessed.

Other Interesting Finds

The nmap scan told us that in addition to port 80 a web server was listening on ports 81, 82, 8000, 8080 and 8086.

Ports 82, 8000 and 8086 were running standard installs of nginx and we didn’t find much of interest at these ports even after we ran dirb on all of them. Port 8080 appeared to be running a proxy or a Jenkins instance.

Port 81 was the most interesting because it was running a nginx server that responded to any queries with a 403 error. When we tried accessing the site via the browser we got an error about corrupted content.

We were unable to identify what the purpose of this site was but it was interesting.

SSH Banner / PHP Shell

The webserver instance running on port 80 had the version set to the following text “This is not* a web server, look for ssh banner Server at private-tunel.wehostservers.ru Port 80” so we went back and investigated the SSH Banner from the ssh server on port 2220. The banner was encrypted and to decrypt the SSH banner, we continuously converted the cipherText from its hex value to ASCII value . It gave us the following results on each conversion

3333333733333333333333373333333333333336333333383333333233333330333333363333333233333336333333313333333633363335333333363336333533333336333333353
3333337333333323333333233333330333333363333333633333336333633363333333733333332333333373333333733333336333333313333333733333332333333363333333433333332333333303333
3337333333333333333633363333333333363333333133333337333333333333333633333338333333323333333033333336333333333333333633363336333333373333333533333336333633333333333
63333333433333332333333303333333633363333333333363333333533333336333333313333333633333334333733393336363633373335373436663230363132307368336c6c2e706870

3337333333373333333633383332333033363332333633313336363533363635333633353337333233323330333633363336363633373332333733373336333133373332333633343332333033373333333
636333336333133373333333633383332333033363333333636363337333533363633333633343332333033363633333633353336333133363334373936663735746f206120sh3ll.php
 37333733363832303632363136653665363537323230363636663732373736313732363432303733366336313733363832303633366637353663363432303663363536313634796f75to a #

ssh banner forward slash could lead you to a #sh3ll.php

Once we got the full decrypted text we knew that there was a potential webshell on the server but it wasn’t apparent where the shell was located. After hit and try failed we turned back to our old faithful dirb to see if it could find the shell.

dirb allows us to specify a custom word list which is used to iterate through the paths and we can also append an extension to each of the words to search for, so we created a file called test with the following content:

suramya@gallifrey:~$ cat test 
shell
sh3ll
sh311

and then ran the following command:

suramya@gallifrey:~$ dirb https://socgen-ctf.0x10.info/ test  -X '.php'

This gave us the location of the shell.


Accessing the link gave us a page with a message “you found a shell, try pinging google via sh3ll.php?exec=ping 8.8.8.8”

Accessing the URL with the additional parameter gave us a page with the following output:

September 27, 2016

How to install Tomato Firmware on Asus RT-N53 Router

Filed under: Computer Software,Knowledgebase,Techie Stuff,Tutorials — Suramya @ 11:43 PM

I know I am supposed to blog about the all the trips I took but wanted to get this down before I forget what I did to get the install working. I will post about the trips soon. I promise 🙂

Installing an alternate firmware on my router is something I have been meaning to do for a few years now but never really had the incentive to investigate in detail as the default firmware worked fine for the most part and I didn’t really miss any of the special features I would have gotten with the new firmware.

Yesterday my router decided to start acting funny, basically every time I started transferring large files from my phone to the desktop via sFTP over wifi the entire router would crash after about a min or so. This is something that hasn’t happened before and I have transferred gigs of data so I was stumped. Luckily I had a spare router lying around thanks to dad who forced me to carry it to Bangalore during my last visit. So I swapped the old router with the new one and got my work done. This gave me an opportunity as I had a spare router sitting on my desk and some time to kill so I decided to install a custom firmware on it to play with it.

I was initially planning on installing dd-wrt on it but their site was refusing to let me download the file for the RT-N53 model even though the wiki said that I should be able to install it. A quick web search suggested that folks have had a good experience with the Tomato by Shibby firmware so I downloaded and installed it by following these steps:

Download the firmware file

First we need to download the firmware file from the Tomato Download site.

  • Visit the Tomato download Section
  • Click on the latest Build folder. (I used build5x-138-MultiWAN)
  • Click on ‘Asus RT-Nxx’ folder
  • Download the ‘MAX’ zip file as that has all the functionality. (I used the tomato-K26-1.28.RT-N5x-MIPSR2-138-Max.zip file.)
  • Save the file locally
  • Extract the ZIP file. The file we are interested in is under the ‘image’ folder with a .trx extension

Restart the Router in Maintenance mode

  • Turn off power to router
  • Turn the power back on while holding down the reset button
  • Keep holding reset until the power light starts flashing which will mean router is in recovery mode

Set a Static IP on the Ethernet adapter of your computer

For some reason, you need to set the IP address of the computer you are using to a static IP of 192.168.1.2 with subnet 255.255.255.0 and gateway 192.168.1.1. If you skip this step then the firmware upload fails with an integrity check error.

Upload the new firmware

  • Connect the router to a computer using a LAN cable
  • Visit 192.168.1.1
  • Login as admin/admin
  • Click Advanced Setting from the navigation menu at the left side of your screen.
  • Under the Administration menu, click Firmware Upgrade.
  • In the New Firmware File field, click Browse to locate the new firmware file that you downloaded in the previous step
  • Click Upload. The uploading process takes about 5 minutes.
  • Then unplug the router, wait 30 seconds.
  • Hold down the WPS button while plugging it back in.
  • Wait 30 seconds and release the WPS button.

Now you should be using the new firmware.

  • Browse to 192.168.1.1
  • Login as admin/password (if that doesn’t work try admin/admin)
  • Click on the ‘reset nvram to defaults’ link in the page that comes up. (I had to do this before the system started working but apparently its not always required.)

Configure your new firmware

That’s it, you have a router with a working Tomato install. Go ahead and configure it as per your requirements. All functionality seems to be working for me except the 5GHz network which seems to have disappeared. I will play around with the settings a bit more to see if I can get it to work but as I hardly ever connected to the 5GHz network its not a big deal for me.

References

The following sites and posts helped me complete the install successfully. Without them I would have spent way longer getting things to work:

Well this is it for now. Will post more later.

– Suramya

February 20, 2016

How to encrypt your Hard-drive in Linux

We have heard multiple stories where someone looses a pendrive or a laptop containing sensitive/private data which is then published by the person who found the drive embarrassing the owner of the data. The best way to prevent something like that from happening to you if you loose a disk is to make sure all your data is encrypted. Historically this used to be quite painful to setup and required a lost of technical know-how. Thankfully this is no longer the case. After trying a bunch of different options I found Linux Unified Key Setup-on-disk-format (LUKS) to be the most user-friendly and easy to setup option for me.

Setting it up is quite easy by following the instructions over at www.cyberciti.biz. However since things on the internet have a tendency of disappearing on a fairly frequent basis, I am using this post to save a paraphrased version of the installation instructions (along with my notes/comments) just in case the original site goes down and I need to reinstall. All credit goes to original author. So without further ado here we go:

Install cryptsetup

First we need to install cryptsetup utility which contains all the utilities we need to encrypt our drive. To install it in Debian/Ubuntu you just issue the following command as root:

apt-get install cryptsetup

Configure LUKS partition

Warning: This will remove all data on the partition that you are encrypting. So make sure you have a working backup before proceeding amd don’t blame me if you manage to destroy your data/device.

Run the following command as root to start the encryption process:

cryptsetup -y -v luksFormat <device>

where <device> is the partition we want to encrypt (e.g. /dev/sda1). The command will ask you for confirmation and a passphrase. This passphrase is not recoverable so make sure you don’t forget it.

Create drive mapping

Once the previous command completes you need to create a mapping of the encrypted drive by issuing the following command:

cryptsetup luksOpen <device> backup2

You can also map a partition to using its UUID (which is what I do) by issuing the following command instead (This works great if you want to script automated backups to an external drive):

cryptsetup luksOpen UUID=88848060-fab7-4e9e-bac2-f9a2323c7c29 backup2

Replace the UUID in the example with the UUID of your drive. (Instructions on how to find the UUID are available here).

Use the following command to see the status for the mapping and to check if the command succeeded:

cryptsetup -v status backup2

Format LUKS partition

Now that we have created the mapping we need to write zeroes to the encrypted device, to ensure that the outside world sees this as random data and protects the system against disclosure of usage by issuing the following command:

dd if=/dev/zero of=/dev/mapper/backup2

Since this command can take a long time to complete depending on the drive size and dd by default doesn’t give any feedback on the percentage completed/remaining I recommend that you use the pv command to monitor the progress by issuing the following command instead:

pv -tpreb /dev/zero | dd of=/dev/mapper/backup2 bs=128M

This will take a while to run so you can go for a walk or read a book while it runs. Once the command completes you can create a filesystem on the device (I prefer to use ext4 but you can use any filesystem you like) by formatting the device:

mkfs.ext4 /dev/mapper/backup2

After the filesystem is created you can mount and use the partition as usual by issuing the following command:

mount /dev/mapper/backup2 /mnt/backup

That’s it. You now have an encrypted partition that shows up as a regular partition in Linux which you can use as a regular drive without having to worry about anything. No special changes are needed to use this partition which means any software can use it without requiring changes.

How to unmount and secure the data

After you are done transferring data to/from the drive you can unmount and secure the partition by issuing the following commands as root:

umount /mnt/backup

followed by

cryptsetup luksClose backup2

Creating a backup of the LUKS headers

Before you start anything else, you should create a backup copy of the LUKS header because if this header gets corrupted somehow then all data in the encrypted partition is lost forever with no way to recover it. From the cryptsetup man page:

“LUKS header: If the header of a LUKS volume gets damaged, all data is permanently lost unless you have a header-backup. If a key-slot is damaged, it can only be restored from a header-backup or if another active key-slot with known passphrase is undamaged. Damaging the LUKS header is something people manage to do with surprising frequency. This risk is the result of a trade-off between security and safety, as LUKS is designed for fast and secure wiping by just overwriting header and key-slot area.”

Create a backup by issuing the following command:

cryptsetup luksHeaderBackup <device> --header-backup-file <file>

Important note: a LUKS header backup can grant access to most or all data, therefore you need to make sure that nobody has access to it.

In case of disaster where our LUKS header gets broken, we can restore it by issuing the following command:

cryptsetup luksHeaderRestore <device> --header-backup-file <file>

How to remount the encrypted partition?

Issue the following commands in sequence to mount the partition:

cryptsetup luksOpen <device> backup2
mount /dev/mapper/backup2 /mnt/backup

Please note that data encrypted by LUKS is quite obvious with most Linux systems identifying it as an encrypted partition automatically. So if someone examines your system they will know you have encrypted data and can force you to divulge the password by various means (including the use of Rubber-hose Cryptanalysis. )

If you want the encrypted partition to be hidden then you can use Deniable encryption/Hidden Partition or use steganography. I haven’t really used either so can’t comment on how to set it up correctly but maybe I can talk about it in a future post after I explore them a bit more.

Well this is all for now, hope you find this useful. Will write more later.

– Suramya

May 6, 2015

How to Root a second generation Moto x running Lollipop

Filed under: Knowledgebase,Techie Stuff,Tutorials — Suramya @ 11:22 PM

I got my new phone today and as usual the first thing I did was root it before I started copying data over so that I don’t loose data when I unlock the boot loader. The process required a bit of work mainly because I was following instructions for KitKat while my phone was running Lollipop. That caused the phone to go into this funky state where the Play Store API’s went MIA and the entire thing stopped working to the point that I had to do a hard reset to get back to a stable state.

BTW, before you continue please note that this will delete all data on the phone so you need to ensure that you have a proper backup before proceeding. Without further ado, here are the steps I followed to get things to work using my Linux (Debian) desktop:

Unlock the Bootloder

The first thing you have to do is unlock the Boot loader on the phone:

  • Install the Android SDK by issuing the following command:
    apt-get install android-tools-adb android-tools-fastboot
  • Run the following command:
    fastboot oem get_unlock_data
  • Take the string returned, which would look something like this:
    (bootloader) 0A40040192024205#4C4D3556313230
    (bootloader) 30373731363031303332323239#BD00
    (bootloader) 8A672BA4746C2CE02328A2AC0C39F95
    (bootloader) 1A3E5#1F53280002000000000000000
    (bootloader) 0000000

    and concatenate the 5 lines of output into one continuous string without (bootloader) or ‘INFO’ or white spaces. Your string needs to look like this:
    0A40040192024205#4C4D355631323030373731363031303332323239#BD008A672BA4746C2CE02328A2AC0C39F951A3E5#1F532800020000000000000000000000

  • Visit the Motorola Website.
  • Paste the string you got in the previous step on the site, and then click on the ‘Can my Device be Unlocked?’ button and if your device is unlockable, a “REQUEST UNLOCK KEY” button will now appear at the bottom of the page.
  • Click on the “REQUEST UNLOCK KEY” Button.
  • You will now receive a mail with the unlock key at your registered email address
  • Start your device in fastboot mode by pushing and holding the power and volume down at the same time. Then release the power button followed by the volume down button. The device will now power up in fastboot mode.
  • Run the following command to unlock the bootloader:
    fastboot oem unlock 
  • If the code was correct then you will see a message confirming that your device was unlocked and the phone will reboot.

Enable Developer Options/USB Debugging

In order to proceed further we need to enable USB Debugging and in order to do that we need to enable Developer Options following these steps:

  • Pull down the notification drawer and tap on ‘Settings’
  • Scroll down to ‘About Phone’
  • Now scroll down to ‘Build Number’
  • Tap on ‘Build Number’ 7 times.
  • It’ll now say that you are a developer. Now press back, You should now see Developer Options above About Phone.

  • Click on ‘Developer Options’
  • Check the box next to ‘USB debugging’ and save

Root the Phone

First we need to download the correct image file for the model of your phone. I had to look up my model on Wikipedia because for some reason my phone decided not to share that information with me. Use the appropriate link for your model in the list below. I have a XT1092 but the XT1097 image worked fine for me.

After downloading the file, extract it. Run the following command:

adb reboot bootloader

This will restart the phone in the fastboot mode. Then boot using the image you downloaded in the previous step using this command:

fastboot boot /path/to/image/file/CF-Auto-Root-victara-victararetbr-xt1097.img

Once you run the command the Device will boot up, install su and quickly reboot (this is automatic, no user intervention is required). After the phone starts up, you need to install Chainfire’s SuperSU from the Play Store.

After that you are done and your phone is rooted. You can verify the same by installing a ‘Root Verifier’ application from the store.
Well this is all for now, will write more later.

– Suramya

April 26, 2015

How to create Electric Ink for projects

Filed under: Interesting Sites,Knowledgebase,Techie Stuff — Suramya @ 9:48 AM

At times using wires in a project might not be the most practical option because of space/weight limitations. If that is the case then you should take a look at Electric Ink for creating cheap circuits. In fact you can make your own Electric Ink using a process which is quite simple. The good folks at the Popular Science site have provided us with an instruction guide that I am reproducing here so that I don’t loose the instructions in case PopSci decides to reorg their site:

Materials:

  • Powdered graphite
  • White vinegar
  • Syringe
  • Elmer’s clear glue (I think any clear glue should work)

Instructions

  • To make the ink, put powdered graphite in a cup, cover with vinegar, and stir. Let it sit for a few minutes.
  • Once the graphite settles on the bottom of the cup, remove the clear liquid on top with a syringe.
  • Stir in about a teaspoon of glue to keep the graphite suspended. A thick line of paint has a resistance of a few kilohms per inch.
  • Draw the circuit, wait for it to dry and then you can test it out.

I was wondering if this would work on T-Shirts, under a laminate or other such protective coating to prevent the circuit from getting washed out. Maybe I should try this out over the weekend on one of my old T-Shirts. Wonder what kinds of design’s I would be able to make before hitting issues if this works.

– Suramya

April 17, 2015

How to find information when Google can’t find it

Filed under: Computer Tips,Interesting Sites,Knowledgebase,Techie Stuff — Suramya @ 10:36 PM

For most people if you can’t find something on Google then it’s not there on the internet. However that is not true and there are other ways to find the information you are looking for even if Google can’t find it. Now some of you might be wondering, how can something be online without Google knowing about it because don’t they index everything? Unfortunately, that is not true. According to studies there are a lot of sites out there that are not indexed by any search engine. This part of the internet is called the Deep Web. Deep web is not to be confused with Dark Net which contains sites that can’t be reached via the regular internet. Deep Web sites are accessible via the regular internet and it is a lot bigger than the visible internet. In-fact some estimates suggest that the deep web is 400 to 550 times larger than the surface web.

So how do you find something that is in the Deep web or just not indexed by Google? Well, you can always try one of the following options depending on what you are looking for.

Wolfram Alpha

For example, if you are making factual queries about data (e.g. facts, figures, etc) then you should take a look at Wolfram Alpha. Their Wikipedia page explains how the engine works:

Users submit queries and computation requests via a text field. Wolfram Alpha then computes answers and relevant visualizations from a knowledge base of curated, structured data that come from other sites. The curated data makes Alpha different from semantic search engines, which index a large number of answers and then try to match the question to one.

Using the Mathematica toolkit, Wolfram Alpha can respond to natural language questions and generate a human-readable answer.

Topsy

Topsy maintains a comprehensive index of tweets and since Twitter is the best place for real-time sharing of thoughts/news then it is a good place to search for current events/trending topics. I just tried it out and it looks to be pretty effective and efficient.

Image Search

If you are trying to identify an image, or find more information about a particular Image then you can always try Google image search. However if that doesn’t return any relevant results then you should try out specialized Image search engines like Tin Eye or yandex.ru. I use a Firefox Extension called Who Stole my Pictures that lets you search across multiple engines in one shot from your context menu. Side note: This also search on Bing but 99.99% of the time Bing doesn’t return any results no matter what you search for.

On the other hand if you are just searching for images you should try PicSearch.com which is a image search service allowing a user to search across over 3 billion pictures (as per the site).

WebForums and Discussion boards

Another great way to find answers is to search on enthusiast forums and discussion boards. These forums have a whole community of folks who are passionate about that particular topic and would love you to point you in the right direction or walk you through figuring out the solution. Just ensure that you are asking Questions The Smart Way.

BoardReader.com allows you to search across multiple discussion boards and forums available on the net. StackExchange.com has multiple sub sections on hundreds of topics, Reditt.com has subreddits that focus on thousands of topics and most of them have actual relevant information as not all of the site is dedicated to cat video’s.

IRC

IRC stands for Internet Relay Chat and is designed to facilitate group communication in discussion forums, called channels hosted on IRC servers. There are channels dedicated to pretty much any topic you can think of on some IRC server somewhere and you can get answers to questions or help with a problem in real time.

The difficult part is finding the appropriate channel to ask your question.

I have used IRC Search in the past to find channels with a good success rate. Another option is ixirc.com/.

In addition to the options listed above, you should also check out the following resources for additional information and search options/methods that you can try out when searching for data:

That pretty much covers what I wanted to talk about in this post so this is all for now. Will post more later.

– Suramya

March 29, 2015

Rosetta Stone for Unix/Linux

Filed under: Knowledgebase,Linux/Unix Related,Techie Stuff — Suramya @ 9:53 PM

If you have been in the industry for a while then you have been in a situation where you need to do something on the server but have no idea what the appropriate command is because you always worked on a different variant/version of the Operating System. Think having to work on Solaris or Linux when all you have worked on is the Mac OS. To make things easier for the poor admins that have to keep switching OS’s, Bruce Hamilton has created a site he calls the ‘Rosetta Stone: A Sysadmin’s Universal Translator‘. This site has a list of tasks and the corresponding command that you would have to run for each of the OS’s. The Stone supports the following OS’s:

  • AIX
  • A/UX
  • DG/UX
  • FreeBSD
  • HP-UX
  • IRIX
  • Linux
  • Mac OS X
  • NCR Unix
  • NetBSD
  • OpenBSD
  • Reliant
  • SCO OpenServer
  • Solaris
  • SunOS 4
  • Tru64
  • Ultrix
  • UNICOS

and covers tasks in the following categories:

  • hardware
  • firmware
  • devices
  • disks
  • kernel
  • boot
  • files
  • networking
  • security
  • software
  • patching, tracing, logging

Check it out, bookmark it. It will save you some grief down the line the next time you are in this situation.

– Suramya

December 14, 2014

Cleaning your Linux computer of cruft and duplicate data

When you use a computer and keep copying data forward everytime you upgrade or work with multiple systems it is easy to end up with multiple copies of the same file. I am very OCD about organizing my data and still I ended up with multiple copies of the same file in various locations. This could have happened because I was recovering data from a drive and needed a temp location to save the copy or forgot that I had saved the same file under another directory (because I changed my mind about how to classify the file). So this weekend I decided to clean up my system.

This was precipitated because after my last system reorg I didn’t have a working backup strategy and needed to get my backups working again. Basically I had moved 3 drives to another server and installed a new drive on my primary system to serve as the Backup drive. Unfortunately this required me to format all these drives because they were originally part of a RAID array and I was breaking it. Once I got the drives setup I didn’t get the chance to copy the backup data to the new drive and re-enable the cron job that took the daily backup snapshots. (Mostly because I was busy with other stuff). Today when I started copying data to the new Backup drive I remembered reading about software that allowed you to search for duplicate data so thought I should try it out before copying data around. It is a good thing I did because I found a lot of duplicates and ended up freeing more than 2 GB of space. (Most of it was due to duplicate copies of ISO images and photos).

I used the following software to clean my system:

Both of them delete files but are designed for different use cases. So let’s look at them in a bit more detail.

FSlint

FSlint is designed to remove lint from your system and that lint can be duplicate files, broken links, empty directories and other cruft that accumulates when a system is in constant use. Installing it is quite easy, on Debian you just need to run the following command as root

apt-get install fslint

Once the software is installed, you can either use the GUI interface or run it from the command line. I used the GUI version because it was easier to visualize the data when seen in a graphical form (Yes I did say that. I am not anti-GUI, I just like CLI more for most tasks). Using the software was as easy as selecting the path to search and then clicking on Find. After the scan completes you get a list of all duplicates along with the path and you can choose to ignore, delete all copies or delete all except one. You need to be a bit careful when you delete because some files might need to be in more than one location. One example for this situation is DLL files installed under Wine, I found multiple copies of the same DLL under different directories and I would have really messed up my install if I had blindly deleted all duplicates.

Flossmanuals.net has a nice FSlint manual that explains all the other options you can use. Check it out if you want to use some of the advanced features. Just ensure that you have a good backup before you start deleting files and don’t blame me when you mess up your system without a working backup.

BleachBit

BleachBit is designed for the privacy conscious user and allows you to get rid of Cache, cookies, Internet history, temporary files, logs etc in a quick and easy way. You also have the option to ensure that the data deleted is really gone by overwriting the file with random data. Obviously this takes time but if you need to ensure data deletion then it is very useful. Bleachbit works on both Windows and Linux and is quite easy to install and use (at least on Linux, I didn’t try it on Windows). The command to install it on Debian is:

apt-get install bleachbit

The usage also is very simple, you just run the software and tick the boxes relevant to the clutter that you want gone and BleachBit will delete it. It does give you a preview of the files it found so that you can decide if you actually want to delete the stuff it identifies before you delete it.

Well this is all for now. Will write more later.

Thanks to How to Sort and Remove Duplicate Photos in Linux for pointing me towards FSlint and Ten Linux freeware apps to feed your penguin for pointing me towards BleachBit.

– Suramya

October 7, 2014

Find Recent Files in Windows with the Run Dialog

Filed under: Computer Tips,Knowledgebase — Suramya @ 5:40 AM

Tip for all you windows 8 users out there, If you want to see a history log of every file that you have touched on your computer, there is a easy built-in way of getting that information without installing any special software on Windows 8 by following these steps:

  • Open the run dialog box by pressing Win + R
  • Type in “recent” (without the quotes)
  • Click ‘OK’

This will display any file you’ve touched, as well as the last time it was modified all in one place. You can also access this data by browsing to the following location using ‘Windows Explorer’:

C:/users/username/recent

Source: lifehacker.com

– Suramya

March 8, 2013

Citrix on Raspberry Pi: Updated instructions and working download image

Filed under: Knowledgebase,Linux/Unix Related,Techie Stuff,Tutorials — Suramya @ 2:36 PM

A couple of folks have reached out to me via email/messages to tell me that the instructions I posted at the Raspberry Pi forums don’t work with the latest version of Rhaspbian. Basically the problem is that the latest version of the Citrix client is not compiled for the armhf architecture (Which is what the latest version of Rhaspbian OS is compiled for), so you need to download and install the armel version of the OS (‘Soft-float Debian “wheezy”’) from http://www.raspberrypi.org/downloads.

To make life simpler for people I have created a snapshot of my Pi install with Citrix installed and configured. You can download it from here. The image is 4GB so you will need to use a card of atleast that size when using this image. Follow these steps to install the image to an SD card in Linux:

  • Download the image file from the mirror (Approx 1GB compressed)
  • Unzip the file using the command
  • unzip Raspberry_Citrix.img.zip
  • Find out what the partition the SD card you are using has been assigned running the following command as root
  • fdisk -l

    Once you run the command, you will get an output that will show you all the disks attached to your system, look for the entry that corresponds to your card. In my case it looked like this:

     Disk /dev/sde: 3965 MB, 3965190144 bytes
    122 heads, 62 sectors/track, 1023 cylinders, total 7744512 sectors
    Units = sectors of 1 * 512 = 512 bytes
    Sector size (logical/physical): 512 bytes / 512 bytes
    I/O size (minimum/optimal): 512 bytes / 512 bytes
    Disk identifier: 0x00016187
    
       Device Boot      Start         End      Blocks   Id  System
    /dev/sde1            8192      122879       57344    c  W95 FAT32 (LBA)
    /dev/sde2          122880     7744511     3810816   83  Linux
    
  • So now we know that the card is at /dev/sde. All we have to do is write the image to the card and that is done using the following command. Make sure you replace the /dev/sde with the correct path otherwise you will end up destroying all data on the wrong drive.
  • dd if=Raspberry_Citrix.img of=/dev/sde bs=4096

    You will not see any output on the screen so don’t worry about it, just let it run and wait for the process to complete as it will take some time because of the amount of data being written. Once the process completes you can eject the card and if all went well you should be able to boot the Raspberry Pi from the card.

The login password for this image is root/password, please do change the password if you use the image. Let me know if you have any questions or have an issue using this image.

Update (3/28/2013): Adding instructions on how to write the image when using windows. (Please note that I haven’t tested the windows instructions as I don’t have a windows machine. Use at your own risk)

Once you download the zip file from the mirror, right-click on it and select extract (I think that’s what it says, but I don’t have a windows machine so can’t confirm). After the image is extracted you will have a file called Raspberry_citrix.img on your computer. Now follow these steps to write the image to an SD card (Instructions taken from eLinux)

  • Insert the SD card into your SD card reader and check what drive letter it was assigned. You can easily see the drive letter (for example G:) by looking in the left column of Windows Explorer. If the card is not new, you should format it and make sure there is only one partition (FAT32 is a good choice); otherwise Win32DiskImager can make corrupt your SD card!
  • Download the Win32DiskImager utility. The download links are on the right hand side of the page, you want the binary zip.
  • Extract the executable from the zip file and run the Win32DiskImager utility. You should run the utility as Administrator!
  • Select the Raspberry_citrix.img image file you extracted earlier
  • Select the drive letter of the SD card in the device box. Be careful to select the correct drive; if you get the wrong one you can destroy your data on the computer’s hard disk!
  • Click Write and wait for the write to complete.
  • Exit the imager and eject the SD card.

You should also go through the Basic setup guide for Raspberry Pi. Hope this helps.

– Suramya

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