Archive for the ‘Tutorials’ Category

Manage, Track And Collaborate Your Projects Online with ClockingIt

Posted by rajivvishwa On March - 17 - 2009

Project management is not a easy job which can be accomplished just with paper and a pencil. What we need is an app which helps you to track the issues, display timelines, collaboration and easier access to required information. Any Project Management app will be utilized by all the team members and maximum productivity is ensured only if that app guarantees collaboration. This leaves us with the only option, an online project management tool.

ClockingIt Screenshot

ClockingIt Screenshot

ClockingIt is a web based app which allows users to manage their project online. It has all the features needed for getting things done and to smoothly run the project. Apart from the ‘must have’ features like issue tracking and charts, this app features email notification, forums, chat etc which helps the users to communicate and share the info at a centralized location.

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Realistic Screen Capture Effect With Gimp In 10 Steps

Posted by rajivvishwa On February - 18 - 2009

Gimp is an amazing photo editor with loads of features which can be explored to create stunning effects. This tutorial helps in creating realistic ‘screen shot’, with a digital camera like effect, with Gimp. The images created with this technique can be used in blog posts and other articles which will definitely attract the readers.

Note: This post is moved from my site previous site http://31nst31n-in-me.com (decommissioned now) hence the screenshots are also taken from that site.

From this…

Initial image

To this…

Final Screen Capture


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Patching Security Holes With OllyDbg (Part 3/3)

Posted by rajivvishwa On February - 10 - 2009
This entry is part 3 of 3 in the series OllyDbg

Tutorial 3 – Deriving the logic of the generated key to create Keygens

Enter any test string to get the error message.

3_crackme_ss

Search for the referenced text strings and locate the message displayed in the error box. After analyzing the text references we find that there are no hardcoded keys or presence of any fragments of keys.

3_searchreferencestring

We have Double click to open the CPU window and set breakpoint by pressing ‘F2′

3_setbreakpoint

Check whether there are any new strings generated at the CPU window (and trust me you wont find any :( ). Now check the memory stack and scroll to the instruction where the userid we have entered is displayed. If you scroll a bit down you can find a ‘Key Like’ string below the userid string. Try to enter that in the key field, it should work.

3_serialfound

There is no point in finding out the key without understanding the logic behind the generation of the key. Once if we find the logic, we can reverse engineer and create a distributable keygens.

We can segregate the userid and corresponding key values as follows

t – D8
e – C9
s – D7
t – D8
e – None
r – None

Now open ‘calc’ in scientific mode – Select Hex mode – Type D8

3_valuehex

Select Dec mode to convert HEX value to Decimal.

3_valuedec

Note down the corresponding Decimal value for each HEX equivalent.

Now open any asciichart and note down the ascii value for the userid chars.

3_testascii

We can notice a difference of 100 between the converted HEX value and ascii value of the userid.

So we can derive the logic to create our own Keygen

Logic Sequence

  1. Take the 4 four characters of the username
  2. Convert chars to corresponding decimal value
  3. Add 100 to the decimal value obtained in step 2
  4. Covert this to HEX and the Key is obtained!

CrackMe App Download : Download Alt: Download

Video
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Conclusion: Always use a multilevel, complex logic to derive your own key. Always advised to use any standard encryption algorithm to generate the key used for comparison.

Note: The apps used in the tutorials are downloaded from the DeathSpawn Website (Not working anymore :( ) and detailed ‘How-to’ is can be read from the text file which is present along with the app package.

References

Patching Security Holes With OllyDbg (Part 2/3)

Posted by rajivvishwa On February - 10 - 2009
This entry is part 2 of 3 in the series OllyDbg

Tutorial 2 – Finding generated key at runtime

Enter any test data and observe the error message displayed.
2_incorrectstringentered

Search for referenced text strings as mentioned in Tutorial-1. Scroll to the location shown below.
2_searchrefstrings

Notice the 2 ‘Key like’ strings in the text strings referenced. If you think that one of them is valid, then you are wrong, but then why and where is it used? And what is the correct key? We can find that out soon.
Double click the message ‘The serial you entered is not correct’ to reach the instruction location in the CPU window. When we analyze the code we come across a few concatenations operations. But unfortunately the keys are concatenated with blanks and finally compared with the user input.

2_stringscpumain

The blank values you see in the comments are not really blank ones. They values are assigned on runtime. We have to set a breakpoint to obtain the dynamic assigned value.

To set a breakpoint, select the instruction and press ‘F2′. Breakpoints highlighted in red over the memory location.

2_settingbreakpoint

Press the ‘Play’ button to run the crackme application. Enter any random data and click the ‘Check’ button. The application pauses at the breakpoint set in the previous step. Go to the same location where you saw the 2 suspicious ‘Key Like’ strings in the previous step.

2_foundserialgenerated

Just before where the breakpoint was set we can find a new long string value displayed instead of blank strings which was displayed earlier. If you reverse engineer now, you can understand that the 2 Keys ‘L2C-5781‘ and ‘4562-ABEX‘ are static ones and are prefixed and suffixed, respectively, with a dynamically generated string. This is what we were looking for; the correct key to this app.


Correct String Entered


CrackMe App Download : Download Alt : Download

Video

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Conclusion : Never hardcode even fragments of static keys which can be helpful to deduce the complete key. Use some kind of logic to generate a dynamic key value.

Patching Security Holes With OllyDbg (Part 1/3)

Posted by rajivvishwa On February - 10 - 2009
This entry is part 1 of 3 in the series OllyDbg

OllyDbg is a 32-bit assembler level analyzing debugger for Microsoft Windows. This machine level debugger is created by Oleh Yuschuk for the 80×86. OllyDbg traces registers, recognizes procedures, loops, API calls, switches, tables, constants and strings. These features can be utilized to understand how an application internals.

Introduction

Ollydbg mainly has 4 windows in the default layout. CPU Window, Registers, Memory Stack and HEX Dump window. We will be working on CPU window most of the time.

ollydbgrefscreen

OllyDbg Download : Download

A set of 3 tutorials illustrated here explains on how effectively can OllyDbg be used to identify the security holes and to ensure that the code written is healthy.

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Creating Portable Apps with UniExtract

Posted by rajivvishwa On December - 30 - 2008

We can carry our favorite portable apps in USB sticks and external harddisks which can be used anywhere without even leaving a trace in the guest PC. There are few sites which allow us to download those for free. But their repository is limited and that might not include the apps we wanted in portable version.

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