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 Forums >>  IDA Pro  >>  Have anyone hacked 'Share' application ?

Topic created on: August 14, 2007 00:37 CDT by jaffersathik2010 .

Hi there,

Mentioned below is my problem.

If I run the share application from inside the IDA Pro without putting breakpoint, it is working.

If I run the share application from inside the IDA pro by
Placing a breakpoint at the �recv ()' function, it is not working.

It seems (but I�m not very sure) that when we place a breakpoint, it adds one more byte to the application resulting wrong CRC value so it is not working.

Right now I am in the process of finding out (manually) the function, which calculates the CRC value. Is there any plug-in available to check the same? Any other short cuts available?

I welcome any kind of your valuable suggestions!

  dennis     August 14, 2007 01:04.35 CDT
You should try placing hardware breakpoints first (right-click a software breakpoint and edit it).
Hardware breakpoints don't modify the process's code.

  jaffersathik2010     August 14, 2007 01:19.38 CDT
Hi dennis,

Thanks. I'll do it and post the results.

--Jaffer

  jms     August 14, 2007 03:15.38 CDT
Of course make sure they aren't making random calls to IsDebuggerPresent, or any other anti-debugging wizardry, this has bitten me in the butt before. And definitely let us know how it goes!

  anonymouse     August 15, 2007 03:17.50 CDT
It seems (but I�m not very sure) that when we place a breakpoint, it adds one more byte to the application resulting wrong CRC value so it is not working.

a breakpoint aka int 03 does not add one more byte
the debugger modifies the byte to oxcc instead of original byte and keeps a record of the original byte and location in its list

a crc algo which checks integrity will be seeing the oxcc instead of the original breakpoint and will result in a differnet crc

you can set a memory breakpoint (page guard trap) and filter out crc algo accesiing this byte (memory access to said byte will happen before it is executed ) in case it also detects and eliminates hardware breakpoint registers with seh or some trickery

  jaffersathik2010     August 16, 2007 01:04.45 CDT
Hi Dennis,

Its amazing for me!!!.

I tried hardware breakpoint, it works really fine. I thank every one who have spent their valuable time for me.

Thanks,
Jaffer.

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