i have searched alot and saw many good info. about CRC's . but haven't found , actually , the info. i'm curious to know neither any tutos about this.
i saw someday some ARmadillo (2.5) Patcher MAde by GlobAl that makes the patched exes read the crc check from original one actually a .bak of the same file that the patcher created

also one day saw/used a patch for FlaX that used the same method ... i tried FlaX before and has a really strong crc check... the author of this patch used a very intelligent smart way as well againts crc checks . he made the patched exe to read the crc check from a backup made by the same patch
i noted this because when i deleted the backup then again the program was not working and crc check was activated!

by that time i was more newbie than now and couldn't check how this work , now i lost those files ... and haven't found any info about this yet .... i believe this is the place to meet specialist + reversers so my cuestion should be responded , one day or another , in here i guess.

How this patching method works againts crc check?

How to made the file to read its own crc check from its original file (in this case a backup made) ?

Can be implemented on any exe or Dll file?

GloBal are you reading this?

Regards

There are infinitely many ways to implement CRC checks, both regarding checksum algorithms and regarding actual implementation, so there is no general way to say "how to patch them to defeat them".

A good guess about how the redirection of the CRC check was made in your example though, is that simply the path parameter to the initial API call getting the handle to the file was patched to point at another file. That might very well be enough to cause this effect, and it's quite a clean patch too.

well guess got some ideas but need an extended explanation.. maybe with examples?? remember i'm a newbie with hungry to Learn

what does the handle mean and how to get it ?


Regards

Please read the following info about file handling in Windows:

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/fileio/base/creating_and_opening_files.asp

Then consider what would happen if someone would change the "lpFileName" parameter of the "CreateFile" API call...

Here's the reference to the CreateFile command, if you by any chance wouldn't manage to find it yourself:

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/fileio/base/createfile.asp

i'm glad that you're helping me dELTA .. i didn't found those info. because i wasn't looking for them.. neither i searched over Billy site .... anyway i see how good this info. is and noted that is related about what i'm looking for...

actually i would prefer some real code injection for example using it on any exe or dll

i'll hope to see Global's reply about this