Article in Hakin9

My Article on reversing exe has got published in Oct issue of "Exploiting Software-Hakin9" magazine. This article is about basic introduction to Reverse Engineering. I have chosen to show reversing of a sample exe file and how to patch it. The article more focuses on showing a practical example of reversing.
It could be downloaded here. The article is from Page no. 38 onwards.

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Breaking Excel password protection

If you came across an excel sheet asking for password for allowing to make any changes into it, you may want to unprotect it. All we need to do is to edit the xml file which comes intrinsically packaged with Excel 2007 or 2010. But what about Excel 2003? For that, open the Excel 2003 file within Excel 2007, save it as xlsx file. So, keep in mind all the Excel files below 2007 version, you need to convert them as Excel 2007 with extension .xlsx. Now here are the steps for doing that: 1. Open the Excel 2003 file (e.g. Secret.xlsx) and save it as .xlsx (Excel 2007) format. If you already have Excel 2007 file, then no need for any conversion. 2. Now change the extension of the above file to .zip and extract the zipped file. Browse through the file in the extracted folder and go to: <LocalPath>\Secret\xl\worksheets. 3. Now open the sheet/ sheets you want to remove protection in any xml editor. Look for keywords such as 'sheetProtection' or 'workbo...

File Upload through Null Byte Injection

Sometimes, during file upload we come across situation wherein there would be check on the file extension at the client side as well as server side too. If the application does allow only .jpeg extension to be uploaded, the client side java script checks for the extension of the file before passing the request. We all know that how easily this can be defeated. Some applications, checks for the extension at the server side also. That's not easy to bypass. However there are some ways with which it still can be bypassed. Most of server side scripts are written in high level languages such as Php, Java etc who still use some C/C++ libraries to read the file name and contents. That leads to the problem. In C/C++ a line ends with /00 or which is called Null Byte. So whenever the interpreter sees a null byte at the end of the a string, it stops reading thinking it has reached at the end of the string. This can be used for the bypass. It works for many servers, specially php servers. T...

Data leakage in JSON

A web application is sending data in this format: {"t":1,"p":1,"r":1,"rows":[{"i":0,"c":["n","H, C","A","5","T","n"]}]} this is a valid JSON, before moving on lets understand an important concept: 1. Javscript expression 2. javascript statement javscript expressions are not executed by javascript parser, but statements are: for ex: <script> {"t":1,"p":1,"r":1,"rows":[{"i":0,"c":["n","H, C","A","5","T","n"]}]} </script> this will not be executed, that is, objects won't be created. The above example is for a javascript expression. But now when it is converted into a statement as given below: <script> [{"t":1,"p":1,"r":1,"rows":[{"i":0,"c":[...

Nilesh Kumar

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