Wednesday, July 22, 2015

Solving "unresolved external symbol ___report_rangecheckfailure" Visual Studio linker errors

Let's say you import a library from Visual Studio 2012 or later into your project in an older version of Visual Studio (e.g. Visual Studio 2008 or Visual Studio 2010) but now get linker errors:

error LNK2019: unresolved external symbol ___report_rangecheckfailure referenced in function ...
error LNK2001: unresolved external symbol ___report_rangecheckfailure ...

Sad day. Especially since you don't really get a say in how that library is being built. Your options are:

  1. Upgrade your version of Visual Studio. That includes going through the whole project upgrade cycle. We know how well that usually goes.
  2. Recompile the library yourself. Sad day turns into sad week.
  3. Hack it.
The function __report_rangecheckfailure() is called when the /GS compiler option is used. The option enabled buffer overflow security cookie checking, which, in this day and age, is a good option to have enabled. Unfortunately, that causes problems with older versions of Visual Studio. Let's take a look at what the function does - the source code from 'VC\crt\src\gs_report.c' has this code:

// Declare stub for rangecheckfailure, since these occur often enough that the code bloat
// of setting up the parameters hurts performance
__declspec(noreturn) void __cdecl __report_rangecheckfailure(void)
Hmm...not really helpful since it calls another function. However, that function contains this very interesting comment after a lot of inline assembler and macros:

     * Raise the security failure by passing it to the unhandled exception
     * filter and then terminate the process.
So, knowing this normally triggers an unhandled exception and exits the process, we can hack it:

__declspec(noreturn) void __cdecl __report_rangecheckfailure(void)
I'm not sure whether to congratulate myself on this evil hack or cry. I think I'll do a little of both. You're welcome.

Oh, and if you work on the Microsoft Visual Studio development team, please develop a compatibility library that implements stuff correctly for older Visual Studio environments. Doesn't have to go back to 1995 VS6, but something reasonable like a 10 year window that addresses issues like these.

Monday, July 06, 2015

The Death Master File...a blackhat's dream come true

First, watch this CBS 60 Minutes special on the Social Security Administration's Death Master File:

The ultimate hack, from a blackhat/rogue government perspective, is the one that has significant negative impact on the financial stability of a country one can figure out who is responsible.

The Death Master File meets all of the prerequisite criteria:

  • Large quantities of data? Check.
  • Has significant financial consequences for anyone who gets into it? Check.
  • Individuals can't readily find out if they are on the file or not? Check.
  • Relatively easy to add anyone to the file? Probably check (e.g. plop some malware on funeral home computers and get remote access to adding entries to the file).
  • Takes years to get off the file? Check.
  • Has recurrent consequences for the rest of the individual's life? Check.
  • No way to track additions back to the original source? Check.
  • The head honcho at the Social Security Administration doesn't really care about "accidental" additions and only seems to care about paying out too much money? Check.

You really couldn't ask for a more perfect combination. It's pretty shocking when you think about it - zero safeguards, no one seems to care, and it has major repercussions for affected individuals (e.g. homelessness). Destroying the U.S. is quite literally available on an unprotected digital silver platter. There are so many different ways that this could go sideways I'm not really sure where to start other than to write a blog post about it to raise awareness.

As a software developer, the one thing that REALLY irks me is this:

There is a $200 annual subscription fee to access the data and is restricted to government entities and businesses with a need for the data. Individuals can't write a script to watch for the unfortunate event of being added to the list. The list is supposedly a very lucrative source of income, which means that every business out there seems to use it. Sorry, but my tax dollars aren't for NTIS to run an e-commerce store. Data for all or data for none.

The U.S. government is ill-equipped to handle modern threats - writing laws and charging money for access to the data doesn't close blatant security holes. Who was the person who decided to not bother with change tracking in this rather critical database? That's ridiculous and they should be fired and drop-kicked out the door. Also, to simply not care about those people whose lives the Social Security Administration has messed up is rather messed up too. The U.S. has enemies who would love nothing more than to destroy the country. Adding people to the Death Master File seems like a pretty easy way to accomplish such a task.