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2008 Underhanded C Contest Officially Open
Xcott Craver writes "The 2008 Underhanded C Contest has just opened. Every year, contestants are asked to write a simple, innocent, readable C program that appears to perform an innocent task — but implements some non-obvious evil behavior. This year's challenge: redact blocks from an image, but do it so that the excised pixels can somehow be retrieved. We also have listed the winners of last year's contest, which was to write a simple encryption utility that mysteriously and undetectably fails between 1 percent and 0.1 percent of the time. The winning entry is truly impressive."
We discussed the first of these contests in 2005.
The Microsoft Windows Operating System, pick your version.
(sorry, couldn't resist, I know they've suffered enough already)
Interactive Visual Medical Dictionary
No, the point is to make a utility that appears to innocently redact part of an image, when in fact the information is retrievable. It's meant to be a malicious utility that people would use without knowing that the 'hacker' could recover their full images.
Something like Photoshop's Swirl filter.
I'm sure it would be nearly impossible to hide the evil code here, because anything that isn't a simple assignment loop is suspicious.
Maybe stick in stuff in the image loader, image temporary copy code, and keep the blackener to the obvious implementation, then stick stuff in the saver.
I thought some crazy stuff involving function pointers as the function to call to return a black pixel might be promising. Maybe use some out of bounds array math to change one function pointer to point to some other code.
More precisely:
The point is to make a utility that - when viewing the source code - appears to innocently...
It is no challenge to make a closed source utility which does something evil even though it appears to do something innocent. Most viruses do that.
The challenge is to hide the the evil behaviour in simple and open source code.
Wouldn't it be nice if the original under the blacked out area could be compressed and then put somewhere else in the image.
It would be much easier if one could just use an algorithm which just displaces the pixels and then forget to randomize the displacement. This could look much more innocent than the above.
That black area has so little expected channel capacity that hiding anything in it is kinda difficult.
Unfortunately the code for the blacking out can be made so small that it is tough to hide anything in it, unless ppm offers some ways to add complexity in some innocent way.
I wonder what means of deciphering the hidden area are allowed, i.e. can I write another program to get the kitty face information back?
That is a really cute picture. I wonder what it is thinking.
Je me souviens.
because the way it dumpes the key into the output is hidden in such a underhanded, innocent way...
HI O WISE PRINCE. WHT TOOK U SO DAM LONG?
Reminds me of a "compression program" back in the early 90's. Seemed to compress better than Zip or RAR and was pretty fast too. You could also test it by compressing and uncompressing a few files, and you got your original back.
Turns out it just copied the contents to a temporary file and "uncompressing" got them back from there, while the "archive" was just random junk. Better yet, the temporary file was just a circular buffer, so when it filled, old data got discarded.
A polar bear is a cartesian bear after a coordinate transform.
Now we can speculate what the authors intentions behind the contest are.
I think their FAQ addresses most points pretty well:
http://underhanded.xcott.com/?page_id=7
I hope sensitizes open source programmers programmers to take great care with peoples submissions to their projects. Only good can come from that.
Je me souviens.
I recently investigated a problem in MS Outlook where an option was set to never show the body of the email when viewing the email, it could only be viewed when forwarding. There were actually a bunch of tick box options to enable and disable this behavior. Reminds me of the Far Side comic with a passenger in an airplane reaching down to adjust his seat and accidentally about to toggle the 'wings stay on / wings fall off' switch.
Wavelet Intelligent Compressor. And it was intellingent, indeed. It had a compression scheme so good it could compress its own .wic files down from megs to bytes.
But what do you mean with "random junk", do you mean my .wic based backups could be in trouble????
Hosting 20G hd, 1Tb bw! ssh $7.95
courtesy of crazy Japanese censorship laws. Google for gmask or see examples at Lecture on masking (Yes, it's SFW)
There seems to be an error in the supplied ppm.c library file:
p.rgb[i] = z.pixel[y][(x+i)*3*z.bpp];
This only ever gets the R component, as all offsets are multiples of 3. I think the right code is:
p.rgb[i] = z.pixel[y][(x*3+i)*z.bpp];
Maybe this is part of the assignment :-).