[incremental] Patch: FYI: add missing bits to checksum

[Paolo Bonzini]

> Paolo> You cannot find a
> Paolo> second pre-image for MD5, but you can find collisions pretty easily,
> Paolo> so it could yield security problems (no I'm not exaggerating it *too
> Paolo> much*---they would be wrong-code bugs, but if somebody plays with MD5
> Paolo> collisions you can assume that they are doing something malicious).
> 
> I have thought about this argument before.  I am not really convinced
> by it.

Frankly, neither am I.  It's not going to be Ken Thompson's attack for 
the 3rd millennium.  But I would find it less worrisome to not have it, 
rather than to know about it.

I attach a SHA1 from glibc with a similar interface to MD5.

> I tried to see this problem in action, but I was unable.  The only MD5
> collision I could easily find yields a program that is rejected by the
> lexer.  If you have a "nice" collision, I'd like to have it.

It's easier to just find a MD5-collision generator and run it until it 
works.  But I think you have to be sure that the hash has processed a 
full block before it is fed the string.

Paolo
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