user input question

[Kristian Hermansen]

On 4/3/07, Eric C <eric at newmag.org> wrote:
> It will kick 'em out before anything else gets done.
> What do you think?

The rule of thumb in securing user input is *NOT* to blacklist what
you think is invalid, but to whitelist only that which is acceptable
input.  If it is a hash of [a-z0-9] only, then make a whitelist on
this grammar.  You see, the world of inputs is possibly infinite, and
you don't want to have cases pertaining to all of them.  Also, I
wouldn't even give an attacker a helpful message like you do in your
patch.  I would give a more generic error like "Something went
wrong..." and use that for every error you encounter!
-- 
Kristian Hermansen

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