Coding securely, was Linux (in)security

[Paul Schmehl <pauls () utdallas edu>]

--On Monday, October 27, 2003 10:23 AM +1100 Brett Hutley 
<brett () hutley net> wrote:
> Also using these type of functions in operating system code is a good way
> to create a *REALLY*  S L O W system. In maybe 80% of system code you are
> going to know who ALL the callers of the function are and are going to be
> working with input that has already been validated further up the call
> tree. Why slow this code down with unnecessary checks? Validation of
> input is important when the input is specified by something external to
> the system - user parameters, environment variables...
If the input is *known* or has already been validated, why would you need 
to check it?  My point is, if you can't know what the input will be, you 
*must* check it.  The problem is that many programmers don't think like 
hackers.  They write code as if every user will input the correct data 
because, after all, they're trying to use it, not abuse it.

That, of course, fails with the first person who types something 
incorrectly on the keyboard (intentionally or unintentionally) or when the 
input from some device is different than what the programmer thought it 
could ever be (for whatever reason.)

Paul Schmehl (pauls () utdallas edu)
Adjunct Information Security Officer
The University of Texas at Dallas
AVIEN Founding Member
http://www.utdallas.edu

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