Re: Buffer overflow?

[Richard Coleman <richardcoleman@xxxxxxxxxxxxxx>]

>     Seriously, though, the C lib has new functions, e.g. snprintf(), and 
>     the only way to avoid most buffer overflow problems is to use these
>     bounded functions and never, ever use the unbounded functions, even
>     if you *know* a particular use will not overflow a buffer.
>
>     The second type of buffer overflow is an array index overflow, where
>     an array index is incorrectly calculated or incorrectly bounded.  For
>     example, consider the age-old misuse of malloc() where beginning 
>     programmers would do something like:  str2 = malloc(strlen(str1)),
>     which doesn't account for the \0 terminating the string, or programmers
>     who check the high side but forget that they are using a signed index
>     variable which could very well be negative.
>
>     If just these two problem areas were cleaned up 99% of all buffer 
>     overflow issues would disappear.
>
> 					-Matt
> 					Matthew Dillon 
> 					<dillon@xxxxxxxxxxxxx>

Have you given any thought to pulling in the changes that OpenBSD made 
to harden against buffer overflows (i.e. canary checking)?  They've 
added some pretty serious mechanisms to make it harder to exploit buffer 
overflows (and made it turned on by default).

I've been surprised that none of the other BSD's have pulled in this code.

Richard Coleman
richardcoleman@xxxxxxxxxxxxxx