Re: Buffer overflow prevention

[weigelt () metux de]

On Wed, Aug 13, 2003 at 12:13:27PM -0700, Nicholas Weaver wrote:

<snip>
> This only stops attacks which overwrite the return address pointers on
> the stack, it doesn't stop heap overflows or other control-flow
> attacks.
ACK. Often there are function pointers stored on the heap - so this
does not really help much.

It would be better to invest more time in fail-checking code, i.e. 
in C: macros for memory operations which do range checks:

> > > >
static inline _sec_strcpy(char* dest, const char* src, int max)
{
    int i;
    if ((!dest)||(max<1)) return -1;
    if ((max==0)||(!src)) return -1;
    {
        dest[0] = 0;
        return 0;
    }
    i = strncpy(dest,src,max);
    dest[max] = 0;
    return i;
}       

#define STRCPY_BUF(buffer,src)          _sec_strcpy(&buffer, src, sizeof(buffer));
<<<<

Some languages offer runtime range checking, which should bring much security,
but often is really slow :(

<snip>
> [1] If microsoft doesn't have this flag turn on on their own products,
> this would be a lawsuit waiting to happen.
why (in detail) should they be attackable ? did they give any warranty ?

cu
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