Re: *BSD's DES-based crypt(3) treats all invalid salt chars as '.'

[Solar Designer <solar () openwall com>]

Christos Zoulas fixed the out of bounds read below in NetBSD (for NetBSD 6).

On Tue, Nov 15, 2011 at 08:16:14AM +0400, Solar Designer wrote:
> Speaking of NetBSD, it also appears to have out of bounds array reads on
> salt characters with the 8th bit set:
>
> static unsigned char a64toi[128];     /* ascii-64 => 0..63 */
> [...]
>               /* get iteration count */
>               num_iter = 0;
>               for (i = 4; --i >= 0; ) {
>                       if ((t = (unsigned char)setting[i]) == '\0')
>                               t = '.';
>                       encp[i] = t;
>                       num_iter = (num_iter<<6) | a64toi[t];
>               }
> [...]
>       salt = 0;
>       for (i = salt_size; --i >= 0; ) {
>               if ((t = (unsigned char)setting[i]) == '\0')
>                       t = '.';
>               encp[i] = t;
>               salt = (salt<<6) | a64toi[t];
>       }
>
> This has no security impact that I can see, though.  Perhaps with PHP
> safe_mode and the like it could be used to read data beyond array
> bounds, but unless the order of variables in .bss is heavily changed by
> the compiler or linker there's nothing interesting to read in the 128
> bytes following a64toi[], and it would not result in a crash either.
>
> Alexander