Re: [PATCH 3/3] Use reverse authenticating ioctl-handler protocal

[olafBuddenhagen]

Hi,

On Wed, Aug 26, 2009 at 04:45:39PM +0200, Carl Fredrik Hammar wrote:

> +  err = EACCES;
> +  euid = geteuid ();
> +  for (i = 0; i < euids_len; i++)
> +    if (euids[i] == euid || euids[i] == 0)
> +      err = 0;

This is not sufficient: privileges of the module are not escalated only
if the sender has access to *all* our user IDs, not just the current
one.

Also, there is no point going on with the loop once you found what you
are looking for :-)

BTW, I wonder whether it's necessary to special-case root on the
receiver's side: in theory, a sender having root privileges can
fabricate any IDs the receiver wants to see. Not sure whether this
approach is preferable though: it is more flexible -- but also requires
a more complicated protocol, and I think it's less consistent with the
root handling in other parts of the Hurd...

-antrik-