Re: Security through Permissiveness: A Zen Riddle?

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chrisat_private

* Shane Kerr (shane@time-travellers.org) wrote:
> <offtopic level="slight">
> 
> This seems like implementation to me - as long as the hooks are there an
> LSM can do what it wishes.  If the hooks work like:
> 
>   if ((port < 1024) && biguglyprocess_struct->uid) {
>       return EPERM;
>   }
>   if (fancykernelhook->lsm->bindhook) {
>       ret = (fancykernelhook->lsm->bindhook)(port);
>       if (ret) return ret;
>   }
> 
> Then no LSM can ever implement a policy to allow non-root users to bind
> low ports.

to be clear:  the code looks like:
 if (snum && snum < PROT_SOCK && !capable(CAP_NET_BIND_SERVICE))
    return -EACCESS;

and we hook in capable...so there is an override mechanism.  yes, you
can make a module that allows any user to bind to protected ports.

-chris

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