linux-kernel - Re: [PATCH] SMACK netfilter smacklabel socket match

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Date:	Tue, 17 Feb 2009 18:52:20 -0500
From:	Paul Moore <paul.moore@...com>
To:	etienne <etienne.basset@...ericable.fr>
Cc:	Casey Schaufler <casey@...aufler-ca.com>,
	"Linux-Kernel" <linux-kernel@...r.kernel.org>,
	linux-security-module@...r.kernel.org
Subject: Re: [PATCH] SMACK netfilter smacklabel socket match

On Tuesday 17 February 2009 03:01:15 pm etienne wrote:
> I realize this patch is a little ugly, a cleaner way would be to insert 
> struct smk_netlbladdr sorted from longest to smallest mask and break the
> loop as soon as we have a match... regards,

Agreed, the address matching code really should be improved; if you feel like 
you could contribute the changes I'm pretty sure Casey would welcome the 
patches :)

Regarding your fix below, I think a cleaner solution would be to do something 
like the following in place of the existing mask check ...

	if ((miap->s_addr & bestmask.s_addr) || (bestmask.s_addr == 0)) {
		bestmask.s_addr = miap->s_addr;
		bestlabel = snp->smk_label;
	}	

... however there is one small problem with this approach (your proposal 
suffers from the same issue): normally the smack_host_label() code prefers the 
first matching entry in the list, the change above preserves that with the 
exception of a 0.0.0.0/0 entry.  Granted, you shouldn't allow that in the 
first place but I believe it is possible so it is something that needs to be 
taken into consideration.

> Signed-off-by: Etienne <etienne.basset@...ericable.fr>
> ------
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 0278bc0..9d2576d 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -1540,7 +1540,7 @@ static char *smack_host_label(struct sockaddr_in
> *sip) * If the list entry mask is less specific than the best * already
> found this entry is uninteresting.
>                  */
> -               if ((miap->s_addr | bestmask.s_addr) == bestmask.s_addr)
> +               if ( ((miap->s_addr | bestmask.s_addr) == bestmask.s_addr)
> &&  (miap->s_addr | bestmask.s_addr) != 0  ) continue;
>                 /*
>                  * This is better than any entry found so far.
> --
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-- 
paul moore
linux @ hp

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