Re: [User-mode-linux-user] Requirement for ethertap daemon.

[Andi K. <ak...@su...>]

On Fri, Aug 25, 2000 at 01:28:42PM +0100, David Woodhouse wrote:
> 
> ku...@ms... said:
> >  Ethertap device has just been replaced. 
> >  netlink_dev is open for removal rather than for improvements. 
> 
> OK. The new Ethertap in 2.4 looks far nicer. 
> 
> 2.2 is still a problem though. I'd like to see either the new Ethertap or
> this patch go in.
> 
> Index: include/net/sock.h
> ===================================================================
> RCS file: /inst/cvs/linux/include/net/sock.h,v
> retrieving revision 1.8
> diff -u -r1.8 sock.h
> --- include/net/sock.h	2000/06/07 09:55:39	1.8
> +++ include/net/sock.h	2000/08/23 12:05:09
> @@ -115,6 +115,7 @@
>  	unsigned		groups;
>  	pid_t			dst_pid;
>  	unsigned		dst_groups;
> +	int			netlink_dev;
>  	int			(*handler)(int unit, struct sk_buff *skb);
>  	atomic_t		locks;
>  	struct netlink_callback	*cb;
> Index: net/netlink/af_netlink.c
> ===================================================================
> RCS file: /inst/cvs/linux/net/netlink/af_netlink.c,v
> retrieving revision 1.5
> diff -u -r1.5 af_netlink.c
> --- net/netlink/af_netlink.c	2000/06/07 09:54:25	1.5
> +++ net/netlink/af_netlink.c	2000/08/23 12:05:50
> @@ -254,7 +254,8 @@
>  		return -EINVAL;
>  
>  	/* Only superuser is allowed to listen multicasts */
> -	if (nladdr->nl_groups && !capable(CAP_NET_ADMIN))
> +	if (nladdr->nl_groups && !sk->protinfo.af_netlink.netlink_dev &&
> +	    !capable(CAP_NET_ADMIN))
>  		return -EPERM;

A nlsocket with opened character devices can still be accessed via sockets too,
so you just opened a security hole.


-Andi