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Date: Wed, 18 May 2016 17:26:12 -0700 (PDT)
From: Don Lewis <truckman@FreeBSD.org>
Subject: Re: svn commit: r300174 - head/sbin/dhclient
To: cem@FreeBSD.org
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On 18 May, Conrad E. Meyer wrote:
> Author: cem
> Date: Wed May 18 23:41:55 2016
> New Revision: 300174
> URL: https://svnweb.freebsd.org/changeset/base/300174
> 
> Log:
>   dhclient: Fix the trivial buffer overruns correctly
>   
>   A DHCP client identifier is simply the hardware type (one byte) concatenated
>   with the hardware address (some variable number of bytes, but at most 16).
>   Limit the size of the temporary buffer to match and the rest of the
>   calculations shake out correctly.
>   
>   This is a follow-up to the incorrect r299512, reverted in r300172.
>   
>   CIDs:		1008682, 1305550
>   Sponsored by:	EMC / Isilon Storage Division
> 
> Modified:
>   head/sbin/dhclient/dhclient.c
> 
> Modified: head/sbin/dhclient/dhclient.c
> ==============================================================================
> --- head/sbin/dhclient/dhclient.c	Wed May 18 23:39:31 2016	(r300173)
> +++ head/sbin/dhclient/dhclient.c	Wed May 18 23:41:55 2016	(r300174)
> @@ -1570,7 +1570,7 @@ make_discover(struct interface_info *ip,
>  	}
>  
>  	/* set unique client identifier */
> -	char client_ident[sizeof(struct hardware)];
> +	char client_ident[sizeof(ip->hw_address.haddr) + 1];
>  	if (!options[DHO_DHCP_CLIENT_IDENTIFIER]) {
>  		int hwlen = (ip->hw_address.hlen < sizeof(client_ident)-1) ?
>  				ip->hw_address.hlen : sizeof(client_ident)-1;
> 

That might work as well.