[SLOF] [PATCH] dhcp: check if the DHCPOFFER matches our MAC

[Thomas Huth]

On 27.07.2016 05:49, Nikunj A Dadhania wrote:
> Add missing check to see that the IP offered is for this mac address.
> 
> Signed-off-by: Nikunj A Dadhania <nikunj at linux.vnet.ibm.com>
> ---
>  clients/net-snk/app/netlib/dhcp.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/clients/net-snk/app/netlib/dhcp.c b/clients/net-snk/app/netlib/dhcp.c
> index 7e2e88c..3f45633 100644
> --- a/clients/net-snk/app/netlib/dhcp.c
> +++ b/clients/net-snk/app/netlib/dhcp.c

Please note that this file has recently been moved to lib/libnet/ instead.

> @@ -865,6 +865,8 @@ int8_t handle_dhcp(int fd, uint8_t * packet, int32_t packetsize)
>  		switch (dhcp_state) {
>  		case DHCP_STATE_SELECT :
>  			if (opt.msg_type == DHCPOFFER) {
> +				if(memcmp(btph->chaddr, get_mac_address(), 6))
> +					break;
>  				dhcp_own_ip = htonl(btph -> yiaddr);
>  				dhcp_server_ip = opt.server_ID;
>  				dhcp_send_request(fd);
> 

Checking the MAC here should be fine, I think. I'm just wondering: Did
you encounter a real world problem here, or did you just find this by
reading the sources? The SLOF code already checks the XID for received
packets, so that should already give a basic protection against wrongly
received broadcast DHCPOFFER messages, shouldn't it? Anyway, let's be
better safe than sorry, so including this additional check is certainly
a good idea!

 Thomas