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[dhcp] Check for matching chaddr in received DHCP packets 

On large networks a DHCP XID collision is possible.  Fix by explicitly
checking the chaddr in received DHCP packets.

Originally-fixed-by: Wissam Shoukair <wissams@mellanox.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
pull/27/merge
Michael Brown 2014-09-22 15:29:13 +01:00
parent 5d9fbf34ee
commit 08bcc0fe01
1 changed files with 37 additions and 0 deletions
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37
src/net/udp/dhcp.c
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@ -130,6 +130,29 @@ static inline const char * dhcp_msgtype_name ( unsigned int msgtype ) {
}
}
/**
* Transcribe DHCP client hardware address (for debugging)
*
* @v chaddr Client hardware address
* @v hlen Client hardware address length
*/
static const char * dhcp_chaddr_ntoa ( const void *chaddr, size_t hlen ) {
static char buf[ 48 /* 16 x ( "xx" + ":" or NUL ) */ ];
const uint8_t *chaddr_bytes = chaddr;
char *tmp = buf;
/* Sanity check */
assert ( hlen < ( sizeof ( buf ) / 3 ) );
/* Transcribe address */
while ( hlen-- ) {
tmp += sprintf ( tmp, "%s%02x", ( ( tmp == buf ) ? "" : ":" ),
*(chaddr_bytes++) );
}
return buf;
}
/****************************************************************************
*
* DHCP session
@ -1159,6 +1182,8 @@ static int dhcp_deliver ( struct dhcp_session *dhcp,
struct dhcphdr *dhcphdr;
uint8_t msgtype = 0;
struct in_addr server_id = { 0 };
uint8_t chaddr[ sizeof ( dhcphdr->chaddr ) ];
unsigned int hlen;
int rc = 0;
/* Sanity checks */
@ -1203,9 +1228,21 @@ static int dhcp_deliver ( struct dhcp_session *dhcp,
goto err_xid;
};
/* Check for matching client hardware address */
hlen = dhcp_chaddr ( dhcp->netdev, chaddr, NULL );
if ( memcmp ( dhcphdr->chaddr, chaddr, hlen ) != 0 ) {
DBGC ( dhcp, "DHCP %p %s from %s:%d has bad chaddr %s\n",
dhcp, dhcp_msgtype_name ( msgtype ),
inet_ntoa ( peer->sin_addr ), ntohs ( peer->sin_port ),
dhcp_chaddr_ntoa ( dhcphdr->chaddr, hlen ) );
rc = -EINVAL;
goto err_chaddr;
}
/* Handle packet based on current state */
dhcp->state->rx ( dhcp, dhcppkt, peer, msgtype, server_id );
err_chaddr:
err_xid:
dhcppkt_put ( dhcppkt );
err_alloc_dhcppkt: