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/*
* dhcp.c
*
* Copyright (C) 2016 - ntop.org
*
* nDPI is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* nDPI is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with nDPI. If not, see <http://www.gnu.org/licenses/>.
*
*/
#include "ndpi_protocols.h"
#ifdef NDPI_PROTOCOL_DHCP
/* freeradius/src/lib/dhcp.c */
#define DHCP_CHADDR_LEN 16
#define DHCP_SNAME_LEN 64
#define DHCP_FILE_LEN 128
#define DHCP_VEND_LEN 308
#define DHCP_OPTION_MAGIC_NUMBER 0x63825363
typedef struct {
uint8_t msgType;
uint8_t htype;
uint8_t hlen;
uint8_t hops;
uint32_t xid;/* 4 */
uint16_t secs;/* 8 */
uint16_t flags;
uint32_t ciaddr;/* 12 */
uint32_t yiaddr;/* 16 */
uint32_t siaddr;/* 20 */
uint32_t giaddr;/* 24 */
uint8_t chaddr[DHCP_CHADDR_LEN]; /* 28 */
uint8_t sname[DHCP_SNAME_LEN]; /* 44 */
uint8_t file[DHCP_FILE_LEN]; /* 108 */
uint32_t magic; /* 236 */
uint8_t options[DHCP_VEND_LEN];
} dhcp_packet_t;
static void ndpi_int_dhcp_add_connection(struct ndpi_detection_module_struct *ndpi_struct, struct ndpi_flow_struct *flow)
{
ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_DHCP, NDPI_PROTOCOL_UNKNOWN);
}
void ndpi_search_dhcp_udp(struct ndpi_detection_module_struct *ndpi_struct, struct ndpi_flow_struct *flow)
{
struct ndpi_packet_struct *packet = &flow->packet;
// struct ndpi_id_struct *src=ndpi_struct->src;
// struct ndpi_id_struct *dst=ndpi_struct->dst;
/* this detection also works for asymmetric dhcp traffic */
/*check standard DHCP 0.0.0.0:68 -> 255.255.255.255:67 */
if(packet->udp) {
dhcp_packet_t *dhcp = (dhcp_packet_t*)packet->payload;
if((packet->payload_packet_len >= 244)
&& (packet->udp->source == htons(67) || packet->udp->source == htons(68))
&& (packet->udp->dest == htons(67) || packet->udp->dest == htons(68))
&& (dhcp->magic == htonl(DHCP_OPTION_MAGIC_NUMBER))) {
int i = 0, foundValidMsgType = 0;
while(i < DHCP_VEND_LEN) {
u_int8_t id = dhcp->options[i];
if(id == 0xFF)
break;
else {
u_int8_t len = dhcp->options[i+1];
if(len == 0) break;
#ifdef DHCP_DEBUG
printf("[DHCP] Id=%d [len=%d]\n", id, len);
#endif
if(id == 53 /* DHCP Message Type */) {
u_int8_t msg_type = dhcp->options[i+2];
if(msg_type <= 8) foundValidMsgType = 1;
} else if(id == 55 /* Parameter Request List / Fingerprint */) {
u_int idx, offset = 0,
hex_len = ndpi_min(len * 2, sizeof(flow->protos.dhcp.fingerprint));
for(idx=0; idx<len; idx++) {
snprintf((char*)&flow->protos.dhcp.fingerprint[offset],
sizeof(flow->protos.dhcp.fingerprint)-offset-1,
"%02X", dhcp->options[i+2+idx] & 0xFF);
offset += 2;
}
} else if(id == 12 /* Host Name */) {
char *name = (char*)&dhcp->options[i+2];
int j = 0;
#ifdef DHCP_DEBUG
printf("[DHCP] ");
while(j < len) { printf("%c", name[j]); j++; }
printf("\n");
#endif
j = ndpi_min(len, sizeof(flow->host_server_name)-1);
strncpy((char*)flow->host_server_name, name, j);
flow->host_server_name[j] = '\0';
}
i += len + 2;
}
}
//get_u_int16_t(packet->payload, 240) == htons(0x3501)) {
if(foundValidMsgType) {
NDPI_LOG(NDPI_PROTOCOL_DHCP, ndpi_struct, NDPI_LOG_DEBUG, "DHCP found\n");
ndpi_int_dhcp_add_connection(ndpi_struct, flow);
}
return;
}
}
NDPI_ADD_PROTOCOL_TO_BITMASK(flow->excluded_protocol_bitmask, NDPI_PROTOCOL_DHCP);
}
void init_dhcp_dissector(struct ndpi_detection_module_struct *ndpi_struct, u_int32_t *id, NDPI_PROTOCOL_BITMASK *detection_bitmask)
{
ndpi_set_bitmask_protocol_detection("DHCP", ndpi_struct, detection_bitmask, *id,
NDPI_PROTOCOL_DHCP,
ndpi_search_dhcp_udp,
NDPI_SELECTION_BITMASK_PROTOCOL_UDP_WITH_PAYLOAD,
SAVE_DETECTION_BITMASK_AS_UNKNOWN,
ADD_TO_DETECTION_BITMASK);
*id += 1;
}
#endif
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