DLLEXPORT uint16_t *trace_checksum_transport(libtrace_packet_t *packet,
uint16_t *csum) {
void *header = NULL;
uint16_t ethertype;
uint32_t remaining;
uint32_t sum = 0;
uint8_t proto = 0;
uint16_t *csum_ptr = NULL;
int plen = 0;
uint8_t safety[65536];
uint8_t *ptr = safety;
header = trace_get_layer3(packet, ðertype, &remaining);
if (header == NULL)
return NULL;
if (ethertype == TRACE_ETHERTYPE_IP) {
libtrace_ip_t *ip = (libtrace_ip_t *)header;
if (remaining < sizeof(libtrace_ip_t))
return NULL;
sum = ipv4_pseudo_checksum(ip);
} else if (ethertype == TRACE_ETHERTYPE_IPV6) {
libtrace_ip6_t *ip = (libtrace_ip6_t *)header;
if (remaining < sizeof(libtrace_ip6_t))
return 0;
sum = ipv6_pseudo_checksum(ip);
}
header = trace_get_transport(packet, &proto, &remaining);
if (proto == TRACE_IPPROTO_TCP) {
libtrace_tcp_t *tcp = (libtrace_tcp_t *)header;
header = trace_get_payload_from_tcp(tcp, &remaining);
csum_ptr = &tcp->check;
memcpy(ptr, tcp, tcp->doff * 4);
tcp = (libtrace_tcp_t *)ptr;
tcp->check = 0;
ptr += (tcp->doff * 4);
}
else if (proto == TRACE_IPPROTO_UDP) {
libtrace_udp_t *udp = (libtrace_udp_t *)header;
header = trace_get_payload_from_udp(udp, &remaining);
csum_ptr = &udp->check;
memcpy(ptr, udp, sizeof(libtrace_udp_t));
udp = (libtrace_udp_t *)ptr;
udp->check = 0;
ptr += sizeof(libtrace_udp_t);
}
else if (proto == TRACE_IPPROTO_ICMP) {
/* ICMP doesn't use the pseudo header */
sum = 0;
libtrace_icmp_t *icmp = (libtrace_icmp_t *)header;
header = trace_get_payload_from_icmp(icmp, &remaining);
csum_ptr = &icmp->checksum;
memcpy(ptr, icmp, sizeof(libtrace_icmp_t));
icmp = (libtrace_icmp_t *)ptr;
icmp->checksum = 0;
ptr += sizeof(libtrace_icmp_t);
}
else {
return NULL;
}
sum += add_checksum(safety, (uint16_t)(ptr - safety));
plen = trace_get_payload_length(packet);
if (plen < 0)
return NULL;
if (remaining < (uint32_t)plen)
return NULL;
if (header == NULL)
return NULL;
sum += add_checksum(header, (uint16_t)plen);
*csum = ntohs(finish_checksum(sum));
//assert(0);
return csum_ptr;
}
/** Implements the process_packet function of the plugin API */
int corsaro_dos_process_packet(corsaro_t *corsaro,
corsaro_packet_t *packet)
{
libtrace_packet_t *ltpacket = LT_PKT(packet);
void *temp = NULL;
uint8_t proto;
uint32_t remaining;
libtrace_ip_t *ip_hdr = NULL;
libtrace_icmp_t *icmp_hdr = NULL;
libtrace_ip_t *inner_ip_hdr = NULL;
/* borrowed from libtrace's protocols.h (used by trace_get_*_port) */
struct ports_t {
uint16_t src; /**< Source port */
uint16_t dst; /**< Destination port */
};
uint16_t attacker_port = 0;
uint16_t target_port = 0;
attack_vector_t findme;
int khret;
khiter_t khiter;
attack_vector_t *vector = NULL;
uint8_t *pkt_buf = NULL;
libtrace_linktype_t linktype;
struct timeval tv;
if((packet->state.flags & CORSARO_PACKET_STATE_FLAG_BACKSCATTER) == 0)
{
/* not a backscatter packet */
return 0;
}
/* backscatter packet, lets find the flow */
/* check for ipv4 */
/* 10/19/12 ak replaced much more verbose code to get header with this */
if((ip_hdr = trace_get_ip(ltpacket)) == NULL)
{
/* non-ipv4 packet */
return 0;
}
/* get the transport header */
if((temp = trace_get_transport(ltpacket, &proto, &remaining)) == NULL)
{
/* not enough payload */
return 0;
}
findme.target_ip = 0;
if(ip_hdr->ip_p == TRACE_IPPROTO_ICMP && remaining >= 2)
{
icmp_hdr = (libtrace_icmp_t *)temp;
if((icmp_hdr->type == 3 ||
icmp_hdr->type == 4 ||
icmp_hdr->type == 5 ||
icmp_hdr->type == 11 ||
icmp_hdr->type == 12) &&
((temp = trace_get_payload_from_icmp(icmp_hdr, &remaining)) != NULL
&& remaining >= 20 && (inner_ip_hdr = (libtrace_ip_t *)temp) &&
inner_ip_hdr->ip_v == 4))
{
/* icmp error message */
if(inner_ip_hdr->ip_src.s_addr != ip_hdr->ip_dst.s_addr)
{
STATE(corsaro)->number_mismatched_packets++;
}
findme.target_ip = ntohl(inner_ip_hdr->ip_dst.s_addr);
/* just extract the first four bytes of payload as ports */
if((temp = trace_get_payload_from_ip(inner_ip_hdr, NULL,
&remaining)) != NULL
&& remaining >= 4)
{
attacker_port = ntohs(((struct ports_t *)temp)->src);
target_port = ntohs(((struct ports_t *)temp)->dst);
}
}
else
{
findme.target_ip = ntohl(ip_hdr->ip_src.s_addr);
attacker_port = ntohs(icmp_hdr->code);
target_port = ntohs(icmp_hdr->type);
}
}
else if((ip_hdr->ip_p == TRACE_IPPROTO_TCP ||
ip_hdr->ip_p == TRACE_IPPROTO_UDP) &&
remaining >= 4)
{
findme.target_ip = ntohl(ip_hdr->ip_src.s_addr);
attacker_port = trace_get_destination_port(ltpacket);
target_port = trace_get_source_port(ltpacket);
}
if(findme.target_ip == 0)
{
/* the packet is none of ICMP, TCP or UDP */
return 0;
}
tv = trace_get_timeval(ltpacket);
/* is this vector in the hash? */
assert(STATE(corsaro)->attack_hash != NULL);
if((khiter = kh_get(av, STATE(corsaro)->attack_hash, &findme))
!= kh_end(STATE(corsaro)->attack_hash))
{
/* the vector is in the hash */
vector = kh_key(STATE(corsaro)->attack_hash, khiter);
if(attack_vector_is_expired(vector, tv.tv_sec) != 0)
{
kh_del(av, STATE(corsaro)->attack_hash, khiter);
attack_vector_free(vector);
vector = NULL;
}
}
if(vector == NULL)
{
/* create a new vector and fill it */
if((vector = attack_vector_init(corsaro)) == NULL)
{
corsaro_log(__func__, corsaro, "failed to create new attack vector");
return -1;
}
/* i think this may be buggy. do it the safe way for now
vector->initial_packet = corsaro_mincopy_packet(packet);
*/
vector->initial_packet_len = trace_get_capture_length(ltpacket);
if((vector->initial_packet = malloc(vector->initial_packet_len)) == NULL)
{
corsaro_log(__func__, corsaro, "could not malloc initial packet");
return -1;
}
if((pkt_buf = trace_get_packet_buffer(ltpacket,
&linktype, NULL)) == NULL)
{
corsaro_log(__func__, corsaro, "could not get packet buffer");
return -1;
}
memcpy(vector->initial_packet, pkt_buf, vector->initial_packet_len);
vector->attacker_ip = ntohl(ip_hdr->ip_dst.s_addr);
vector->responder_ip = ntohl(ip_hdr->ip_src.s_addr);
vector->target_ip = findme.target_ip;
vector->start_time = tv;
vector->ppm_window.window_start = tv.tv_sec;
/* add to the hash */
khiter = kh_put(av, STATE(corsaro)->attack_hash, vector, &khret);
}
assert(vector != NULL);
vector->packet_cnt++;
vector->interval_packet_cnt++;
vector->byte_cnt += ntohs(ip_hdr->ip_len);
vector->interval_byte_cnt += ntohs(ip_hdr->ip_len);
vector->latest_time = tv;
/* update the pps window */
attack_vector_update_ppm_window(vector, tv);
/* add the attacker ip to the hash */
kh_put(32xx, vector->attack_ip_hash, ntohl(ip_hdr->ip_dst.s_addr), &khret);
/* add the ports to the hashes */
kh_put(32xx, vector->attack_port_hash, attacker_port, &khret);
kh_put(32xx, vector->target_port_hash, target_port, &khret);
return 0;
}