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#ifndef WIN32
#include <netinet/in.h>
#include <arpa/inet.h>
#include <pthread.h>
#endif
#include <sys/time.h>
#include "ptunnel.h"
#include "pkt.h"
#include "pdesc.h"
#include "options.h"
#include "utils.h"
/* handle_proxy_packet:
* Processes incoming ICMP packets for the proxy. The packet can come either from the
* packet capture lib, or from the actual socket or both.
* Input: A buffer pointing at the start of an IP header, the buffer length and the proxy
* descriptor chain.
*/
void handle_packet(char *buf, unsigned bytes, int is_pcap, struct sockaddr_in *addr, int icmp_sock) {
ip_packet_t *ip_pkt;
icmp_echo_packet_t *pkt;
ping_tunnel_pkt_t *pt_pkt;
proxy_desc_t *cur;
uint32_t type_flag, pkt_flag, init_state, proxy_flag;
challenge_t *challenge;
struct timeval tt;
proxy_flag = kProxy_flag;
if (bytes < sizeof(icmp_echo_packet_t)+sizeof(ping_tunnel_pkt_t))
pt_log(kLog_verbose, "Skipping this packet - too short. "
"Expect: %d+%d = %d ; Got: %d\n",
sizeof(icmp_echo_packet_t),
sizeof(ping_tunnel_pkt_t),
sizeof(icmp_echo_packet_t) +
sizeof(ping_tunnel_pkt_t), bytes);
else {
if (opts.udp) {
ip_pkt = 0;
pkt = (icmp_echo_packet_t*)buf;
pt_pkt = (ping_tunnel_pkt_t*)pkt->data;
}
else {
ip_pkt = (ip_packet_t*)buf;
pkt = (icmp_echo_packet_t*)ip_pkt->data;
pt_pkt = (ping_tunnel_pkt_t*)pkt->data;
}
if (ntohl(pt_pkt->magic) == opts.magic) {
pt_pkt->state = ntohl(pt_pkt->state);
pkt->identifier = ntohs(pkt->identifier);
pt_pkt->id_no = ntohs(pt_pkt->id_no);
pt_pkt->seq_no = ntohs(pt_pkt->seq_no);
/* Find the relevant connection, if it exists */
pthread_mutex_lock(&chain_lock);
for (cur=chain;cur;cur=cur->next) {
if (cur->id_no == pt_pkt->id_no)
break;
}
pthread_mutex_unlock(&chain_lock);
/* Handle the packet if it comes from "the other end." This is a bit tricky
* to get right, since we receive both our own and the other end's packets.
* Basically, a proxy will accept any packet from a user, regardless if it
* has a valid connection or not. A user will only accept the packet if there
* exists a connection to handle it.
*/
if (cur) {
type_flag = cur->type_flag;
if (type_flag == (uint32_t)kProxy_flag)
cur->icmp_id = pkt->identifier;
if (!is_pcap)
cur->xfer.icmp_in++;
}
else
type_flag = kProxy_flag;
pkt_flag = pt_pkt->state & kFlag_mask;
pt_pkt->state &= ~kFlag_mask;
pt_log(kLog_sendrecv, "Recv: %d [%d] bytes "
"[seq = %d] [type = %s] "
"[ack = %d] [icmp = %d] "
"[user = %s] [pcap = %d]\n",
bytes, ntohl(pt_pkt->data_len),
pt_pkt->seq_no, state_name[pt_pkt->state & (~kFlag_mask)],
ntohl(pt_pkt->ack), pkt->type,
(pkt_flag == kUser_flag ? "yes" : "no"), is_pcap);
/* This test essentially verifies that the packet comes from someone who isn't us. */
if ((pkt_flag == kUser_flag && type_flag == proxy_flag) ||
(pkt_flag == proxy_flag && type_flag == kUser_flag))
{
pt_pkt->data_len = ntohl(pt_pkt->data_len);
pt_pkt->ack = ntohl(pt_pkt->ack);
if (pt_pkt->state == kProxy_start) {
if (!cur && type_flag == proxy_flag) {
pt_log(kLog_info, "Incoming tunnel request from %s.\n",
inet_ntoa(*(struct in_addr *)&addr->sin_addr));
gettimeofday(&tt, 0);
if (tt.tv_sec < seq_expiry_tbl[pt_pkt->id_no]) {
pt_log(kLog_verbose, "Dropping request: ID was recently in use.\n");
return;
}
pt_log(kLog_info, "Starting new session to %s:%d with ID %d\n",
inet_ntoa(*(struct in_addr *)&pt_pkt->dst_ip),
ntohl(pt_pkt->dst_port), pt_pkt->id_no);
if ((opts.given_dst_ip && opts.given_dst_ip != pt_pkt->dst_ip) ||
((uint32_t)-1 != opts.given_dst_port && opts.given_dst_port != ntohl(pt_pkt->dst_port)))
{
pt_log(kLog_info, "Destination administratively prohibited!\n");
return;
}
if (opts.password)
init_state = kProto_authenticate;
else
init_state = kProto_data;
cur = create_and_insert_proxy_desc(pt_pkt->id_no, pkt->identifier, 0,
addr, pt_pkt->dst_ip,
ntohl(pt_pkt->dst_port),
init_state, kProxy_flag);
if (init_state == kProto_authenticate) {
pt_log(kLog_debug, "Sending authentication challenge..\n");
/* Send challenge */
cur->challenge = generate_challenge();
memcpy(cur->buf, cur->challenge, sizeof(challenge_t));
queue_packet(icmp_sock, cur->pkt_type, cur->buf,
sizeof(challenge_t), cur->id_no,
cur->icmp_id, &cur->my_seq, cur->send_ring,
&cur->send_idx, &cur->send_wait_ack, 0, 0,
kProto_authenticate | cur->type_flag,
&cur->dest_addr, cur->next_remote_seq,
&cur->send_first_ack, &cur->ping_seq);
}
}
else if (type_flag == kUser_flag) {
pt_log(kLog_error, "Dropping proxy session request - we are not a proxy!\n");
return;
}
else
pt_log(kLog_error, "Dropping duplicate proxy session request.\n");
}
else if (cur && pt_pkt->state == kProto_authenticate) {
/* Sanity check packet length, and make sure it matches what we expect */
if (pt_pkt->data_len != sizeof(challenge_t)) {
pt_log(kLog_error, "Received challenge packet, but data length "
"is not as expected.\n");
pt_log(kLog_debug, "Data length: %d Expected: %d\n",
pt_pkt->data_len, sizeof (challenge_t));
cur->should_remove = 1;
return;
}
/* Prevent packet data from being forwarded over TCP! */
pt_pkt->data_len = 0;
challenge = (challenge_t*)pt_pkt->data;
/* If client: Compute response to challenge */
if (type_flag == kUser_flag) {
if (!opts.password) {
pt_log(kLog_error, "This proxy requires a password! "
"Please supply one usin g the -x switch.\n");
send_termination_msg(cur, icmp_sock);
cur->should_remove = 1;
return;
}
pt_log(kLog_debug, "Got authentication challenge - sending response\n");
generate_response(challenge);
queue_packet(icmp_sock, cur->pkt_type, (char*)challenge,
sizeof(challenge_t), cur->id_no, cur->icmp_id,
&cur->my_seq, cur->send_ring, &cur->send_idx,
&cur->send_wait_ack, 0, 0,
kProto_authenticate | cur->type_flag, &cur->dest_addr,
cur->next_remote_seq, &cur->send_first_ack, &cur-> ping_seq);
/* We have authenticated locally.
* It's up to the proxy now if it accepts our response or not..
*/
cur->authenticated = 1;
handle_data(pkt, bytes, cur->recv_ring, &cur->recv_wait_send,
&cur->recv_idx, &cur->next_remote_seq);
return;
}
/* If proxy: Handle client's response to challenge */
else if (type_flag == proxy_flag) {
pt_log(kLog_debug, "Received remote challenge response.\n");
if (validate_challenge(cur->challenge, challenge) ||
cur->authenticated)
{
pt_log(kLog_verbose, "Remote end authenticated successfully.\n");
/* Authentication has succeeded, so now we can proceed
* to handle incoming TCP data.
*/
cur->authenticated = 1;
cur->state = kProto_data;
/* Insert the packet into the receive ring, to avoid
* confusing the reliab ility mechanism.
*/
handle_data(pkt, bytes, cur->recv_ring, &cur->recv_wait_send,
&cur->recv_idx, &cur->next_remote_seq);
}
else {
pt_log(kLog_info, "Remote end failed authentication.\n");
send_termination_msg(cur, icmp_sock);
cur->should_remove = 1;
}
return;
}
}
/* Handle close-messages for connections we know about */
if (cur && pt_pkt->state == kProto_close) {
pt_log(kLog_info, "Received session close from remote peer.\n");
cur->should_remove = 1;
return;
}
/* The proxy will ignore any other packets from the client
* until it has been authenticated. The packet resend mechanism
* insures that this isn't problematic.
*/
if (type_flag == proxy_flag && opts.password &&
cur && !cur->authenticated)
{
pt_log(kLog_debug, "Ignoring packet with seq-no %d "
"- not authenticated yet.\n", pt_pkt->seq_no);
return;
}
if (cur && cur->sock) {
if (pt_pkt->state == kProto_data || pt_pkt->state == kProxy_start ||
pt_pkt->state == kProto_ack)
{
handle_data(pkt, bytes, cur->recv_ring, &cur->recv_wait_send,
&cur->recv_idx, &cur->next_remote_seq);
}
handle_ack((uint16_t)pt_pkt->ack, cur->send_ring, &cur->send_wait_ack,
0, cur->send_idx, &cur->send_first_ack, &cur->remote_ack_val,
is_pcap);
cur->last_activity = time_as_double();
}
}
}
else
pt_log(kLog_verbose, "Ignored incoming packet.\n");
}
}
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