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/*
* ZMap Copyright 2013 Regents of the University of Michigan
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy
* of the License at http://www.apache.org/licenses/LICENSE-2.0
*/
// probe module for performing TCP SYN scans
#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <unistd.h>
#include <string.h>
#include <assert.h>
#include "../../lib/includes.h"
#include "../fieldset.h"
#include "probe_modules.h"
#include "packet.h"
probe_module_t module_tcp_synscan;
static uint32_t num_ports;
int synscan_global_initialize(struct state_conf *state)
{
num_ports = state->source_port_last - state->source_port_first + 1;
return EXIT_SUCCESS;
}
int synscan_init_perthread(void* buf, macaddr_t *src,
macaddr_t *gw, port_h_t dst_port,
__attribute__((unused)) void **arg_ptr)
{
memset(buf, 0, MAX_PACKET_SIZE);
struct ether_header *eth_header = (struct ether_header *) buf;
make_eth_header(eth_header, src, gw);
struct ip *ip_header = (struct ip*)(&eth_header[1]);
uint16_t len = htons(sizeof(struct ip) + sizeof(struct tcphdr));
make_ip_header(ip_header, IPPROTO_TCP, len);
struct tcphdr *tcp_header = (struct tcphdr*)(&ip_header[1]);
make_tcp_header(tcp_header, dst_port, TH_SYN);
return EXIT_SUCCESS;
}
int synscan_make_packet(void *buf, ipaddr_n_t src_ip, ipaddr_n_t dst_ip,
uint32_t *validation, int probe_num, __attribute__((unused)) void *arg)
{
struct ether_header *eth_header = (struct ether_header *)buf;
struct ip *ip_header = (struct ip*)(&eth_header[1]);
struct tcphdr *tcp_header = (struct tcphdr*)(&ip_header[1]);
uint32_t tcp_seq = validation[0];
ip_header->ip_src.s_addr = src_ip;
ip_header->ip_dst.s_addr = dst_ip;
tcp_header->th_sport = htons(get_src_port(num_ports,
probe_num, validation));
tcp_header->th_seq = tcp_seq;
tcp_header->th_sum = 0;
tcp_header->th_sum = tcp_checksum(sizeof(struct tcphdr),
ip_header->ip_src.s_addr, ip_header->ip_dst.s_addr, tcp_header);
ip_header->ip_sum = 0;
ip_header->ip_sum = zmap_ip_checksum((unsigned short *) ip_header);
return EXIT_SUCCESS;
}
void synscan_print_packet(FILE *fp, void* packet)
{
struct ether_header *ethh = (struct ether_header *) packet;
struct ip *iph = (struct ip *) &ethh[1];
struct tcphdr *tcph = (struct tcphdr *) &iph[1];
fprintf(fp, "tcp { source: %u | dest: %u | seq: %u | checksum: %#04X }\n",
ntohs(tcph->th_sport),
ntohs(tcph->th_dport),
ntohl(tcph->th_seq),
ntohs(tcph->th_sum));
fprintf_ip_header(fp, iph);
fprintf_eth_header(fp, ethh);
fprintf(fp, "------------------------------------------------------\n");
}
int synscan_validate_packet(const struct ip *ip_hdr, uint32_t len,
__attribute__((unused))uint32_t *src_ip,
uint32_t *validation)
{
if (ip_hdr->ip_p != IPPROTO_TCP) {
return 0;
}
if ((4*ip_hdr->ip_hl + sizeof(struct tcphdr)) > len) {
// buffer not large enough to contain expected tcp header
return 0;
}
struct tcphdr *tcp = (struct tcphdr*)((char *) ip_hdr + 4*ip_hdr->ip_hl);
uint16_t sport = tcp->th_sport;
uint16_t dport = tcp->th_dport;
// validate source port
if (ntohs(sport) != zconf.target_port) {
return 0;
}
// validate destination port
if (!check_dst_port(ntohs(dport), num_ports, validation)) {
return 0;
}
// validate tcp acknowledgement number
if (htonl(tcp->th_ack) != htonl(validation[0])+1) {
return 0;
}
return 1;
}
void synscan_process_packet(const u_char *packet,
__attribute__((unused)) uint32_t len, fieldset_t *fs,
__attribute__((unused)) uint32_t *validation)
{
struct ip *ip_hdr = (struct ip *)&packet[sizeof(struct ether_header)];
struct tcphdr *tcp = (struct tcphdr*)((char *)ip_hdr
+ 4*ip_hdr->ip_hl);
fs_add_uint64(fs, "sport", (uint64_t) ntohs(tcp->th_sport));
fs_add_uint64(fs, "dport", (uint64_t) ntohs(tcp->th_dport));
fs_add_uint64(fs, "seqnum", (uint64_t) ntohl(tcp->th_seq));
fs_add_uint64(fs, "acknum", (uint64_t) ntohl(tcp->th_ack));
fs_add_uint64(fs, "window", (uint64_t) ntohs(tcp->th_win));
if (tcp->th_flags & TH_RST) { // RST packet
fs_add_string(fs, "classification", (char*) "rst", 0);
fs_add_bool(fs, "success", 0);
} else { // SYNACK packet
fs_add_string(fs, "classification", (char*) "synack", 0);
fs_add_bool(fs, "success", 1);
}
}
static fielddef_t fields[] = {
{.name = "sport", .type = "int", .desc = "TCP source port"},
{.name = "dport", .type = "int", .desc = "TCP destination port"},
{.name = "seqnum", .type = "int", .desc = "TCP sequence number"},
{.name = "acknum", .type = "int", .desc = "TCP acknowledgement number"},
{.name = "window", .type = "int", .desc = "TCP window"},
{.name = "classification", .type="string", .desc = "packet classification"},
{.name = "success", .type="bool", .desc = "is response considered success"}
};
probe_module_t module_tcp_synscan = {
.name = "tcp_synscan",
.packet_length = 54,
.pcap_filter = "tcp && tcp[13] & 4 != 0 || tcp[13] == 18",
.pcap_snaplen = 96,
.port_args = 1,
.global_initialize = &synscan_global_initialize,
.thread_initialize = &synscan_init_perthread,
.make_packet = &synscan_make_packet,
.print_packet = &synscan_print_packet,
.process_packet = &synscan_process_packet,
.validate_packet = &synscan_validate_packet,
.close = NULL,
.helptext = "Probe module that sends a TCP SYN packet to a specific "
"port. Possible classifications are: synack and rst. A "
"SYN-ACK packet is considered a success and a reset packet "
"is considered a failed response.",
.output_type = OUTPUT_TYPE_STATIC,
.fields = fields,
.numfields = 7};