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desync.c
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#define _GNU_SOURCE
#include <string.h>
#include <errno.h>
#include "desync.h"
#include "protocol.h"
#include "params.h"
#include "helpers.h"
#include "hostlist.h"
#include "ipset.h"
#include "conntrack.h"
const char *fake_http_request_default = "GET / HTTP/1.1\r\nHost: www.iana.org\r\n"
"User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:109.0) Gecko/20100101 Firefox/109.0\r\n"
"Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8\r\n"
"Accept-Encoding: gzip, deflate, br\r\n\r\n";
// random : +11 size 32
// random : +44 size 32
// sni : gatech.edu +125 size 11
const uint8_t fake_tls_clienthello_default[648] = {
0x16,0x03,0x01,0x02,0x83,0x01,0x00,0x02,0x7f,0x03,0x03,0x98,0xfb,0x69,0x1d,0x31,
0x66,0xc4,0xd8,0x07,0x25,0x2b,0x74,0x47,0x01,0x44,0x09,0x08,0xcf,0x13,0x67,0xe0,
0x46,0x19,0x1f,0xcb,0xee,0xe6,0x8e,0x33,0xb9,0x91,0xa0,0x20,0xf2,0xed,0x56,0x73,
0xa4,0x0a,0xce,0xa6,0xad,0xd2,0xfd,0x71,0xb8,0xb9,0xfd,0x06,0x0e,0xdd,0xf0,0x57,
0x37,0x7d,0x96,0xb5,0x80,0x6e,0x54,0xe2,0x15,0xce,0x5f,0xff,0x00,0x22,0x13,0x01,
0x13,0x03,0x13,0x02,0xc0,0x2b,0xc0,0x2f,0xcc,0xa9,0xcc,0xa8,0xc0,0x2c,0xc0,0x30,
0xc0,0x0a,0xc0,0x09,0xc0,0x13,0xc0,0x14,0x00,0x9c,0x00,0x9d,0x00,0x2f,0x00,0x35,
0x01,0x00,0x02,0x14,0x00,0x00,0x00,0x0f,0x00,0x0d,0x00,0x00,0x0a,0x67,0x61,0x74,
0x65,0x63,0x68,0x2e,0x65,0x64,0x75,0x00,0x17,0x00,0x00,0xff,0x01,0x00,0x01,0x00,
0x00,0x0a,0x00,0x0e,0x00,0x0c,0x00,0x1d,0x00,0x17,0x00,0x18,0x00,0x19,0x01,0x00,
0x01,0x01,0x00,0x0b,0x00,0x02,0x01,0x00,0x00,0x10,0x00,0x0e,0x00,0x0c,0x02,0x68,
0x32,0x08,0x68,0x74,0x74,0x70,0x2f,0x31,0x2e,0x31,0x00,0x05,0x00,0x05,0x01,0x00,
0x00,0x00,0x00,0x00,0x22,0x00,0x0a,0x00,0x08,0x04,0x03,0x05,0x03,0x06,0x03,0x02,
0x03,0x00,0x33,0x00,0x6b,0x00,0x69,0x00,0x1d,0x00,0x20,0x72,0xe5,0xce,0x58,0x31,
0x3c,0x08,0xaa,0x2f,0xa8,0x40,0xe7,0x7a,0xdf,0x46,0x5b,0x63,0x62,0xc7,0xfa,0x49,
0x18,0xac,0xa1,0x00,0x7c,0x42,0xc5,0x02,0x94,0x5c,0x44,0x00,0x17,0x00,0x41,0x04,
0x8f,0x3e,0x5f,0xd4,0x7f,0x37,0x47,0xd3,0x33,0x70,0x38,0x7f,0x11,0x35,0xc1,0x55,
0x8a,0x6c,0xc7,0x5a,0xd4,0xf7,0x31,0xbb,0x9e,0xee,0xd1,0x8f,0x74,0xdd,0x9b,0xbb,
0x91,0xa1,0x72,0xda,0xeb,0xf6,0xc6,0x82,0x84,0xfe,0xb7,0xfd,0x7b,0xe1,0x9f,0xd2,
0xb9,0x3e,0x83,0xa6,0x9c,0xac,0x81,0xe2,0x00,0xd5,0x19,0x55,0x91,0xa7,0x0c,0x29,
0x00,0x2b,0x00,0x05,0x04,0x03,0x04,0x03,0x03,0x00,0x0d,0x00,0x18,0x00,0x16,0x04,
0x03,0x05,0x03,0x06,0x03,0x08,0x04,0x08,0x05,0x08,0x06,0x04,0x01,0x05,0x01,0x06,
0x01,0x02,0x03,0x02,0x01,0x00,0x1c,0x00,0x02,0x40,0x01,0xfe,0x0d,0x01,0x19,0x00,
0x00,0x01,0x00,0x01,0xfe,0x00,0x20,0xae,0x8b,0x30,0x3c,0xf0,0xa9,0x0d,0xa1,0x69,
0x95,0xb8,0xe2,0xed,0x08,0x6d,0x48,0xdf,0xf7,0x5b,0x9d,0x66,0xef,0x15,0x97,0xbc,
0x2c,0x99,0x91,0x12,0x7a,0x35,0xd0,0x00,0xef,0xb1,0x8d,0xff,0x61,0x57,0x52,0xef,
0xd6,0xea,0xbf,0xf3,0x6d,0x78,0x14,0x38,0xff,0xeb,0x58,0xe8,0x9d,0x59,0x4b,0xd5,
0x9f,0x59,0x12,0xf9,0x03,0x9a,0x20,0x37,0x85,0x77,0xb1,0x4c,0xd8,0xef,0xa6,0xc8,
0x54,0x8d,0x07,0x27,0x95,0xce,0xd5,0x37,0x4d,0x69,0x18,0xd4,0xfd,0x5e,0xdf,0x64,
0xcc,0x10,0x2f,0x7f,0x0e,0xc9,0xfd,0xd4,0xd0,0x18,0x61,0x1b,0x57,0x8f,0x41,0x7f,
0x6f,0x4f,0x5c,0xad,0x04,0xc6,0x5e,0x74,0x54,0x87,0xba,0x28,0xe6,0x11,0x0b,0x9d,
0x3f,0x0b,0x6d,0xf4,0x2d,0xfc,0x31,0x4e,0xfd,0x49,0xe7,0x15,0x96,0xaf,0xee,0x9a,
0x48,0x1b,0xae,0x5e,0x7c,0x20,0xbe,0xb4,0xec,0x68,0xb6,0x74,0x22,0xa0,0xec,0xff,
0x19,0x96,0xe4,0x10,0x8f,0x3c,0x91,0x88,0xa1,0xcc,0x78,0xef,0x4e,0x0e,0xe3,0xb6,
0x57,0x8c,0x33,0xef,0xaa,0xb0,0x1d,0x45,0x1c,0x02,0x4c,0xe2,0x80,0x30,0xe8,0x48,
0x7a,0x09,0x71,0x94,0x7c,0xb6,0x75,0x81,0x1c,0xae,0xe3,0x3f,0xde,0xea,0x2b,0x45,
0xcc,0xe3,0x64,0x09,0xf7,0x60,0x26,0x0c,0x7d,0xad,0x55,0x65,0xb6,0xf5,0x85,0x04,
0x64,0x2f,0x97,0xd0,0x6a,0x06,0x36,0xcd,0x25,0xda,0x51,0xab,0xd6,0xf7,0x5e,0xeb,
0xd4,0x03,0x39,0xa4,0xc4,0x2a,0x9c,0x17,0xe8,0xb0,0x9f,0xc0,0xd3,0x8c,0x76,0xdd,
0xa1,0x0b,0x76,0x9f,0x23,0xfa,0xed,0xfb,0xd7,0x78,0x0f,0x00,0xf7,0x45,0x03,0x04,
0x84,0x66,0x6b,0xec,0xc7,0xed,0xbc,0xe4
};
#define PKTDATA_MAXDUMP 32
#define IP_MAXDUMP 80
bool desync_valid_zero_stage(enum dpi_desync_mode mode)
{
return mode==DESYNC_SYNACK || mode==DESYNC_SYNDATA;
}
bool desync_valid_first_stage(enum dpi_desync_mode mode)
{
return mode==DESYNC_FAKE || mode==DESYNC_FAKE_KNOWN || mode==DESYNC_RST || mode==DESYNC_RSTACK || mode==DESYNC_HOPBYHOP || mode==DESYNC_DESTOPT || mode==DESYNC_IPFRAG1;
}
bool desync_only_first_stage(enum dpi_desync_mode mode)
{
return false;
}
bool desync_valid_second_stage(enum dpi_desync_mode mode)
{
return mode==DESYNC_NONE || mode==DESYNC_FAKEDDISORDER || mode==DESYNC_FAKEDSPLIT || mode==DESYNC_MULTISPLIT || mode==DESYNC_MULTIDISORDER || mode==DESYNC_IPFRAG2 || mode==DESYNC_UDPLEN || mode==DESYNC_TAMPER;
}
bool desync_valid_second_stage_tcp(enum dpi_desync_mode mode)
{
return mode==DESYNC_NONE || mode==DESYNC_FAKEDDISORDER || mode==DESYNC_FAKEDSPLIT || mode==DESYNC_MULTISPLIT || mode==DESYNC_MULTIDISORDER || mode==DESYNC_IPFRAG2;
}
bool desync_valid_second_stage_udp(enum dpi_desync_mode mode)
{
return mode==DESYNC_NONE || mode==DESYNC_UDPLEN || mode==DESYNC_TAMPER || mode==DESYNC_IPFRAG2;
}
enum dpi_desync_mode desync_mode_from_string(const char *s)
{
if (!s)
return DESYNC_NONE;
else if (!strcmp(s,"fake"))
return DESYNC_FAKE;
else if (!strcmp(s,"fakeknown"))
return DESYNC_FAKE_KNOWN;
else if (!strcmp(s,"rst"))
return DESYNC_RST;
else if (!strcmp(s,"rstack"))
return DESYNC_RSTACK;
else if (!strcmp(s,"synack"))
return DESYNC_SYNACK;
else if (!strcmp(s,"syndata"))
return DESYNC_SYNDATA;
else if (!strcmp(s,"fakeddisorder") || !strcmp(s,"disorder"))
return DESYNC_FAKEDDISORDER;
else if (!strcmp(s,"fakedsplit") || !strcmp(s,"split"))
return DESYNC_FAKEDSPLIT;
else if (!strcmp(s,"multisplit") || !strcmp(s,"split2"))
return DESYNC_MULTISPLIT;
else if (!strcmp(s,"multidisorder") || !strcmp(s,"disorder2"))
return DESYNC_MULTIDISORDER;
else if (!strcmp(s,"ipfrag2"))
return DESYNC_IPFRAG2;
else if (!strcmp(s,"hopbyhop"))
return DESYNC_HOPBYHOP;
else if (!strcmp(s,"destopt"))
return DESYNC_DESTOPT;
else if (!strcmp(s,"ipfrag1"))
return DESYNC_IPFRAG1;
else if (!strcmp(s,"udplen"))
return DESYNC_UDPLEN;
else if (!strcmp(s,"tamper"))
return DESYNC_TAMPER;
return DESYNC_INVALID;
}
static bool dp_match(
struct desync_profile *dp,
uint8_t l3proto, const struct sockaddr *dest, const char *hostname, t_l7proto l7proto,
bool *bCheckDone, bool *bCheckResult, bool *bExcluded)
{
bool bHostlistsEmpty;
if (bCheckDone) *bCheckDone = false;
if (!HostlistsReloadCheckForProfile(dp)) return false;
if ((dest->sa_family==AF_INET && !dp->filter_ipv4) || (dest->sa_family==AF_INET6 && !dp->filter_ipv6))
// L3 filter does not match
return false;
if ((l3proto==IPPROTO_TCP && !port_filters_in_range(&dp->pf_tcp,saport(dest))) || (l3proto==IPPROTO_UDP && !port_filters_in_range(&dp->pf_udp,saport(dest))))
// L4 filter does not match
return false;
if (dp->filter_l7 && !l7_proto_match(l7proto, dp->filter_l7))
// L7 filter does not match
return false;
bHostlistsEmpty = PROFILE_HOSTLISTS_EMPTY(dp);
if (!dp->hostlist_auto && !hostname && !bHostlistsEmpty)
// avoid cpu consuming ipset check. profile cannot win if regular hostlists are present without auto hostlist and hostname is unknown.
return false;
if (!IpsetCheck(dp, dest->sa_family==AF_INET ? &((struct sockaddr_in*)dest)->sin_addr : NULL, dest->sa_family==AF_INET6 ? &((struct sockaddr_in6*)dest)->sin6_addr : NULL))
// target ip does not match
return false;
// autohostlist profile matching l3/l4/l7 filter always win
if (dp->hostlist_auto) return true;
if (bHostlistsEmpty)
// profile without hostlist filter wins
return true;
else
{
// if hostlists are present profile matches only if hostname is known and satisfy profile hostlists
if (hostname)
{
if (bCheckDone) *bCheckDone = true;
bool b;
b = HostlistCheck(dp, hostname, bExcluded, true);
if (bCheckResult) *bCheckResult = b;
return b;
}
}
return false;
}
static struct desync_profile *dp_find(
struct desync_profile_list_head *head,
uint8_t l3proto, const struct sockaddr *dest, const char *hostname, t_l7proto l7proto,
bool *bCheckDone, bool *bCheckResult, bool *bExcluded)
{
struct desync_profile_list *dpl;
if (params.debug)
{
char ip_port[48];
ntop46_port(dest, ip_port,sizeof(ip_port));
DLOG("desync profile search for %s target=%s l7proto=%s hostname='%s'\n", proto_name(l3proto), ip_port, l7proto_str(l7proto), hostname ? hostname : "");
}
if (bCheckDone) *bCheckDone = false;
LIST_FOREACH(dpl, head, next)
{
if (dp_match(&dpl->dp,l3proto,dest,hostname,l7proto,bCheckDone,bCheckResult,bExcluded))
{
DLOG("desync profile %d matches\n",dpl->dp.n);
return &dpl->dp;
}
}
DLOG("desync profile not found\n");
return NULL;
}
// auto creates internal socket and uses it for subsequent calls
static bool rawsend_rep(int repeats, const struct sockaddr* dst,uint32_t fwmark,const char *ifout,const void *data,size_t len)
{
for (int i=0;i<repeats;i++)
if (!rawsend(dst,fwmark,ifout,data,len))
return false;
return true;
}
static uint64_t cutoff_get_limit(const t_ctrack *ctrack, char mode)
{
switch(mode)
{
case 'n': return ctrack->pcounter_orig;
case 'd': return ctrack->pdcounter_orig;
case 's': return ctrack->seq_last - ctrack->seq0;
default: return 0;
}
}
static bool cutoff_test(const t_ctrack *ctrack, uint64_t cutoff, char mode)
{
return cutoff && cutoff_get_limit(ctrack, mode)>=cutoff;
}
static void maybe_cutoff(t_ctrack *ctrack, uint8_t proto)
{
if (ctrack && ctrack->dp)
{
if (proto==IPPROTO_TCP)
ctrack->b_wssize_cutoff |= cutoff_test(ctrack, ctrack->dp->wssize_cutoff, ctrack->dp->wssize_cutoff_mode);
ctrack->b_desync_cutoff |= cutoff_test(ctrack, ctrack->dp->desync_cutoff, ctrack->dp->desync_cutoff_mode);
// in MULTI STRATEGY concept conntrack entry holds desync profile
// we do not want to remove conntrack entries ASAP anymore
/*
// we do not need conntrack entry anymore if all cutoff conditions are either not defined or reached
// do not drop udp entry because it will be recreated when next packet arrives
if (proto==IPPROTO_TCP)
ctrack->b_cutoff |= \
(!ctrack->dp->wssize || ctrack->b_wssize_cutoff) &&
(!ctrack->dp->desync_cutoff || ctrack->b_desync_cutoff) &&
(!ctrack->hostname_ah_check || ctrack->req_retrans_counter==RETRANS_COUNTER_STOP) &&
ReasmIsEmpty(&ctrack->reasm_orig);
*/
}
}
static void wssize_cutoff(t_ctrack *ctrack)
{
if (ctrack)
{
ctrack->b_wssize_cutoff = true;
maybe_cutoff(ctrack, IPPROTO_TCP);
}
}
static void forced_wssize_cutoff(t_ctrack *ctrack)
{
if (ctrack && ctrack->dp && ctrack->dp->wssize && !ctrack->b_wssize_cutoff)
{
DLOG("forced wssize-cutoff\n");
wssize_cutoff(ctrack);
}
}
static void ctrack_stop_retrans_counter(t_ctrack *ctrack)
{
if (ctrack && ctrack->hostname_ah_check)
{
ctrack->req_retrans_counter = RETRANS_COUNTER_STOP;
maybe_cutoff(ctrack, IPPROTO_TCP);
}
}
static void auto_hostlist_reset_fail_counter(struct desync_profile *dp, const char *hostname, const char *client_ip_port, t_l7proto l7proto)
{
if (hostname)
{
hostfail_pool *fail_counter;
fail_counter = HostFailPoolFind(dp->hostlist_auto_fail_counters, hostname);
if (fail_counter)
{
HostFailPoolDel(&dp->hostlist_auto_fail_counters, fail_counter);
DLOG("auto hostlist (profile %d) : %s : fail counter reset. website is working.\n", dp->n, hostname);
HOSTLIST_DEBUGLOG_APPEND("%s : profile %d : client %s : proto %s : fail counter reset. website is working.", hostname, dp->n, client_ip_port, l7proto_str(l7proto));
}
}
}
// return true if retrans trigger fires
static bool auto_hostlist_retrans(t_ctrack *ctrack, uint8_t l4proto, int threshold, const char *client_ip_port, t_l7proto l7proto)
{
if (ctrack && ctrack->dp && ctrack->hostname_ah_check && ctrack->req_retrans_counter!=RETRANS_COUNTER_STOP)
{
if (l4proto==IPPROTO_TCP)
{
if (!ctrack->req_seq_finalized || ctrack->req_seq_abandoned)
return false;
if (!seq_within(ctrack->seq_last, ctrack->req_seq_start, ctrack->req_seq_end))
{
DLOG("req retrans : tcp seq %u not within the req range %u-%u. stop tracking.\n", ctrack->seq_last, ctrack->req_seq_start, ctrack->req_seq_end);
ctrack_stop_retrans_counter(ctrack);
auto_hostlist_reset_fail_counter(ctrack->dp, ctrack->hostname, client_ip_port, l7proto);
return false;
}
}
ctrack->req_retrans_counter++;
if (ctrack->req_retrans_counter >= threshold)
{
DLOG("req retrans threshold reached : %u/%u\n",ctrack->req_retrans_counter, threshold);
ctrack_stop_retrans_counter(ctrack);
return true;
}
DLOG("req retrans counter : %u/%u\n",ctrack->req_retrans_counter, threshold);
}
return false;
}
static void auto_hostlist_failed(struct desync_profile *dp, const char *hostname, const char *client_ip_port, t_l7proto l7proto)
{
hostfail_pool *fail_counter;
fail_counter = HostFailPoolFind(dp->hostlist_auto_fail_counters, hostname);
if (!fail_counter)
{
fail_counter = HostFailPoolAdd(&dp->hostlist_auto_fail_counters, hostname, dp->hostlist_auto_fail_time);
if (!fail_counter)
{
DLOG_ERR("HostFailPoolAdd: out of memory\n");
return;
}
}
fail_counter->counter++;
DLOG("auto hostlist (profile %d) : %s : fail counter %d/%d\n", dp->n, hostname, fail_counter->counter, dp->hostlist_auto_fail_threshold);
HOSTLIST_DEBUGLOG_APPEND("%s : profile %d : client %s : proto %s : fail counter %d/%d", hostname, dp->n, client_ip_port, l7proto_str(l7proto), fail_counter->counter, dp->hostlist_auto_fail_threshold);
if (fail_counter->counter >= dp->hostlist_auto_fail_threshold)
{
DLOG("auto hostlist (profile %d) : fail threshold reached. about to add %s to auto hostlist\n", dp->n, hostname);
HostFailPoolDel(&dp->hostlist_auto_fail_counters, fail_counter);
DLOG("auto hostlist (profile %d) : rechecking %s to avoid duplicates\n", dp->n, hostname);
bool bExcluded=false;
if (!HostlistCheck(dp, hostname, &bExcluded, false) && !bExcluded)
{
DLOG("auto hostlist (profile %d) : adding %s to %s\n", dp->n, hostname, dp->hostlist_auto->filename);
HOSTLIST_DEBUGLOG_APPEND("%s : profile %d : client %s : proto %s : adding to %s", hostname, dp->n, client_ip_port, l7proto_str(l7proto), dp->hostlist_auto->filename);
if (!StrPoolAddStr(&dp->hostlist_auto->hostlist, hostname))
{
DLOG_ERR("StrPoolAddStr out of memory\n");
return;
}
if (!append_to_list_file(dp->hostlist_auto->filename, hostname))
{
DLOG_PERROR("write to auto hostlist:");
return;
}
if (!file_mod_signature(dp->hostlist_auto->filename, &dp->hostlist_auto->mod_sig))
DLOG_PERROR("file_mod_signature");
}
else
{
DLOG("auto hostlist (profile %d) : NOT adding %s\n", dp->n, hostname);
HOSTLIST_DEBUGLOG_APPEND("%s : profile %d : client %s : proto %s : NOT adding, duplicate detected", hostname, dp->n, client_ip_port, l7proto_str(l7proto));
}
}
}
static void process_retrans_fail(t_ctrack *ctrack, uint8_t proto, const struct sockaddr *client)
{
char client_ip_port[48];
if (*params.hostlist_auto_debuglog)
ntop46_port((struct sockaddr*)client,client_ip_port,sizeof(client_ip_port));
else
*client_ip_port=0;
if (ctrack && ctrack->dp && ctrack->hostname && auto_hostlist_retrans(ctrack, proto, ctrack->dp->hostlist_auto_retrans_threshold, client_ip_port, ctrack->l7proto))
{
HOSTLIST_DEBUGLOG_APPEND("%s : profile %d : client %s : proto %s : retrans threshold reached", ctrack->hostname, ctrack->dp->n, client_ip_port, l7proto_str(ctrack->l7proto));
auto_hostlist_failed(ctrack->dp, ctrack->hostname, client_ip_port, ctrack->l7proto);
}
}
static bool send_delayed(t_ctrack *ctrack)
{
if (!rawpacket_queue_empty(&ctrack->delayed))
{
DLOG("SENDING %u delayed packets\n", rawpacket_queue_count(&ctrack->delayed));
return rawsend_queue(&ctrack->delayed);
}
return true;
}
static bool reasm_start(t_ctrack *ctrack, t_reassemble *reasm, uint8_t proto, size_t sz, size_t szMax, const uint8_t *data_payload, size_t len_payload)
{
ReasmClear(reasm);
if (sz<=szMax)
{
uint32_t seq = (proto==IPPROTO_TCP) ? ctrack->seq_last : 0;
if (ReasmInit(reasm,sz,seq))
{
ReasmFeed(reasm,seq,data_payload,len_payload);
DLOG("starting reassemble. now we have %zu/%zu\n",reasm->size_present,reasm->size);
return true;
}
else
DLOG("reassemble init failed. out of memory\n");
}
else
DLOG("unexpected large payload for reassemble: size=%zu\n",sz);
return false;
}
static bool reasm_orig_start(t_ctrack *ctrack, uint8_t proto, size_t sz, size_t szMax, const uint8_t *data_payload, size_t len_payload)
{
return reasm_start(ctrack,&ctrack->reasm_orig,proto,sz,szMax,data_payload,len_payload);
}
static bool reasm_feed(t_ctrack *ctrack, t_reassemble *reasm, uint8_t proto, const uint8_t *data_payload, size_t len_payload)
{
if (ctrack && !ReasmIsEmpty(reasm))
{
uint32_t seq = (proto==IPPROTO_TCP) ? ctrack->seq_last : (uint32_t)reasm->size_present;
if (ReasmFeed(reasm, seq, data_payload, len_payload))
{
DLOG("reassemble : feeding data payload size=%zu. now we have %zu/%zu\n", len_payload,reasm->size_present,reasm->size);
return true;
}
else
{
ReasmClear(reasm);
DLOG("reassemble session failed\n");
send_delayed(ctrack);
}
}
return false;
}
static bool reasm_orig_feed(t_ctrack *ctrack, uint8_t proto, const uint8_t *data_payload, size_t len_payload)
{
return reasm_feed(ctrack, &ctrack->reasm_orig, proto, data_payload, len_payload);
}
static void reasm_orig_stop(t_ctrack *ctrack, const char *dlog_msg)
{
if (ctrack)
{
if (!ReasmIsEmpty(&ctrack->reasm_orig))
{
DLOG("%s",dlog_msg);
ReasmClear(&ctrack->reasm_orig);
}
send_delayed(ctrack);
}
}
static void reasm_orig_cancel(t_ctrack *ctrack)
{
reasm_orig_stop(ctrack, "reassemble session cancelled\n");
}
static void reasm_orig_fin(t_ctrack *ctrack)
{
reasm_orig_stop(ctrack, "reassemble session finished\n");
}
static uint8_t ct_new_postnat_fix(const t_ctrack *ctrack, struct ip *ip, struct ip6_hdr *ip6, uint8_t proto, struct udphdr *udp, struct tcphdr *tcp, size_t *len_pkt)
{
#ifdef __linux__
// if used in postnat chain, dropping initial packet will cause conntrack connection teardown
// so we need to workaround this.
// we can't use low ttl because TCP/IP stack listens to ttl expired ICMPs and notify socket
// we also can't use fooling because DPI would accept fooled packets
if (ctrack && ctrack->pcounter_orig==1)
{
DLOG("applying linux postnat conntrack workaround\n");
if (proto==IPPROTO_UDP && udp && len_pkt)
{
// make malformed udp packet with zero length and invalid checksum
udp->uh_ulen = 0; // invalid length. must be >=8
udp_fix_checksum(udp,sizeof(struct udphdr),ip,ip6);
udp->uh_sum ^= htons(0xBEAF);
// truncate packet
*len_pkt = (uint8_t*)udp - (ip ? (uint8_t*)ip : (uint8_t*)ip6) + sizeof(struct udphdr);
if (ip)
{
ip->ip_len = htons((uint16_t)*len_pkt);
ip4_fix_checksum(ip);
}
else if (ip6)
ip6->ip6_ctlun.ip6_un1.ip6_un1_plen = (uint16_t)htons(sizeof(struct udphdr));
}
else if (proto==IPPROTO_TCP && tcp)
{
// only SYN here is expected
// make flags invalid and also corrupt checksum
tcp->th_flags = 0;
}
if (ip) ip->ip_sum ^= htons(0xBEAF);
return VERDICT_MODIFY | VERDICT_NOCSUM;
}
#endif
return VERDICT_DROP;
}
static uint8_t ct_new_postnat_fix_tcp(const t_ctrack *ctrack, struct ip *ip, struct ip6_hdr *ip6, struct tcphdr *tcphdr)
{
return ct_new_postnat_fix(ctrack,ip,ip6,IPPROTO_TCP,NULL,tcphdr,NULL);
}
static uint8_t ct_new_postnat_fix_udp(const t_ctrack *ctrack, struct ip *ip, struct ip6_hdr *ip6, struct udphdr *udphdr, size_t *len_pkt)
{
return ct_new_postnat_fix(ctrack,ip,ip6,IPPROTO_UDP,udphdr,NULL,len_pkt);
}
static bool check_desync_interval(const struct desync_profile *dp, const t_ctrack *ctrack)
{
if (dp)
{
if (dp->desync_start)
{
if (ctrack)
{
if (!cutoff_test(ctrack, dp->desync_start, dp->desync_start_mode))
{
DLOG("desync-start not reached (mode %c): %llu/%u . not desyncing\n", dp->desync_start_mode, (unsigned long long)cutoff_get_limit(ctrack,dp->desync_start_mode), dp->desync_start);
return false;
}
DLOG("desync-start reached (mode %c): %llu/%u\n", dp->desync_start_mode, (unsigned long long)cutoff_get_limit(ctrack,dp->desync_start_mode), dp->desync_start);
}
else
{
DLOG("not desyncing. desync-start is set but conntrack entry is missing\n");
return false;
}
}
if (dp->desync_cutoff)
{
if (ctrack)
{
if (ctrack->b_desync_cutoff)
{
DLOG("desync-cutoff reached (mode %c): %llu/%u . not desyncing\n", dp->desync_cutoff_mode, (unsigned long long)cutoff_get_limit(ctrack,dp->desync_cutoff_mode), dp->desync_cutoff);
return false;
}
DLOG("desync-cutoff not reached (mode %c): %llu/%u\n", dp->desync_cutoff_mode, (unsigned long long)cutoff_get_limit(ctrack,dp->desync_cutoff_mode), dp->desync_cutoff);
}
else
{
DLOG("not desyncing. desync-cutoff is set but conntrack entry is missing\n");
return false;
}
}
}
return true;
}
static bool process_desync_interval(const struct desync_profile *dp, t_ctrack *ctrack)
{
if (check_desync_interval(dp, ctrack))
return true;
else
{
reasm_orig_cancel(ctrack);
return false;
}
}
static bool replay_queue(struct rawpacket_tailhead *q);
static size_t pos_normalize(size_t split_pos, size_t reasm_offset, size_t len_payload)
{
return (split_pos>reasm_offset && (split_pos-reasm_offset)<len_payload) ? split_pos-reasm_offset : 0;
}
static void autottl_discover(t_ctrack *ctrack, bool bIpv6)
{
if (ctrack && ctrack->incoming_ttl)
{
autottl *attl = bIpv6 ? &ctrack->dp->desync_autottl6 : &ctrack->dp->desync_autottl;
if (AUTOTTL_ENABLED(*attl))
{
ctrack->autottl = autottl_guess(ctrack->incoming_ttl, attl);
if (ctrack->autottl)
DLOG("autottl: guessed %u\n",ctrack->autottl);
else
DLOG("autottl: could not guess\n");
}
else
ctrack->autottl = 0;
}
}
#ifdef BSD
// BSD pass to divert socket ip_id=0 and does not auto set it if sent via divert socket
static uint16_t IP4_IP_ID_FIX(const struct ip *ip)
{
return ip ? ip->ip_id ? ip->ip_id : (uint16_t)random() : 0;
}
#define IP4_IP_ID_NEXT(ip_id) net16_add(ip_id,+1)
#define IP4_IP_ID_PREV(ip_id) net16_add(ip_id,-1)
#else
// in linux kernel sets increasing ip_id if it's zero
#define IP4_IP_ID_FIX(x) 0
#define IP4_IP_ID_NEXT(ip_id) ip_id
#define IP4_IP_ID_PREV(ip_id) ip_id
#endif
// fake_mod buffer must at least sizeof(desync_profile->fake_tls)
// size does not change
// return : true - altered, false - not altered
static bool runtime_tls_mod(const struct desync_profile *dp, uint8_t *fake_mod, const uint8_t *payload, size_t payload_len)
{
bool b=false;
if (dp->fake_tls_mod & FAKE_TLS_MOD_PADENCAP)
{
size_t sz_rec = pntoh16(dp->fake_tls+3) + payload_len;
size_t sz_handshake = pntoh24(dp->fake_tls+6) + payload_len;
size_t sz_ext = pntoh16(dp->fake_tls+dp->fake_tls_extlen_offset) + payload_len;
size_t sz_pad = pntoh16(dp->fake_tls+dp->fake_tls_padlen_offset) + payload_len;
if ((sz_rec & ~0xFFFF) || (sz_handshake & ~0xFFFFFF) || (sz_ext & ~0xFFFF) || (sz_pad & ~0xFFFF))
DLOG("cannot apply padencap tls mod. length overflow.\n");
else
{
memcpy(fake_mod,dp->fake_tls,dp->fake_tls_size);
phton16(fake_mod+3,(uint16_t)sz_rec);
phton24(fake_mod+6,(uint32_t)sz_handshake);
phton16(fake_mod+dp->fake_tls_extlen_offset,(uint16_t)sz_ext);
phton16(fake_mod+dp->fake_tls_padlen_offset,(uint16_t)sz_pad);
b=true;
}
}
if (dp->fake_tls_mod & FAKE_TLS_MOD_RND)
{
if (!b) memcpy(fake_mod,dp->fake_tls,dp->fake_tls_size);
fill_random_bytes(fake_mod+11,32); // random
fill_random_bytes(fake_mod+44,fake_mod[43]); // session id
b=true;
}
if (dp->fake_tls_mod & FAKE_TLS_MOD_DUP_SID)
{
if (dp->fake_tls[43]!=payload[43])
DLOG("cannot apply dupsid tls mod. fake and orig session id length mismatch.\n");
else if (payload_len<(44+payload[43]))
DLOG("cannot apply dupsid tls mod. data payload is not valid.\n");
else
{
if (!b) memcpy(fake_mod,dp->fake_tls,dp->fake_tls_size);
memcpy(fake_mod+44,payload+44,fake_mod[43]); // session id
b=true;
}
}
return b;
}
static uint8_t dpi_desync_tcp_packet_play(bool replay, size_t reasm_offset, uint32_t fwmark, const char *ifout, struct dissect *dis)
{
uint8_t verdict=VERDICT_PASS;
// additional safety check
if (!!dis->ip == !!dis->ip6) return verdict;
struct desync_profile *dp = NULL;
t_ctrack *ctrack=NULL, *ctrack_replay=NULL;
bool bReverse=false;
struct sockaddr_storage src, dst;
uint8_t pkt1[DPI_DESYNC_MAX_FAKE_LEN+100], pkt2[DPI_DESYNC_MAX_FAKE_LEN+100];
size_t pkt1_len, pkt2_len;
uint8_t ttl_orig,ttl_fake,flags_orig,scale_factor;
uint32_t *timestamps;
ttl_orig = dis->ip ? dis->ip->ip_ttl : dis->ip6->ip6_ctlun.ip6_un1.ip6_un1_hlim;
uint32_t desync_fwmark = fwmark | params.desync_fwmark;
extract_endpoints(dis->ip, dis->ip6, dis->tcp, NULL, &src, &dst);
if (replay)
{
// in replay mode conntrack_replay is not NULL and ctrack is NULL
//ConntrackPoolDump(¶ms.conntrack);
if (!ConntrackPoolDoubleSearch(¶ms.conntrack, dis->ip, dis->ip6, dis->tcp, NULL, &ctrack_replay, &bReverse) || bReverse)
return verdict;
dp = ctrack_replay->dp;
if (dp)
DLOG("using cached desync profile %d\n",dp->n);
else if (!ctrack_replay->dp_search_complete)
{
dp = ctrack_replay->dp = dp_find(¶ms.desync_profiles, IPPROTO_TCP, (struct sockaddr *)&dst, ctrack_replay->hostname, ctrack_replay->l7proto, NULL, NULL, NULL);
ctrack_replay->dp_search_complete = true;
}
if (!dp)
{
DLOG("matching desync profile not found\n");
return verdict;
}
}
else
{
// in real mode ctrack may be NULL or not NULL, conntrack_replay is equal to ctrack
ConntrackPoolPurge(¶ms.conntrack);
if (ConntrackPoolFeed(¶ms.conntrack, dis->ip, dis->ip6, dis->tcp, NULL, dis->len_payload, &ctrack, &bReverse))
{
dp = ctrack->dp;
ctrack_replay = ctrack;
}
if (dp)
DLOG("using cached desync profile %d\n",dp->n);
else if (!ctrack || !ctrack->dp_search_complete)
{
dp = dp_find(¶ms.desync_profiles, IPPROTO_TCP, (struct sockaddr *)&dst, ctrack ? ctrack->hostname : NULL, ctrack ? ctrack->l7proto : UNKNOWN, NULL, NULL, NULL);
if (ctrack)
{
ctrack->dp = dp;
ctrack->dp_search_complete = true;
}
}
if (!dp)
{
DLOG("matching desync profile not found\n");
return verdict;
}
maybe_cutoff(ctrack, IPPROTO_TCP);
HostFailPoolPurgeRateLimited(&dp->hostlist_auto_fail_counters);
//ConntrackPoolDump(¶ms.conntrack);
if (dp->wsize && tcp_synack_segment(dis->tcp))
{
tcp_rewrite_winsize(dis->tcp, dp->wsize, dp->wscale);
verdict=VERDICT_MODIFY;
}
if (bReverse)
{
if (ctrack)
{
if (!ctrack->incoming_ttl)
{
DLOG("incoming TTL %u\n",ttl_orig);
ctrack->incoming_ttl = ttl_orig;
}
if (!ctrack->autottl) autottl_discover(ctrack,!!dis->ip6);
}
// process reply packets for auto hostlist mode
// by looking at RSTs or HTTP replies we decide whether original request looks like DPI blocked
// we only process first-sequence replies. do not react to subsequent redirects or RSTs
if (ctrack && ctrack->hostname && ctrack->hostname_ah_check && (ctrack->ack_last-ctrack->ack0)==1)
{
bool bFail=false;
char client_ip_port[48];
if (*params.hostlist_auto_debuglog)
ntop46_port((struct sockaddr*)&dst,client_ip_port,sizeof(client_ip_port));
else
*client_ip_port=0;
if (dis->tcp->th_flags & TH_RST)
{
DLOG("incoming RST detected for hostname %s\n", ctrack->hostname);
HOSTLIST_DEBUGLOG_APPEND("%s : profile %d : client %s : proto %s : incoming RST", ctrack->hostname, ctrack->dp->n, client_ip_port, l7proto_str(ctrack->l7proto));
bFail = true;
}
else if (dis->len_payload && ctrack->l7proto==HTTP)
{
if (IsHttpReply(dis->data_payload,dis->len_payload))
{
DLOG("incoming HTTP reply detected for hostname %s\n", ctrack->hostname);
bFail = HttpReplyLooksLikeDPIRedirect(dis->data_payload, dis->len_payload, ctrack->hostname);
if (bFail)
{
DLOG("redirect to another domain detected. possibly DPI redirect.\n");
HOSTLIST_DEBUGLOG_APPEND("%s : profile %d : client %s : proto %s : redirect to another domain", ctrack->hostname, ctrack->dp->n, client_ip_port, l7proto_str(ctrack->l7proto));
}
else
DLOG("local or in-domain redirect detected. it's not a DPI redirect.\n");
}
else
{
// received not http reply. do not monitor this connection anymore
DLOG("incoming unknown HTTP data detected for hostname %s\n", ctrack->hostname);
}
}
if (bFail)
auto_hostlist_failed(dp, ctrack->hostname, client_ip_port, ctrack->l7proto);
else
if (dis->len_payload)
auto_hostlist_reset_fail_counter(dp, ctrack->hostname, client_ip_port, ctrack->l7proto);
if (dis->tcp->th_flags & TH_RST)
ConntrackClearHostname(ctrack); // do not react to further dup RSTs
}
return verdict; // nothing to do. do not waste cpu
}
if (dp->wssize)
{
if (ctrack)
{
if (ctrack->b_wssize_cutoff)
{
DLOG("wssize-cutoff reached (mode %c): %llu/%u . not changing wssize.\n", dp->wssize_cutoff_mode, (unsigned long long)cutoff_get_limit(ctrack,dp->wssize_cutoff_mode), dp->wssize_cutoff);
}
else
{
if (dp->wssize_cutoff) DLOG("wssize-cutoff not reached (mode %c): %llu/%u\n", dp->wssize_cutoff_mode, (unsigned long long)cutoff_get_limit(ctrack,dp->wssize_cutoff_mode), dp->wssize_cutoff);
tcp_rewrite_winsize(dis->tcp, dp->wssize, dp->wsscale);
verdict=VERDICT_MODIFY;
}
}
else
{
DLOG("not changing wssize. wssize is set but conntrack entry is missing\n");
}
}
} // !replay
ttl_fake = (ctrack_replay && ctrack_replay->autottl) ? ctrack_replay->autottl : (dis->ip6 ? (dp->desync_ttl6 ? dp->desync_ttl6 : ttl_orig) : (dp->desync_ttl ? dp->desync_ttl : ttl_orig));
flags_orig = *((uint8_t*)dis->tcp+13);
scale_factor = tcp_find_scale_factor(dis->tcp);
timestamps = tcp_find_timestamps(dis->tcp);
if (!replay)
{
// start and cutoff limiters
if (!process_desync_interval(dp, ctrack)) return verdict;
if (tcp_syn_segment(dis->tcp))
{
switch (dp->desync_mode0)
{
case DESYNC_SYNACK:
pkt1_len = sizeof(pkt1);
if (!prepare_tcp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, TH_SYN|TH_ACK, dis->tcp->th_seq, dis->tcp->th_ack, dis->tcp->th_win, scale_factor, timestamps,
ttl_fake,IP4_TOS(dis->ip),IP4_IP_ID_FIX(dis->ip),IP6_FLOW(dis->ip6),
dp->desync_fooling_mode,dp->desync_badseq_increment,dp->desync_badseq_ack_increment,
NULL, 0, pkt1, &pkt1_len))
{
return verdict;
}
DLOG("sending fake SYNACK\n");
if (!rawsend_rep(dp->desync_repeats,(struct sockaddr *)&dst, desync_fwmark, ifout , pkt1, pkt1_len))
return verdict;
break;
case DESYNC_SYNDATA:
// make sure we are not breaking TCP fast open
if (tcp_has_fastopen(dis->tcp))
{
DLOG("received SYN with TCP fast open option. syndata desync is not applied.\n");
break;
}
if (dis->len_payload)
{
DLOG("received SYN with data payload. syndata desync is not applied.\n");
break;
}
pkt1_len = sizeof(pkt1);
if (!prepare_tcp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, flags_orig, dis->tcp->th_seq, dis->tcp->th_ack, dis->tcp->th_win, scale_factor, timestamps,
ttl_orig,IP4_TOS(dis->ip),IP4_IP_ID_FIX(dis->ip),IP6_FLOW(dis->ip6),
0,0,0, dp->fake_syndata,dp->fake_syndata_size, pkt1,&pkt1_len))
{
return verdict;
}
DLOG("sending SYN with fake data : ");
hexdump_limited_dlog(dp->fake_syndata,dp->fake_syndata_size,PKTDATA_MAXDUMP); DLOG("\n");
if (!rawsend_rep(dp->desync_repeats,(struct sockaddr *)&dst, desync_fwmark, ifout , pkt1, pkt1_len))
return verdict;
verdict = ct_new_postnat_fix_tcp(ctrack, dis->ip, dis->ip6, dis->tcp);
break;
default:
break;
}
// can do nothing else with SYN packet
return verdict;
}
} // !replay
if (!(dis->tcp->th_flags & TH_SYN) && dis->len_payload)
{
const uint8_t *fake;
size_t fake_size;
char host[256];
bool bHaveHost=false;
uint8_t *p, *phost=NULL;
const uint8_t *rdata_payload = dis->data_payload;
size_t rlen_payload = dis->len_payload;
size_t split_pos, seqovl_pos;
size_t multisplit_pos[MAX_SPLITS];
int multisplit_count;
int i;
uint16_t ip_id;
t_l7proto l7proto = UNKNOWN;
uint8_t fake_mod[sizeof(dp->fake_tls)];
if (replay)
{
rdata_payload = ctrack_replay->reasm_orig.packet;
rlen_payload = ctrack_replay->reasm_orig.size_present;
}
else if (reasm_orig_feed(ctrack,IPPROTO_TCP,dis->data_payload,dis->len_payload))
{
rdata_payload = ctrack->reasm_orig.packet;
rlen_payload = ctrack->reasm_orig.size_present;
}
process_retrans_fail(ctrack, IPPROTO_TCP, (struct sockaddr*)&src);
if (IsHttp(rdata_payload,rlen_payload))
{
DLOG("packet contains HTTP request\n");
l7proto = HTTP;
if (ctrack && ctrack->l7proto==UNKNOWN) ctrack->l7proto = l7proto;
// we do not reassemble http
reasm_orig_cancel(ctrack);
forced_wssize_cutoff(ctrack);
bHaveHost=HttpExtractHost(rdata_payload,rlen_payload,host,sizeof(host));
if (!bHaveHost)
{
DLOG("not applying tampering to HTTP without Host:\n");
return verdict;
}
if (ctrack)
{
// we do not reassemble http
if (!ctrack->req_seq_present)
{
ctrack->req_seq_start=ctrack->seq_last;
ctrack->req_seq_end=ctrack->pos_orig-1;
ctrack->req_seq_present=ctrack->req_seq_finalized=true;
DLOG("req retrans : tcp seq interval %u-%u\n",ctrack->req_seq_start,ctrack->req_seq_end);
}
}
}
else if (IsTLSClientHello(rdata_payload,rlen_payload,TLS_PARTIALS_ENABLE))
{
bool bReqFull = IsTLSRecordFull(rdata_payload,rlen_payload);
DLOG(bReqFull ? "packet contains full TLS ClientHello\n" : "packet contains partial TLS ClientHello\n");
l7proto = TLS;
bHaveHost=TLSHelloExtractHost(rdata_payload,rlen_payload,host,sizeof(host),TLS_PARTIALS_ENABLE);
if (ctrack)
{
if (!ctrack->l7proto) ctrack->l7proto = l7proto;
// do not reasm retransmissions
if (!bReqFull && ReasmIsEmpty(&ctrack->reasm_orig) && !ctrack->req_seq_abandoned &&
!(ctrack->req_seq_finalized && seq_within(ctrack->seq_last, ctrack->req_seq_start, ctrack->req_seq_end)))
{
// do not reconstruct unexpected large payload (they are feeding garbage ?)
if (!reasm_orig_start(ctrack,IPPROTO_TCP,TLSRecordLen(dis->data_payload),16384,dis->data_payload,dis->len_payload))
{
reasm_orig_cancel(ctrack);
return verdict;
}
}
if (!ctrack->req_seq_finalized)
{
if (!ctrack->req_seq_present)
{
// lower bound of request seq interval
ctrack->req_seq_start=ctrack->seq_last;
ctrack->req_seq_present=true;
}
// upper bound of request seq interval
// it can grow on every packet until request is complete. then interval is finalized and never touched again.
ctrack->req_seq_end=ctrack->pos_orig-1;
DLOG("req retrans : seq interval %u-%u\n",ctrack->req_seq_start,ctrack->req_seq_end);
ctrack->req_seq_finalized |= bReqFull;
}
if (bReqFull || ReasmIsEmpty(&ctrack->reasm_orig)) forced_wssize_cutoff(ctrack);
if (!ReasmIsEmpty(&ctrack->reasm_orig))
{
verdict_tcp_csum_fix(verdict, dis->tcp, dis->transport_len, dis->ip, dis->ip6);
if (rawpacket_queue(&ctrack->delayed, &dst, desync_fwmark, ifout, dis->data_pkt, dis->len_pkt, dis->len_payload))
{
DLOG("DELAY desync until reasm is complete (#%u)\n", rawpacket_queue_count(&ctrack->delayed));
}
else
{
DLOG_ERR("rawpacket_queue failed !\n");
reasm_orig_cancel(ctrack);
return verdict;
}
if (ReasmIsFull(&ctrack->reasm_orig))
{
replay_queue(&ctrack->delayed);
reasm_orig_fin(ctrack);
}
return VERDICT_DROP;
}
}
if (dp->desync_skip_nosni && !bHaveHost)
{