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8a53c03eb6
zapret/nfq/desync.c
bol-van 8a53c03eb6 nfqws: use BSD udphdr
2024-08-20 17:13:02 +03:00

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#define _GNU_SOURCE
#include "desync.h"
#include "protocol.h"
#include "params.h"
#include "helpers.h"
#include "hostlist.h"
#include "conntrack.h"
#include <string.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";
const uint8_t fake_tls_clienthello_default[517] = {
0x16, 0x03, 0x01, 0x02, 0x00, 0x01, 0x00, 0x01, 0xFC, 0x03, 0x03, 0x6F, 0x0B, 0xB6, 0x85, 0x58, 0x28, 0x59, 0xD5, 0x0D, 0x6C, 0x78, 0x39, 0x7F, 0x2B, 0x0B, 0x45, 0xA3, 0x71, 0x4F, 0x49, 0xD6, 0x34, 0x17, 0xC6, 0x59, 0xA5, 0x1D, 0x89, 0x01,
0xE1, 0x72, 0x1D, 0x20, 0x9D, 0x2C, 0xAB, 0x26, 0x58, 0xA7, 0x83, 0xBF, 0xB7, 0xDC, 0x5F, 0x28, 0xAA, 0x11, 0xA7, 0x63, 0x54, 0x19, 0xCB, 0xC6, 0xC4, 0x0E, 0xA4, 0x15, 0x46, 0xCC, 0x2F, 0x25, 0x13, 0x9A, 0x14, 0x54, 0x00, 0x3E, 0x13, 0x02,
0x13, 0x03, 0x13, 0x01, 0xC0, 0x2C, 0xC0, 0x30, 0x00, 0x9F, 0xCC, 0xA9, 0xCC, 0xA8, 0xCC, 0xAA, 0xC0, 0x2B, 0xC0, 0x2F, 0x00, 0x9E, 0xC0, 0x24, 0xC0, 0x28, 0x00, 0x6B, 0xC0, 0x23, 0xC0, 0x27, 0x00, 0x67, 0xC0, 0x0A, 0xC0, 0x14, 0x00, 0x39,
0xC0, 0x09, 0xC0, 0x13, 0x00, 0x33, 0x00, 0x9D, 0x00, 0x9C, 0x00, 0x3D, 0x00, 0x3C, 0x00, 0x35, 0x00, 0x2F, 0x00, 0xFF, 0x01, 0x00, 0x01, 0x75, 0x00, 0x00, 0x00, 0x0D, 0x00, 0x0B, 0x00, 0x00, 0x08, 0x69, 0x61, 0x6E, 0x61, 0x2E, 0x6F, 0x72,
0x67, 0x00, 0x0B, 0x00, 0x04, 0x03, 0x00, 0x01, 0x02, 0x00, 0x0A, 0x00, 0x0C, 0x00, 0x0A, 0x00, 0x1D, 0x00, 0x17, 0x00, 0x1E, 0x00, 0x19, 0x00, 0x18, 0x33, 0x74, 0x00, 0x00, 0x00, 0x10, 0x00, 0x0E, 0x00, 0x0C, 0x02, 0x68, 0x32, 0x08, 0x68,
0x74, 0x74, 0x70, 0x2F, 0x31, 0x2E, 0x31, 0x00, 0x16, 0x00, 0x00, 0x00, 0x17, 0x00, 0x00, 0x00, 0x31, 0x00, 0x00, 0x00, 0x0D, 0x00, 0x30, 0x00, 0x2E, 0x04, 0x03, 0x05, 0x03, 0x06, 0x03, 0x08, 0x07, 0x08, 0x08, 0x08, 0x09, 0x08, 0x0A, 0x08,
0x0B, 0x08, 0x04, 0x08, 0x05, 0x08, 0x06, 0x04, 0x01, 0x05, 0x01, 0x06, 0x01, 0x03, 0x03, 0x02, 0x03, 0x03, 0x01, 0x02, 0x01, 0x03, 0x02, 0x02, 0x02, 0x04, 0x02, 0x05, 0x02, 0x06, 0x02, 0x00, 0x2B, 0x00, 0x09, 0x08, 0x03, 0x04, 0x03, 0x03,
0x03, 0x02, 0x03, 0x01, 0x00, 0x2D, 0x00, 0x02, 0x01, 0x01, 0x00, 0x33, 0x00, 0x26, 0x00, 0x24, 0x00, 0x1D, 0x00, 0x20, 0x1B, 0xB3, 0xF5, 0x23, 0x6E, 0x05, 0x98, 0x5D, 0x92, 0x30, 0x8A, 0xAC, 0x64, 0x61, 0x1F, 0xD7, 0x0A, 0x6D, 0xB1, 0xA5,
0x74, 0xF9, 0x44, 0x07, 0xC0, 0x55, 0xD8, 0x8B, 0x0C, 0xEA, 0x29, 0x27, 0x00, 0x15, 0x00, 0xB5, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
};
#define PKTDATA_MAXDUMP 32
#define IP_MAXDUMP 80
static uint8_t zeropkt[DPI_DESYNC_MAX_FAKE_LEN];
void desync_init(void)
{
memset(zeropkt, 0, sizeof(zeropkt));
}
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_DISORDER || mode==DESYNC_DISORDER2 || mode==DESYNC_SPLIT || mode==DESYNC_SPLIT2 || 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_DISORDER || mode==DESYNC_DISORDER2 || mode==DESYNC_SPLIT || mode==DESYNC_SPLIT2 || 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,"disorder"))
return DESYNC_DISORDER;
else if (!strcmp(s,"disorder2"))
return DESYNC_DISORDER2;
else if (!strcmp(s,"split"))
return DESYNC_SPLIT;
else if (!strcmp(s,"split2"))
return DESYNC_SPLIT2;
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;
}
// auto creates internal socket and uses it for subsequent calls
static bool rawsend_rep(const struct sockaddr* dst,uint32_t fwmark,const char *ifout,const void *data,size_t len)
{
for (int i=0;i<params.desync_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)
{
if (proto==IPPROTO_TCP)
ctrack->b_wssize_cutoff |= cutoff_test(ctrack, params.wssize_cutoff, params.wssize_cutoff_mode);
ctrack->b_desync_cutoff |= cutoff_test(ctrack, params.desync_cutoff, params.desync_cutoff_mode);
// 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 |= \
(!params.wssize || ctrack->b_wssize_cutoff) &&
(!params.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 && params.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(const char *hostname)
{
if (hostname)
{
hostfail_pool *fail_counter;
fail_counter = HostFailPoolFind(params.hostlist_auto_fail_counters, hostname);
if (fail_counter)
{
HostFailPoolDel(&params.hostlist_auto_fail_counters, fail_counter);
DLOG("auto hostlist : %s : fail counter reset. website is working.\n", hostname);
HOSTLIST_DEBUGLOG_APPEND("%s : fail counter reset. website is working.", hostname);
}
}
}
// return true if retrans trigger fires
static bool auto_hostlist_retrans(t_ctrack *ctrack, uint8_t l4proto, int threshold)
{
if (ctrack && 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->hostname);
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(const char *hostname)
{
hostfail_pool *fail_counter;
fail_counter = HostFailPoolFind(params.hostlist_auto_fail_counters, hostname);
if (!fail_counter)
{
fail_counter = HostFailPoolAdd(&params.hostlist_auto_fail_counters, hostname, params.hostlist_auto_fail_time);
if (!fail_counter)
{
fprintf(stderr, "HostFailPoolAdd: out of memory\n");
return;
}
}
fail_counter->counter++;
DLOG("auto hostlist : %s : fail counter %d/%d\n", hostname, fail_counter->counter, params.hostlist_auto_fail_threshold);
HOSTLIST_DEBUGLOG_APPEND("%s : fail counter %d/%d", hostname, fail_counter->counter, params.hostlist_auto_fail_threshold);
if (fail_counter->counter >= params.hostlist_auto_fail_threshold)
{
DLOG("auto hostlist : fail threshold reached. about to add %s to auto hostlist\n", hostname);
HostFailPoolDel(&params.hostlist_auto_fail_counters, fail_counter);
DLOG("auto hostlist : rechecking %s to avoid duplicates\n", hostname);
bool bExcluded=false;
if (!HostlistCheck(hostname, &bExcluded) && !bExcluded)
{
DLOG("auto hostlist : adding %s\n", hostname);
HOSTLIST_DEBUGLOG_APPEND("%s : adding", hostname);
if (!StrPoolAddStr(&params.hostlist, hostname))
{
fprintf(stderr, "StrPoolAddStr out of memory\n");
return;
}
if (!append_to_list_file(params.hostlist_auto_filename, hostname))
{
perror("write to auto hostlist:");
return;
}
params.hostlist_auto_mod_time = file_mod_time(params.hostlist_auto_filename);
}
else
{
DLOG("auto hostlist : NOT adding %s\n", hostname);
HOSTLIST_DEBUGLOG_APPEND("%s : NOT adding, duplicate detected", hostname);
}
}
}
static void process_retrans_fail(t_ctrack *ctrack, uint8_t proto)
{
if (ctrack && ctrack->hostname && auto_hostlist_retrans(ctrack, proto, params.hostlist_auto_retrans_threshold))
{
HOSTLIST_DEBUGLOG_APPEND("%s : tcp retrans threshold reached", ctrack->hostname);
auto_hostlist_failed(ctrack->hostname);
}
}
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 t_ctrack *ctrack)
{
if (params.desync_start)
{
if (ctrack)
{
if (!cutoff_test(ctrack, params.desync_start, params.desync_start_mode))
{
DLOG("desync-start not reached (mode %c): %llu/%u . not desyncing\n", params.desync_start_mode, (unsigned long long)cutoff_get_limit(ctrack,params.desync_start_mode), params.desync_start);
return false;
}
DLOG("desync-start reached (mode %c): %llu/%u\n", params.desync_start_mode, (unsigned long long)cutoff_get_limit(ctrack,params.desync_start_mode), params.desync_start);
}
else
{
DLOG("not desyncing. desync-start is set but conntrack entry is missing\n");
return false;
}
}
if (params.desync_cutoff)
{
if (ctrack)
{
if (ctrack->b_desync_cutoff)
{
DLOG("desync-cutoff reached (mode %c): %llu/%u . not desyncing\n", params.desync_cutoff_mode, (unsigned long long)cutoff_get_limit(ctrack,params.desync_cutoff_mode), params.desync_cutoff);
return false;
}
DLOG("desync-cutoff not reached (mode %c): %llu/%u\n", params.desync_cutoff_mode, (unsigned long long)cutoff_get_limit(ctrack,params.desync_cutoff_mode), params.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(t_ctrack *ctrack)
{
if (check_desync_interval(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)
{
size_t rsplit_pos = split_pos;
// normalize split pos to current packet
split_pos=(split_pos>reasm_offset && (split_pos-reasm_offset)<len_payload) ? split_pos-reasm_offset : 0;
if (rsplit_pos)
{
if (split_pos==rsplit_pos)
DLOG("split pos %zu\n",split_pos)
else
{
if (split_pos)
DLOG("split pos was normalized to packet data offset : %zu -> %zu\n",rsplit_pos,split_pos)
else
DLOG("split pos %zu is outside of this packet %zu-%zu\n",rsplit_pos,reasm_offset,reasm_offset+len_payload)
}
}
return split_pos;
}
static uint8_t dpi_desync_tcp_packet_play(bool replay, size_t reasm_offset, uint32_t fwmark, const char *ifout, uint8_t *data_pkt, size_t *len_pkt, struct ip *ip, struct ip6_hdr *ip6hdr, struct tcphdr *tcphdr, size_t transport_len, uint8_t *data_payload, size_t len_payload)
{
uint8_t verdict=VERDICT_PASS;
// additional safety check
if (!!ip == !!ip6hdr) return verdict;
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 = ip ? ip->ip_ttl : ip6hdr->ip6_ctlun.ip6_un1.ip6_un1_hlim;
uint32_t desync_fwmark = fwmark | params.desync_fwmark;
if (replay)
{
// in replay mode conntrack_replay is not NULL and ctrack is NULL
//ConntrackPoolDump(&params.conntrack);
if (!ConntrackPoolDoubleSearch(&params.conntrack, ip, ip6hdr, tcphdr, NULL, &ctrack_replay, &bReverse) || bReverse)
return verdict;
}
else
{
// in real mode ctrack may be NULL or not NULL, conntrack_replay is equal to ctrack
ConntrackPoolPurge(&params.conntrack);
if (ConntrackPoolFeed(&params.conntrack, ip, ip6hdr, tcphdr, NULL, len_payload, &ctrack, &bReverse))
{
ctrack_replay = ctrack;
maybe_cutoff(ctrack, IPPROTO_TCP);
}
HostFailPoolPurgeRateLimited(&params.hostlist_auto_fail_counters);
//ConntrackPoolDump(&params.conntrack);
if (params.wsize && tcp_synack_segment(tcphdr))
{
tcp_rewrite_winsize(tcphdr, params.wsize, params.wscale);
verdict=VERDICT_MODIFY;
}
if (bReverse)
{
if (ctrack && !ctrack->autottl && ctrack->pcounter_reply==1)
{
autottl *attl = ip ? &params.desync_autottl : &params.desync_autottl6;
if (AUTOTTL_ENABLED(*attl))
{
ctrack->autottl = autottl_guess(ttl_orig, attl);
if (ctrack->autottl)
DLOG("autottl: guessed %u\n",ctrack->autottl)
else
DLOG("autottl: could not guess\n")
}
}
// 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;
if (tcphdr->th_flags & TH_RST)
{
DLOG("incoming RST detected for hostname %s\n", ctrack->hostname);
HOSTLIST_DEBUGLOG_APPEND("%s : incoming RST", ctrack->hostname);
bFail = true;
}
else if (len_payload && ctrack->l7proto==HTTP)
{
if (IsHttpReply(data_payload,len_payload))
{
DLOG("incoming HTTP reply detected for hostname %s\n", ctrack->hostname);
bFail = HttpReplyLooksLikeDPIRedirect(data_payload, len_payload, ctrack->hostname);
if (bFail)
{
DLOG("redirect to another domain detected. possibly DPI redirect.\n")
HOSTLIST_DEBUGLOG_APPEND("%s : redirect to another domain", ctrack->hostname);
}
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(ctrack->hostname);
else
if (len_payload)
auto_hostlist_reset_fail_counter(ctrack->hostname);
if (tcphdr->th_flags & TH_RST)
ConntrackClearHostname(ctrack); // do not react to further dup RSTs
}
return verdict; // nothing to do. do not waste cpu
}
if (params.wssize)
{
if (ctrack)
{
if (ctrack->b_wssize_cutoff)
{
DLOG("not changing wssize. wssize-cutoff reached\n");
}
else
{
if (params.wssize_cutoff) DLOG("wssize-cutoff not reached (mode %c): %llu/%u\n", params.wssize_cutoff_mode, (unsigned long long)cutoff_get_limit(ctrack,params.wssize_cutoff_mode), params.wssize_cutoff);
tcp_rewrite_winsize(tcphdr, params.wssize, params.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 : (ip6hdr ? (params.desync_ttl6 ? params.desync_ttl6 : ttl_orig) : (params.desync_ttl ? params.desync_ttl : ttl_orig));
flags_orig = *((uint8_t*)tcphdr+13);
scale_factor = tcp_find_scale_factor(tcphdr);
timestamps = tcp_find_timestamps(tcphdr);
extract_endpoints(ip, ip6hdr, tcphdr, NULL, &src, &dst);
if (!replay)
{
if (tcp_syn_segment(tcphdr))
{
switch (params.desync_mode0)
{
case DESYNC_SYNACK:
pkt1_len = sizeof(pkt1);
if (!prepare_tcp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, TH_SYN|TH_ACK, tcphdr->th_seq, tcphdr->th_ack, tcphdr->th_win, scale_factor, timestamps,
ttl_fake,params.desync_fooling_mode,params.desync_badseq_increment,params.desync_badseq_ack_increment,
NULL, 0, pkt1, &pkt1_len))
{
return verdict;
}
DLOG("sending fake SYNACK\n");
if (!rawsend_rep((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(tcphdr))
{
DLOG("received SYN with TCP fast open option. syndata desync is not applied.\n");
break;
}
if (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, tcphdr->th_seq, tcphdr->th_ack, tcphdr->th_win, scale_factor, timestamps,
ttl_orig,0,0,0, params.fake_syndata,params.fake_syndata_size, pkt1,&pkt1_len))
{
return verdict;
}
DLOG("sending SYN with fake data : ");
hexdump_limited_dlog(params.fake_syndata,params.fake_syndata_size,PKTDATA_MAXDUMP); DLOG("\n")
if (!rawsend_rep((struct sockaddr *)&dst, desync_fwmark, ifout , pkt1, pkt1_len))
return verdict;
verdict = ct_new_postnat_fix_tcp(ctrack, ip, ip6hdr, tcphdr);
break;
}
// can do nothing else with SYN packet
return verdict;
}
// start and cutoff limiters
if (!process_desync_interval(ctrack)) return verdict;
} // !replay
if (!params.wssize && params.desync_mode==DESYNC_NONE && !params.hostcase && !params.hostnospace && !params.domcase && !*params.hostlist_auto_filename) return verdict; // nothing to do. do not waste cpu
if (!(tcphdr->th_flags & TH_SYN) && len_payload)
{
const uint8_t *fake;
size_t fake_size;
char host[256];
bool bHaveHost=false;
bool bIsHttp;
bool bKnownProtocol = false;
uint8_t *p, *phost;
const uint8_t *rdata_payload = data_payload;
size_t rlen_payload = len_payload;
size_t split_pos;
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,data_payload,len_payload))
{
rdata_payload = ctrack->reasm_orig.packet;
rlen_payload = ctrack->reasm_orig.size_present;
}
process_retrans_fail(ctrack, IPPROTO_TCP);
if ((bIsHttp = IsHttp(rdata_payload,rlen_payload)))
{
DLOG("packet contains HTTP request\n")
if (ctrack && !ctrack->l7proto) ctrack->l7proto = HTTP;
// we do not reassemble http
reasm_orig_cancel(ctrack);
forced_wssize_cutoff(ctrack);
fake = params.fake_http;
fake_size = params.fake_http_size;
if (params.hostlist || params.hostlist_exclude)
{
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);
}
}
split_pos = HttpPos(params.desync_split_http_req, params.desync_split_pos, rdata_payload, rlen_payload);
bKnownProtocol = true;
}
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")
bHaveHost=TLSHelloExtractHost(rdata_payload,rlen_payload,host,sizeof(host),TLS_PARTIALS_ENABLE);
if (ctrack)
{
if (!ctrack->l7proto) ctrack->l7proto = TLS;
// 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(data_payload),16384,data_payload,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, tcphdr, transport_len, ip, ip6hdr);
if (rawpacket_queue(&ctrack->delayed, &dst, desync_fwmark, ifout, data_pkt, *len_pkt, len_payload))
{
DLOG("DELAY desync until reasm is complete (#%u)\n", rawpacket_queue_count(&ctrack->delayed));
}
else
{
fprintf(stderr, "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 (params.desync_skip_nosni && !bHaveHost)
{
DLOG("not applying tampering to TLS ClientHello without hostname in the SNI\n")
reasm_orig_cancel(ctrack);
return verdict;
}
fake = params.fake_tls;
fake_size = params.fake_tls_size;
split_pos = TLSPos(params.desync_split_tls, params.desync_split_pos, rdata_payload, rlen_payload, 0);
bKnownProtocol = true;
}
else
split_pos=params.desync_split_pos;
reasm_orig_cancel(ctrack);
rdata_payload=NULL;
if (ctrack && ctrack->req_seq_finalized)
{
uint32_t dseq = ctrack->seq_last - ctrack->req_seq_end;
// do not react to 32-bit overflowed sequence numbers. allow 16 Mb grace window then cutoff.
if (dseq>=0x1000000 && !(dseq & 0x80000000)) ctrack->req_seq_abandoned=true;
}
if (bHaveHost)
{
DLOG("hostname: %s\n",host)
if (params.hostlist || params.hostlist_exclude)
{
bool bBypass;
if (HostlistCheck(host, &bBypass))
ctrack_stop_retrans_counter(ctrack_replay);
else
{
if (ctrack_replay)
{
ctrack_replay->hostname_ah_check = *params.hostlist_auto_filename && !bBypass;
if (ctrack_replay->hostname_ah_check)
{
if (!ctrack_replay->hostname) ctrack_replay->hostname=strdup(host);
}
else
ctrack_stop_retrans_counter(ctrack_replay);
}
DLOG("not applying tampering to this request\n")
return verdict;
}
}
}
if (!bKnownProtocol)
{
if (!params.desync_any_proto) return verdict;
DLOG("applying tampering to unknown protocol\n")
fake = params.fake_unknown;
fake_size = params.fake_unknown_size;
}
if (bIsHttp && (params.hostcase || params.hostnospace || params.domcase) && (phost = (uint8_t*)memmem(data_payload, len_payload, "\r\nHost: ", 8)))
{
if (params.hostcase)
{
DLOG("modifying Host: => %c%c%c%c:\n", params.hostspell[0], params.hostspell[1], params.hostspell[2], params.hostspell[3])
memcpy(phost + 2, params.hostspell, 4);
verdict=VERDICT_MODIFY;
}
if (params.domcase)
{
DLOG("mixing domain case\n");
for (p = phost+7; p < (data_payload + len_payload) && *p != '\r' && *p != '\n'; p++)
*p = (((size_t)p) & 1) ? tolower(*p) : toupper(*p);
verdict=VERDICT_MODIFY;
}
uint8_t *pua;
if (params.hostnospace &&
(pua = (uint8_t*)memmem(data_payload, len_payload, "\r\nUser-Agent: ", 14)) &&
(pua = (uint8_t*)memmem(pua + 1, len_payload - (pua - data_payload) - 1, "\r\n", 2)))
{
DLOG("removing space after Host: and adding it to User-Agent:\n")
if (pua > phost)
{
memmove(phost + 7, phost + 8, pua - phost - 8);
phost[pua - phost - 1] = ' ';
}
else
{
memmove(pua + 1, pua, phost - pua + 7);
*pua = ' ';
}
verdict=VERDICT_MODIFY;
}
}
if (params.desync_mode==DESYNC_NONE) return verdict;
if (params.debug)
{
printf("dpi desync src=");
print_sockaddr((struct sockaddr *)&src);
printf(" dst=");
print_sockaddr((struct sockaddr *)&dst);
printf("\n");
}
if (!split_pos || split_pos>rlen_payload) split_pos=1;
split_pos=pos_normalize(split_pos,reasm_offset,len_payload);
enum dpi_desync_mode desync_mode = params.desync_mode;
uint32_t fooling_orig = FOOL_NONE;
bool b;
pkt1_len = sizeof(pkt1);
b = false;
switch(desync_mode)
{
case DESYNC_FAKE_KNOWN:
if (reasm_offset)
{
desync_mode = params.desync_mode2;
break;
}
if (!bKnownProtocol)
{
DLOG("not applying fake because of unknown protocol\n");
desync_mode = params.desync_mode2;
break;
}
case DESYNC_FAKE:
if (reasm_offset) break;
if (!prepare_tcp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, flags_orig, tcphdr->th_seq, tcphdr->th_ack, tcphdr->th_win, scale_factor, timestamps,
ttl_fake,params.desync_fooling_mode,params.desync_badseq_increment,params.desync_badseq_ack_increment,
fake, fake_size, pkt1, &pkt1_len))
{
return verdict;
}
DLOG("sending fake request : ");
hexdump_limited_dlog(fake,fake_size,PKTDATA_MAXDUMP); DLOG("\n")
b = true;
break;
case DESYNC_RST:
case DESYNC_RSTACK:
if (reasm_offset) break;
if (!prepare_tcp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, TH_RST | (desync_mode==DESYNC_RSTACK ? TH_ACK:0), tcphdr->th_seq, tcphdr->th_ack, tcphdr->th_win, scale_factor, timestamps,
ttl_fake,params.desync_fooling_mode,params.desync_badseq_increment,params.desync_badseq_ack_increment,
NULL, 0, pkt1, &pkt1_len))
{
return verdict;
}
DLOG("sending fake RST/RSTACK\n");
b = true;
break;
case DESYNC_HOPBYHOP:
case DESYNC_DESTOPT:
case DESYNC_IPFRAG1:
fooling_orig = (desync_mode==DESYNC_HOPBYHOP) ? FOOL_HOPBYHOP : (desync_mode==DESYNC_DESTOPT) ? FOOL_DESTOPT : FOOL_IPFRAG1;
desync_mode = params.desync_mode2;
if (ip6hdr && (desync_mode==DESYNC_NONE || !desync_valid_second_stage_tcp(desync_mode) ||
(!split_pos && (desync_mode==DESYNC_SPLIT || desync_mode==DESYNC_SPLIT2 || desync_mode==DESYNC_DISORDER || desync_mode==DESYNC_DISORDER2))))
{
if (!prepare_tcp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, flags_orig, tcphdr->th_seq, tcphdr->th_ack, tcphdr->th_win, scale_factor, timestamps,
ttl_orig,fooling_orig,0,0,
data_payload, len_payload, pkt1, &pkt1_len))
{
return verdict;
}
DLOG("resending original packet with extension header\n");
if (!rawsend((struct sockaddr *)&dst, desync_fwmark, ifout , pkt1, pkt1_len))
return verdict;
// this mode is final, no other options available
return VERDICT_DROP;
}
default:
// fix code analyzer warning
pkt1_len=0;
break;
}
if (b)
{
if (!rawsend_rep((struct sockaddr *)&dst, desync_fwmark, ifout , pkt1, pkt1_len))
return verdict;
if (params.desync_mode2==DESYNC_NONE || !desync_valid_second_stage_tcp(params.desync_mode2))
{
DLOG("reinjecting original packet. len=%zu len_payload=%zu\n", *len_pkt, len_payload)
verdict_tcp_csum_fix(verdict, tcphdr, transport_len, ip, ip6hdr);
if (!rawsend((struct sockaddr *)&dst, desync_fwmark, ifout , data_pkt, *len_pkt))
return verdict;
return VERDICT_DROP;
}
desync_mode = params.desync_mode2;
}
pkt1_len = sizeof(pkt1);
switch(desync_mode)
{
case DESYNC_DISORDER:
case DESYNC_DISORDER2:
if (split_pos)
{
uint8_t fakeseg[DPI_DESYNC_MAX_FAKE_LEN+100], *seg;
size_t seg_len;
if (params.desync_seqovl>=split_pos)
{
DLOG("seqovl>=split_pos. desync is not possible.\n")
return verdict;
}
if (split_pos<len_payload)
{
if (params.desync_seqovl)
{
seg_len = len_payload-split_pos+params.desync_seqovl;
if (seg_len>sizeof(fakeseg))
{
DLOG("seqovl is too large\n")
return verdict;
}
fill_pattern(fakeseg,params.desync_seqovl,params.seqovl_pattern,sizeof(params.seqovl_pattern));
memcpy(fakeseg+params.desync_seqovl,data_payload+split_pos,len_payload-split_pos);
seg = fakeseg;
}
else
{
seg = data_payload+split_pos;
seg_len = len_payload-split_pos;
}
if (!prepare_tcp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, flags_orig, net32_add(net32_add(tcphdr->th_seq,split_pos),-params.desync_seqovl), tcphdr->th_ack, tcphdr->th_win, scale_factor, timestamps,
ttl_orig,fooling_orig,params.desync_badseq_increment,params.desync_badseq_ack_increment,
seg, seg_len, pkt1, &pkt1_len))
return verdict;
DLOG("sending 2nd out-of-order tcp segment %zu-%zu len=%zu seqovl=%u : ",split_pos,len_payload-1, len_payload-split_pos, params.desync_seqovl)
hexdump_limited_dlog(seg,seg_len,PKTDATA_MAXDUMP); DLOG("\n")
if (!rawsend((struct sockaddr *)&dst, desync_fwmark, ifout , pkt1, pkt1_len))
return verdict;
}
if (desync_mode==DESYNC_DISORDER)
{
seg_len = sizeof(fakeseg);
if (!prepare_tcp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, flags_orig, tcphdr->th_seq, tcphdr->th_ack, tcphdr->th_win, scale_factor, timestamps,
ttl_fake,params.desync_fooling_mode,params.desync_badseq_increment,params.desync_badseq_ack_increment,
zeropkt, split_pos, fakeseg, &seg_len))
return verdict;
DLOG("sending fake(1) 1st out-of-order tcp segment 0-%zu len=%zu : ",split_pos-1, split_pos)
hexdump_limited_dlog(zeropkt,split_pos,PKTDATA_MAXDUMP); DLOG("\n")
if (!rawsend_rep((struct sockaddr *)&dst, desync_fwmark, ifout , fakeseg, seg_len))
return verdict;
}
pkt1_len = sizeof(pkt1);
if (!prepare_tcp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, flags_orig, tcphdr->th_seq, tcphdr->th_ack, tcphdr->th_win, scale_factor, timestamps,
ttl_orig,fooling_orig,params.desync_badseq_increment,params.desync_badseq_ack_increment,
data_payload, split_pos, pkt1, &pkt1_len))
return verdict;
DLOG("sending 1st out-of-order tcp segment 0-%zu len=%zu : ",split_pos-1, split_pos)
hexdump_limited_dlog(data_payload,split_pos,PKTDATA_MAXDUMP); DLOG("\n")
if (!rawsend((struct sockaddr *)&dst, desync_fwmark, ifout , pkt1, pkt1_len))
return verdict;
if (desync_mode==DESYNC_DISORDER)
{
DLOG("sending fake(2) 1st out-of-order tcp segment 0-%zu len=%zu : ",split_pos-1, split_pos)
hexdump_limited_dlog(zeropkt,split_pos,PKTDATA_MAXDUMP); DLOG("\n")
if (!rawsend_rep((struct sockaddr *)&dst, desync_fwmark, ifout , fakeseg, seg_len))
return verdict;
}
return VERDICT_DROP;
}
break;
case DESYNC_SPLIT:
case DESYNC_SPLIT2:
if (split_pos)
{
uint8_t fakeseg[DPI_DESYNC_MAX_FAKE_LEN+100],ovlseg[DPI_DESYNC_MAX_FAKE_LEN+100], *seg;
size_t fakeseg_len,seg_len;
if (desync_mode==DESYNC_SPLIT)
{
fakeseg_len = sizeof(fakeseg);
if (!prepare_tcp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, flags_orig, tcphdr->th_seq, tcphdr->th_ack, tcphdr->th_win, scale_factor, timestamps,
ttl_fake,params.desync_fooling_mode,params.desync_badseq_increment,params.desync_badseq_ack_increment,
zeropkt, split_pos, fakeseg, &fakeseg_len))
return verdict;
DLOG("sending fake(1) 1st tcp segment 0-%zu len=%zu : ",split_pos-1, split_pos)
hexdump_limited_dlog(zeropkt,split_pos,PKTDATA_MAXDUMP); DLOG("\n")
if (!rawsend_rep((struct sockaddr *)&dst, desync_fwmark, ifout , fakeseg, fakeseg_len))
return verdict;
}
if (params.desync_seqovl)
{
seg_len = split_pos+params.desync_seqovl;
if (seg_len>sizeof(ovlseg))
{
DLOG("seqovl is too large")
return verdict;
}
fill_pattern(ovlseg,params.desync_seqovl,params.seqovl_pattern,sizeof(params.seqovl_pattern));
memcpy(ovlseg+params.desync_seqovl,data_payload,split_pos);
seg = ovlseg;
}
else
{
seg = data_payload;
seg_len = split_pos;
}
if (!prepare_tcp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, flags_orig, net32_add(tcphdr->th_seq,-params.desync_seqovl), tcphdr->th_ack, tcphdr->th_win, scale_factor, timestamps,
ttl_orig,fooling_orig,params.desync_badseq_increment,params.desync_badseq_ack_increment,
seg, seg_len, pkt1, &pkt1_len))
return verdict;
DLOG("sending 1st tcp segment 0-%zu len=%zu seqovl=%u : ",split_pos-1, split_pos, params.desync_seqovl)
hexdump_limited_dlog(seg,seg_len,PKTDATA_MAXDUMP); DLOG("\n")
if (!rawsend((struct sockaddr *)&dst, desync_fwmark, ifout , pkt1, pkt1_len))
return verdict;
if (desync_mode==DESYNC_SPLIT)
{
DLOG("sending fake(2) 1st tcp segment 0-%zu len=%zu : ",split_pos-1, split_pos)
hexdump_limited_dlog(zeropkt,split_pos,PKTDATA_MAXDUMP); DLOG("\n")
if (!rawsend_rep((struct sockaddr *)&dst, desync_fwmark, ifout , fakeseg, fakeseg_len))
return verdict;
}
if (split_pos<len_payload)
{
pkt1_len = sizeof(pkt1);
if (!prepare_tcp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, flags_orig, net32_add(tcphdr->th_seq,split_pos), tcphdr->th_ack, tcphdr->th_win, scale_factor, timestamps,
ttl_orig,fooling_orig,params.desync_badseq_increment,params.desync_badseq_ack_increment,
data_payload+split_pos, len_payload-split_pos, pkt1, &pkt1_len))
return verdict;
DLOG("sending 2nd tcp segment %zu-%zu len=%zu : ",split_pos,len_payload-1, len_payload-split_pos)
hexdump_limited_dlog(data_payload+split_pos,len_payload-split_pos,PKTDATA_MAXDUMP); DLOG("\n")
if (!rawsend((struct sockaddr *)&dst, desync_fwmark, ifout , pkt1, pkt1_len))
return verdict;
}
return VERDICT_DROP;
}
break;
case DESYNC_IPFRAG2:
if (!reasm_offset)
{
verdict_tcp_csum_fix(verdict, tcphdr, transport_len, ip, ip6hdr);
uint8_t pkt3[DPI_DESYNC_MAX_FAKE_LEN+100], *pkt_orig;
size_t pkt_orig_len;
size_t ipfrag_pos = (params.desync_ipfrag_pos_tcp && params.desync_ipfrag_pos_tcp<transport_len) ? params.desync_ipfrag_pos_tcp : 24;
uint32_t ident = ip ? ip->ip_id ? ip->ip_id : htons(1+random()%0xFFFF) : htonl(1+random()%0xFFFFFFFF);
pkt1_len = sizeof(pkt1);
pkt2_len = sizeof(pkt2);
if (ip6hdr && (fooling_orig==FOOL_HOPBYHOP || fooling_orig==FOOL_DESTOPT))
{
pkt_orig_len = sizeof(pkt3);
if (!ip6_insert_simple_hdr(fooling_orig==FOOL_HOPBYHOP ? IPPROTO_HOPOPTS : IPPROTO_DSTOPTS, data_pkt, *len_pkt, pkt3, &pkt_orig_len))
return verdict;
pkt_orig = pkt3;
}
else
{
pkt_orig = data_pkt;
pkt_orig_len = *len_pkt;
}
if (!ip_frag(pkt_orig, pkt_orig_len, ipfrag_pos, ident, pkt1, &pkt1_len, pkt2, &pkt2_len))
return verdict;
DLOG("sending 1st ip fragment 0-%zu ip_payload_len=%zu : ", ipfrag_pos-1, ipfrag_pos)
hexdump_limited_dlog(pkt1,pkt1_len,IP_MAXDUMP); DLOG("\n")
if (!rawsend((struct sockaddr *)&dst, desync_fwmark, ifout , pkt1, pkt1_len))
return verdict;
DLOG("sending 2nd ip fragment %zu-%zu ip_payload_len=%zu : ", ipfrag_pos, transport_len-1, transport_len-ipfrag_pos)
hexdump_limited_dlog(pkt2,pkt2_len,IP_MAXDUMP); DLOG("\n")
if (!rawsend((struct sockaddr *)&dst, desync_fwmark, ifout , pkt2, pkt2_len))
return verdict;
return VERDICT_DROP;
}
}
}
return verdict;
}
// return : true - should continue, false - should stop with verdict
static bool quic_reasm_cancel(t_ctrack *ctrack, const char *reason)
{
reasm_orig_cancel(ctrack);
if (params.desync_any_proto)
{
DLOG("%s. applying tampering because desync_any_proto is set\n",reason)
return true;
}
else
{
DLOG("%s. not applying tampering because desync_any_proto is not set\n",reason)
return false;
}
}
static uint8_t dpi_desync_udp_packet_play(bool replay, size_t reasm_offset, uint32_t fwmark, const char *ifout, uint8_t *data_pkt, size_t *len_pkt, struct ip *ip, struct ip6_hdr *ip6hdr, struct udphdr *udphdr, size_t transport_len, uint8_t *data_payload, size_t len_payload)
{
uint8_t verdict=VERDICT_PASS;
// additional safety check
if (!!ip == !!ip6hdr) return verdict;
// no need to desync middle packets in reasm session
if (reasm_offset) return verdict;
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;
if (replay)
{
// in replay mode conntrack_replay is not NULL and ctrack is NULL
//ConntrackPoolDump(&params.conntrack);
if (!ConntrackPoolDoubleSearch(&params.conntrack, ip, ip6hdr, NULL, udphdr, &ctrack_replay, &bReverse) || bReverse)
return verdict;
}
else
{
// in real mode ctrack may be NULL or not NULL, conntrack_replay is equal to ctrack
ConntrackPoolPurge(&params.conntrack);
if (ConntrackPoolFeed(&params.conntrack, ip, ip6hdr, NULL, udphdr, len_payload, &ctrack, &bReverse))
{
ctrack_replay = ctrack;
maybe_cutoff(ctrack, IPPROTO_UDP);
}
HostFailPoolPurgeRateLimited(&params.hostlist_auto_fail_counters);
//ConntrackPoolDump(&params.conntrack);
}
if (bReverse) return verdict; // nothing to do. do not waste cpu
if (params.desync_mode==DESYNC_NONE && !*params.hostlist_auto_filename) return verdict; // do not waste cpu
// start and cutoff limiters
if (!replay && !process_desync_interval(ctrack)) return verdict;
uint32_t desync_fwmark = fwmark | params.desync_fwmark;
ttl_orig = ip ? ip->ip_ttl : ip6hdr->ip6_ctlun.ip6_un1.ip6_un1_hlim;
if (ip6hdr) ttl_fake = params.desync_ttl6 ? params.desync_ttl6 : ttl_orig;
else ttl_fake = params.desync_ttl ? params.desync_ttl : ttl_orig;
extract_endpoints(ip, ip6hdr, NULL, udphdr, &src, &dst);
if (len_payload)
{
const uint8_t *fake;
size_t fake_size;
bool b;
char host[256];
bool bHaveHost=false;
bool bKnownProtocol=false;
if (IsQUICInitial(data_payload,len_payload))
{
DLOG("packet contains QUIC initial\n")
if (ctrack && !ctrack->l7proto) ctrack->l7proto = QUIC;
uint8_t clean[16384], *pclean;
size_t clean_len;
bool bIsHello = false;
if (replay)
{
clean_len = ctrack_replay->reasm_orig.size_present;
pclean = ctrack_replay->reasm_orig.packet;
}
else
{
clean_len = sizeof(clean);
pclean = QUICDecryptInitial(data_payload,len_payload,clean,&clean_len) ? clean : NULL;
}
if (pclean)
{
if (ctrack && !ReasmIsEmpty(&ctrack->reasm_orig))
{
if (ReasmHasSpace(&ctrack->reasm_orig, clean_len))
{
reasm_orig_feed(ctrack,IPPROTO_UDP,clean,clean_len);
pclean = ctrack->reasm_orig.packet;
clean_len = ctrack->reasm_orig.size_present;
}
else
{
DLOG("QUIC reasm is too long. cancelling.\n");
reasm_orig_cancel(ctrack);
return verdict; // cannot be first packet
}
}
uint8_t defrag[16384];
size_t hello_offset, hello_len, defrag_len = sizeof(defrag);
if (QUICDefragCrypto(pclean,clean_len,defrag,&defrag_len))
{
bool bIsHello = IsQUICCryptoHello(defrag, defrag_len, &hello_offset, &hello_len);
bool bReqFull = bIsHello ? IsTLSHandshakeFull(defrag+hello_offset,hello_len) : false;
DLOG(bIsHello ? bReqFull ? "packet contains full TLS ClientHello\n" : "packet contains partial TLS ClientHello\n" : "packet does not contain TLS ClientHello\n")
if (ctrack)
{
if (bIsHello && !bReqFull && ReasmIsEmpty(&ctrack->reasm_orig))
{
// preallocate max buffer to avoid reallocs that cause memory copy
if (!reasm_orig_start(ctrack,IPPROTO_UDP,16384,16384,clean,clean_len))
{
reasm_orig_cancel(ctrack);
return verdict;
}
}
if (!ReasmIsEmpty(&ctrack->reasm_orig))
{
verdict_udp_csum_fix(verdict, udphdr, transport_len, ip, ip6hdr);
if (rawpacket_queue(&ctrack->delayed, &dst, desync_fwmark, ifout, data_pkt, *len_pkt, len_payload))
{
DLOG("DELAY desync until reasm is complete (#%u)\n", rawpacket_queue_count(&ctrack->delayed));
}
else
{
fprintf(stderr, "rawpacket_queue failed !'\n");
reasm_orig_cancel(ctrack);
return verdict;
}
if (bReqFull)
{
replay_queue(&ctrack->delayed);
reasm_orig_fin(ctrack);
}
return ct_new_postnat_fix_udp(ctrack, ip, ip6hdr, udphdr, len_pkt);
}
}
if (bIsHello)
{
bHaveHost = TLSHelloExtractHostFromHandshake(defrag + hello_offset, hello_len, host, sizeof(host), TLS_PARTIALS_ENABLE);
if (!bHaveHost && params.desync_skip_nosni)
{
reasm_orig_cancel(ctrack);
DLOG("not applying tampering to QUIC ClientHello without hostname in the SNI\n")
return verdict;
}
}
else
{
if (!quic_reasm_cancel(ctrack,"QUIC initial without ClientHello")) return verdict;
}
}
else
{
// defrag failed
if (!quic_reasm_cancel(ctrack,"QUIC initial defrag CRYPTO failed")) return verdict;
}
}
else
{
// decrypt failed
if (!quic_reasm_cancel(ctrack,"QUIC initial decryption failed")) return verdict;
}
fake = params.fake_quic;
fake_size = params.fake_quic_size;
bKnownProtocol = true;
}
else // not QUIC initial
{
// received payload without host. it means we are out of the request retransmission phase. stop counter
ctrack_stop_retrans_counter(ctrack);
reasm_orig_cancel(ctrack);
if (IsWireguardHandshakeInitiation(data_payload,len_payload))
{
DLOG("packet contains wireguard handshake initiation\n")
if (ctrack && !ctrack->l7proto) ctrack->l7proto = WIREGUARD;
fake = params.fake_wg;
fake_size = params.fake_wg_size;
bKnownProtocol = true;
}
else if (IsDhtD1(data_payload,len_payload))
{
DLOG("packet contains DHT d1...e\n")
if (ctrack && !ctrack->l7proto) ctrack->l7proto = DHT;
fake = params.fake_dht;
fake_size = params.fake_dht_size;
bKnownProtocol = true;
}
else
{
if (!params.desync_any_proto) return verdict;
DLOG("applying tampering to unknown protocol\n")
fake = params.fake_unknown_udp;
fake_size = params.fake_unknown_udp_size;
}
}
if (bHaveHost)
{
DLOG("hostname: %s\n",host)
if (params.hostlist || params.hostlist_exclude)
{
bool bBypass;
if (!HostlistCheck(host, &bBypass))
{
if (ctrack_replay)
{
ctrack_replay->hostname_ah_check = *params.hostlist_auto_filename && !bBypass;
if (ctrack_replay->hostname_ah_check)
{
// first request is not retrans
if (ctrack_replay->hostname)
process_retrans_fail(ctrack_replay, IPPROTO_UDP);
else
ctrack_replay->hostname=strdup(host);
}
}
DLOG("not applying tampering to this request\n")
return verdict;
}
}
}
enum dpi_desync_mode desync_mode = params.desync_mode;
uint32_t fooling_orig = FOOL_NONE;
if (params.debug)
{
printf("dpi desync src=");
print_sockaddr((struct sockaddr *)&src);
printf(" dst=");
print_sockaddr((struct sockaddr *)&dst);
printf("\n");
}
pkt1_len = sizeof(pkt1);
b = false;
switch(desync_mode)
{
case DESYNC_FAKE_KNOWN:
if (!bKnownProtocol)
{
DLOG("not applying fake because of unknown protocol\n");
desync_mode = params.desync_mode2;
break;
}
case DESYNC_FAKE:
if (!prepare_udp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, ttl_fake, params.desync_fooling_mode, NULL, 0, 0, fake, fake_size, pkt1, &pkt1_len))
return verdict;
DLOG("sending fake request : ");
hexdump_limited_dlog(fake,fake_size,PKTDATA_MAXDUMP); DLOG("\n")
if (!rawsend_rep((struct sockaddr *)&dst, desync_fwmark, ifout , pkt1, pkt1_len))
return verdict;
b = true;
break;
case DESYNC_HOPBYHOP:
case DESYNC_DESTOPT:
case DESYNC_IPFRAG1:
fooling_orig = (desync_mode==DESYNC_HOPBYHOP) ? FOOL_HOPBYHOP : (desync_mode==DESYNC_DESTOPT) ? FOOL_DESTOPT : FOOL_IPFRAG1;
if (ip6hdr && (params.desync_mode2==DESYNC_NONE || !desync_valid_second_stage_udp(params.desync_mode2)))
{
if (!prepare_udp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst,
ttl_orig,fooling_orig,NULL,0,0,
data_payload, len_payload, pkt1, &pkt1_len))
{
return verdict;
}
DLOG("resending original packet with extension header\n");
if (!rawsend((struct sockaddr *)&dst, desync_fwmark, ifout , pkt1, pkt1_len))
return verdict;
// this mode is final, no other options available
return ct_new_postnat_fix_udp(ctrack, ip, ip6hdr, udphdr, len_pkt);
}
desync_mode = params.desync_mode2;
break;
default:
// fix code analyzer warning
pkt1_len=0;
break;
}
if (b)
{
if (params.desync_mode2==DESYNC_NONE || !desync_valid_second_stage_udp(params.desync_mode2))
{
DLOG("reinjecting original packet. len=%zu len_payload=%zu\n", *len_pkt, len_payload)
verdict_udp_csum_fix(verdict, udphdr, transport_len, ip, ip6hdr);
if (!rawsend((struct sockaddr *)&dst, desync_fwmark, ifout , data_pkt, *len_pkt))
return verdict;
return ct_new_postnat_fix_udp(ctrack, ip, ip6hdr, udphdr, len_pkt);
}
desync_mode = params.desync_mode2;
}
switch(desync_mode)
{
case DESYNC_UDPLEN:
pkt1_len = sizeof(pkt1);
if (!prepare_udp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, ttl_orig,fooling_orig, params.udplen_pattern, sizeof(params.udplen_pattern), params.udplen_increment, data_payload, len_payload, pkt1, &pkt1_len))
{
DLOG("could not construct packet with modified length. too large ?\n");
return verdict;
}
DLOG("resending original packet with increased by %d length\n", params.udplen_increment);
if (!rawsend((struct sockaddr *)&dst, desync_fwmark, ifout , pkt1, pkt1_len))
return verdict;
return ct_new_postnat_fix_udp(ctrack, ip, ip6hdr, udphdr, len_pkt);
case DESYNC_TAMPER:
if (IsDhtD1(data_payload,len_payload))
{
size_t szbuf,szcopy;
memcpy(pkt2,"d2:001:x",8);
pkt2_len=8;
szbuf=sizeof(pkt2)-pkt2_len;
szcopy=len_payload-1;
if (szcopy>szbuf)
{
DLOG("packet is too long to tamper");
return verdict;
}
memcpy(pkt2+pkt2_len,data_payload+1,szcopy);
pkt2_len+=szcopy;
pkt1_len = sizeof(pkt1);
if (!prepare_udp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, ttl_orig,fooling_orig, NULL, 0 , 0, pkt2, pkt2_len, pkt1, &pkt1_len))
{
DLOG("could not construct packet with modified length. too large ?\n");
return verdict;
}
DLOG("resending tampered DHT\n");
if (!rawsend((struct sockaddr *)&dst, desync_fwmark, ifout , pkt1, pkt1_len))
return verdict;
return ct_new_postnat_fix_udp(ctrack, ip, ip6hdr, udphdr, len_pkt);
}
else
{
DLOG("payload is not tamperable\n");
return verdict;
}
case DESYNC_IPFRAG2:
{
verdict_udp_csum_fix(verdict, udphdr, transport_len, ip, ip6hdr);
uint8_t pkt3[DPI_DESYNC_MAX_FAKE_LEN+100], *pkt_orig;
size_t pkt_orig_len;
size_t ipfrag_pos = (params.desync_ipfrag_pos_udp && params.desync_ipfrag_pos_udp<transport_len) ? params.desync_ipfrag_pos_udp : sizeof(struct udphdr);
// freebsd do not set ip.id
uint32_t ident = ip ? ip->ip_id ? ip->ip_id : htons(1+random()%0xFFFF) : htonl(1+random()%0xFFFFFFFF);
pkt1_len = sizeof(pkt1);
pkt2_len = sizeof(pkt2);
if (ip6hdr && (fooling_orig==FOOL_HOPBYHOP || fooling_orig==FOOL_DESTOPT))
{
pkt_orig_len = sizeof(pkt3);
if (!ip6_insert_simple_hdr(fooling_orig==FOOL_HOPBYHOP ? IPPROTO_HOPOPTS : IPPROTO_DSTOPTS, data_pkt, *len_pkt, pkt3, &pkt_orig_len))
return verdict;
pkt_orig = pkt3;
}
else
{
pkt_orig = data_pkt;
pkt_orig_len = *len_pkt;
}
if (!ip_frag(pkt_orig, pkt_orig_len, ipfrag_pos, ident, pkt1, &pkt1_len, pkt2, &pkt2_len))
return verdict;
DLOG("sending 1st ip fragment 0-%zu ip_payload_len=%zu : ", ipfrag_pos-1, ipfrag_pos)
hexdump_limited_dlog(pkt1,pkt1_len,IP_MAXDUMP); DLOG("\n")
if (!rawsend((struct sockaddr *)&dst, desync_fwmark, ifout , pkt1, pkt1_len))
return verdict;
DLOG("sending 2nd ip fragment %zu-%zu ip_payload_len=%zu : ", ipfrag_pos, transport_len-1, transport_len-ipfrag_pos)
hexdump_limited_dlog(pkt2,pkt2_len,IP_MAXDUMP); DLOG("\n")
if (!rawsend((struct sockaddr *)&dst, desync_fwmark, ifout , pkt2, pkt2_len))
return verdict;
return ct_new_postnat_fix_udp(ctrack, ip, ip6hdr, udphdr, len_pkt);
}
}
}
return verdict;
}
static void packet_debug(bool replay, uint8_t proto, const struct ip *ip, const struct ip6_hdr *ip6hdr, const struct tcphdr *tcphdr, const struct udphdr *udphdr, const uint8_t *data_payload, size_t len_payload)
{
if (params.debug)
{
if (replay) printf("REPLAY ");
if (ip)
{
printf("IP4: ");
print_ip(ip);
}
else if (ip6hdr)
{
printf("IP6: ");
print_ip6hdr(ip6hdr, proto);
}
if (tcphdr)
{
printf(" ");
print_tcphdr(tcphdr);
printf("\n");
if (len_payload) { printf("TCP: "); hexdump_limited_dlog(data_payload, len_payload, 32); printf("\n"); }
}
else if (udphdr)
{
printf(" ");
print_udphdr(udphdr);
printf("\n");
if (len_payload) { printf("UDP: "); hexdump_limited_dlog(data_payload, len_payload, 32); printf("\n"); }
}
else
printf("\n");
}
}
static uint8_t dpi_desync_packet_play(bool replay, size_t reasm_offset, uint32_t fwmark, const char *ifout, uint8_t *data_pkt, size_t *len_pkt)
{
struct ip *ip;
struct ip6_hdr *ip6hdr;
struct tcphdr *tcphdr;
struct udphdr *udphdr;
size_t transport_len;
uint8_t *data_payload,proto;
size_t len_payload;
uint8_t verdict = VERDICT_PASS;
proto_dissect_l3l4(data_pkt,*len_pkt,&ip,&ip6hdr,&proto,&tcphdr,&udphdr,&transport_len,&data_payload,&len_payload);
if (!!ip != !!ip6hdr)
{
packet_debug(replay, proto, ip, ip6hdr, tcphdr, udphdr, data_payload, len_payload);
switch(proto)
{
case IPPROTO_TCP:
if (tcphdr)
{
verdict = dpi_desync_tcp_packet_play(replay, reasm_offset, fwmark, ifout, data_pkt, len_pkt, ip, ip6hdr, tcphdr, transport_len, data_payload, len_payload);
verdict_tcp_csum_fix(verdict, tcphdr, transport_len, ip, ip6hdr);
}
break;
case IPPROTO_UDP:
if (udphdr)
{
verdict = dpi_desync_udp_packet_play(replay, reasm_offset, fwmark, ifout, data_pkt, len_pkt, ip, ip6hdr, udphdr, transport_len, data_payload, len_payload);
verdict_udp_csum_fix(verdict, udphdr, transport_len, ip, ip6hdr);
}
break;
}
}
return verdict;
}
uint8_t dpi_desync_packet(uint32_t fwmark, const char *ifout, uint8_t *data_pkt, size_t *len_pkt)
{
return dpi_desync_packet_play(false, 0, fwmark, ifout, data_pkt, len_pkt);
}
static bool replay_queue(struct rawpacket_tailhead *q)
{
struct rawpacket *rp;
size_t offset;
unsigned int i;
bool b = true;
for (i=1,offset=0 ; (rp=rawpacket_dequeue(q)) ; offset+=rp->len_payload, rawpacket_free(rp), i++)
{
DLOG("REPLAYING delayed packet #%u offset %zu\n",i,offset)
uint8_t verdict = dpi_desync_packet_play(true, offset, rp->fwmark, rp->ifout, rp->packet, &rp->len);
switch(verdict & VERDICT_MASK)
{
case VERDICT_MODIFY:
DLOG("SENDING delayed packet #%u modified\n", i)
b &= rawsend_rp(rp);
break;
case VERDICT_PASS:
DLOG("SENDING delayed packet #%u unmodified\n", i)
b &= rawsend_rp(rp);
break;
case VERDICT_DROP:
DLOG("DROPPING delayed packet #%u\n", i)
break;
}
}
return b;
}
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