#define _GNU_SOURCE #include "desync.h" #include "protocol.h" #include "params.h" #include "helpers.h" #include "hostlist.h" #include "ipset.h" #include "conntrack.h" #include 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 }; static const char * tld[]={"com","org","net","edu","gov","biz"}; void randomize_default_tls_payload(uint8_t *p) { fill_random_bytes(p+11,32); fill_random_bytes(p+44,32); fill_random_az(p+125,1); fill_random_az09(p+126,5); memcpy(p+132,tld[random()%(sizeof(tld)/sizeof(*tld))],3); } #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; } static bool dp_match_l3l4(struct desync_profile *dp, uint8_t l3proto, const struct sockaddr *dest) { return ((dest->sa_family==AF_INET && dp->filter_ipv4) || (dest->sa_family==AF_INET6 && dp->filter_ipv6)) && (l3proto==IPPROTO_TCP && pf_in_range(saport(dest), &dp->pf_tcp) || l3proto==IPPROTO_UDP && pf_in_range(saport(dest), &dp->pf_tcp)) && 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); } static bool dp_impossible(struct desync_profile *dp, const char *hostname, t_l7proto l7proto) { return !PROFILE_IPSETS_EMPTY(dp) && ((dp->filter_l7 && !l7_proto_match(l7proto, dp->filter_l7)) || (!*dp->hostlist_auto_filename && !hostname && (dp->hostlist || dp->hostlist_exclude))); } 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) { if (bCheckDone) *bCheckDone = false; // impossible case, hard filter // impossible check avoids relatively slow ipset search if (!dp_impossible(dp,hostname,l7proto) && dp_match_l3l4(dp,l3proto,dest)) { // soft filter if (dp->filter_l7 && !l7_proto_match(l7proto, dp->filter_l7)) return false; // autohostlist profile matching l3/l4 filter always win if (*dp->hostlist_auto_filename) return true; if (dp->hostlist || dp->hostlist_exclude) { // without known hostname first profile matching l3/l4 filter and without hostlist filter wins if (hostname) { if (bCheckDone) *bCheckDone = true; bool b; b = HostlistCheck(dp, hostname, bExcluded); if (bCheckResult) *bCheckResult = b; return b; } } else // profile without hostlist filter wins return true; } 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;ipcounter_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) && !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, 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; } dp->hostlist_auto_mod_time = file_mod_time(dp->hostlist_auto_filename); } 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 : tcp 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) { size_t rsplit_pos = split_pos; // normalize split pos to current packet split_pos=(split_pos>reasm_offset && (split_pos-reasm_offset) %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 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"); } } } 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; 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 = ip ? ip->ip_ttl : ip6hdr->ip6_ctlun.ip6_un1.ip6_un1_hlim; uint32_t desync_fwmark = fwmark | params.desync_fwmark; extract_endpoints(ip, ip6hdr, tcphdr, NULL, &src, &dst); if (replay) { // in replay mode conntrack_replay is not NULL and ctrack is NULL //ConntrackPoolDump(¶ms.conntrack); if (!ConntrackPoolDoubleSearch(¶ms.conntrack, ip, ip6hdr, tcphdr, 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, ip, ip6hdr, tcphdr, NULL, 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(tcphdr)) { tcp_rewrite_winsize(tcphdr, 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,!!ip6hdr); } // 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 (tcphdr->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 (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 : 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 (len_payload) auto_hostlist_reset_fail_counter(dp, ctrack->hostname, client_ip_port, ctrack->l7proto); 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 (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(tcphdr, 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 : (ip6hdr ? (dp->desync_ttl6 ? dp->desync_ttl6 : ttl_orig) : (dp->desync_ttl ? dp->desync_ttl : ttl_orig)); flags_orig = *((uint8_t*)tcphdr+13); scale_factor = tcp_find_scale_factor(tcphdr); timestamps = tcp_find_timestamps(tcphdr); if (!replay) { // start and cutoff limiters if (!process_desync_interval(dp, ctrack)) return verdict; if (tcp_syn_segment(tcphdr)) { 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, tcphdr->th_seq, tcphdr->th_ack, tcphdr->th_win, scale_factor, timestamps, ttl_fake,IP4_TOS(ip),IP6_FLOW(ip6hdr), 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(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,IP4_TOS(ip),IP6_FLOW(ip6hdr), 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, ip, ip6hdr, tcphdr); break; default: break; } // can do nothing else with SYN packet return verdict; } } // !replay if (!(tcphdr->th_flags & TH_SYN) && len_payload) { const uint8_t *fake; size_t fake_size; char host[256]; bool bHaveHost=false; uint8_t *p, *phost; const uint8_t *rdata_payload = data_payload; size_t rlen_payload = len_payload; size_t split_pos; t_l7proto l7proto = UNKNOWN; 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, (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(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 { 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) { DLOG("not applying tampering to TLS ClientHello without hostname in the SNI\n"); reasm_orig_cancel(ctrack); return verdict; } } 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); bool bDiscoveredL7; if (ctrack_replay) { bDiscoveredL7 = !ctrack_replay->l7proto_discovered && ctrack_replay->l7proto!=UNKNOWN; ctrack_replay->l7proto_discovered=true; } else bDiscoveredL7 = !ctrack_replay && l7proto!=UNKNOWN; if (bDiscoveredL7) DLOG("discovered l7 protocol\n"); bool bDiscoveredHostname = bHaveHost && !(ctrack_replay && ctrack_replay->hostname); if (bDiscoveredHostname) { DLOG("discovered hostname\n"); if (ctrack_replay) { ctrack_replay->hostname=strdup(host); if (!ctrack_replay->hostname) { DLOG_ERR("hostname dup : out of memory"); reasm_orig_cancel(ctrack); return verdict; } } } bool bCheckDone=false, bCheckResult=false, bCheckExcluded=false; if (bDiscoveredL7 || bDiscoveredHostname) { struct desync_profile *dp_prev = dp; dp = dp_find(¶ms.desync_profiles, IPPROTO_TCP, (struct sockaddr *)&dst, ctrack_replay ? ctrack_replay->hostname : host, ctrack_replay ? ctrack_replay->l7proto : l7proto, &bCheckDone, &bCheckResult, &bCheckExcluded); if (ctrack_replay) { ctrack_replay->dp = dp; ctrack_replay->dp_search_complete = true; ctrack_replay->bCheckDone = bCheckDone; ctrack_replay->bCheckResult = bCheckResult; ctrack_replay->bCheckExcluded = bCheckExcluded; } if (!dp) { reasm_orig_cancel(ctrack); return verdict; } if (dp!=dp_prev) { DLOG("desync profile changed by revealed l7 protocol or hostname !\n"); // rediscover autottl autottl_discover(ctrack_replay,!!ip6hdr); // re-evaluate start/cutoff limiters if (!replay) { maybe_cutoff(ctrack, IPPROTO_TCP); if (!process_desync_interval(dp, ctrack)) { reasm_orig_cancel(ctrack); return verdict; } } } } else if (ctrack_replay) { bCheckDone = ctrack_replay->bCheckDone; bCheckResult = ctrack_replay->bCheckResult; bCheckExcluded = ctrack_replay->bCheckExcluded; } if (bHaveHost && (dp->hostlist || dp->hostlist_exclude)) { if (!bCheckDone) bCheckResult = HostlistCheck(dp, host, &bCheckExcluded); if (bCheckResult) ctrack_stop_retrans_counter(ctrack_replay); else { if (ctrack_replay) { ctrack_replay->hostname_ah_check = *dp->hostlist_auto_filename && !bCheckExcluded; if (!ctrack_replay->hostname_ah_check) ctrack_stop_retrans_counter(ctrack_replay); } DLOG("not applying tampering to this request\n"); reasm_orig_cancel(ctrack); return verdict; } } // desync profile may have changed after hostname was revealed switch(l7proto) { case HTTP: fake = dp->fake_http; fake_size = dp->fake_http_size; split_pos = HttpPos(dp->desync_split_http_req, dp->desync_split_pos, rdata_payload, rlen_payload); break; case TLS: fake = dp->fake_tls; fake_size = dp->fake_tls_size; split_pos = TLSPos(dp->desync_split_tls, dp->desync_split_pos, rdata_payload, rlen_payload, 0); break; default: fake = dp->fake_unknown; fake_size = dp->fake_unknown_size; split_pos=dp->desync_split_pos; break; } // we do not need reasm buffer anymore reasm_orig_cancel(ctrack); rdata_payload=NULL; if (l7proto==UNKNOWN) { if (!dp->desync_any_proto) { DLOG("not applying tampering to unknown protocol\n"); return verdict; } DLOG("applying tampering to unknown protocol\n"); } ttl_fake = (ctrack_replay && ctrack_replay->autottl) ? ctrack_replay->autottl : (ip6hdr ? (dp->desync_ttl6 ? dp->desync_ttl6 : ttl_orig) : (dp->desync_ttl ? dp->desync_ttl : ttl_orig)); if ((l7proto == HTTP) && (dp->hostcase || dp->hostnospace || dp->domcase) && HttpFindHost(&phost,data_payload,len_payload)) { if (dp->hostcase) { DLOG("modifying Host: => %c%c%c%c:\n", dp->hostspell[0], dp->hostspell[1], dp->hostspell[2], dp->hostspell[3]); memcpy(phost, dp->hostspell, 4); verdict=VERDICT_MODIFY; } if (dp->domcase) { DLOG("mixing domain case\n"); for (p = phost+5; 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 (dp->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 + 5, phost + 6, pua - phost - 6); pua[-1]=' '; } else { memmove(pua + 1, pua, phost - pua + 5); *pua = ' '; } verdict=VERDICT_MODIFY; } } if (dp->desync_mode==DESYNC_NONE) return verdict; if (params.debug) { char s1[48],s2[48]; ntop46_port((struct sockaddr *)&src, s1, sizeof(s1)); ntop46_port((struct sockaddr *)&dst, s2, sizeof(s2)); DLOG("dpi desync src=%s dst=%s\n",s1,s2); } 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 = dp->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 = dp->desync_mode2; break; } if (l7proto==UNKNOWN) { DLOG("not applying fake because of unknown protocol\n"); desync_mode = dp->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,IP4_TOS(ip),IP6_FLOW(ip6hdr), dp->desync_fooling_mode,dp->desync_badseq_increment,dp->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,IP4_TOS(ip),IP6_FLOW(ip6hdr), dp->desync_fooling_mode,dp->desync_badseq_increment,dp->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 = dp->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,IP4_TOS(ip),IP6_FLOW(ip6hdr), 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: pkt1_len=0; break; } if (b) { if (!rawsend_rep(dp->desync_repeats,(struct sockaddr *)&dst, desync_fwmark, ifout , pkt1, pkt1_len)) return verdict; if (dp->desync_mode2==DESYNC_NONE || !desync_valid_second_stage_tcp(dp->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 = dp->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 (dp->desync_seqovl>=split_pos) { DLOG("seqovl>=split_pos. desync is not possible.\n"); return verdict; } if (split_posdesync_seqovl) { seg_len = len_payload-split_pos+dp->desync_seqovl; if (seg_len>sizeof(fakeseg)) { DLOG("seqovl is too large\n"); return verdict; } fill_pattern(fakeseg,dp->desync_seqovl,dp->seqovl_pattern,sizeof(dp->seqovl_pattern)); memcpy(fakeseg+dp->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),-dp->desync_seqovl), tcphdr->th_ack, tcphdr->th_win, scale_factor, timestamps, ttl_orig,IP4_TOS(ip),IP6_FLOW(ip6hdr), fooling_orig,dp->desync_badseq_increment,dp->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, dp->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,IP4_TOS(ip),IP6_FLOW(ip6hdr), dp->desync_fooling_mode,dp->desync_badseq_increment,dp->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(dp->desync_repeats,(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,IP4_TOS(ip),IP6_FLOW(ip6hdr), fooling_orig,dp->desync_badseq_increment,dp->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(dp->desync_repeats,(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,IP4_TOS(ip),IP6_FLOW(ip6hdr), dp->desync_fooling_mode,dp->desync_badseq_increment,dp->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(dp->desync_repeats,(struct sockaddr *)&dst, desync_fwmark, ifout , fakeseg, fakeseg_len)) return verdict; } if (dp->desync_seqovl) { seg_len = split_pos+dp->desync_seqovl; if (seg_len>sizeof(ovlseg)) { DLOG("seqovl is too large"); return verdict; } fill_pattern(ovlseg,dp->desync_seqovl,dp->seqovl_pattern,sizeof(dp->seqovl_pattern)); memcpy(ovlseg+dp->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,-dp->desync_seqovl), tcphdr->th_ack, tcphdr->th_win, scale_factor, timestamps, ttl_orig,IP4_TOS(ip),IP6_FLOW(ip6hdr), fooling_orig,dp->desync_badseq_increment,dp->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, dp->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(dp->desync_repeats,(struct sockaddr *)&dst, desync_fwmark, ifout , fakeseg, fakeseg_len)) return verdict; } if (split_posth_seq,split_pos), tcphdr->th_ack, tcphdr->th_win, scale_factor, timestamps, ttl_orig,IP4_TOS(ip),IP6_FLOW(ip6hdr), fooling_orig,dp->desync_badseq_increment,dp->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 = (dp->desync_ipfrag_pos_tcp && dp->desync_ipfrag_pos_tcpdesync_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; } default: break; } } 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 (ctrack && ctrack->dp && ctrack->dp->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; 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; t_l7proto l7proto = UNKNOWN; ttl_orig = ip ? ip->ip_ttl : ip6hdr->ip6_ctlun.ip6_un1.ip6_un1_hlim; extract_endpoints(ip, ip6hdr, NULL, udphdr, &src, &dst); if (replay) { // in replay mode conntrack_replay is not NULL and ctrack is NULL //ConntrackPoolDump(¶ms.conntrack); if (!ConntrackPoolDoubleSearch(¶ms.conntrack, ip, ip6hdr, NULL, udphdr, &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_UDP, (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, ip, ip6hdr, NULL, udphdr, 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_UDP, (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_UDP); HostFailPoolPurgeRateLimited(&dp->hostlist_auto_fail_counters); //ConntrackPoolDump(¶ms.conntrack); } if (bReverse && ctrack) { if (!ctrack->incoming_ttl) { DLOG("incoming TTL %u\n",ttl_orig); ctrack->incoming_ttl = ttl_orig; } if (!ctrack->autottl) autottl_discover(ctrack,!!ip6hdr); return verdict; // nothing to do. do not waste cpu } // start and cutoff limiters if (!replay && !process_desync_interval(dp, ctrack)) return verdict; uint32_t desync_fwmark = fwmark | params.desync_fwmark; if (len_payload) { const uint8_t *fake; size_t fake_size; bool b; char host[256]; bool bHaveHost=false; if (IsQUICInitial(data_payload,len_payload)) { DLOG("packet contains QUIC initial\n"); l7proto = QUIC; if (ctrack && ctrack->l7proto==UNKNOWN) ctrack->l7proto = l7proto; uint8_t clean[16384], *pclean; size_t clean_len; 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 { DLOG_ERR("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 && dp->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; } } 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"); l7proto = WIREGUARD; if (ctrack && ctrack->l7proto==UNKNOWN) ctrack->l7proto = l7proto; } else if (IsDhtD1(data_payload,len_payload)) { DLOG("packet contains DHT d1...e\n"); l7proto = DHT; if (ctrack && ctrack->l7proto==UNKNOWN) ctrack->l7proto = l7proto; } else { if (!dp->desync_any_proto) { DLOG("not applying tampering to unknown protocol\n"); return verdict; } DLOG("applying tampering to unknown protocol\n"); } } if (bHaveHost) DLOG("hostname: %s\n",host); bool bDiscoveredL7; if (ctrack_replay) { bDiscoveredL7 = !ctrack_replay->l7proto_discovered && ctrack_replay->l7proto!=UNKNOWN; ctrack_replay->l7proto_discovered=true; } else bDiscoveredL7 = !ctrack_replay && l7proto!=UNKNOWN; if (bDiscoveredL7) DLOG("discovered l7 protocol\n"); bool bDiscoveredHostname = bHaveHost && !(ctrack_replay && ctrack_replay->hostname); if (bDiscoveredHostname) { DLOG("discovered hostname\n"); if (ctrack_replay) { ctrack_replay->hostname=strdup(host); if (!ctrack_replay->hostname) { DLOG_ERR("hostname dup : out of memory"); return verdict; } } } bool bCheckDone=false, bCheckResult=false, bCheckExcluded=false; if (bDiscoveredL7 || bDiscoveredHostname) { struct desync_profile *dp_prev = dp; dp = dp_find(¶ms.desync_profiles, IPPROTO_UDP, (struct sockaddr *)&dst, ctrack_replay ? ctrack_replay->hostname : host, ctrack_replay ? ctrack_replay->l7proto : l7proto, &bCheckDone, &bCheckResult, &bCheckExcluded); if (ctrack_replay) { ctrack_replay->dp = dp; ctrack_replay->dp_search_complete = true; ctrack_replay->bCheckDone = bCheckDone; ctrack_replay->bCheckResult = bCheckResult; ctrack_replay->bCheckExcluded = bCheckExcluded; } if (!dp) { reasm_orig_cancel(ctrack); return verdict; } if (dp!=dp_prev) { DLOG("desync profile changed by revealed l7 protocol or hostname !\n"); // rediscover autottl autottl_discover(ctrack_replay,!!ip6hdr); // re-evaluate start/cutoff limiters if (!replay) { maybe_cutoff(ctrack, IPPROTO_UDP); if (!process_desync_interval(dp, ctrack)) return verdict; } } } else if (ctrack_replay) { bCheckDone = ctrack_replay->bCheckDone; bCheckResult = ctrack_replay->bCheckResult; bCheckExcluded = ctrack_replay->bCheckExcluded; } if (bHaveHost && (dp->hostlist || dp->hostlist_exclude)) { if (!bCheckDone) bCheckResult = HostlistCheck(dp, host, &bCheckExcluded); if (bCheckResult) ctrack_stop_retrans_counter(ctrack_replay); else { if (ctrack_replay) { ctrack_replay->hostname_ah_check = *dp->hostlist_auto_filename && !bCheckExcluded; if (ctrack_replay->hostname_ah_check) { // first request is not retrans if (ctrack_replay->hostname) process_retrans_fail(ctrack_replay, IPPROTO_UDP, (struct sockaddr*)&src); else ctrack_replay->hostname=strdup(host); } } DLOG("not applying tampering to this request\n"); return verdict; } } // desync profile may have changed after hostname was revealed switch(l7proto) { case QUIC: fake = dp->fake_quic; fake_size = dp->fake_quic_size; break; case WIREGUARD: fake = dp->fake_wg; fake_size = dp->fake_wg_size; break; case DHT: fake = dp->fake_dht; fake_size = dp->fake_dht_size; break; default: fake = dp->fake_unknown_udp; fake_size = dp->fake_unknown_udp_size; break; } ttl_fake = (ctrack_replay && ctrack_replay->autottl) ? ctrack_replay->autottl : (ip6hdr ? (dp->desync_ttl6 ? dp->desync_ttl6 : ttl_orig) : (dp->desync_ttl ? dp->desync_ttl : ttl_orig)); enum dpi_desync_mode desync_mode = dp->desync_mode; uint32_t fooling_orig = FOOL_NONE; if (params.debug) { char s1[48],s2[48]; ntop46_port((struct sockaddr *)&src, s1, sizeof(s1)); ntop46_port((struct sockaddr *)&dst, s2, sizeof(s2)); DLOG("dpi desync src=%s dst=%s\n",s1,s2); } pkt1_len = sizeof(pkt1); b = false; switch(desync_mode) { case DESYNC_FAKE_KNOWN: if (l7proto==UNKNOWN) { DLOG("not applying fake because of unknown protocol\n"); desync_mode = dp->desync_mode2; break; } case DESYNC_FAKE: if (!prepare_udp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, ttl_fake, IP4_TOS(ip),IP6_FLOW(ip6hdr), dp->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(dp->desync_repeats,(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 && (dp->desync_mode2==DESYNC_NONE || !desync_valid_second_stage_udp(dp->desync_mode2))) { if (!prepare_udp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, ttl_orig,IP4_TOS(ip),IP6_FLOW(ip6hdr), 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 = dp->desync_mode2; break; default: pkt1_len=0; break; } if (b) { if (dp->desync_mode2==DESYNC_NONE || !desync_valid_second_stage_udp(dp->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 = dp->desync_mode2; } switch(desync_mode) { case DESYNC_UDPLEN: pkt1_len = sizeof(pkt1); if (!prepare_udp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, ttl_orig,IP4_TOS(ip),IP6_FLOW(ip6hdr), fooling_orig, dp->udplen_pattern, sizeof(dp->udplen_pattern), dp->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", dp->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,IP4_TOS(ip),IP6_FLOW(ip6hdr), 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 = (dp->desync_ipfrag_pos_udp && dp->desync_ipfrag_pos_udpdesync_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); } default: break; } } 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) DLOG("REPLAY "); if (ip) { char s[66]; str_ip(s,sizeof(s),ip); DLOG("IP4: %s",s); } else if (ip6hdr) { char s[128]; str_ip6hdr(s,sizeof(s),ip6hdr, proto); DLOG("IP6: %s",s); } if (tcphdr) { char s[80]; str_tcphdr(s,sizeof(s),tcphdr); DLOG(" %s\n",s); if (len_payload) { DLOG("TCP: "); hexdump_limited_dlog(data_payload, len_payload, 32); DLOG("\n"); } } else if (udphdr) { char s[30]; str_udphdr(s,sizeof(s),udphdr); DLOG(" %s\n",s); if (len_payload) { DLOG("UDP: "); hexdump_limited_dlog(data_payload, len_payload, 32); DLOG("\n"); } } else DLOG("\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; }