#define _GNU_SOURCE #include "desync.h" #include "protocol.h" #include "params.h" #include "helpers.h" #include "hostlist.h" #include "conntrack.h" #include const char *fake_http_request_default = "GET / HTTP/1.1\r\nHost: www.w3.org\r\n" "User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:70.0) Gecko/20100101 Firefox/70.0\r\n" "Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8\r\n" "Accept-Encoding: gzip, deflate\r\n\r\n"; const uint8_t fake_tls_clienthello_default[517] = { 0x16, 0x03, 0x01, 0x02, 0x00, 0x01, 0x00, 0x01, 0xfc, 0x03, 0x03, 0x9a, 0x8f, 0xa7, 0x6a, 0x5d, 0x57, 0xf3, 0x62, 0x19, 0xbe, 0x46, 0x82, 0x45, 0xe2, 0x59, 0x5c, 0xb4, 0x48, 0x31, 0x12, 0x15, 0x14, 0x79, 0x2c, 0xaa, 0xcd, 0xea, 0xda, 0xf0, 0xe1, 0xfd, 0xbb, 0x20, 0xf4, 0x83, 0x2a, 0x94, 0xf1, 0x48, 0x3b, 0x9d, 0xb6, 0x74, 0xba, 0x3c, 0x81, 0x63, 0xbc, 0x18, 0xcc, 0x14, 0x45, 0x57, 0x6c, 0x80, 0xf9, 0x25, 0xcf, 0x9c, 0x86, 0x60, 0x50, 0x31, 0x2e, 0xe9, 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, 0x33, 0x00, 0x39, 0x00, 0x2f, 0x00, 0x35, 0x01, 0x00, 0x01, 0x91, 0x00, 0x00, 0x00, 0x0f, 0x00, 0x0d, 0x00, 0x00, 0x0a, 0x77, 0x77, 0x77, 0x2e, 0x77, 0x33, 0x2e, 0x6f, 0x72, 0x67, 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, 0x23, 0x00, 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, 0x33, 0x00, 0x6b, 0x00, 0x69, 0x00, 0x1d, 0x00, 0x20, 0xb0, 0xe4, 0xda, 0x34, 0xb4, 0x29, 0x8d, 0xd3, 0x5c, 0x70, 0xd3, 0xbe, 0xe8, 0xa7, 0x2a, 0x6b, 0xe4, 0x11, 0x19, 0x8b, 0x18, 0x9d, 0x83, 0x9a, 0x49, 0x7c, 0x83, 0x7f, 0xa9, 0x03, 0x8c, 0x3c, 0x00, 0x17, 0x00, 0x41, 0x04, 0x4c, 0x04, 0xa4, 0x71, 0x4c, 0x49, 0x75, 0x55, 0xd1, 0x18, 0x1e, 0x22, 0x62, 0x19, 0x53, 0x00, 0xde, 0x74, 0x2f, 0xb3, 0xde, 0x13, 0x54, 0xe6, 0x78, 0x07, 0x94, 0x55, 0x0e, 0xb2, 0x6c, 0xb0, 0x03, 0xee, 0x79, 0xa9, 0x96, 0x1e, 0x0e, 0x98, 0x17, 0x78, 0x24, 0x44, 0x0c, 0x88, 0x80, 0x06, 0x8b, 0xd4, 0x80, 0xbf, 0x67, 0x7c, 0x37, 0x6a, 0x5b, 0x46, 0x4c, 0xa7, 0x98, 0x6f, 0xb9, 0x22, 0x00, 0x2b, 0x00, 0x09, 0x08, 0x03, 0x04, 0x03, 0x03, 0x03, 0x02, 0x03, 0x01, 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, 0x2d, 0x00, 0x02, 0x01, 0x01, 0x00, 0x1c, 0x00, 0x02, 0x40, 0x01, 0x00, 0x15, 0x00, 0x96, 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() { memset(zeropkt, 0, sizeof(zeropkt)); } bool desync_valid_zero_stage(enum dpi_desync_mode mode) { return mode==DESYNC_SYNACK; } bool desync_valid_first_stage(enum dpi_desync_mode mode) { return mode==DESYNC_FAKE || 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; } 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,"rst")) return DESYNC_RST; else if (!strcmp(s,"rstack")) return DESYNC_RSTACK; else if (!strcmp(s,"synack")) return DESYNC_SYNACK; 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; 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 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(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); if (proto==IPPROTO_TCP) // 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 ctrack->b_cutoff |= (!params.wssize || ctrack->b_wssize_cutoff) && (!params.desync_cutoff || ctrack->b_desync_cutoff); } } static void wssize_cutoff(t_ctrack *ctrack) { if (ctrack) { ctrack->b_wssize_cutoff = true; maybe_cutoff(ctrack, IPPROTO_TCP); } } #define CONNTRACK_REQUIRED (params.wssize || params.desync_cutoff) // result : true - drop original packet, false = dont drop packet_process_result dpi_desync_tcp_packet(uint8_t *data_pkt, size_t len_pkt, struct ip *ip, struct ip6_hdr *ip6hdr, struct tcphdr *tcphdr, size_t len_tcp, uint8_t *data_payload, size_t len_payload) { packet_process_result res=pass; t_ctrack *ctrack=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; if (!!ip == !!ip6hdr) return res; // one and only one must be present if (CONNTRACK_REQUIRED) { ConntrackPoolPurge(¶ms.conntrack); if (ConntrackPoolFeed(¶ms.conntrack, ip, ip6hdr, tcphdr, NULL, len_payload, &ctrack, &bReverse)) maybe_cutoff(ctrack, IPPROTO_TCP); } //ConntrackPoolDump(¶ms.conntrack); if (params.wsize && tcp_synack_segment(tcphdr)) { tcp_rewrite_winsize(tcphdr, params.wsize, params.wscale); res=modify; } if (bReverse) return res; // 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); res=modify; } } else { DLOG("not changing wssize. wssize is set but conntrack entry is missing\n"); } } if (params.desync_mode0!=DESYNC_NONE || params.desync_mode!=DESYNC_NONE) // save some cpu { 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; 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 (params.desync_mode0==DESYNC_SYNACK && tcp_syn_segment(tcphdr)) { 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 res; } DLOG("sending fake SYNACK\n"); if (!rawsend_rep((struct sockaddr *)&dst, params.desync_fwmark, pkt1, pkt1_len)) return res; } if (params.desync_cutoff) { if (ctrack) { if (ctrack->b_desync_cutoff) { DLOG("not desyncing. desync-cutoff reached (mode %c): %llu/%u\n", params.desync_cutoff_mode, (unsigned long long)cutoff_get_limit(ctrack,params.desync_cutoff_mode), params.desync_cutoff); return res; } 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 res; } } if (!params.wssize && params.desync_mode==DESYNC_NONE && !params.hostcase && !params.hostnospace && !params.domcase) return res; // 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; uint8_t *p, *phost; if ((bIsHttp = IsHttp(data_payload,len_payload))) { DLOG("packet contains HTTP request\n") if (params.wssize) DLOG("forced wssize-cutoff\n"); wssize_cutoff(ctrack); fake = params.fake_http; fake_size = params.fake_http_size; if (params.hostlist || params.debug) bHaveHost=HttpExtractHost(data_payload,len_payload,host,sizeof(host)); if (params.hostlist && !bHaveHost) { DLOG("not applying tampering to HTTP without Host:\n") return res; } } else if (IsTLSClientHello(data_payload,len_payload)) { DLOG("packet contains TLS ClientHello\n") if (params.wssize) DLOG("forced wssize-cutoff\n"); wssize_cutoff(ctrack); fake = params.fake_tls; fake_size = params.fake_tls_size; if (params.hostlist || params.desync_skip_nosni || params.debug) { bHaveHost=TLSHelloExtractHost(data_payload,len_payload,host,sizeof(host)); if (params.desync_skip_nosni && !bHaveHost) { DLOG("not applying tampering to TLS ClientHello without hostname in the SNI\n") return res; } } } else { if (!params.desync_any_proto) return res; DLOG("applying tampering to unknown protocol\n") fake = params.fake_unknown; fake_size = params.fake_unknown_size; } if (bHaveHost) { DLOG("hostname: %s\n",host) if (params.hostlist && !SearchHostList(params.hostlist,host,params.debug)) { DLOG("not applying tampering to this request\n") return res; } } 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); res=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); res=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 = ' '; } res=modify; } } if (params.desync_mode==DESYNC_NONE) return res; if (params.debug) { printf("dpi desync src="); print_sockaddr((struct sockaddr *)&src); printf(" dst="); print_sockaddr((struct sockaddr *)&dst); printf("\n"); } enum dpi_desync_mode desync_mode = params.desync_mode; uint8_t fooling_orig = FOOL_NONE; bool b; pkt1_len = sizeof(pkt1); b = false; switch(desync_mode) { case DESYNC_FAKE: 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 res; } DLOG("sending fake request : "); hexdump_limited_dlog(fake,fake_size,PKTDATA_MAXDUMP); DLOG("\n") b = true; break; case DESYNC_RST: case DESYNC_RSTACK: 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 res; } 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; if (ip6hdr && params.desync_mode2==DESYNC_NONE) { 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 res; } DLOG("resending original packet with extension header\n"); if (!rawsend((struct sockaddr *)&dst, params.desync_fwmark, pkt1, pkt1_len)) return res; // this mode is final, no other options available return drop; } desync_mode = params.desync_mode2; } if (b) { if (!rawsend_rep((struct sockaddr *)&dst, params.desync_fwmark, pkt1, pkt1_len)) return res; if (params.desync_mode2==DESYNC_NONE) { if (params.desync_retrans) { DLOG("dropping original packet to force retransmission. len=%zu len_payload=%zu\n", len_pkt, len_payload) } else { DLOG("reinjecting original packet. len=%zu len_payload=%zu\n", len_pkt, len_payload) #ifdef __FreeBSD__ // FreeBSD tend to pass ipv6 frames with wrong checksum if (res==modify || ip6hdr) #else // if original packet was tampered earlier it needs checksum fixed if (res==modify) #endif tcp_fix_checksum(tcphdr,len_tcp,ip,ip6hdr); if (!rawsend((struct sockaddr *)&dst, params.desync_fwmark, data_pkt, len_pkt)) return res; } return drop; } desync_mode = params.desync_mode2; } size_t split_pos=len_payload>params.desync_split_pos ? params.desync_split_pos : 1; pkt1_len = sizeof(pkt1); switch(desync_mode) { case DESYNC_DISORDER: case DESYNC_DISORDER2: { uint8_t fakeseg[DPI_DESYNC_MAX_FAKE_LEN+100]; size_t fakeseg_len; if (split_posth_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 res; DLOG("sending 2nd out-of-order 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, params.desync_fwmark, pkt1, pkt1_len)) return res; } if (desync_mode==DESYNC_DISORDER) { 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 res; 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, params.desync_fwmark, fakeseg, fakeseg_len)) return res; } 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 res; 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, params.desync_fwmark, pkt1, pkt1_len)) return res; 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, params.desync_fwmark, fakeseg, fakeseg_len)) return res; } return drop; } break; case DESYNC_SPLIT: case DESYNC_SPLIT2: { uint8_t fakeseg[DPI_DESYNC_MAX_FAKE_LEN+100]; size_t fakeseg_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 res; 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, params.desync_fwmark, fakeseg, fakeseg_len)) return res; } 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 res; DLOG("sending 1st 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, params.desync_fwmark, pkt1, pkt1_len)) return res; 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, params.desync_fwmark, fakeseg, fakeseg_len)) return res; } if (split_posth_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 res; 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, params.desync_fwmark, pkt1, pkt1_len)) return res; } return drop; } break; case DESYNC_IPFRAG2: { #ifdef __FreeBSD__ // FreeBSD tend to pass ipv6 frames with wrong checksum if (res==modify || ip6hdr) #else // if original packet was tampered earlier it needs checksum fixed if (res==modify) #endif tcp_fix_checksum(tcphdr,len_tcp,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_tcpip_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 res; 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 res; DLOG("sending 1st ip fragment 0-%zu len=%zu : ", ipfrag_pos-1, ipfrag_pos) hexdump_limited_dlog(pkt1,pkt1_len,IP_MAXDUMP); DLOG("\n") if (!rawsend((struct sockaddr *)&dst, params.desync_fwmark, pkt2, pkt2_len)) return res; DLOG("sending 2nd ip fragment %zu-%zu len=%zu : ", ipfrag_pos, len_tcp-1, len_tcp-ipfrag_pos) hexdump_limited_dlog(pkt2,pkt2_len,IP_MAXDUMP); DLOG("\n") if (!rawsend((struct sockaddr *)&dst, params.desync_fwmark, pkt1, pkt1_len)) return res; return frag; } } } return res; } packet_process_result dpi_desync_udp_packet(uint8_t *data_pkt, size_t len_pkt, struct ip *ip, struct ip6_hdr *ip6hdr, struct udphdr *udphdr, uint8_t *data_payload, size_t len_payload) { packet_process_result res=pass; t_ctrack *ctrack=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 (!!ip == !!ip6hdr) return res; // one and only one must be present if (CONNTRACK_REQUIRED) { ConntrackPoolPurge(¶ms.conntrack); if (ConntrackPoolFeed(¶ms.conntrack, ip, ip6hdr, NULL, udphdr, len_payload, &ctrack, &bReverse)) maybe_cutoff(ctrack, IPPROTO_UDP); } //ConntrackPoolDump(¶ms.conntrack); if (bReverse) return res; // nothing to do. do not waste cpu if (params.desync_cutoff) { if (ctrack) { if (ctrack->b_desync_cutoff) { DLOG("not desyncing. desync-cutoff reached (mode %c): %llu/%u\n", params.desync_cutoff_mode, (unsigned long long)cutoff_get_limit(ctrack,params.desync_cutoff_mode), params.desync_cutoff); return res; } 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 res; } } if (params.desync_mode==DESYNC_NONE) return res; if (len_payload) { const uint8_t *fake; size_t fake_size; bool b; if (IsQUICInitial(data_payload,len_payload)) { DLOG("packet contains QUIC initial\n") fake = params.fake_quic; fake_size = params.fake_quic_size; } else { if (!params.desync_any_proto) return res; DLOG("applying tampering to unknown protocol\n") fake = params.fake_unknown_udp; fake_size = params.fake_unknown_udp_size; } enum dpi_desync_mode desync_mode = params.desync_mode; uint8_t fooling_orig = FOOL_NONE; 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 (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: if (!prepare_udp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, ttl_fake, params.desync_fooling_mode, fake, fake_size, pkt1, &pkt1_len)) return res; DLOG("sending fake request : "); hexdump_limited_dlog(fake,fake_size,PKTDATA_MAXDUMP); DLOG("\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; if (ip6hdr && params.desync_mode2==DESYNC_NONE) { if (!prepare_udp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, ttl_orig,fooling_orig, data_payload, len_payload, pkt1, &pkt1_len)) { return res; } DLOG("resending original packet with extension header\n"); if (!rawsend((struct sockaddr *)&dst, params.desync_fwmark, pkt1, pkt1_len)) return res; // this mode is final, no other options available return drop; } desync_mode = params.desync_mode2; } if (b) { if (params.desync_mode2==DESYNC_NONE) { if (!rawsend_rep((struct sockaddr *)&dst, params.desync_fwmark, pkt1, pkt1_len)) return res; DLOG("reinjecting original packet. len=%zu len_payload=%zu\n", len_pkt, len_payload) #ifdef __FreeBSD__ // FreeBSD tend to pass ipv6 frames with wrong checksum if (res==modify || ip6hdr) #else // if original packet was tampered earlier it needs checksum fixed if (res==modify) #endif udp_fix_checksum(udphdr,sizeof(struct udphdr)+len_payload,ip,ip6hdr); if (!rawsend((struct sockaddr *)&dst, params.desync_fwmark, data_pkt, len_pkt)) return res; return drop; } desync_mode = params.desync_mode2; } switch(desync_mode) { case DESYNC_IPFRAG2: { #ifdef __FreeBSD__ // FreeBSD tend to pass ipv6 frames with wrong checksum if (res==modify || ip6hdr) #else // if original packet was tampered earlier it needs checksum fixed if (res==modify) #endif udp_fix_checksum(udphdr,sizeof(struct udphdr)+len_payload,ip,ip6hdr); uint8_t pkt3[DPI_DESYNC_MAX_FAKE_LEN+100], *pkt_orig; size_t pkt_orig_len; size_t len_transport = len_payload + sizeof(struct udphdr); size_t ipfrag_pos = (params.desync_ipfrag_pos_udp && params.desync_ipfrag_pos_udpip_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 res; 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 res; DLOG("sending 1st ip fragment 0-%zu len=%zu : ", ipfrag_pos-1, ipfrag_pos) hexdump_limited_dlog(pkt1,pkt1_len,IP_MAXDUMP); DLOG("\n") if (!rawsend((struct sockaddr *)&dst, params.desync_fwmark, pkt2, pkt2_len)) return res; DLOG("sending 2nd ip fragment %zu-%zu len=%zu : ", ipfrag_pos, len_transport-1, len_transport-ipfrag_pos) hexdump_limited_dlog(pkt2,pkt2_len,IP_MAXDUMP); DLOG("\n") if (!rawsend((struct sockaddr *)&dst, params.desync_fwmark, pkt1, pkt1_len)) return res; return frag; } } } return res; }