zapret/nfq/desync.c
2022-01-01 20:22:04 +03:00

633 lines
23 KiB
C

#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.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 PKT_MAXDUMP 32
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;
}
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;
}
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;
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;i<params.desync_repeats;i++)
if (!rawsend(dst,fwmark,data,len))
return false;
return true;
}
static uint64_t cutoff_get_limit(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(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 newdata[DPI_DESYNC_MAX_FAKE_LEN+100];
size_t newlen;
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(&params.conntrack);
if (ConntrackPoolFeed(&params.conntrack, ip, ip6hdr, tcphdr, NULL, len_payload, &ctrack, &bReverse))
maybe_cutoff(ctrack, IPPROTO_TCP);
}
//ConntrackPoolDump(&params.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))
{
newlen = sizeof(newdata);
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, newdata, &newlen))
{
return res;
}
DLOG("sending fake SYNACK\n");
if (!rawsend_rep((struct sockaddr *)&dst, params.desync_fwmark, newdata, newlen))
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;
bool b;
newlen = sizeof(newdata);
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, newdata, &newlen))
{
return res;
}
DLOG("sending fake request : ");
hexdump_limited_dlog(fake,fake_size,PKT_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, newdata, &newlen))
{
return res;
}
DLOG("sending fake RST/RSTACK\n");
b = true;
break;
}
if (b)
{
if (!rawsend_rep((struct sockaddr *)&dst, params.desync_fwmark, newdata, newlen))
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;
}
newlen = sizeof(newdata);
switch(desync_mode)
{
case DESYNC_DISORDER:
case DESYNC_DISORDER2:
{
size_t split_pos=len_payload>params.desync_split_pos ? params.desync_split_pos : 1;
uint8_t fakeseg[DPI_DESYNC_MAX_FAKE_LEN+100];
size_t fakeseg_len;
if (split_pos<len_payload)
{
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,FOOL_NONE,params.desync_badseq_increment,params.desync_badseq_ack_increment,
data_payload+split_pos, len_payload-split_pos, newdata, &newlen))
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,PKT_MAXDUMP); DLOG("\n")
if (!rawsend_rep((struct sockaddr *)&dst, params.desync_fwmark, newdata, newlen))
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,PKT_MAXDUMP); DLOG("\n")
if (!rawsend_rep((struct sockaddr *)&dst, params.desync_fwmark, fakeseg, fakeseg_len))
return res;
}
newlen = sizeof(newdata);
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,FOOL_NONE,params.desync_badseq_increment,params.desync_badseq_ack_increment,
data_payload, split_pos, newdata, &newlen))
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,PKT_MAXDUMP); DLOG("\n")
if (!rawsend_rep((struct sockaddr *)&dst, params.desync_fwmark, newdata, newlen))
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,PKT_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:
{
size_t split_pos=len_payload>params.desync_split_pos ? params.desync_split_pos : 1;
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,PKT_MAXDUMP); DLOG("\n")
if (!rawsend_rep((struct sockaddr *)&dst, params.desync_fwmark, fakeseg, fakeseg_len))
return res;
}
newlen = sizeof(newdata);
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,FOOL_NONE,params.desync_badseq_increment,params.desync_badseq_ack_increment,
data_payload, split_pos, newdata, &newlen))
return res;
DLOG("sending 1st tcp segment 0-%zu len=%zu : ",split_pos-1, split_pos)
hexdump_limited_dlog(data_payload,split_pos,PKT_MAXDUMP); DLOG("\n")
if (!rawsend_rep((struct sockaddr *)&dst, params.desync_fwmark, newdata, newlen))
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,PKT_MAXDUMP); DLOG("\n")
if (!rawsend_rep((struct sockaddr *)&dst, params.desync_fwmark, fakeseg, fakeseg_len))
return res;
}
if (split_pos<len_payload)
{
newlen = sizeof(newdata);
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,FOOL_NONE,params.desync_badseq_increment,params.desync_badseq_ack_increment,
data_payload+split_pos, len_payload-split_pos, newdata, &newlen))
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,PKT_MAXDUMP); DLOG("\n")
if (!rawsend_rep((struct sockaddr *)&dst, params.desync_fwmark, newdata, newlen))
return res;
}
return drop;
}
break;
}
}
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 newdata[DPI_DESYNC_MAX_FAKE_LEN+100];
size_t newlen;
uint8_t ttl_orig,ttl_fake;
if (!!ip == !!ip6hdr) return res; // one and only one must be present
if (CONNTRACK_REQUIRED)
{
ConntrackPoolPurge(&params.conntrack);
if (ConntrackPoolFeed(&params.conntrack, ip, ip6hdr, NULL, udphdr, len_payload, &ctrack, &bReverse))
maybe_cutoff(ctrack, IPPROTO_UDP);
}
//ConntrackPoolDump(&params.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;
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;
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;
if (params.debug)
{
printf("dpi desync src=");
print_sockaddr((struct sockaddr *)&src);
printf(" dst=");
print_sockaddr((struct sockaddr *)&dst);
printf("\n");
}
newlen = sizeof(newdata);
b = false;
switch(params.desync_mode)
{
case DESYNC_FAKE:
if (!prepare_udp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, ttl_fake, params.desync_fooling_mode, fake, fake_size, newdata, &newlen))
return res;
DLOG("sending fake request : ");
hexdump_limited_dlog(fake,fake_size,PKT_MAXDUMP); DLOG("\n")
b = true;
break;
}
if (b)
{
if (!rawsend_rep((struct sockaddr *)&dst, params.desync_fwmark, newdata, newlen))
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;
}
}
return res;
}