#define _GNU_SOURCE
#include "desync.h"
#include "protocol.h"
#include "params.h"
#include "helpers.h"
#include "hostlist.h"
#include <string.h>
static const char fake_http_request[] = "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";
static const uint8_t fake_https_request[] = {
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
};
static uint8_t zeropkt[DPI_DESYNC_MAX_FAKE_LEN];
void desync_init()
{
memset(zeropkt, 0, sizeof(zeropkt));
}
// result : true - drop original packet, false = dont drop
packet_process_result dpi_desync_packet(uint8_t *data_pkt, size_t len_pkt, struct iphdr *iphdr, struct ip6_hdr *ip6hdr, struct tcphdr *tcphdr, size_t len_tcp, uint8_t *data_payload, size_t len_payload)
{
packet_process_result res=pass;
if (!!iphdr == !!ip6hdr) return res; // one and only one must be present
if (params.desync_mode==DESYNC_NONE && !params.hostcase && !params.hostnospace) return res; // nothing to do. do not waste cpu
if (!tcphdr->syn && len_payload)
{
struct sockaddr_storage src, dst;
const uint8_t *fake;
size_t fake_size;
char host[256];
bool bHaveHost=false;
bool bIsHttp;
if (bIsHttp = IsHttp(data_payload,len_payload))
{
DLOG("packet contains HTTP request\n")
fake = (uint8_t*)fake_http_request;
fake_size = sizeof(fake_http_request);
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")
fake = (uint8_t*)fake_https_request;
fake_size = sizeof(fake_https_request);
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 = zeropkt;
fake_size = 256;
}
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;
}
uint8_t *phost;
if (bIsHttp && (params.hostcase || params.hostnospace) && (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;
}
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;
extract_endpoints(iphdr, ip6hdr, tcphdr, &src, &dst);
if (params.debug)
{
printf("dpi desync src=");
print_sockaddr((struct sockaddr *)&src);
printf(" dst=");
print_sockaddr((struct sockaddr *)&dst);
printf("\n");
}
uint8_t newdata[DPI_DESYNC_MAX_FAKE_LEN+100];
size_t newlen = sizeof(newdata);
uint8_t ttl_orig = iphdr ? iphdr->ttl : ip6hdr->ip6_ctlun.ip6_un1.ip6_un1_hlim;
uint8_t ttl_fake = params.desync_ttl ? params.desync_ttl : ttl_orig;
uint8_t flags_orig = *((uint8_t*)tcphdr+13);
uint32_t *timestamps = tcp_find_timestamps(tcphdr);
switch(params.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)
{
DLOG("sending 2nd out-of-order tcp segment %zu-%zu len=%zu\n",split_pos,len_payload-1, len_payload-split_pos)
if (!prepare_tcp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, flags_orig, net32_add(tcphdr->seq,split_pos), tcphdr->ack_seq, tcphdr->window, timestamps,
ttl_orig,TCP_FOOL_NONE,
data_payload+split_pos, len_payload-split_pos, newdata, &newlen) ||
!rawsend((struct sockaddr *)&dst, params.desync_fwmark, newdata, newlen))
{
return res;
}
}
if (params.desync_mode==DESYNC_DISORDER)
{
DLOG("sending fake(1) 1st out-of-order tcp segment 0-%zu len=%zu\n",split_pos-1, split_pos)
fakeseg_len = sizeof(fakeseg);
if (!prepare_tcp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, flags_orig, tcphdr->seq, tcphdr->ack_seq, tcphdr->window, timestamps,
ttl_fake,params.desync_tcp_fooling_mode,
zeropkt, split_pos, fakeseg, &fakeseg_len) ||
!rawsend((struct sockaddr *)&dst, params.desync_fwmark, fakeseg, fakeseg_len))
{
return res;
}
}
DLOG("sending 1st out-of-order tcp segment 0-%zu len=%zu\n",split_pos-1, split_pos)
newlen = sizeof(newdata);
if (!prepare_tcp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, flags_orig, tcphdr->seq, tcphdr->ack_seq, tcphdr->window, timestamps,
ttl_orig,TCP_FOOL_NONE,
data_payload, split_pos, newdata, &newlen) ||
!rawsend((struct sockaddr *)&dst, params.desync_fwmark, newdata, newlen))
{
return res;
}
if (params.desync_mode==DESYNC_DISORDER)
{
DLOG("sending fake(2) 1st out-of-order tcp segment 0-%zu len=%zu\n",split_pos-1, split_pos)
if (!rawsend((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 (params.desync_mode==DESYNC_SPLIT)
{
DLOG("sending fake(1) 1st tcp segment 0-%zu len=%zu\n",split_pos-1, split_pos)
fakeseg_len = sizeof(fakeseg);
if (!prepare_tcp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, flags_orig, tcphdr->seq, tcphdr->ack_seq, tcphdr->window, timestamps,
ttl_fake,params.desync_tcp_fooling_mode,
zeropkt, split_pos, fakeseg, &fakeseg_len) ||
!rawsend((struct sockaddr *)&dst, params.desync_fwmark, fakeseg, fakeseg_len))
{
return res;
}
}
DLOG("sending 1st tcp segment 0-%zu len=%zu\n",split_pos-1, split_pos)
newlen = sizeof(newdata);
if (!prepare_tcp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, flags_orig, tcphdr->seq, tcphdr->ack_seq, tcphdr->window, timestamps,
ttl_orig,TCP_FOOL_NONE,
data_payload, split_pos, newdata, &newlen) ||
!rawsend((struct sockaddr *)&dst, params.desync_fwmark, newdata, newlen))
{
return res;
}
if (params.desync_mode==DESYNC_SPLIT)
{
DLOG("sending fake(2) 1st tcp segment 0-%zu len=%zu\n",split_pos-1, split_pos)
if (!rawsend((struct sockaddr *)&dst, params.desync_fwmark, fakeseg, fakeseg_len))
return res;
}
if (split_pos<len_payload)
{
DLOG("sending 2nd tcp segment %zu-%zu len=%zu\n",split_pos,len_payload-1, len_payload-split_pos)
newlen = sizeof(newdata);
if (!prepare_tcp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, flags_orig, net32_add(tcphdr->seq,split_pos), tcphdr->ack_seq, tcphdr->window, timestamps,
ttl_orig,TCP_FOOL_NONE,
data_payload+split_pos, len_payload-split_pos, newdata, &newlen) ||
!rawsend((struct sockaddr *)&dst, params.desync_fwmark, newdata, newlen))
{
return res;
}
}
return drop;
}
break;
case DESYNC_FAKE:
if (!prepare_tcp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, flags_orig, tcphdr->seq, tcphdr->ack_seq, tcphdr->window, timestamps,
ttl_fake,params.desync_tcp_fooling_mode,
fake, fake_size, newdata, &newlen))
{
return res;
}
break;
case DESYNC_RST:
case DESYNC_RSTACK:
if (!prepare_tcp_segment((struct sockaddr *)&src, (struct sockaddr *)&dst, TH_RST | (params.desync_mode==DESYNC_RSTACK ? TH_ACK:0), tcphdr->seq, tcphdr->ack_seq, tcphdr->window, timestamps,
ttl_fake,params.desync_tcp_fooling_mode,
NULL, 0, newdata, &newlen))
{
return res;
}
break;
default:
return res;
}
if (!rawsend((struct sockaddr *)&dst, params.desync_fwmark, newdata, newlen))
return res;
if (params.desync_retrans)
DLOG("dropping 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)
// if original packet was tampered earlier it needs checksum fixed
if (res==modify) tcp_fix_checksum(tcphdr,len_tcp,iphdr,ip6hdr);
if (!rawsend((struct sockaddr *)&dst, params.desync_fwmark, data_pkt, len_pkt))
return res;
}
return drop;
}
return res;
}