Fragment packet by the beginning of SNI value. #357

It has been reported that the DPI systems in Saudi Arabia and
United Arab Emirates are started to search for the beginning of
SNI extension header and its value, without parsing the TLS ClientHello
packet, in any part of TCP session.

Workaround the issue by splitting the packet right after the end
of extension headers and before its value.

https://ntc.party/t/goodbyedpi-in-saudi-arabia/7884
https://ntc.party/t/goodbyedpi-in-uae/7914

Author: ValdikSS

README.md

@@ -43,6 +43,7 @@ Usage: goodbyedpi.exe [OPTION...]
                           supplied text file (HTTP Host/TLS SNI).
                           This option can be supplied multiple times.
  --allow-no-sni           perform circumvention if TLS SNI can't be detected with --blacklist enabled.
+ --frag-by-sni            if SNI is detected in TLS packet, fragment the packet right before SNI value.
  --set-ttl     <value>    activate Fake Request Mode and send it with supplied TTL value.
                           DANGEROUS! May break websites in unexpected ways. Use with care (or --blacklist).
  --auto-ttl    [a1-a2-m]  activate Fake Request Mode, automatically detect TTL and decrease

src/goodbyedpi.c

@@ -162,6 +162,7 @@ static struct option long_options[] = {
     {"dns-verb",    no_argument,       0,  'v' },
     {"blacklist",   required_argument, 0,  'b' },
     {"allow-no-sni",no_argument,       0,  ']' },
+    {"frag-by-sni", no_argument,       0,  '>' },
     {"ip-id",       required_argument, 0,  'i' },
     {"set-ttl",     required_argument, 0,  '$' },
     {"min-ttl",     required_argument, 0,  '[' },
@@ -568,6 +569,7 @@ int main(int argc, char *argv[]) {
         do_dnsv4_redirect = 0, do_dnsv6_redirect = 0,
         do_dns_verb = 0, do_tcp_verb = 0, do_blacklist = 0,
         do_allow_no_sni = 0,
+        do_fragment_by_sni = 0,
         do_fake_packet = 0,
         do_auto_ttl = 0,
         do_wrong_chksum = 0,
@@ -806,6 +808,9 @@ int main(int argc, char *argv[]) {
             case ']': // --allow-no-sni
                 do_allow_no_sni = 1;
                 break;
+            case '>': // --frag-by-sni
+                do_fragment_by_sni = 1;
+                break;
             case '$': // --set-ttl
                 do_auto_ttl = auto_ttl_1 = auto_ttl_2 = auto_ttl_max = 0;
                 do_fake_packet = 1;
@@ -899,6 +904,7 @@ int main(int argc, char *argv[]) {
                 "                          supplied text file (HTTP Host/TLS SNI).\n"
                 "                          This option can be supplied multiple times.\n"
                 " --allow-no-sni           perform circumvention if TLS SNI can't be detected with --blacklist enabled.\n"
+                " --frag-by-sni            if SNI is detected in TLS packet, fragment the packet right before SNI value.\n"
                 " --set-ttl     <value>    activate Fake Request Mode and send it with supplied TTL value.\n"
                 "                          DANGEROUS! May break websites in unexpected ways. Use with care (or --blacklist).\n"
                 " --auto-ttl    [a1-a2-m]  activate Fake Request Mode, automatically detect TTL and decrease\n"
@@ -957,6 +963,7 @@ int main(int argc, char *argv[]) {
            "Fragment HTTP: %u\n"                    /* 2 */
            "Fragment persistent HTTP: %u\n"         /* 3 */
            "Fragment HTTPS: %u\n"                   /* 4 */
+           "Fragment by SNI: %u\n"                  /* 5 */
            "Native fragmentation (splitting): %d\n" /* 5 */
            "Fragments sending in reverse: %d\n"     /* 6 */
            "hoSt: %d\n"                             /* 7 */
@@ -976,23 +983,24 @@ int main(int argc, char *argv[]) {
            (do_fragment_http ? http_fragment_size : 0),           /* 2 */
            (do_fragment_http_persistent ? http_fragment_size : 0),/* 3 */
            (do_fragment_https ? https_fragment_size : 0),         /* 4 */
-           do_native_frag,        /* 5 */
-           do_reverse_frag,       /* 6 */
-           do_host,               /* 7 */
-           do_host_removespace,   /* 8 */
-           do_additional_space,   /* 9 */
-           do_host_mixedcase,     /* 10 */
-           do_http_allports,      /* 11 */
-           do_fragment_http_persistent_nowait, /* 12 */
-           do_dnsv4_redirect,                  /* 13 */
-           do_dnsv6_redirect,                  /* 14 */
-           do_allow_no_sni,                    /* 15 */
-           do_auto_ttl ? "auto" : (do_fake_packet ? "fixed" : "disabled"),  /* 16 */
+           do_fragment_by_sni,    /* 5 */
+           do_native_frag,        /* 6 */
+           do_reverse_frag,       /* 7 */
+           do_host,               /* 8 */
+           do_host_removespace,   /* 9 */
+           do_additional_space,   /* 10 */
+           do_host_mixedcase,     /* 11 */
+           do_http_allports,      /* 12 */
+           do_fragment_http_persistent_nowait, /* 13 */
+           do_dnsv4_redirect,                  /* 14 */
+           do_dnsv6_redirect,                  /* 15 */
+           do_allow_no_sni,                    /* 16 */
+           do_auto_ttl ? "auto" : (do_fake_packet ? "fixed" : "disabled"),  /* 17 */
                ttl_of_fake_packet, do_auto_ttl ? auto_ttl_1 : 0, do_auto_ttl ? auto_ttl_2 : 0,
                do_auto_ttl ? auto_ttl_max : 0, ttl_min_nhops,
-           do_wrong_chksum, /* 17 */
-           do_wrong_seq,    /* 18 */
-           max_payload_size /* 19 */
+           do_wrong_chksum, /* 18 */
+           do_wrong_seq,    /* 19 */
+           max_payload_size /* 20 */
           );
 
     if (do_fragment_http && http_fragment_size > 2 && !do_native_frag) {
@@ -1046,6 +1054,7 @@ int main(int argc, char *argv[]) {
                    packetLen);
             should_reinject = 1;
             should_recalc_checksum = 0;
+            sni_ok = 0;
 
             ppIpHdr = (PWINDIVERT_IPHDR)NULL;
             ppIpV6Hdr = (PWINDIVERT_IPV6HDR)NULL;
@@ -1131,7 +1140,7 @@ int main(int argc, char *argv[]) {
                     if ((packet_dataLen == 2 && memcmp(packet_data, "\x16\x03", 2) == 0) ||
                         (packet_dataLen >= 3 && ( memcmp(packet_data, "\x16\x03\x01", 3) == 0 || memcmp(packet_data, "\x16\x03\x03", 3) == 0 )))
                     {
-                        if (do_blacklist) {
+                        if (do_blacklist || do_fragment_by_sni) {
                             sni_ok = extract_sni(packet_data, packet_dataLen,
                                         &host_addr, &host_len);
                         }
@@ -1284,7 +1293,11 @@ int main(int argc, char *argv[]) {
                         current_fragment_size = http_fragment_size;
                     }
                     else if (do_fragment_https && ppTcpHdr->DstPort != htons(80)) {
-                        current_fragment_size = https_fragment_size;
+                        if (do_fragment_by_sni && sni_ok) {
+                            current_fragment_size = (void*)host_addr - packet_data;
+                        } else {
+                            current_fragment_size = https_fragment_size;
+                        }
                     }
 
                     if (current_fragment_size) {