Update Makefile

We can't reliably distinguish HTTP data from other data on port 80 when fragmentation is used.
HTTP method code has a special case which tries to find HTTP method when fragmentation = 1 or 2 is used,
but not for other values.

Makefile

@@ -7,7 +7,8 @@ LIBS = -L $(WINDIVERTLIBS) -lWinDivert -lws2_32
 CC = $(CPREFIX)-gcc
 CCWINDRES = $(CPREFIX)-windres
 CFLAGS = -Wall -I $(WINDIVERTHEADERS) -L $(WINDIVERTLIBS) \
-         -O2 -fPIE -Wformat -Werror=format-security -D_FORTIFY_SOURCE=2
+         -O2 -pie -fPIE -Wformat -Werror=format-security -D_FORTIFY_SOURCE=2
+LDFLAGS = -pie
 
 .PHONY: default all clean
 

goodbyedpi.c

@@ -53,15 +53,6 @@ static const char *http_methods[] = {
     "DELETE ",
     "CONNECT ",
     "OPTIONS ",
-    "TRACE ",
-    "PATCH ",
-    "PROPFIND ",
-    "PROPPATCH ",
-    "MKCOL ",
-    "COPY ",
-    "MOVE ",
-    "LOCK ",
-    "UNLOCK ",
 };
 
 static char* dumb_memmem(const char* haystack, int hlen, const char* needle, int nlen) {
@@ -139,12 +130,20 @@ static void change_window_size(const char *pkt, int size) {
 }
 
 /* HTTP method end without trailing space */
-static PVOID find_http_method_end(const char *pkt) {
+static PVOID find_http_method_end(const char *pkt, int offset) {
     int i;
     for (i = 0; i<(sizeof(http_methods) / sizeof(*http_methods)); i++) {
         if (memcmp(pkt, http_methods[i], strlen(http_methods[i])) == 0) {
             return (char*)pkt + strlen(http_methods[i]) - 1;
         }
+        /* Try to find HTTP method in a second part of fragmented packet */
+        if ((offset == 1 || offset == 2) &&
+            memcmp(pkt, http_methods[i] + offset,
+                   strlen(http_methods[i]) - offset) == 0
+           )
+        {
+            return (char*)pkt + strlen(http_methods[i]) - offset - 1;
+        }
     }
     return NULL;
 }
@@ -152,7 +151,7 @@ static PVOID find_http_method_end(const char *pkt) {
 int main(int argc, char *argv[]) {
     static const char fragment_size_message[] =
                 "Fragment size should be in range [0 - 65535]\n";
-    int i, should_reinject = 0;
+    int i, should_reinject, should_recalc_checksum = 0;
     int opt;
     HANDLE w_filter = NULL;
     WINDIVERT_ADDRESS addr;
@@ -249,6 +248,12 @@ int main(int argc, char *argv[]) {
            (do_fragment_https ? https_fragment_size : 0),
            do_host, do_host_removespace, do_additional_space);
 
+    if (do_fragment_http && http_fragment_size > 2) {
+        printf("WARNING: HTTP fragmentation values > 2 are not fully compatible "
+               "with other options. Please use values <= 2 or disable HTTP fragmentation "
+               "completely.\n");
+    }
+
     printf("\nOpening filter\n");
     filter_num = 0;
 
@@ -294,6 +299,7 @@ int main(int argc, char *argv[]) {
             //printf("Got %s packet, len=%d!\n", addr.Direction ? "inbound" : "outbound",
             //       packetLen);
             should_reinject = 1;
+            should_recalc_checksum = 0;
 
             if (WinDivertHelperParsePacket(packet, packetLen, &ppIpHdr,
                 NULL, NULL, NULL, &ppTcpHdr, NULL, &packet_data, &packet_dataLen)) {
@@ -313,8 +319,10 @@ int main(int argc, char *argv[]) {
                 /* Handle OUTBOUND packet, search for Host header */
                 else if (addr.Direction == WINDIVERT_DIRECTION_OUTBOUND && 
                         packet_dataLen > 16 && ppTcpHdr->DstPort == htons(80) &&
-                        find_http_method_end(packet_data) &&
+                        find_http_method_end(packet_data,
-                        (do_host || do_host_removespace)) {
+                                             (do_fragment_http ? http_fragment_size : 0)) &&
+                        (do_host || do_host_removespace))
+                {
 
                     data_addr = find_host_header(packet_data, packet_dataLen);
                     if (data_addr) {
@@ -322,16 +330,19 @@ int main(int argc, char *argv[]) {
                         if (do_host) {
                             /* Replace "Host: " with "hoSt: " */
                             memcpy(data_addr, http_host_replace, strlen(http_host_replace));
+                            should_recalc_checksum = 1;
                             //printf("Replaced Host header!\n");
                         }
 
                         if (do_additional_space && do_host_removespace) {
                             /* End of "Host:" without trailing space */
                             host_addr = data_addr + strlen(http_host_find) - 1;
-                            method_addr = find_http_method_end(packet_data);
+                            method_addr = find_http_method_end(packet_data,
+                                                            (do_fragment_http ? http_fragment_size : 0));
 
                             if (method_addr) {
                                 memmove(method_addr + 1, method_addr, (PVOID)host_addr - (PVOID)method_addr);
+                                should_recalc_checksum = 1;
                             }
                         }
                         else if (do_host_removespace) {
@@ -350,9 +361,7 @@ int main(int argc, char *argv[]) {
                                  */
                                 host_len = data_addr_rn - host_addr;
                                 useragent_addr = find_useragent_header(packet_data, packet_dataLen);
-                                if (host_len <= 253 && useragent_addr && useragent_addr > host_addr) {
+                                if (host_len <= 253 && useragent_addr) {
-                                    /* Performing action only if User-Agent header goes after Host */
-
                                     useragent_addr += strlen(http_useragent_find);
                                     /* useragent_addr is in the beginning of User-Agent value */
 
@@ -362,24 +371,40 @@ int main(int argc, char *argv[]) {
                                     /* data_addr_rn is in the end of User-Agent value */
 
                                     if (data_addr_rn) {
+                                        if (useragent_addr > host_addr) {
+                                            /* User-Agent goes AFTER Host header */
                                             data_len = (PVOID)data_addr_rn - (PVOID)host_addr;
 
-                                        /* Move one byte to the left from "Host:"
+                                            /* Move one byte to the LEFT from "Host:"
-                                         * to the end of User-Agen
+                                            * to the end of User-Agent
                                             */
                                             memmove(host_addr - 1, host_addr, data_len);
                                             /* Put space in the end of User-Agent header */
                                             *(char*)(data_addr_rn - 1) = ' ';
+                                            should_recalc_checksum = 1;
                                             //printf("Replaced Host header!\n");
                                         }
-                                }
+                                        else {
-                            }
+                                            /* User-Agent goes BEFORE Host header */
-                        }
+                                            data_len = (PVOID)host_addr - (PVOID)data_addr_rn - 1;
 
-                        WinDivertHelperCalcChecksums(packet, packetLen, 0);
+                                            /* Move one byte to the RIGHT from the end of User-Agent
-                    }
+                                            * to the "Host:"
-                }
+                                            */
+                                            memmove(data_addr_rn + 1, data_addr_rn, data_len);
+                                            /* Put space in the end of User-Agent header */
+                                            *(char*)(data_addr_rn) = ' ';
+                                            should_recalc_checksum = 1;
+                                            //printf("Replaced Host header!\n");
                                         }
+                                    } /* if (dara_addr_rn) */
+                                } /* if (host_len <= 253 && useragent_addr) */
+                            } /* if (data_addr_rn) */
+                        } /* else if (do_host_removespace) */
+                    } /* if (data_addr) */
+                } /* Handle OUTBOUND packet with data */
+            } /* Handle packet with data */
+
             /* Else if we got TCP packet without data */
             else if (WinDivertHelperParsePacket(packet, packetLen, &ppIpHdr,
                 NULL, NULL, NULL, &ppTcpHdr, NULL, NULL, NULL)) {
@@ -389,17 +414,24 @@ int main(int argc, char *argv[]) {
                     //printf("Changing Window Size!\n");
                     if (do_fragment_http && ppTcpHdr->SrcPort == htons(80)) {
                         change_window_size(packet, http_fragment_size);
-                        WinDivertHelperCalcChecksums(packet, packetLen, 0);
+                        should_recalc_checksum = 1;
                     }
                     else if (do_fragment_https && ppTcpHdr->SrcPort != htons(80)) {
                         change_window_size(packet, https_fragment_size);
-                        WinDivertHelperCalcChecksums(packet, packetLen, 0);
+                        should_recalc_checksum = 1;
                     }
                 }
             }
 
             if (should_reinject) {
                 //printf("Re-injecting!\n");
+                if (should_recalc_checksum) {
+                    WinDivertHelperCalcChecksums(packet, packetLen, 0);
+                }
+                else {
+                    WinDivertHelperCalcChecksums(packet, packetLen,
+                                                 WINDIVERT_HELPER_NO_REPLACE);
+                }
                 WinDivertSend(w_filter, packet, packetLen, &addr, NULL);
             }
         }