mirror of
https://github.com/bol-van/zapret.git
synced 2024-09-22 17:52:53 +05:00
272 lines
7.7 KiB
C
272 lines
7.7 KiB
C
#define _GNU_SOURCE
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#include "tamper.h"
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#include "params.h"
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#include "hostlist.h"
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#include "protocol.h"
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#include "helpers.h"
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#include <string.h>
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#include <stdio.h>
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// pHost points to "Host: ..."
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bool find_host(uint8_t **pHost,uint8_t *buf,size_t bs)
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{
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if (!*pHost)
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{
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*pHost = memmem(buf, bs, "\nHost:", 6);
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if (*pHost)
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{
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(*pHost)++;
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VPRINT("Found Host: at pos %td",*pHost - buf)
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}
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}
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return !!*pHost;
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}
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static const char *http_methods[] = { "GET /","POST /","HEAD /","OPTIONS /","PUT /","DELETE /","CONNECT /","TRACE /",NULL };
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// segment buffer has at least 5 extra bytes to extend data block
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void modify_tcp_segment(uint8_t *segment,size_t segment_buffer_size,size_t *size,size_t *split_pos)
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{
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uint8_t *p, *pp, *pHost = NULL;
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size_t method_len = 0, pos;
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const char **method;
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bool bIsHttp = false, bBypass = false;
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char bRemovedHostSpace = 0;
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char *pc, Host[128];
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*split_pos=0;
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for (method = http_methods; *method; method++)
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{
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method_len = strlen(*method);
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if (method_len <= *size && !memcmp(segment, *method, method_len))
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{
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bIsHttp = true;
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method_len -= 2; // "GET /" => "GET"
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break;
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}
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}
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if (bIsHttp)
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{
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VPRINT("Data block looks like http request start : %s", *method)
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// cpu saving : we search host only if and when required. we do not research host every time we need its position
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if ((params.hostlist || params.hostlist_exclude) && find_host(&pHost,segment,*size))
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{
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p = pHost + 5;
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while (p < (segment + *size) && (*p == ' ' || *p == '\t')) p++;
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pp = p;
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while (pp < (segment + *size) && (pp - p) < (sizeof(Host) - 1) && *pp != '\r' && *pp != '\n') pp++;
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memcpy(Host, p, pp - p);
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Host[pp - p] = '\0';
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VPRINT("Requested Host is : %s", Host)
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for(pc = Host; *pc; pc++) *pc=tolower(*pc);
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bBypass = !HostlistCheck(params.hostlist, params.hostlist_exclude, Host);
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}
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if (!bBypass)
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{
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if (params.unixeol)
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{
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p = pp = segment;
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while ((p = memmem(p, segment + *size - p, "\r\n", 2)))
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{
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*p = '\n'; p++;
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memmove(p, p + 1, segment + *size - p - 1);
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(*size)--;
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if (pp == (p - 1))
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{
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// probably end of http headers
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VPRINT("Found double EOL at pos %td. Stop replacing.", pp - segment)
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break;
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}
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pp = p;
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}
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pHost = NULL; // invalidate
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}
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if (params.methodeol && (*size+1+!params.unixeol)<=segment_buffer_size)
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{
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VPRINT("Adding EOL before method")
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if (params.unixeol)
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{
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memmove(segment + 1, segment, *size);
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(*size)++;;
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segment[0] = '\n';
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}
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else
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{
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memmove(segment + 2, segment, *size);
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*size += 2;
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segment[0] = '\r';
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segment[1] = '\n';
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}
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pHost = NULL; // invalidate
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}
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if (params.methodspace && *size<segment_buffer_size)
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{
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// we only work with data blocks looking as HTTP query, so method is at the beginning
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VPRINT("Adding extra space after method")
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p = segment + method_len + 1;
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pos = method_len + 1;
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memmove(p + 1, p, *size - pos);
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*p = ' '; // insert extra space
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(*size)++; // block will grow by 1 byte
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if (pHost) pHost++; // Host: position will move by 1 byte
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}
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if ((params.hostdot || params.hosttab) && *size<segment_buffer_size && find_host(&pHost,segment,*size))
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{
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p = pHost + 5;
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while (p < (segment + *size) && *p != '\r' && *p != '\n') p++;
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if (p < (segment + *size))
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{
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pos = p - segment;
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VPRINT("Adding %s to host name at pos %zu", params.hostdot ? "dot" : "tab", pos)
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memmove(p + 1, p, *size - pos);
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*p = params.hostdot ? '.' : '\t'; // insert dot or tab
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(*size)++; // block will grow by 1 byte
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}
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}
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if (params.domcase && find_host(&pHost,segment,*size))
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{
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p = pHost + 5;
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pos = p - segment;
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VPRINT("Mixing domain case at pos %zu",pos)
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for (; p < (segment + *size) && *p != '\r' && *p != '\n'; p++)
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*p = (((size_t)p) & 1) ? tolower(*p) : toupper(*p);
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}
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if (params.hostnospace && find_host(&pHost,segment,*size) && (pHost+5)<(segment+*size) && pHost[5] == ' ')
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{
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p = pHost + 6;
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pos = p - segment;
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VPRINT("Removing space before host name at pos %zu", pos)
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memmove(p - 1, p, *size - pos);
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(*size)--; // block will shrink by 1 byte
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bRemovedHostSpace = 1;
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}
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if (params.hostcase && find_host(&pHost,segment,*size))
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{
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VPRINT("Changing 'Host:' => '%c%c%c%c:' at pos %td", params.hostspell[0], params.hostspell[1], params.hostspell[2], params.hostspell[3], pHost - segment)
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memcpy(pHost, params.hostspell, 4);
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}
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if (params.hostpad && find_host(&pHost,segment,*size))
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{
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// add : XXXXX: <padding?[\r\n|\n]
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char s[8];
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size_t hsize = params.unixeol ? 8 : 9;
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size_t hostpad = params.hostpad<hsize ? hsize : params.hostpad;
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if ((hsize+*size)>segment_buffer_size)
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VPRINT("could not add host padding : buffer too small")
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else
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{
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if ((hostpad+*size)>segment_buffer_size)
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{
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hostpad=segment_buffer_size-*size;
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VPRINT("host padding reduced to %zu bytes : buffer too small", hostpad)
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}
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else
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VPRINT("host padding with %zu bytes", hostpad)
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p = pHost;
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pos = p - segment;
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memmove(p + hostpad, p, *size - pos);
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(*size) += hostpad;
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while(hostpad)
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{
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#define MAX_HDR_SIZE 2048
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size_t padsize = hostpad > hsize ? hostpad-hsize : 0;
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if (padsize>MAX_HDR_SIZE) padsize=MAX_HDR_SIZE;
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// if next header would be too small then add extra padding to the current one
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if ((hostpad-padsize-hsize)<hsize) padsize+=hostpad-padsize-hsize;
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snprintf(s,sizeof(s),"%c%04x: ", 'a'+rand()%('z'-'a'+1), rand() & 0xFFFF);
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memcpy(p,s,7);
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p+=7;
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memset(p,'a'+rand()%('z'-'a'+1),padsize);
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p+=padsize;
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if (params.unixeol)
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*p++='\n';
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else
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{
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*p++='\r';
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*p++='\n';
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}
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hostpad-=hsize+padsize;
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}
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pHost = NULL; // invalidate
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}
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}
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switch (params.split_http_req)
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{
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case split_method:
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*split_pos = method_len - 1 + params.methodeol + (params.methodeol && !params.unixeol);
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break;
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case split_host:
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if (find_host(&pHost,segment,*size))
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*split_pos = pHost + 6 - bRemovedHostSpace - segment;
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break;
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default:
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if (params.split_pos < *size) *split_pos = params.split_pos;
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}
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}
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else
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{
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VPRINT("Not acting on this request")
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}
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return;
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}
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if (IsTLSClientHello(segment,*size))
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{
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char host[256];
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size_t tpos=0,elen;
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const uint8_t *ext;
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VPRINT("packet contains TLS ClientHello")
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// we need host only if hostlist is present
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if ((params.hostlist || params.hostlist_exclude) && TLSHelloExtractHost((uint8_t*)segment,*size,host,sizeof(host)))
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{
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VPRINT("hostname: %s",host)
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if (!HostlistCheck(params.hostlist, params.hostlist_exclude, host))
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{
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VPRINT("Not acting on this request")
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return;
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}
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}
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switch(params.tlsrec)
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{
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case tlsrec_sni:
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if (TLSFindExt(segment,*size,0,&ext,&elen))
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tpos = ext-segment+1; // between typical 1st and 2nd char of hostname
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break;
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case tlsrec_pos:
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tpos = params.tlsrec_pos;
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break;
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default:
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break;
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}
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if (tpos)
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{
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// construct 2 TLS records from one
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uint16_t l = pntoh16(segment+3); // length
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if (l>=2)
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{
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// length is checked in IsTLSClientHello and cannot exceed buffer size
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if (tpos>=l) tpos=1;
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VPRINT("making 2 TLS records at pos %zu",tpos)
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memmove(segment+5+tpos+5,segment+5+tpos,l-tpos);
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segment[5+tpos] = segment[0];
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segment[5+tpos+1] = segment[1];
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segment[5+tpos+2] = segment[2];
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phton16(segment+5+tpos+3,l-tpos);
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phton16(segment+3,tpos);
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*size += 5;
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}
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}
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if (params.split_pos < *size)
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*split_pos = params.split_pos;
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return;
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}
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if (params.split_any_protocol && params.split_pos < *size)
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*split_pos = params.split_pos;
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}
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