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smbfilter.c

/* 
   Unix SMB/Netbios implementation.
   Version 2
   SMB filter/socket plugin
   Copyright (C) Andrew Tridgell 1999
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include "includes.h"
#include "smb.h"

#define SECURITY_MASK 0
#define SECURITY_SET  0

/* this forces non-unicode */
#define CAPABILITY_MASK (CAP_NT_SMBS | CAP_RPC_REMOTE_APIS)
#define CAPABILITY_SET  0

/* and non-unicode for the client too */
#define CLI_CAPABILITY_MASK 0
#define CLI_CAPABILITY_SET  0

static char *netbiosname;
static char packet[BUFFER_SIZE];

static void filter_reply(char *buf)
{
      int msg_type = CVAL(buf,0);
      int type = CVAL(buf,smb_com);
      unsigned x;

      if (msg_type) return;

      switch (type) {

      case SMBnegprot:
            /* force the security bits */
            x = CVAL(buf, smb_vwv1);
            x = (x | SECURITY_SET) & ~SECURITY_MASK;
            SCVAL(buf, smb_vwv1, x);

            /* force the capabilities */
            x = IVAL(buf,smb_vwv9+1);
            x = (x | CAPABILITY_SET) & ~CAPABILITY_MASK;
            SIVAL(buf, smb_vwv9+1, x);
            break;

      }
}

static void filter_request(char *buf)
{
      int msg_type = CVAL(buf,0);
      int type = CVAL(buf,smb_com);
      pstring name1,name2;
      unsigned x;

      if (msg_type) {
            /* it's a netbios special */
            switch (msg_type) {
            case 0x81:
                  /* session request */
                  name_extract(buf,4,name1);
                  name_extract(buf,4 + name_len(buf + 4),name2);
                  DEBUG(0,("sesion_request: %s -> %s\n",
                         name1, name2));
                  if (netbiosname) {
                        /* replace the destination netbios name */
                        name_mangle(netbiosname, buf+4, 0x20);
                  }
            }
            return;
      }

      /* it's an ordinary SMB request */
      switch (type) {
      case SMBsesssetupX:
            /* force the client capabilities */
            x = IVAL(buf,smb_vwv11);
            x = (x | CLI_CAPABILITY_SET) & ~CLI_CAPABILITY_MASK;
            SIVAL(buf, smb_vwv11, x);
            break;
      }

}


static void filter_child(int c, struct in_addr dest_ip)
{
      int s;

      /* we have a connection from a new client, now connect to the server */
      s = open_socket_out(SOCK_STREAM, &dest_ip, 139, LONG_CONNECT_TIMEOUT);

      if (s == -1) {
            DEBUG(0,("Unable to connect to %s\n", inet_ntoa(dest_ip)));
            exit(1);
      }

      while (c != -1 || s != -1) {
            fd_set fds;
            int num;
            
            FD_ZERO(&fds);
            if (s != -1) FD_SET(s, &fds);
            if (c != -1) FD_SET(c, &fds);

            num = sys_select_intr(MAX(s+1, c+1),&fds,NULL,NULL,NULL);
            if (num <= 0) continue;
            
            if (c != -1 && FD_ISSET(c, &fds)) {
                  if (!receive_smb(c, packet, 0)) {
                        DEBUG(0,("client closed connection\n"));
                        exit(0);
                  }
                  filter_request(packet);
                  if (!send_smb(s, packet)) {
                        DEBUG(0,("server is dead\n"));
                        exit(1);
                  }                 
            }
            if (s != -1 && FD_ISSET(s, &fds)) {
                  if (!receive_smb(s, packet, 0)) {
                        DEBUG(0,("server closed connection\n"));
                        exit(0);
                  }
                  filter_reply(packet);
                  if (!send_smb(c, packet)) {
                        DEBUG(0,("client is dead\n"));
                        exit(1);
                  }                 
            }
      }
      DEBUG(0,("Connection closed\n"));
      exit(0);
}


static void start_filter(char *desthost)
{
      int s, c;
      struct in_addr dest_ip;

      CatchChild();

      /* start listening on port 139 locally */
      s = open_socket_in(SOCK_STREAM, 139, 0, 0, True);
      
      if (s == -1) {
            DEBUG(0,("bind failed\n"));
            exit(1);
      }

      if (listen(s, 5) == -1) {
            DEBUG(0,("listen failed\n"));
      }

      if (!resolve_name(desthost, &dest_ip, 0x20)) {
            DEBUG(0,("Unable to resolve host %s\n", desthost));
            exit(1);
      }

      while (1) {
            fd_set fds;
            int num;
            struct sockaddr addr;
            socklen_t in_addrlen = sizeof(addr);
            
            FD_ZERO(&fds);
            FD_SET(s, &fds);

            num = sys_select_intr(s+1,&fds,NULL,NULL,NULL);
            if (num > 0) {
                  c = accept(s, &addr, &in_addrlen);
                  if (c != -1) {
                        if (fork() == 0) {
                              close(s);
                              filter_child(c, dest_ip);
                              exit(0);
                        } else {
                              close(c);
                        }
                  }
            }
      }
}


int main(int argc, char *argv[])
{
      char *desthost;
      pstring configfile;

      TimeInit();

      setup_logging(argv[0],True);
  
      charset_initialise();

      pstrcpy(configfile,CONFIGFILE);
 
      if (argc < 2) {
            fprintf(stderr,"smbfilter <desthost> <netbiosname>\n");
            exit(1);
      }

      desthost = argv[1];
      if (argc > 2) {
            netbiosname = argv[2];
      }

      if (!lp_load(configfile,True,False,False)) {
            DEBUG(0,("Unable to load config file\n"));
      }

      start_filter(desthost);
      return 0;
}

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