enable_passive.c

   1 /*
   2  * User FTP Server,  Share folders over FTP without being root.
   3  * Copyright (C) 2008  Isaac Jurado
   4  *
   5  * This program is free software; you can redistribute it and/or modify it under
   6  * the terms of the GNU General Public License as published by the Free Software
   7  * Foundation; either version 2 of the License, or (at your option) any later
   8  * version.
   9  *
  10  * This program is distributed in the hope that it will be useful, but WITHOUT
  11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  12  * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
  13  * details.
  14  *
  15  * You should have received a copy of the GNU General Public License along with
  16  * this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
  18  */
  19
  20 #include "uftps.h"
  21 #include <sys/socket.h>
  22 #include <netinet/in.h>
  23 #include <arpa/inet.h>
  24 #include <unistd.h>
  25 #include <string.h>
  26 #include <stdlib.h>
  27 #include <stdio.h>
  28
  29
  30 void enable_passive (void)
  31 {
  32         int                 bsk, l, e;
  33         struct sockaddr_in  sai;
  34         socklen_t           sai_len = sizeof(struct sockaddr_in);
  35         unsigned char       addr[6];
  36         char                pasv_reply[32];
  37
  38         /* Safety check in case there was some error before */
  39         if (SS.passive_sk != -1)
  40         {
  41                 e = close(SS.passive_sk);
  42                 if (e == -1)
  43                         error("Closing unused passive socket");
  44                 SS.passive_sk   = -1;
  45                 SS.passive_mode = 0;
  46         }
  47
  48         bsk = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
  49         if (bsk == -1)
  50         {
  51                 error("Creating passive socket");
  52                 goto error;
  53         }
  54         e = 1;
  55         setsockopt(bsk, SOL_SOCKET, SO_REUSEADDR, &e, sizeof(int));
  56
  57         sai_len = sizeof(struct sockaddr_in);
  58         memcpy(&sai, &SS.local_address, sizeof(struct sockaddr_in));
  59         sai.sin_port = 0;
  60         e = bind(bsk, (struct sockaddr *) &sai, sai_len);
  61         if (e == -1)
  62         {
  63                 error("Binding to a random port");
  64                 goto error_close;
  65         }
  66         e = listen(bsk, 1);
  67         if (e == -1)
  68         {
  69                 error("Listening on passive socket");
  70                 goto error_close;
  71         }
  72
  73         e = getsockname(bsk, (struct sockaddr *) &sai, &sai_len);
  74         if (e == -1)
  75         {
  76                 error("Retrieving passive socket information");
  77                 goto error_close;
  78         }
  79         memcpy(&addr[0], &sai.sin_addr, 4);
  80         memcpy(&addr[4], &sai.sin_port, 2);
  81
  82         debug("Passive mode listening on port %d", ntohs(sai.sin_port));
  83
  84         SS.passive_mode = 1;
  85         SS.passive_sk   = bsk;
  86         l = snprintf(pasv_reply, 32, "227 =%u,%u,%u,%u,%u,%u\r\n", addr[0],
  87                      addr[1], addr[2], addr[3], addr[4], addr[5]);
  88
  89         reply(pasv_reply, l);
  90         return;
  91
  92 error_close:
  93         e = close(bsk);
  94         if (e == -1)
  95                 error("Closing passive socket");
  96 error:
  97         reply_c("425 No way to open a port for you.\r\n");
  98 }
  99