parse_port_argument.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 #ifndef __MINGW32__
  22 #  include <sys/socket.h>
  23 #  include <arpa/inet.h>
  24 #endif
  25 #include <stdlib.h>
  26 #include <string.h>
  27
  28 /* This is needed by Solaris */
  29 #ifndef INADDR_NONE
  30 #  define INADDR_NONE  -1
  31 #endif
  32
  33
  34 /*
  35  * Parse a PORT argument and convert it to a internet address structure.
  36  * Returns -1 when a parsing error occurs.
  37  *
  38  * The argument has the syntax "h1,h2,h3,h4,p1,p2".  First, we need to split IP
  39  * and port information "h1.h2.h3.h4\0p1,p2" (two strings).  The IP string is
  40  * finally parsed by inet_addr() into a 'in_addr_t' value.  Finally, the port
  41  * number is obtained as p1 * 256 + p2 and translated to network byte ordering
  42  * with htons().
  43  */
  44 void parse_port_argument (void)
  45 {
  46         int                 commas, port, i, j;
  47         struct sockaddr_in  sai;
  48
  49         if (SS.arg == NULL)
  50         {
  51                 warning("PORT without argument");
  52                 reply_c("501 Argument required.\r\n");
  53                 return;
  54         }
  55
  56         /* "h1,h2,h3,h4,p1,p2" ==> "h1.h2.h3.h4"  "p1,p2" */
  57         i      = 0;
  58         commas = 0;
  59         while (commas < 4)
  60         {
  61                 if (SS.arg[i] == '\0')
  62                 {
  63                         warning("PORT invalid parameter '%s'", SS.arg);
  64                         reply_c("501 Invalid PORT parameter.\r\n");
  65                         return;
  66                 }
  67
  68                 if (SS.arg[i] == ',')
  69                 {
  70                         commas++;
  71                         SS.arg[i] = '.';
  72                 }
  73                 i++;
  74         }
  75         SS.arg[i - 1] = '\0';
  76
  77         /* "h1.h2.h3.h4" ==> struct in_addr */
  78         sai.sin_addr.s_addr = inet_addr(SS.arg);
  79         if (sai.sin_addr.s_addr == INADDR_NONE)
  80         {
  81                 error("PORT Translating IP '%s'", SS.arg);
  82                 reply_c("501 Invalid PORT parameter.\r\n");
  83                 return;
  84         }
  85         /* Check if destination IP is the same as the client's */
  86         if (sai.sin_addr.s_addr != SS.client_address.sin_addr.s_addr)
  87         {
  88                 warning("PORT IP %s is not the same as the client's", SS.arg);
  89                 reply_c("501 Invalid PORT parameter.\r\n");
  90                 return;
  91         }
  92
  93         /* "p1,p2" ==> int (port number) */
  94         j = i;
  95         while (SS.arg[j] != ',')
  96                 j++;
  97         SS.arg[j] = '\0';
  98         port      = atoi(&SS.arg[i]) * 256 + atoi(&SS.arg[j + 1]);
  99
 100         /* Save PORT information for later use when opening the data channel */
 101         memset(&SS.port_destination, 0, sizeof(struct sockaddr_in));
 102         SS.port_destination.sin_family = AF_INET;
 103         SS.port_destination.sin_addr   = sai.sin_addr;
 104         SS.port_destination.sin_port   = htons(port & 0x00FFFF);
 105
 106         SS.mode = ACTIVE_MODE;
 107         debug("PORT parsing results %s:%d\n", SS.arg, port & 0x00FFFF);
 108         reply_c("200 PORT Command OK.\r\n");
 109 }
 110