command_loop.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 #include "uftps.h"
  20
  21 /*
  22  * Main FTP server loop which attends one client.
  23  *
  24  * It seems unbelievable but it's possible to implement a FTP server without
  25  * the need of select() or poll().  In fact, this kind of complexity is present
  26  * in the client.
  27  *
  28  * Commands not implemented are interpreted as unknown.  There used to be
  29  * dedicated dummy messages for some of them but code simplicity is preferred.
  30  */
  31
  32 #include <ctype.h>
  33 #include <unistd.h>
  34 #include <stdlib.h>
  35 #include <stdio.h>
  36
  37
  38 void command_loop (void)
  39 {
  40         while (1) {
  41                 switch (next_command()) {
  42
  43                 /*
  44                  * Straightforward implementations.
  45                  */
  46                 case FTP_NOOP:
  47                         send_reply(S_cmd_sk, "200 I'm alive, don't worry\r\n");
  48                         break;
  49
  50                 case FTP_FEAT:
  51                         send_reply(S_cmd_sk,
  52                                    "211-Feature list:\r\n"
  53                                    "211- MDTM\r\n"
  54                                    "211- REST STREAM\r\n"
  55                                    "211- SIZE\r\n"
  56                                    "211- TVFS\r\n"
  57                                    "211 End.\r\n");
  58                         break;
  59
  60                 case FTP_PASS:
  61                 case FTP_USER:
  62                         send_reply(S_cmd_sk, "230 I don't care.\r\n");
  63                         break;
  64
  65                 case FTP_SYST:
  66                         send_reply(S_cmd_sk, "215 UNIX Type: L8\r\n");
  67                         break;
  68
  69                 case FTP_OPTS:
  70                         send_reply(S_cmd_sk, "501 Option not understood.\r\n");
  71                         break;
  72
  73                 case FTP_ACCT:
  74                 case FTP_SMNT:
  75                         send_reply(S_cmd_sk, "202 Unimplemented, ignored.\r\n");
  76                         break;
  77
  78                 case FTP_REIN:
  79                         send_reply(S_cmd_sk, "220 Nothing to REIN.\r\n");
  80                         break;
  81
  82                 /*
  83                  * A bit more complex commands.
  84                  */
  85                 case FTP_MODE:
  86                         if (toupper(S_arg[0]) == 'S')
  87                                 send_reply(S_cmd_sk,
  88                                            "200 MODE set to stream.\r\n");
  89                         else
  90                                 send_reply(S_cmd_sk,
  91                                            "504 Mode not supported.\r\n");
  92                         break;
  93
  94                 case FTP_STRU:
  95                         if (toupper(S_arg[0]) == 'F')
  96                                 send_reply(S_cmd_sk,
  97                                            "200 STRUcture set to file.\r\n");
  98                         else
  99                                 send_reply(S_cmd_sk,
 100                                            "504 Structure not supported.\r\n");
 101                         break;
 102
 103                 case FTP_TYPE:
 104                         switch (toupper(S_arg[0])) {
 105                         case 'I':
 106                         case 'A':
 107                         case 'L':
 108                                 send_reply(S_cmd_sk, "200 Whatever.\r\n");
 109                                 break;
 110                         default:
 111                                 send_reply(S_cmd_sk,
 112                                            "501 Invalid type.\r\n");
 113                         }
 114                         break;
 115
 116                 case FTP_QUIT:
 117                         send_reply(S_cmd_sk, "221 Goodbye.\r\n");
 118                         close(S_cmd_sk);
 119                         close(S_passive_bind_sk);
 120                         exit(EXIT_SUCCESS);
 121                         break;
 122
 123                 case FTP_PASV:
 124                         S_passive_mode = 1;
 125                         send_reply(S_cmd_sk, S_passive_str);
 126                         break;
 127
 128                 case FTP_PWD:
 129                         getcwd(AuxBuf, LINE_SIZE);
 130                         /* Root directory santy check */
 131                         if (AuxBuf[Basedir_len] == '\0') {
 132                                 AuxBuf[Basedir_len] = '/';
 133                                 AuxBuf[Basedir_len + 1] = '\0';
 134                         }
 135                         /* We can overwrite the line buffer as no useful
 136                          * argument will be present */
 137                         snprintf(LineBuf, LINE_SIZE, "257 \"%s\"\r\n",
 138                                  AuxBuf + Basedir_len);
 139                         send_reply(S_cmd_sk, LineBuf);
 140                         break;
 141
 142                 case FTP_REST:
 143                         /* We don't need str_to_ll() as sscanf() does de job */
 144                         sscanf(S_arg, "%lld", &S_offset);
 145                         snprintf(AuxBuf, LINE_SIZE, "350 Got it (%lld).\r\n",
 146                                  S_offset);
 147                         send_reply(S_cmd_sk, AuxBuf);
 148                         break;
 149
 150                 /*
 151                  * Complex commands implemented separately.
 152                  */
 153                 case FTP_PORT:
 154                         client_port();
 155                         break;
 156
 157                 case FTP_NLST:
 158                         list_dir(0);
 159                         break;
 160
 161                 case FTP_LIST:
 162                         list_dir(1);
 163                         break;
 164
 165                 case FTP_MDTM:
 166                         file_stats(0);
 167                         break;
 168
 169                 case FTP_SIZE:
 170                         file_stats(1);
 171                         break;
 172
 173                 case FTP_CWD:
 174                         change_dir();
 175                         break;
 176
 177                 case FTP_RETR:
 178                         send_file();
 179                         break;
 180
 181                 case FTP_NONE:
 182                 default:
 183                         send_reply(S_cmd_sk, "500 Command unrecognized.\r\n");
 184                 }
 185         }
 186 }
 187