change_dir.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  * CWD command implementation.
  23  *
  24  * As we don't have root privileges, we can't execute the server within a
  25  * chroot() environment.  Therefore, we must impose a couple of restrictions
  26  * when the client tries to change the current working directory:
  27  *
  28  * 1. The command argument (i.e. the path we are being requested for) cannot
  29  *    contain any reference to the self directory "." nor to the parent
  30  *    directory ".."
  31  *
  32  * 2. If the argument begins with '/', it will be understood as an absolute path
  33  *    and then will be concatenated with the base directory (not visible to the
  34  *    client).
  35  *
  36  * 3. In any other case the parameter will be interpreted as a relative path, so
  37  *    it will simply be appended to the current working path.
  38  *
  39  * The complete working directory is retrieved via getcwd().  Given that we want
  40  * to hide part of it (the base path), BdLen contains the number of characters
  41  * we have to skip.  All this just to emulate chroot().
  42  *
  43  */
  44
  45 #include <unistd.h>
  46
  47
  48 void change_dir (void)
  49 {
  50         int err;
  51
  52         if (!path_is_secure(S_arg)) {
  53                 send_reply(S_cmd_sk, "550 Path is insecure.\r\n");
  54                 return;
  55         }
  56
  57         err = chdir(expanded_arg());
  58
  59         if (err == -1) {
  60                 send_reply(S_cmd_sk, "550 Could not change dir.\r\n");
  61                 return;
  62         }
  63
  64         send_reply(S_cmd_sk, "250 Directory changed.\r\n");
  65 }
  66