path.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  * FUTURE IDEAS:
  23  *
  24  *    - Check every component to see if it is a symbolic link in order to
  25  *      protect the shared hierarchy even more.  This may come at a cost in
  26  *      performance though.
  27  */
  28
  29 #include <string.h>
  30
  31
  32 /*
  33  * Apply new path components to an existing working directory.  The working
  34  * directory is contained (full path) in wd, which is a buffer with a capacity
  35  * of size bytes.  This working directory path length is len bytes (counting the
  36  * null ending).
  37  *
  38  * The function returns the length of the resulting path after walking the path
  39  * argument from the working directory.  In case the working directory would
  40  * exceed size bytes (at any stage), -1 is returning.
  41  */
  42 static int apply_path (const char *path, char *wd, int len)
  43 {
  44         int  i;
  45
  46         if (*path == '/')
  47         {
  48                 /* Absolute path, truncate wd */
  49                 wd[0] = '.';
  50                 wd[1] = '/';
  51                 wd[2] = '\0';
  52                 len   = 3;
  53         }
  54
  55         do {
  56                 /* Combine delimiters */
  57                 while (*path == '/')
  58                         path++;
  59
  60                 if (*path == '\0')
  61                         /* No more components to apply */
  62                         break;
  63
  64                 /* Isolate next component */
  65                 i = 0;
  66                 while (path[i] != '/' && path[i] != '\0')
  67                         i++;
  68
  69                 if (i == 2 && path[0] == '.' && path[1] == '.')
  70                 {
  71                         /* Return to parent directory, found ".." */
  72                         while (wd[len] != '/')
  73                                 len--;
  74                         if (len == 1)
  75                                 len++;  /* Root reached, fix */
  76                         wd[len] = '\0';
  77                         len++;
  78                 }
  79                 else if (i != 1 || path[0] != '.')
  80                 {
  81                         if (len + i >= LINE_SIZE)
  82                                 return -1;
  83
  84                         /* Apply component, because it is different than "." */
  85                         if (len > 3)
  86                                 wd[len - 1] = '/';
  87                         else
  88                                 len--;   /* Skip delimiter at root */
  89
  90                         memcpy(wd + len, path, i);
  91                         len        += i + 1;
  92                         wd[len - 1] = '\0';
  93                 }
  94
  95                 /* Now skip to the next component */
  96                 path += i;
  97         } while (1);
  98
  99         return len;
 100 }
 101
 102
 103 void change_dir (void)
 104 {
 105         int  len;
 106
 107         if (SS.arg == NULL)
 108         {
 109                 reply_c("501 Argument required.\r\n");
 110                 return;
 111         }
 112
 113         len = apply_path(SS.arg, SS.cwd, SS.cwd_len);
 114         if (len == -1)
 115         {
 116                 reply_c("552 Path overflow.\r\n");
 117                 fatal("Path overflow in CWD");
 118         }
 119
 120         SS.cwd_len = len;
 121         reply_c("250 Directory changed.\r\n");
 122         debug("Directory changed to '%s'", SS.cwd);
 123 }
 124
 125
 126 int expand_arg (void)
 127 {
 128         int  len = SS.cwd_len;
 129
 130         strncpy(SS.aux, SS.cwd, len);
 131
 132         if (SS.arg != NULL)
 133         {
 134                 len = apply_path(SS.arg, SS.aux, SS.cwd_len);
 135                 if (len == -1)
 136                 {
 137                         reply_c("552 Path overflow.\r\n");
 138                         fatal("Path overflow");
 139                 }
 140         }
 141
 142         SS.arg = SS.aux;
 143         debug("Argument expanded to '%s'", SS.arg);
 144         return len;
 145 }
 146