apply_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
  20 #include "uftps.h"
  21 #include <string.h>
  22
  23
  24 /*
  25  * Apply new path components to an existing working directory.  The working
  26  * directory is contained (full path) in wd, which is a buffer with a capacity
  27  * of size bytes.  This working directory path length is len bytes (counting the
  28  * null ending).
  29  *
  30  * The function returns the length of the resulting path after walking the path
  31  * argument from the working directory.  In case the working directory would
  32  * exceed size bytes (at any stage), -1 is returning.
  33  */
  34 int apply_path (const char *path, char *wd, int len)
  35 {
  36         int  i;
  37
  38         if (*path == '/')
  39         {
  40                 /* Absolute path, truncate wd */
  41                 wd[0] = '.';
  42                 wd[1] = '/';
  43                 wd[2] = '\0';
  44                 len   = 3;
  45         }
  46
  47         do {
  48                 /* Combine delimiters */
  49                 while (*path == '/')
  50                         path++;
  51
  52                 if (*path == '\0')
  53                         /* No more components to apply */
  54                         break;
  55
  56                 /* Isolate next component */
  57                 i = 0;
  58                 while (path[i] != '/' && path[i] != '\0')
  59                         i++;
  60
  61                 if (i == 2 && path[0] == '.' && path[1] == '.')
  62                 {
  63                         /* Return to parent directory, found ".." */
  64                         while (wd[len] != '/')
  65                                 len--;
  66                         if (len == 1)
  67                                 len++;  /* Root reached, fix */
  68                         wd[len] = '\0';
  69                         len++;
  70                 }
  71                 else if (i != 1 || path[0] != '.')
  72                 {
  73                         if (len + i >= LINE_SIZE)
  74                                 return -1;
  75
  76                         /* Apply component, because it is different than "." */
  77                         if (len > 3)
  78                                 wd[len - 1] = '/';
  79                         else
  80                                 len--;   /* Skip delimiter at root */
  81
  82                         memcpy(wd + len, path, i);
  83                         len        += i + 1;
  84                         wd[len - 1] = '\0';
  85                 }
  86
  87                 /* Now skip to the next component */
  88                 path += i;
  89         } while (1);
  90
  91         return len;
  92 }
  93