lib/libc/stdlib/realpath.c

   1 /*
   2  * Copyright (c) 2003 Constantin S. Svintsoff <kostik@iclub.nsu.ru>
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  * 3. The names of the authors may not be used to endorse or promote
  13  *    products derived from this software without specific prior written
  14  *    permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  26  * SUCH DAMAGE.
  27  *
  28  * @(#)realpath.c       8.1 (Berkeley) 2/16/94
  29  * $FreeBSD: head/lib/libc/stdlib/realpath.c 264417 2014-04-13 19:48:28Z jilles $
  30  */
  31
  32 #include "namespace.h"
  33 #include <sys/param.h>
  34 #include <sys/stat.h>
  35
  36 #include <errno.h>
  37 #include <stdio.h>
  38 #include <stdlib.h>
  39 #include <string.h>
  40 #include <unistd.h>
  41 #include "un-namespace.h"
  42
  43 int     __realpath(const char *path, char *rbuf, size_t len);
  44
  45 /*
  46  * Find the real name of path, by removing all ".", ".." and symlink
  47  * components.  Returns (resolved) on success, or (NULL) on failure,
  48  * in which case the path which caused trouble is left in (resolved).
  49  */
  50 char *
  51 realpath(const char * __restrict path, char * __restrict resolved)
  52 {
  53         struct stat sb;
  54         char *p, *q, *s;
  55         size_t left_len, resolved_len;
  56         unsigned symlinks;
  57         int m, slen;
  58         char left[PATH_MAX], next_token[PATH_MAX], my_symlink[PATH_MAX];
  59
  60         if (path == NULL) {
  61                 errno = EINVAL;
  62                 return (NULL);
  63         }
  64         if (path[0] == '\0') {
  65                 errno = ENOENT;
  66                 return (NULL);
  67         }
  68         if (resolved == NULL) {
  69                 resolved = malloc(PATH_MAX);
  70                 if (resolved == NULL)
  71                         return (NULL);
  72                 m = 1;
  73         } else {
  74                 m = 0;
  75         }
  76
  77         if (getosreldate() >= 500710) {
  78                 if (__realpath(path, resolved, PATH_MAX) < 0) {
  79                         if (m) {
  80                                 free(resolved);
  81                         } else {
  82                                 snprintf(resolved, PATH_MAX, "%s", path);
  83                         }
  84                         return (NULL);
  85                 }
  86                 return resolved;
  87         }
  88
  89         symlinks = 0;
  90         if (path[0] == '/') {
  91                 resolved[0] = '/';
  92                 resolved[1] = '\0';
  93                 if (path[1] == '\0')
  94                         return (resolved);
  95                 resolved_len = 1;
  96                 left_len = strlcpy(left, path + 1, sizeof(left));
  97         } else {
  98                 if (getcwd(resolved, PATH_MAX) == NULL) {
  99                         if (m) {
 100                                 free(resolved);
 101                         } else {
 102                                 resolved[0] = '.';
 103                                 resolved[1] = '\0';
 104                         }
 105                         return (NULL);
 106                 }
 107                 resolved_len = strlen(resolved);
 108                 left_len = strlcpy(left, path, sizeof(left));
 109         }
 110         if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) {
 111                 if (m)
 112                         free(resolved);
 113                 errno = ENAMETOOLONG;
 114                 return (NULL);
 115         }
 116
 117         /*
 118          * Iterate over path components in `left'.
 119          */
 120         while (left_len != 0) {
 121                 /*
 122                  * Extract the next path component and adjust `left'
 123                  * and its length.
 124                  */
 125                 p = strchr(left, '/');
 126                 s = p ? p : left + left_len;
 127                 if (s - left >= sizeof(next_token)) {
 128                         if (m)
 129                                 free(resolved);
 130                         errno = ENAMETOOLONG;
 131                         return (NULL);
 132                 }
 133                 memcpy(next_token, left, s - left);
 134                 next_token[s - left] = '\0';
 135                 left_len -= s - left;
 136                 if (p != NULL)
 137                         memmove(left, s + 1, left_len + 1);
 138                 if (resolved[resolved_len - 1] != '/') {
 139                         if (resolved_len + 1 >= PATH_MAX) {
 140                                 if (m)
 141                                         free(resolved);
 142                                 errno = ENAMETOOLONG;
 143                                 return (NULL);
 144                         }
 145                         resolved[resolved_len++] = '/';
 146                         resolved[resolved_len] = '\0';
 147                 }
 148                 if (next_token[0] == '\0') {
 149                         /* Handle consequential slashes. */
 150                         continue;
 151                 } else if (strcmp(next_token, ".") == 0) {
 152                         continue;
 153                 } else if (strcmp(next_token, "..") == 0) {
 154                         /*
 155                          * Strip the last path component except when we have
 156                          * single "/"
 157                          */
 158                         if (resolved_len > 1) {
 159                                 resolved[resolved_len - 1] = '\0';
 160                                 q = strrchr(resolved, '/') + 1;
 161                                 *q = '\0';
 162                                 resolved_len = q - resolved;
 163                         }
 164                         continue;
 165                 }
 166
 167                 /*
 168                  * Append the next path component and lstat() it.
 169                  */
 170                 resolved_len = strlcat(resolved, next_token, PATH_MAX);
 171                 if (resolved_len >= PATH_MAX) {
 172                         if (m)
 173                                 free(resolved);
 174                         errno = ENAMETOOLONG;
 175                         return (NULL);
 176                 }
 177                 if (lstat(resolved, &sb) != 0) {
 178                         if (m)
 179                                 free(resolved);
 180                         return (NULL);
 181                 }
 182                 if (S_ISLNK(sb.st_mode)) {
 183                         if (symlinks++ > MAXSYMLINKS) {
 184                                 if (m)
 185                                         free(resolved);
 186                                 errno = ELOOP;
 187                                 return (NULL);
 188                         }
 189                         slen = readlink(resolved, my_symlink, sizeof(my_symlink) - 1);
 190                         if (slen < 0) {
 191                                 if (m)
 192                                         free(resolved);
 193                                 return (NULL);
 194                         }
 195                         my_symlink[slen] = '\0';
 196                         if (my_symlink[0] == '/') {
 197                                 resolved[1] = 0;
 198                                 resolved_len = 1;
 199                         } else if (resolved_len > 1) {
 200                                 /* Strip the last path component. */
 201                                 resolved[resolved_len - 1] = '\0';
 202                                 q = strrchr(resolved, '/') + 1;
 203                                 *q = '\0';
 204                                 resolved_len = q - resolved;
 205                         }
 206
 207                         /*
 208                          * If there are any path components left, then
 209                          * append them to symlink. The result is placed
 210                          * in `left'.
 211                          */
 212                         if (p != NULL) {
 213                                 if (my_symlink[slen - 1] != '/') {
 214                                         if (slen + 1 >= (int)sizeof(my_symlink)) {
 215                                                 if (m)
 216                                                         free(resolved);
 217                                                 errno = ENAMETOOLONG;
 218                                                 return (NULL);
 219                                         }
 220                                         my_symlink[slen] = '/';
 221                                         my_symlink[slen + 1] = 0;
 222                                 }
 223                                 left_len = strlcat(my_symlink, left,
 224                                     sizeof(my_symlink));
 225                                 if (left_len >= sizeof(left)) {
 226                                         if (m)
 227                                                 free(resolved);
 228                                         errno = ENAMETOOLONG;
 229                                         return (NULL);
 230                                 }
 231                         }
 232                         left_len = strlcpy(left, my_symlink, sizeof(left));
 233                 } else if (!S_ISDIR(sb.st_mode) && p != NULL) {
 234                         if (m)
 235                                 free(resolved);
 236                         errno = ENOTDIR;
 237                         return (NULL);
 238                 }
 239         }
 240
 241         /*
 242          * Remove trailing slash except when the resolved pathname
 243          * is a single "/".
 244          */
 245         if (resolved_len > 1 && resolved[resolved_len - 1] == '/')
 246                 resolved[resolved_len - 1] = '\0';
 247         return (resolved);
 248 }