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
  29 #if defined(LIBC_SCCS) && !defined(lint)
  30 static char sccsid[] = "@(#)realpath.c  8.1 (Berkeley) 2/16/94";
  31 #endif /* LIBC_SCCS and not lint */
  32 #include <sys/cdefs.h>
  33 __FBSDID("$FreeBSD$");
  34
  35 #include "namespace.h"
  36 #include <sys/param.h>
  37 #include <sys/stat.h>
  38
  39 #include <errno.h>
  40 #include <stdlib.h>
  41 #include <string.h>
  42 #include <unistd.h>
  43 #include "un-namespace.h"
  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 static char *
  51 realpath1(const char *path, char *resolved)
  52 {
  53         struct stat sb;
  54         char *p, *q;
  55         size_t left_len, resolved_len, next_token_len;
  56         unsigned symlinks;
  57         ssize_t slen;
  58         char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX];
  59
  60         symlinks = 0;
  61         if (path[0] == '/') {
  62                 resolved[0] = '/';
  63                 resolved[1] = '\0';
  64                 if (path[1] == '\0')
  65                         return (resolved);
  66                 resolved_len = 1;
  67                 left_len = strlcpy(left, path + 1, sizeof(left));
  68         } else {
  69                 if (getcwd(resolved, PATH_MAX) == NULL) {
  70                         resolved[0] = '.';
  71                         resolved[1] = '\0';
  72                         return (NULL);
  73                 }
  74                 resolved_len = strlen(resolved);
  75                 left_len = strlcpy(left, path, sizeof(left));
  76         }
  77         if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) {
  78                 errno = ENAMETOOLONG;
  79                 return (NULL);
  80         }
  81
  82         /*
  83          * Iterate over path components in `left'.
  84          */
  85         while (left_len != 0) {
  86                 /*
  87                  * Extract the next path component and adjust `left'
  88                  * and its length.
  89                  */
  90                 p = strchr(left, '/');
  91
  92                 next_token_len = p ? p - left : left_len;
  93                 memcpy(next_token, left, next_token_len);
  94                 next_token[next_token_len] = '\0';
  95
  96                 if (p != NULL) {
  97                         left_len -= next_token_len + 1;
  98                         memmove(left, p + 1, left_len + 1);
  99                 } else {
 100                         left[0] = '\0';
 101                         left_len = 0;
 102                 }
 103
 104                 if (resolved[resolved_len - 1] != '/') {
 105                         if (resolved_len + 1 >= PATH_MAX) {
 106                                 errno = ENAMETOOLONG;
 107                                 return (NULL);
 108                         }
 109                         resolved[resolved_len++] = '/';
 110                         resolved[resolved_len] = '\0';
 111                 }
 112                 if (next_token[0] == '\0') {
 113                         /* Handle consequential slashes. */
 114                         continue;
 115                 }
 116                 else if (strcmp(next_token, ".") == 0)
 117                         continue;
 118                 else if (strcmp(next_token, "..") == 0) {
 119                         /*
 120                          * Strip the last path component except when we have
 121                          * single "/"
 122                          */
 123                         if (resolved_len > 1) {
 124                                 resolved[resolved_len - 1] = '\0';
 125                                 q = strrchr(resolved, '/') + 1;
 126                                 *q = '\0';
 127                                 resolved_len = q - resolved;
 128                         }
 129                         continue;
 130                 }
 131
 132                 /*
 133                  * Append the next path component and lstat() it.
 134                  */
 135                 resolved_len = strlcat(resolved, next_token, PATH_MAX);
 136                 if (resolved_len >= PATH_MAX) {
 137                         errno = ENAMETOOLONG;
 138                         return (NULL);
 139                 }
 140                 if (lstat(resolved, &sb) != 0)
 141                         return (NULL);
 142                 if (S_ISLNK(sb.st_mode)) {
 143                         if (symlinks++ > MAXSYMLINKS) {
 144                                 errno = ELOOP;
 145                                 return (NULL);
 146                         }
 147                         slen = readlink(resolved, symlink, sizeof(symlink));
 148                         if (slen <= 0 || slen >= sizeof(symlink)) {
 149                                 if (slen < 0) {
 150                                         /* keep errno from readlink(2) call */
 151                                 } else if (slen == 0) {
 152                                         errno = ENOENT;
 153                                 } else {
 154                                         errno = ENAMETOOLONG;
 155                                 }
 156                                 return (NULL);
 157                         }
 158                         symlink[slen] = '\0';
 159                         if (symlink[0] == '/') {
 160                                 resolved[1] = 0;
 161                                 resolved_len = 1;
 162                         } else {
 163                                 /* Strip the last path component. */
 164                                 q = strrchr(resolved, '/') + 1;
 165                                 *q = '\0';
 166                                 resolved_len = q - resolved;
 167                         }
 168
 169                         /*
 170                          * If there are any path components left, then
 171                          * append them to symlink. The result is placed
 172                          * in `left'.
 173                          */
 174                         if (p != NULL) {
 175                                 if (symlink[slen - 1] != '/') {
 176                                         if (slen + 1 >= sizeof(symlink)) {
 177                                                 errno = ENAMETOOLONG;
 178                                                 return (NULL);
 179                                         }
 180                                         symlink[slen] = '/';
 181                                         symlink[slen + 1] = 0;
 182                                 }
 183                                 left_len = strlcat(symlink, left,
 184                                     sizeof(symlink));
 185                                 if (left_len >= sizeof(symlink)) {
 186                                         errno = ENAMETOOLONG;
 187                                         return (NULL);
 188                                 }
 189                         }
 190                         left_len = strlcpy(left, symlink, sizeof(left));
 191                 } else if (!S_ISDIR(sb.st_mode) && p != NULL) {
 192                         errno = ENOTDIR;
 193                         return (NULL);
 194                 }
 195         }
 196
 197         /*
 198          * Remove trailing slash except when the resolved pathname
 199          * is a single "/".
 200          */
 201         if (resolved_len > 1 && resolved[resolved_len - 1] == '/')
 202                 resolved[resolved_len - 1] = '\0';
 203         return (resolved);
 204 }
 205
 206 char *
 207 realpath(const char * __restrict path, char * __restrict resolved)
 208 {
 209         char *m, *res;
 210
 211         if (path == NULL) {
 212                 errno = EINVAL;
 213                 return (NULL);
 214         }
 215         if (path[0] == '\0') {
 216                 errno = ENOENT;
 217                 return (NULL);
 218         }
 219         if (resolved != NULL) {
 220                 m = NULL;
 221         } else {
 222                 m = resolved = malloc(PATH_MAX);
 223                 if (resolved == NULL)
 224                         return (NULL);
 225         }
 226         res = realpath1(path, resolved);
 227         if (res == NULL)
 228                 free(m);
 229         return (res);
 230 }