openbsd-compat/realpath.c

   1 /*      $OpenBSD: realpath.c,v 1.13 2005/08/08 08:05:37 espie Exp $ */
   2 /*
   3  * Copyright (c) 2003 Constantin S. Svintsoff <kostik@iclub.nsu.ru>
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. The names of the authors may not be used to endorse or promote
  14  *    products derived from this software without specific prior written
  15  *    permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  */
  29
  30 /* OPENBSD ORIGINAL: lib/libc/stdlib/realpath.c */
  31
  32 #include "includes.h"
  33
  34 #if !defined(HAVE_REALPATH) || defined(BROKEN_REALPATH)
  35
  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
  44 /*
  45  * char *realpath(const char *path, char resolved[PATH_MAX]);
  46  *
  47  * Find the real name of path, by removing all ".", ".." and symlink
  48  * components.  Returns (resolved) on success, or (NULL) on failure,
  49  * in which case the path which caused trouble is left in (resolved).
  50  */
  51 char *
  52 realpath(const char *path, char resolved[PATH_MAX])
  53 {
  54         struct stat sb;
  55         char *p, *q, *s;
  56         size_t left_len, resolved_len;
  57         unsigned symlinks;
  58         int serrno, slen;
  59         char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX];
  60
  61         serrno = errno;
  62         symlinks = 0;
  63         if (path[0] == '/') {
  64                 resolved[0] = '/';
  65                 resolved[1] = '\0';
  66                 if (path[1] == '\0')
  67                         return (resolved);
  68                 resolved_len = 1;
  69                 left_len = strlcpy(left, path + 1, sizeof(left));
  70         } else {
  71                 if (getcwd(resolved, PATH_MAX) == NULL) {
  72                         strlcpy(resolved, ".", PATH_MAX);
  73                         return (NULL);
  74                 }
  75                 resolved_len = strlen(resolved);
  76                 left_len = strlcpy(left, path, sizeof(left));
  77         }
  78         if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) {
  79                 errno = ENAMETOOLONG;
  80                 return (NULL);
  81         }
  82
  83         /*
  84          * Iterate over path components in `left'.
  85          */
  86         while (left_len != 0) {
  87                 /*
  88                  * Extract the next path component and adjust `left'
  89                  * and its length.
  90                  */
  91                 p = strchr(left, '/');
  92                 s = p ? p : left + left_len;
  93                 if (s - left >= sizeof(next_token)) {
  94                         errno = ENAMETOOLONG;
  95                         return (NULL);
  96                 }
  97                 memcpy(next_token, left, s - left);
  98                 next_token[s - left] = '\0';
  99                 left_len -= s - left;
 100                 if (p != NULL)
 101                         memmove(left, s + 1, left_len + 1);
 102                 if (resolved[resolved_len - 1] != '/') {
 103                         if (resolved_len + 1 >= PATH_MAX) {
 104                                 errno = ENAMETOOLONG;
 105                                 return (NULL);
 106                         }
 107                         resolved[resolved_len++] = '/';
 108                         resolved[resolved_len] = '\0';
 109                 }
 110                 if (next_token[0] == '\0')
 111                         continue;
 112                 else if (strcmp(next_token, ".") == 0)
 113                         continue;
 114                 else if (strcmp(next_token, "..") == 0) {
 115                         /*
 116                          * Strip the last path component except when we have
 117                          * single "/"
 118                          */
 119                         if (resolved_len > 1) {
 120                                 resolved[resolved_len - 1] = '\0';
 121                                 q = strrchr(resolved, '/') + 1;
 122                                 *q = '\0';
 123                                 resolved_len = q - resolved;
 124                         }
 125                         continue;
 126                 }
 127
 128                 /*
 129                  * Append the next path component and lstat() it. If
 130                  * lstat() fails we still can return successfully if
 131                  * there are no more path components left.
 132                  */
 133                 resolved_len = strlcat(resolved, next_token, PATH_MAX);
 134                 if (resolved_len >= PATH_MAX) {
 135                         errno = ENAMETOOLONG;
 136                         return (NULL);
 137                 }
 138                 if (lstat(resolved, &sb) != 0) {
 139                         if (errno == ENOENT && p == NULL) {
 140                                 errno = serrno;
 141                                 return (resolved);
 142                         }
 143                         return (NULL);
 144                 }
 145                 if (S_ISLNK(sb.st_mode)) {
 146                         if (symlinks++ > MAXSYMLINKS) {
 147                                 errno = ELOOP;
 148                                 return (NULL);
 149                         }
 150                         slen = readlink(resolved, symlink, sizeof(symlink) - 1);
 151                         if (slen < 0)
 152                                 return (NULL);
 153                         symlink[slen] = '\0';
 154                         if (symlink[0] == '/') {
 155                                 resolved[1] = 0;
 156                                 resolved_len = 1;
 157                         } else if (resolved_len > 1) {
 158                                 /* Strip the last path component. */
 159                                 resolved[resolved_len - 1] = '\0';
 160                                 q = strrchr(resolved, '/') + 1;
 161                                 *q = '\0';
 162                                 resolved_len = q - resolved;
 163                         }
 164
 165                         /*
 166                          * If there are any path components left, then
 167                          * append them to symlink. The result is placed
 168                          * in `left'.
 169                          */
 170                         if (p != NULL) {
 171                                 if (symlink[slen - 1] != '/') {
 172                                         if (slen + 1 >= sizeof(symlink)) {
 173                                                 errno = ENAMETOOLONG;
 174                                                 return (NULL);
 175                                         }
 176                                         symlink[slen] = '/';
 177                                         symlink[slen + 1] = 0;
 178                                 }
 179                                 left_len = strlcat(symlink, left, sizeof(left));
 180                                 if (left_len >= sizeof(left)) {
 181                                         errno = ENAMETOOLONG;
 182                                         return (NULL);
 183                                 }
 184                         }
 185                         left_len = strlcpy(left, symlink, sizeof(left));
 186                 }
 187         }
 188
 189         /*
 190          * Remove trailing slash except when the resolved pathname
 191          * is a single "/".
 192          */
 193         if (resolved_len > 1 && resolved[resolved_len - 1] == '/')
 194                 resolved[resolved_len - 1] = '\0';
 195         return (resolved);
 196 }
 197 #endif /* !defined(HAVE_REALPATH) || defined(BROKEN_REALPATH) */