crypto/openssh/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/types.h>
  37 #include <sys/param.h>
  38 #include <sys/stat.h>
  39
  40 #include <errno.h>
  41 #include <stdlib.h>
  42 #include <stddef.h>
  43 #include <string.h>
  44 #include <unistd.h>
  45
  46 /*
  47  * char *realpath(const char *path, char resolved[PATH_MAX]);
  48  *
  49  * Find the real name of path, by removing all ".", ".." and symlink
  50  * components.  Returns (resolved) on success, or (NULL) on failure,
  51  * in which case the path which caused trouble is left in (resolved).
  52  */
  53 char *
  54 realpath(const char *path, char resolved[PATH_MAX])
  55 {
  56         struct stat sb;
  57         char *p, *q, *s;
  58         size_t left_len, resolved_len;
  59         unsigned symlinks;
  60         int serrno, slen;
  61         char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX];
  62
  63         serrno = errno;
  64         symlinks = 0;
  65         if (path[0] == '/') {
  66                 resolved[0] = '/';
  67                 resolved[1] = '\0';
  68                 if (path[1] == '\0')
  69                         return (resolved);
  70                 resolved_len = 1;
  71                 left_len = strlcpy(left, path + 1, sizeof(left));
  72         } else {
  73                 if (getcwd(resolved, PATH_MAX) == NULL) {
  74                         strlcpy(resolved, ".", PATH_MAX);
  75                         return (NULL);
  76                 }
  77                 resolved_len = strlen(resolved);
  78                 left_len = strlcpy(left, path, sizeof(left));
  79         }
  80         if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) {
  81                 errno = ENAMETOOLONG;
  82                 return (NULL);
  83         }
  84
  85         /*
  86          * Iterate over path components in `left'.
  87          */
  88         while (left_len != 0) {
  89                 /*
  90                  * Extract the next path component and adjust `left'
  91                  * and its length.
  92                  */
  93                 p = strchr(left, '/');
  94                 s = p ? p : left + left_len;
  95                 if (s - left >= (ptrdiff_t)sizeof(next_token)) {
  96                         errno = ENAMETOOLONG;
  97                         return (NULL);
  98                 }
  99                 memcpy(next_token, left, s - left);
 100                 next_token[s - left] = '\0';
 101                 left_len -= s - left;
 102                 if (p != NULL)
 103                         memmove(left, s + 1, left_len + 1);
 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                         continue;
 114                 else if (strcmp(next_token, ".") == 0)
 115                         continue;
 116                 else if (strcmp(next_token, "..") == 0) {
 117                         /*
 118                          * Strip the last path component except when we have
 119                          * single "/"
 120                          */
 121                         if (resolved_len > 1) {
 122                                 resolved[resolved_len - 1] = '\0';
 123                                 q = strrchr(resolved, '/') + 1;
 124                                 *q = '\0';
 125                                 resolved_len = q - resolved;
 126                         }
 127                         continue;
 128                 }
 129
 130                 /*
 131                  * Append the next path component and lstat() it. If
 132                  * lstat() fails we still can return successfully if
 133                  * there are no more path components left.
 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                         if (errno == ENOENT && p == NULL) {
 142                                 errno = serrno;
 143                                 return (resolved);
 144                         }
 145                         return (NULL);
 146                 }
 147                 if (S_ISLNK(sb.st_mode)) {
 148                         if (symlinks++ > MAXSYMLINKS) {
 149                                 errno = ELOOP;
 150                                 return (NULL);
 151                         }
 152                         slen = readlink(resolved, symlink, sizeof(symlink) - 1);
 153                         if (slen < 0)
 154                                 return (NULL);
 155                         symlink[slen] = '\0';
 156                         if (symlink[0] == '/') {
 157                                 resolved[1] = 0;
 158                                 resolved_len = 1;
 159                         } else if (resolved_len > 1) {
 160                                 /* Strip the last path component. */
 161                                 resolved[resolved_len - 1] = '\0';
 162                                 q = strrchr(resolved, '/') + 1;
 163                                 *q = '\0';
 164                                 resolved_len = q - resolved;
 165                         }
 166
 167                         /*
 168                          * If there are any path components left, then
 169                          * append them to symlink. The result is placed
 170                          * in `left'.
 171                          */
 172                         if (p != NULL) {
 173                                 if (symlink[slen - 1] != '/') {
 174                                         if (slen + 1 >=
 175                                             (ptrdiff_t)sizeof(symlink)) {
 176                                                 errno = ENAMETOOLONG;
 177                                                 return (NULL);
 178                                         }
 179                                         symlink[slen] = '/';
 180                                         symlink[slen + 1] = 0;
 181                                 }
 182                                 left_len = strlcat(symlink, left, sizeof(left));
 183                                 if (left_len >= sizeof(left)) {
 184                                         errno = ENAMETOOLONG;
 185                                         return (NULL);
 186                                 }
 187                         }
 188                         left_len = strlcpy(left, symlink, sizeof(left));
 189                 }
 190         }
 191
 192         /*
 193          * Remove trailing slash except when the resolved pathname
 194          * is a single "/".
 195          */
 196         if (resolved_len > 1 && resolved[resolved_len - 1] == '/')
 197                 resolved[resolved_len - 1] = '\0';
 198         return (resolved);
 199 }
 200 #endif /* !defined(HAVE_REALPATH) || defined(BROKEN_REALPATH) */