usr/src/lib/libdevinfo/devinfo_realpath.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 /*
  22  * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
  23  * Use is subject to license terms.
  24  */
  25
  26 #pragma ident   "%Z%%M% %I%     %E% SMI"
  27
  28 /*
  29  * Copyright (c) 2003 Constantin S. Svintsoff <kostik@iclub.nsu.ru>
  30  *
  31  * Redistribution and use in source and binary forms, with or without
  32  * modification, are permitted provided that the following conditions
  33  * are met:
  34  * 1. Redistributions of source code must retain the above copyright
  35  *    notice, this list of conditions and the following disclaimer.
  36  * 2. Redistributions in binary form must reproduce the above copyright
  37  *    notice, this list of conditions and the following disclaimer in the
  38  *    documentation and/or other materials provided with the distribution.
  39  * 3. The names of the authors may not be used to endorse or promote
  40  *    products derived from this software without specific prior written
  41  *    permission.
  42  *
  43  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  44  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  45  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  46  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  47  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  48  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  49  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  50  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  51  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  52  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  53  * SUCH DAMAGE.
  54  */
  55 /*
  56  * http://www.openbsd.org/cgi-bin/cvsweb/src/lib/libc/stdlib/realpath.c
  57  * $OpenBSD: realpath.c,v 1.13 2005/08/08 08:05:37 espie Exp $
  58  */
  59
  60 #include <stdio.h>
  61 #include <unistd.h>
  62 #include <string.h>
  63 #include <limits.h>
  64 #include <errno.h>
  65 #include <sys/types.h>
  66 #include <sys/stat.h>
  67 #include <sys/param.h>
  68
  69 /*
  70  * char *s_realpath(const char *path, char resolved_path[MAXPATHLEN]);
  71  *
  72  * Find the real name of path, by removing all ".", ".." and symlink
  73  * components.  Returns (resolved) on success, or (NULL) on failure,
  74  * in which case the path which caused trouble is left in (resolved).
  75  *
  76  * DEVINFO: For libdevinfo we have added code to special case symlinks into
  77  * /devices - the path below that point is known to not point to any
  78  * additional symlinks.  This knowledge allows us to avoid causing attach.
  79  */
  80 char *
  81 s_realpath(const char *path, char *resolved)
  82 {
  83         struct stat sb;
  84         char *p, *q, *s;
  85         size_t left_len, resolved_len;
  86         unsigned symlinks;
  87         int serrno, slen;
  88         char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX];
  89
  90         serrno = errno;
  91         symlinks = 0;
  92         if (path[0] == '/') {
  93                 resolved[0] = '/';
  94                 resolved[1] = '\0';
  95                 if (path[1] == '\0')
  96                         return (resolved);
  97                 resolved_len = 1;
  98                 left_len = strlcpy(left, path + 1, sizeof (left));
  99         } else {
 100                 if (getcwd(resolved, PATH_MAX) == NULL) {
 101                         (void) strlcpy(resolved, ".", PATH_MAX);
 102                         return (NULL);
 103                 }
 104                 resolved_len = strlen(resolved);
 105                 left_len = strlcpy(left, path, sizeof (left));
 106         }
 107         if (left_len >= sizeof (left) || resolved_len >= PATH_MAX) {
 108                 errno = ENAMETOOLONG;
 109                 return (NULL);
 110         }
 111
 112         /*
 113          * Iterate over path components in `left'.
 114          */
 115         while (left_len != 0) {
 116                 /*
 117                  * Extract the next path component and adjust `left'
 118                  * and its length.
 119                  */
 120                 p = strchr(left, '/');
 121                 s = p ? p : left + left_len;
 122                 if (s - left >= sizeof (next_token)) {
 123                         errno = ENAMETOOLONG;
 124                         return (NULL);
 125                 }
 126                 (void) memcpy(next_token, left, s - left);
 127                 next_token[s - left] = '\0';
 128                 left_len -= s - left;
 129                 if (p != NULL)
 130                         (void) memmove(left, s + 1, left_len + 1);
 131                 if (resolved[resolved_len - 1] != '/') {
 132                         if (resolved_len + 1 >= PATH_MAX) {
 133                                 errno = ENAMETOOLONG;
 134                                 return (NULL);
 135                         }
 136                         resolved[resolved_len++] = '/';
 137                         resolved[resolved_len] = '\0';
 138                 }
 139                 if (next_token[0] == '\0')
 140                         continue;
 141                 else if (strcmp(next_token, ".") == 0)
 142                         continue;
 143                 else if (strcmp(next_token, "..") == 0) {
 144                         /*
 145                          * Strip the last path component except when we have
 146                          * single "/"
 147                          */
 148                         if (resolved_len > 1) {
 149                                 resolved[resolved_len - 1] = '\0';
 150                                 q = strrchr(resolved, '/') + 1;
 151                                 *q = '\0';
 152                                 resolved_len = q - resolved;
 153                         }
 154                         continue;
 155                 }
 156
 157                 /*
 158                  * Append the next path component and lstat() it. If
 159                  * lstat() fails we still can return successfully if
 160                  * there are no more path components left.
 161                  */
 162                 resolved_len = strlcat(resolved, next_token, PATH_MAX);
 163                 if (resolved_len >= PATH_MAX) {
 164                         errno = ENAMETOOLONG;
 165                         return (NULL);
 166                 }
 167
 168                 /*
 169                  * DEVINFO: Check if link points into /devices and resolve
 170                  * without causing attach if that is the case - there are no
 171                  * further symlinks in /devices.
 172                  */
 173                 if (strcmp(resolved, "/devices") == 0) {
 174                         resolved[resolved_len] = '/';
 175                         resolved_len = strlcat(resolved, left, sizeof (left));
 176                         left_len = 0;
 177                         continue;
 178                 }
 179
 180                 if (lstat(resolved, &sb) != 0) {
 181                         if (errno == ENOENT && p == NULL) {
 182                                 errno = serrno;
 183                                 return (resolved);
 184                         }
 185                         return (NULL);
 186                 }
 187
 188                 if (S_ISLNK(sb.st_mode)) {
 189                         if (symlinks++ > MAXSYMLINKS) {
 190                                 errno = ELOOP;
 191                                 return (NULL);
 192                         }
 193                         slen = readlink(resolved, symlink,
 194                             sizeof (symlink) - 1);
 195                         if (slen < 0)
 196                                 return (NULL);
 197                         symlink[slen] = '\0';
 198
 199                         if (symlink[0] == '/') {
 200                                 resolved[1] = 0;
 201                                 resolved_len = 1;
 202                         } else if (resolved_len > 1) {
 203                                 /* Strip the last path component. */
 204                                 resolved[resolved_len - 1] = '\0';
 205                                 q = strrchr(resolved, '/') + 1;
 206                                 *q = '\0';
 207                                 resolved_len = q - resolved;
 208                         }
 209
 210                         /*
 211                          * If there are any path components left, then
 212                          * append them to symlink. The result is placed
 213                          * in `left'.
 214                          */
 215                         if (p != NULL) {
 216                                 if (symlink[slen - 1] != '/') {
 217                                         if (slen + 1 >= sizeof (symlink)) {
 218                                                 errno = ENAMETOOLONG;
 219                                                 return (NULL);
 220                                         }
 221                                         symlink[slen] = '/';
 222                                         symlink[slen + 1] = 0;
 223                                 }
 224                                 left_len = strlcat(symlink, left,
 225                                     sizeof (left));
 226                                 if (left_len >= sizeof (left)) {
 227                                         errno = ENAMETOOLONG;
 228                                         return (NULL);
 229                                 }
 230                         }
 231                         left_len = strlcpy(left, symlink, sizeof (left));
 232                 }
 233         }
 234
 235         /*
 236          * Remove trailing slash except when the resolved pathname
 237          * is a single "/".
 238          */
 239         if (resolved_len > 1 && resolved[resolved_len - 1] == '/')
 240                 resolved[resolved_len - 1] = '\0';
 241         return (resolved);
 242 }