stdlib/realpath-fbsd.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: src/lib/libc/stdlib/realpath.c,v 1.20 2003/05/28 08:23:01 fjoe Exp $");
  34
  35 #include "namespace.h"
  36 #include <sys/param.h>
  37 #include <sys/stat.h>
  38 #include <sys/mount.h>
  39
  40 #include <errno.h>
  41 #include <stdlib.h>
  42 #include <string.h>
  43 #include <unistd.h>
  44 #include <sys/attr.h>
  45 #include <sys/vnode.h>
  46 #include "un-namespace.h"
  47
  48 struct attrs {
  49         u_int32_t len;
  50         attrreference_t name;
  51         dev_t dev;
  52         fsobj_type_t type;
  53         fsobj_id_t id;
  54         char buf[PATH_MAX];
  55 };
  56
  57 #ifndef BUILDING_VARIANT
  58 __private_extern__ struct attrlist _rp_alist = {
  59         ATTR_BIT_MAP_COUNT,
  60         0,
  61         ATTR_CMN_NAME | ATTR_CMN_DEVID | ATTR_CMN_OBJTYPE | ATTR_CMN_OBJID,
  62         0,
  63         0,
  64         0,
  65         0,
  66 };
  67 #else /* BUILDING_VARIANT */
  68 __private_extern__ struct attrlist _rp_alist;
  69 #endif /* BUILDING_VARIANT */
  70
  71 extern char * __private_getcwd(char *, size_t, int);
  72
  73 /*
  74  * char *realpath(const char *path, char resolved[PATH_MAX]);
  75  *
  76  * Find the real name of path, by removing all ".", ".." and symlink
  77  * components.  Returns (resolved) on success, or (NULL) on failure,
  78  * in which case the path which caused trouble is left in (resolved).
  79  */
  80 char *
  81 realpath(const char *path, char resolved[PATH_MAX])
  82 {
  83         struct attrs attrs;
  84         struct stat sb;
  85         char *p, *q, *s;
  86         size_t left_len, resolved_len, save_resolved_len;
  87         unsigned symlinks;
  88         int serrno, slen, useattrs, islink;
  89         char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX];
  90         dev_t dev, lastdev;
  91         struct statfs sfs;
  92         static dev_t rootdev;
  93         static int rootdev_inited = 0;
  94         ino_t inode;
  95
  96         if (path == NULL) {
  97                 errno = EINVAL;
  98                 return (NULL);
  99         }
 100 #if __DARWIN_UNIX03
 101         if (*path == 0) {
 102                 errno = ENOENT;
 103                 return (NULL);
 104         }
 105 #endif /* __DARWIN_UNIX03 */
 106         if (!rootdev_inited) {
 107                 rootdev_inited = 1;
 108                 if (stat("/", &sb) < 0) {
 109                         return (NULL);
 110                         }
 111                 rootdev = sb.st_dev;
 112         }
 113         serrno = errno;
 114         symlinks = 0;
 115         if (path[0] == '/') {
 116                 resolved[0] = '/';
 117                 resolved[1] = '\0';
 118                 if (path[1] == '\0') {
 119                         return (resolved);
 120                 }
 121                 resolved_len = 1;
 122                 left_len = strlcpy(left, path + 1, sizeof(left));
 123         } else {
 124 #if !defined(VARIANT_DARWINEXTSN) && __DARWIN_UNIX03
 125                 /* 4447159: don't use GETPATH, so this will fail if */
 126                 /* if parent directories are not readable, as per POSIX */
 127                 if (__private_getcwd(resolved, PATH_MAX, 0) == NULL)
 128 #else /* VARIANT_DARWINEXTSN || !__DARWIN_UNIX03 */
 129                 if (__private_getcwd(resolved, PATH_MAX, 1) == NULL)
 130 #endif /* !VARIANT_DARWINEXTSN && __DARWIN_UNIX03 */
 131                 {
 132                         strlcpy(resolved, ".", PATH_MAX);
 133                         return (NULL);
 134                 }
 135                 resolved_len = strlen(resolved);
 136                 left_len = strlcpy(left, path, sizeof(left));
 137         }
 138         if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) {
 139                 errno = ENAMETOOLONG;
 140                 return (NULL);
 141         }
 142         if (resolved_len > 1) {
 143                 if (stat(resolved, &sb) < 0) {
 144                         return (NULL);
 145                 }
 146                 lastdev = sb.st_dev;
 147         } else
 148                 lastdev = rootdev;
 149
 150         /*
 151          * Iterate over path components in `left'.
 152          */
 153         while (left_len != 0) {
 154                 /*
 155                  * Extract the next path component and adjust `left'
 156                  * and its length.
 157                  */
 158                 p = strchr(left, '/');
 159                 s = p ? p : left + left_len;
 160                 if (s - left >= sizeof(next_token)) {
 161                         errno = ENAMETOOLONG;
 162                         return (NULL);
 163                 }
 164                 memcpy(next_token, left, s - left);
 165                 next_token[s - left] = '\0';
 166                 left_len -= s - left;
 167                 if (p != NULL)
 168                         memmove(left, s + 1, left_len + 1);
 169                 if (resolved[resolved_len - 1] != '/') {
 170                         if (resolved_len + 1 >= PATH_MAX) {
 171                                 errno = ENAMETOOLONG;
 172                                 return (NULL);
 173                         }
 174                         resolved[resolved_len++] = '/';
 175                         resolved[resolved_len] = '\0';
 176                 }
 177                 if (next_token[0] == '\0')
 178                         continue;
 179                 else if (strcmp(next_token, ".") == 0)
 180                         continue;
 181                 else if (strcmp(next_token, "..") == 0) {
 182                         /*
 183                          * Strip the last path component except when we have
 184                          * single "/"
 185                          */
 186                         if (resolved_len > 1) {
 187                                 resolved[resolved_len - 1] = '\0';
 188                                 q = strrchr(resolved, '/') + 1;
 189                                 *q = '\0';
 190                                 resolved_len = q - resolved;
 191                         }
 192                         continue;
 193                 }
 194
 195                 /*
 196                  * Save resolved_len, so that we can later null out
 197                  * the the appended next_token, and replace with the
 198                  * real name (matters on case-insensitive filesystems).
 199                  */
 200                 save_resolved_len = resolved_len;
 201
 202                 /*
 203                  * Append the next path component and lstat() it. If
 204                  * lstat() fails we still can return successfully if
 205                  * there are no more path components left.
 206                  */
 207                 resolved_len = strlcat(resolved, next_token, PATH_MAX);
 208                 if (resolved_len >= PATH_MAX) {
 209                         errno = ENAMETOOLONG;
 210                         return (NULL);
 211                 }
 212                 if (getattrlist(resolved, &_rp_alist, &attrs, sizeof(attrs), FSOPT_NOFOLLOW) == 0) {
 213                         useattrs = 1;
 214                         islink = (attrs.type == VLNK);
 215                         dev = attrs.dev;
 216                         inode = attrs.id.fid_objno;
 217                 } else if (errno == ENOTSUP || errno == EINVAL) {
 218                         if ((useattrs = lstat(resolved, &sb)) == 0) {
 219                                 islink = S_ISLNK(sb.st_mode);
 220                                 dev = sb.st_dev;
 221                                 inode = sb.st_ino;
 222                         }
 223                 } else
 224                         useattrs = -1;
 225                 if (useattrs < 0) {
 226 #if !__DARWIN_UNIX03
 227                         if (errno == ENOENT && p == NULL) {
 228                                 errno = serrno;
 229                                 return (resolved);
 230                         }
 231 #endif /* !__DARWIN_UNIX03 */
 232                         return (NULL);
 233                 }
 234                 if (dev != lastdev) {
 235                         /*
 236                          * We have crossed a mountpoint.  For volumes like UDF
 237                          * the getattrlist name may not match the actual
 238                          * mountpoint, so we just copy the mountpoint directly.
 239                          * (3703138).  However, the mountpoint may not be
 240                          * accessible, as when chroot-ed, so check first.
 241                          * There may be a file on the chroot-ed volume with
 242                          * the same name as the mountpoint, so compare device
 243                          * and inode numbers.
 244                          */
 245                         lastdev = dev;
 246                         if (statfs(resolved, &sfs) == 0 && lstat(sfs.f_mntonname, &sb) == 0 && dev == sb.st_dev && inode == sb.st_ino) {
 247                                 /*
 248                                  * However, it's possible that the mountpoint
 249                                  * path matches, even though it isn't the real
 250                                  * path in the chroot-ed environment, so check
 251                                  * that each component of the mountpoint
 252                                  * is a directory (and not a symlink)
 253                                  */
 254                                 char temp[MNAMELEN];
 255                                 char *cp;
 256                                 int ok = 1;
 257
 258                                 strcpy(temp, sfs.f_mntonname);
 259                                 for(;;) {
 260                                         if ((cp = strrchr(temp, '/')) == NULL) {
 261                                                 ok = 0;
 262                                                 break;
 263                                         }
 264                                         if (cp <= temp)
 265                                                 break;
 266                                         *cp = 0;
 267                                         if (lstat(temp, &sb) < 0 || (sb.st_mode & S_IFMT) != S_IFDIR) {
 268                                                 ok = 0;
 269                                                 break;
 270                                         }
 271                                 }
 272                                 if (ok) {
 273                                         resolved_len = strlcpy(resolved, sfs.f_mntonname, PATH_MAX);
 274                                         continue;
 275                                 }
 276                         }
 277                         /* if we fail, use the other methods. */
 278                 }
 279                 if (islink) {
 280                         if (symlinks++ > MAXSYMLINKS) {
 281                                 errno = ELOOP;
 282                                 return (NULL);
 283                         }
 284                         slen = readlink(resolved, symlink, sizeof(symlink) - 1);
 285                         if (slen < 0) {
 286                                 return (NULL);
 287                         }
 288                         symlink[slen] = '\0';
 289                         if (symlink[0] == '/') {
 290                                 resolved[1] = 0;
 291                                 resolved_len = 1;
 292                                 lastdev = rootdev;
 293                         } else if (resolved_len > 1) {
 294                                 /* Strip the last path component. */
 295                                 resolved[resolved_len - 1] = '\0';
 296                                 q = strrchr(resolved, '/') + 1;
 297                                 *q = '\0';
 298                                 resolved_len = q - resolved;
 299                         }
 300
 301                         /*
 302                          * If there are any path components left, then
 303                          * append them to symlink. The result is placed
 304                          * in `left'.
 305                          */
 306                         if (p != NULL) {
 307                                 if (symlink[slen - 1] != '/') {
 308                                         if (slen + 1 >= sizeof(symlink)) {
 309                                                 errno = ENAMETOOLONG;
 310                                                 return (NULL);
 311                                         }
 312                                         symlink[slen] = '/';
 313                                         symlink[slen + 1] = 0;
 314                                 }
 315                                 left_len = strlcat(symlink, left, sizeof(left));
 316                                 if (left_len >= sizeof(left)) {
 317                                         errno = ENAMETOOLONG;
 318                                         return (NULL);
 319                                 }
 320                         }
 321                         left_len = strlcpy(left, symlink, sizeof(left));
 322                 } else if (useattrs) {
 323                         /*
 324                          * attrs already has the real name.
 325                          */
 326
 327                         resolved[save_resolved_len] = '\0';
 328                         resolved_len = strlcat(resolved, (const char *)&attrs.name + attrs.name.attr_dataoffset, PATH_MAX);
 329                         if (resolved_len >= PATH_MAX) {
 330                                 errno = ENAMETOOLONG;
 331                                 return (NULL);
 332                         }
 333                 }
 334                 /*
 335                  * For the case of useattrs == 0, we could scan the directory
 336                  * and try to match the inode.  There are many problems with
 337                  * this: (1) the directory may not be readable, (2) for multiple
 338                  * hard links, we would find the first, but not necessarily
 339                  * the one specified in the path, (3) we can't try to do
 340                  * a case-insensitive search to match the right one in (2),
 341                  * because the underlying filesystem may do things like
 342                  * decompose composed characters.  For most cases, doing
 343                  * nothing is the right thing when useattrs == 0, so we punt
 344                  * for now.
 345                  */
 346         }
 347
 348         /*
 349          * Remove trailing slash except when the resolved pathname
 350          * is a single "/".
 351          */
 352         if (resolved_len > 1 && resolved[resolved_len - 1] == '/')
 353                 resolved[resolved_len - 1] = '\0';
 354         return (resolved);
 355 }