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 inresolved[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         char *resolved;
  96
  97         if (path == NULL) {
  98                 errno = EINVAL;
  99                 return (NULL);
 100         }
 101 #if __DARWIN_UNIX03
 102         if (*path == 0) {
 103                 errno = ENOENT;
 104                 return (NULL);
 105         }
 106 #endif /* __DARWIN_UNIX03 */
 107         /*
 108          * Extension to the standard; if inresolved == NULL, allocate memory
 109          * (first on the stack, then use strdup())
 110          */
 111         if (!inresolved) {
 112             if ((resolved = alloca(PATH_MAX)) == NULL) return (NULL);
 113         } else {
 114             resolved = inresolved;
 115         }
 116         if (!rootdev_inited) {
 117                 rootdev_inited = 1;
 118                 if (stat("/", &sb) < 0) {
 119                         return (NULL);
 120                         }
 121                 rootdev = sb.st_dev;
 122         }
 123         serrno = errno;
 124         symlinks = 0;
 125         if (path[0] == '/') {
 126                 resolved[0] = '/';
 127                 resolved[1] = '\0';
 128                 if (path[1] == '\0') {
 129                         return (resolved);
 130                 }
 131                 resolved_len = 1;
 132                 left_len = strlcpy(left, path + 1, sizeof(left));
 133         } else {
 134 #if !defined(VARIANT_DARWINEXTSN) && __DARWIN_UNIX03
 135                 /* 4447159: don't use GETPATH, so this will fail if */
 136                 /* if parent directories are not readable, as per POSIX */
 137                 if (__private_getcwd(resolved, PATH_MAX, 0) == NULL)
 138 #else /* VARIANT_DARWINEXTSN || !__DARWIN_UNIX03 */
 139                 if (__private_getcwd(resolved, PATH_MAX, 1) == NULL)
 140 #endif /* !VARIANT_DARWINEXTSN && __DARWIN_UNIX03 */
 141                 {
 142                         strlcpy(resolved, ".", PATH_MAX);
 143                         return (NULL);
 144                 }
 145                 resolved_len = strlen(resolved);
 146                 left_len = strlcpy(left, path, sizeof(left));
 147         }
 148         if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) {
 149                 errno = ENAMETOOLONG;
 150                 return (NULL);
 151         }
 152         if (resolved_len > 1) {
 153                 if (stat(resolved, &sb) < 0) {
 154                         return (NULL);
 155                 }
 156                 lastdev = sb.st_dev;
 157         } else
 158                 lastdev = rootdev;
 159
 160         /*
 161          * Iterate over path components in `left'.
 162          */
 163         while (left_len != 0) {
 164                 /*
 165                  * Extract the next path component and adjust `left'
 166                  * and its length.
 167                  */
 168                 p = strchr(left, '/');
 169                 s = p ? p : left + left_len;
 170                 if (s - left >= sizeof(next_token)) {
 171                         errno = ENAMETOOLONG;
 172                         return (NULL);
 173                 }
 174                 memcpy(next_token, left, s - left);
 175                 next_token[s - left] = '\0';
 176                 left_len -= s - left;
 177                 if (p != NULL)
 178                         memmove(left, s + 1, left_len + 1);
 179                 if (resolved[resolved_len - 1] != '/') {
 180                         if (resolved_len + 1 >= PATH_MAX) {
 181                                 errno = ENAMETOOLONG;
 182                                 return (NULL);
 183                         }
 184                         resolved[resolved_len++] = '/';
 185                         resolved[resolved_len] = '\0';
 186                 }
 187                 if (next_token[0] == '\0')
 188                         continue;
 189                 else if (strcmp(next_token, ".") == 0)
 190                         continue;
 191                 else if (strcmp(next_token, "..") == 0) {
 192                         /*
 193                          * Strip the last path component except when we have
 194                          * single "/"
 195                          */
 196                         if (resolved_len > 1) {
 197                                 resolved[resolved_len - 1] = '\0';
 198                                 q = strrchr(resolved, '/') + 1;
 199                                 *q = '\0';
 200                                 resolved_len = q - resolved;
 201                         }
 202                         continue;
 203                 }
 204
 205                 /*
 206                  * Save resolved_len, so that we can later null out
 207                  * the the appended next_token, and replace with the
 208                  * real name (matters on case-insensitive filesystems).
 209                  */
 210                 save_resolved_len = resolved_len;
 211
 212                 /*
 213                  * Append the next path component and lstat() it. If
 214                  * lstat() fails we still can return successfully if
 215                  * there are no more path components left.
 216                  */
 217                 resolved_len = strlcat(resolved, next_token, PATH_MAX);
 218                 if (resolved_len >= PATH_MAX) {
 219                         errno = ENAMETOOLONG;
 220                         return (NULL);
 221                 }
 222                 if (getattrlist(resolved, &_rp_alist, &attrs, sizeof(attrs), FSOPT_NOFOLLOW) == 0) {
 223                         useattrs = 1;
 224                         islink = (attrs.type == VLNK);
 225                         dev = attrs.dev;
 226                         inode = attrs.id.fid_objno;
 227                 } else if (errno == ENOTSUP || errno == EINVAL) {
 228                         if ((useattrs = lstat(resolved, &sb)) == 0) {
 229                                 islink = S_ISLNK(sb.st_mode);
 230                                 dev = sb.st_dev;
 231                                 inode = sb.st_ino;
 232                         }
 233                 } else
 234                         useattrs = -1;
 235                 if (useattrs < 0) {
 236 #if !__DARWIN_UNIX03
 237                         if (errno == ENOENT && p == NULL) {
 238                                 errno = serrno;
 239                                 return (resolved);
 240                         }
 241 #endif /* !__DARWIN_UNIX03 */
 242                         return (NULL);
 243                 }
 244                 if (dev != lastdev) {
 245                         /*
 246                          * We have crossed a mountpoint.  For volumes like UDF
 247                          * the getattrlist name may not match the actual
 248                          * mountpoint, so we just copy the mountpoint directly.
 249                          * (3703138).  However, the mountpoint may not be
 250                          * accessible, as when chroot-ed, so check first.
 251                          * There may be a file on the chroot-ed volume with
 252                          * the same name as the mountpoint, so compare device
 253                          * and inode numbers.
 254                          */
 255                         lastdev = dev;
 256                         if (statfs(resolved, &sfs) == 0 && lstat(sfs.f_mntonname, &sb) == 0 && dev == sb.st_dev && inode == sb.st_ino) {
 257                                 /*
 258                                  * However, it's possible that the mountpoint
 259                                  * path matches, even though it isn't the real
 260                                  * path in the chroot-ed environment, so check
 261                                  * that each component of the mountpoint
 262                                  * is a directory (and not a symlink)
 263                                  */
 264                                 char temp[sizeof(sfs.f_mntonname)];
 265                                 char *cp;
 266                                 int ok = 1;
 267
 268                                 strcpy(temp, sfs.f_mntonname);
 269                                 for(;;) {
 270                                         if ((cp = strrchr(temp, '/')) == NULL) {
 271                                                 ok = 0;
 272                                                 break;
 273                                         }
 274                                         if (cp <= temp)
 275                                                 break;
 276                                         *cp = 0;
 277                                         if (lstat(temp, &sb) < 0 || (sb.st_mode & S_IFMT) != S_IFDIR) {
 278                                                 ok = 0;
 279                                                 break;
 280                                         }
 281                                 }
 282                                 if (ok) {
 283                                         resolved_len = strlcpy(resolved, sfs.f_mntonname, PATH_MAX);
 284                                         continue;
 285                                 }
 286                         }
 287                         /* if we fail, use the other methods. */
 288                 }
 289                 if (islink) {
 290                         if (symlinks++ > MAXSYMLINKS) {
 291                                 errno = ELOOP;
 292                                 return (NULL);
 293                         }
 294                         slen = readlink(resolved, symlink, sizeof(symlink) - 1);
 295                         if (slen < 0) {
 296                                 return (NULL);
 297                         }
 298                         symlink[slen] = '\0';
 299                         if (symlink[0] == '/') {
 300                                 resolved[1] = 0;
 301                                 resolved_len = 1;
 302                                 lastdev = rootdev;
 303                         } else if (resolved_len > 1) {
 304                                 /* Strip the last path component. */
 305                                 resolved[resolved_len - 1] = '\0';
 306                                 q = strrchr(resolved, '/') + 1;
 307                                 *q = '\0';
 308                                 resolved_len = q - resolved;
 309                         }
 310
 311                         /*
 312                          * If there are any path components left, then
 313                          * append them to symlink. The result is placed
 314                          * in `left'.
 315                          */
 316                         if (p != NULL) {
 317                                 if (symlink[slen - 1] != '/') {
 318                                         if (slen + 1 >= sizeof(symlink)) {
 319                                                 errno = ENAMETOOLONG;
 320                                                 return (NULL);
 321                                         }
 322                                         symlink[slen] = '/';
 323                                         symlink[slen + 1] = 0;
 324                                 }
 325                                 left_len = strlcat(symlink, left, sizeof(left));
 326                                 if (left_len >= sizeof(left)) {
 327                                         errno = ENAMETOOLONG;
 328                                         return (NULL);
 329                                 }
 330                         }
 331                         left_len = strlcpy(left, symlink, sizeof(left));
 332                 } else if (useattrs) {
 333                         /*
 334                          * attrs already has the real name.
 335                          */
 336
 337                         resolved[save_resolved_len] = '\0';
 338                         resolved_len = strlcat(resolved, (const char *)&attrs.name + attrs.name.attr_dataoffset, PATH_MAX);
 339                         if (resolved_len >= PATH_MAX) {
 340                                 errno = ENAMETOOLONG;
 341                                 return (NULL);
 342                         }
 343                 }
 344                 /*
 345                  * For the case of useattrs == 0, we could scan the directory
 346                  * and try to match the inode.  There are many problems with
 347                  * this: (1) the directory may not be readable, (2) for multiple
 348                  * hard links, we would find the first, but not necessarily
 349                  * the one specified in the path, (3) we can't try to do
 350                  * a case-insensitive search to match the right one in (2),
 351                  * because the underlying filesystem may do things like
 352                  * decompose composed characters.  For most cases, doing
 353                  * nothing is the right thing when useattrs == 0, so we punt
 354                  * for now.
 355                  */
 356         }
 357
 358         /*
 359          * Remove trailing slash except when the resolved pathname
 360          * is a single "/".
 361          */
 362         if (resolved_len > 1 && resolved[resolved_len - 1] == '/')
 363                 resolved[resolved_len - 1] = '\0';
 364         if (!inresolved) resolved = strdup(resolved);
 365         return (resolved);
 366 }