stdlib/FreeBSD/realpath.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__ const 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__ const 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          */
 110         if (!inresolved) {
 111             if ((resolved = malloc(PATH_MAX)) == NULL) return (NULL);
 112         } else {
 113             resolved = inresolved;
 114         }
 115         if (!rootdev_inited) {
 116                 rootdev_inited = 1;
 117                 if (stat("/", &sb) < 0) {
 118 error_return:
 119                         if (!inresolved) {
 120                                 int e = errno;
 121                                 free(resolved);
 122                                 errno = e;
 123                         }
 124                         return (NULL);
 125                 }
 126                 rootdev = sb.st_dev;
 127         }
 128         serrno = errno;
 129         symlinks = 0;
 130         if (path[0] == '/') {
 131                 resolved[0] = '/';
 132                 resolved[1] = '\0';
 133                 if (path[1] == '\0') {
 134                         return (resolved);
 135                 }
 136                 resolved_len = 1;
 137                 left_len = strlcpy(left, path + 1, sizeof(left));
 138         } else {
 139 #if !defined(VARIANT_DARWINEXTSN) && __DARWIN_UNIX03
 140                 /* 4447159: don't use GETPATH, so this will fail if */
 141                 /* if parent directories are not readable, as per POSIX */
 142                 if (__private_getcwd(resolved, PATH_MAX, 0) == NULL)
 143 #else /* VARIANT_DARWINEXTSN || !__DARWIN_UNIX03 */
 144                 if (__private_getcwd(resolved, PATH_MAX, 1) == NULL)
 145 #endif /* !VARIANT_DARWINEXTSN && __DARWIN_UNIX03 */
 146                 {
 147                         strlcpy(resolved, ".", PATH_MAX);
 148                         goto error_return;
 149                 }
 150                 resolved_len = strlen(resolved);
 151                 left_len = strlcpy(left, path, sizeof(left));
 152         }
 153         if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) {
 154                 errno = ENAMETOOLONG;
 155                 goto error_return;
 156         }
 157         if (resolved_len > 1) {
 158                 if (stat(resolved, &sb) < 0) {
 159                         goto error_return;
 160                 }
 161                 lastdev = sb.st_dev;
 162         } else
 163                 lastdev = rootdev;
 164
 165         /*
 166          * Iterate over path components in `left'.
 167          */
 168         while (left_len != 0) {
 169                 /*
 170                  * Extract the next path component and adjust `left'
 171                  * and its length.
 172                  */
 173                 p = strchr(left, '/');
 174                 s = p ? p : left + left_len;
 175                 if (s - left >= sizeof(next_token)) {
 176                         errno = ENAMETOOLONG;
 177                         goto error_return;
 178                 }
 179                 memcpy(next_token, left, s - left);
 180                 next_token[s - left] = '\0';
 181                 left_len -= s - left;
 182                 if (p != NULL)
 183                         memmove(left, s + 1, left_len + 1);
 184                 if (resolved[resolved_len - 1] != '/') {
 185                         if (resolved_len + 1 >= PATH_MAX) {
 186                                 errno = ENAMETOOLONG;
 187                                 goto error_return;
 188                         }
 189                         resolved[resolved_len++] = '/';
 190                         resolved[resolved_len] = '\0';
 191                 }
 192                 if (next_token[0] == '\0')
 193                         continue;
 194                 else if (strcmp(next_token, ".") == 0)
 195                         continue;
 196                 else if (strcmp(next_token, "..") == 0) {
 197                         /*
 198                          * Strip the last path component except when we have
 199                          * single "/"
 200                          */
 201                         if (resolved_len > 1) {
 202                                 resolved[resolved_len - 1] = '\0';
 203                                 q = strrchr(resolved, '/') + 1;
 204                                 *q = '\0';
 205                                 resolved_len = q - resolved;
 206                         }
 207                         continue;
 208                 }
 209
 210                 /*
 211                  * Save resolved_len, so that we can later null out
 212                  * the the appended next_token, and replace with the
 213                  * real name (matters on case-insensitive filesystems).
 214                  */
 215                 save_resolved_len = resolved_len;
 216
 217                 /*
 218                  * Append the next path component and lstat() it. If
 219                  * lstat() fails we still can return successfully if
 220                  * there are no more path components left.
 221                  */
 222                 resolved_len = strlcat(resolved, next_token, PATH_MAX);
 223                 if (resolved_len >= PATH_MAX) {
 224                         errno = ENAMETOOLONG;
 225                         goto error_return;
 226                 }
 227                 if (getattrlist(resolved, (void *)&_rp_alist, &attrs, sizeof(attrs), FSOPT_NOFOLLOW) == 0) {
 228                         useattrs = 1;
 229                         islink = (attrs.type == VLNK);
 230                         dev = attrs.dev;
 231                         inode = attrs.id.fid_objno;
 232                 } else if (errno == ENOTSUP || errno == EINVAL) {
 233                         if ((useattrs = lstat(resolved, &sb)) == 0) {
 234                                 islink = S_ISLNK(sb.st_mode);
 235                                 dev = sb.st_dev;
 236                                 inode = sb.st_ino;
 237                         }
 238                 } else
 239                         useattrs = -1;
 240                 if (useattrs < 0) {
 241 #if !__DARWIN_UNIX03
 242                         if (errno == ENOENT && p == NULL) {
 243                                 errno = serrno;
 244                                 return (resolved);
 245                         }
 246 #endif /* !__DARWIN_UNIX03 */
 247                         goto error_return;
 248                 }
 249                 if (dev != lastdev) {
 250                         /*
 251                          * We have crossed a mountpoint.  For volumes like UDF
 252                          * the getattrlist name may not match the actual
 253                          * mountpoint, so we just copy the mountpoint directly.
 254                          * (3703138).  However, the mountpoint may not be
 255                          * accessible, as when chroot-ed, so check first.
 256                          * There may be a file on the chroot-ed volume with
 257                          * the same name as the mountpoint, so compare device
 258                          * and inode numbers.
 259                          */
 260                         lastdev = dev;
 261                         if (statfs(resolved, &sfs) == 0 && lstat(sfs.f_mntonname, &sb) == 0 && dev == sb.st_dev && inode == sb.st_ino) {
 262                                 /*
 263                                  * However, it's possible that the mountpoint
 264                                  * path matches, even though it isn't the real
 265                                  * path in the chroot-ed environment, so check
 266                                  * that each component of the mountpoint
 267                                  * is a directory (and not a symlink)
 268                                  */
 269                                 char temp[sizeof(sfs.f_mntonname)];
 270                                 char *cp;
 271                                 int ok = 1;
 272
 273                                 strcpy(temp, sfs.f_mntonname);
 274                                 for(;;) {
 275                                         if ((cp = strrchr(temp, '/')) == NULL) {
 276                                                 ok = 0;
 277                                                 break;
 278                                         }
 279                                         if (cp <= temp)
 280                                                 break;
 281                                         *cp = 0;
 282                                         if (lstat(temp, &sb) < 0 || (sb.st_mode & S_IFMT) != S_IFDIR) {
 283                                                 ok = 0;
 284                                                 break;
 285                                         }
 286                                 }
 287                                 if (ok) {
 288                                         resolved_len = strlcpy(resolved, sfs.f_mntonname, PATH_MAX);
 289                                         continue;
 290                                 }
 291                         }
 292                         /* if we fail, use the other methods. */
 293                 }
 294                 if (islink) {
 295                         if (symlinks++ > MAXSYMLINKS) {
 296                                 errno = ELOOP;
 297                                 goto error_return;
 298                         }
 299                         slen = readlink(resolved, symlink, sizeof(symlink) - 1);
 300                         if (slen < 0) {
 301                                 goto error_return;
 302                         }
 303                         symlink[slen] = '\0';
 304                         if (symlink[0] == '/') {
 305                                 resolved[1] = 0;
 306                                 resolved_len = 1;
 307                                 lastdev = rootdev;
 308                         } else if (resolved_len > 1) {
 309                                 /* Strip the last path component. */
 310                                 resolved[resolved_len - 1] = '\0';
 311                                 q = strrchr(resolved, '/') + 1;
 312                                 *q = '\0';
 313                                 resolved_len = q - resolved;
 314                         }
 315
 316                         /*
 317                          * If there are any path components left, then
 318                          * append them to symlink. The result is placed
 319                          * in `left'.
 320                          */
 321                         if (p != NULL) {
 322                                 if (symlink[slen - 1] != '/') {
 323                                         if (slen + 1 >= sizeof(symlink)) {
 324                                                 errno = ENAMETOOLONG;
 325                                                 goto error_return;
 326                                         }
 327                                         symlink[slen] = '/';
 328                                         symlink[slen + 1] = 0;
 329                                 }
 330                                 left_len = strlcat(symlink, left, sizeof(symlink));
 331                                 if (left_len >= sizeof(left)) {
 332                                         errno = ENAMETOOLONG;
 333                                         goto error_return;
 334                                 }
 335                         }
 336                         left_len = strlcpy(left, symlink, sizeof(left));
 337                 } else if (useattrs) {
 338                         /*
 339                          * attrs already has the real name.
 340                          */
 341
 342                         resolved[save_resolved_len] = '\0';
 343                         resolved_len = strlcat(resolved, (const char *)&attrs.name + attrs.name.attr_dataoffset, PATH_MAX);
 344                         if (resolved_len >= PATH_MAX) {
 345                                 errno = ENAMETOOLONG;
 346                                 goto error_return;
 347                         }
 348                 }
 349                 /*
 350                  * For the case of useattrs == 0, we could scan the directory
 351                  * and try to match the inode.  There are many problems with
 352                  * this: (1) the directory may not be readable, (2) for multiple
 353                  * hard links, we would find the first, but not necessarily
 354                  * the one specified in the path, (3) we can't try to do
 355                  * a case-insensitive search to match the right one in (2),
 356                  * because the underlying filesystem may do things like
 357                  * decompose composed characters.  For most cases, doing
 358                  * nothing is the right thing when useattrs == 0, so we punt
 359                  * for now.
 360                  */
 361         }
 362
 363         /*
 364          * Remove trailing slash except when the resolved pathname
 365          * is a single "/".
 366          */
 367         if (resolved_len > 1 && resolved[resolved_len - 1] == '/')
 368                 resolved[resolved_len - 1] = '\0';
 369         return (resolved);
 370 }