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
  49 struct attrs {
  50         u_int32_t len;
  51         attrreference_t name;
  52         dev_t dev;
  53         fsobj_type_t type;
  54         fsobj_id_t id;
  55         char buf[PATH_MAX];
  56 };
  57
  58 #ifndef BUILDING_VARIANT
  59 __private_extern__ const struct attrlist _rp_alist = {
  60         ATTR_BIT_MAP_COUNT,
  61         0,
  62         ATTR_CMN_NAME | ATTR_CMN_DEVID | ATTR_CMN_OBJTYPE | ATTR_CMN_OBJID,
  63         0,
  64         0,
  65         0,
  66         0,
  67 };
  68 #else /* BUILDING_VARIANT */
  69 extern const struct attrlist _rp_alist;
  70 #endif /* BUILDING_VARIANT */
  71
  72 extern char * __private_getcwd(char *, size_t, int);
  73
  74 /*
  75  * char *realpath(const char *path, char resolved[PATH_MAX]);
  76  *
  77  * Find the real name of path, by removing all ".", ".." and symlink
  78  * components.  Returns (resolved) on success, or (NULL) on failure,
  79  * in which case the path which caused trouble is left in (resolved).
  80  */
  81 char *
  82 realpath(const char *path, char inresolved[PATH_MAX])
  83 {
  84         struct attrs attrs;
  85         struct stat sb;
  86         char *p, *q;
  87         size_t left_len, resolved_len, save_resolved_len, next_token_len;
  88         unsigned symlinks;
  89         int serrno, useattrs, islink;
  90         ssize_t slen;
  91         char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX];
  92         dev_t dev, lastdev;
  93         struct statfs sfs;
  94         static dev_t rootdev;
  95         static int rootdev_inited = 0;
  96         ino_t inode;
  97         char *resolved;
  98
  99         if (path == NULL) {
 100                 errno = EINVAL;
 101                 return (NULL);
 102         }
 103 #if __DARWIN_UNIX03
 104         if (*path == 0) {
 105                 errno = ENOENT;
 106                 return (NULL);
 107         }
 108 #endif /* __DARWIN_UNIX03 */
 109
 110         /*
 111          * Extension to the standard; if inresolved == NULL, allocate memory
 112          */
 113         if (!inresolved) {
 114             if ((resolved = malloc(PATH_MAX)) == NULL) return (NULL);
 115         } else {
 116             resolved = inresolved;
 117         }
 118         if (!rootdev_inited) {
 119                 rootdev_inited = 1;
 120                 if (stat("/", &sb) < 0) {
 121 error_return:
 122                         if (!inresolved) {
 123                                 int e = errno;
 124                                 free(resolved);
 125                                 errno = e;
 126                         }
 127                         return (NULL);
 128                 }
 129                 rootdev = sb.st_dev;
 130         }
 131         serrno = errno;
 132         symlinks = 0;
 133         if (path[0] == '/') {
 134                 resolved[0] = '/';
 135                 resolved[1] = '\0';
 136                 if (path[1] == '\0') {
 137                         return (resolved);
 138                 }
 139                 resolved_len = 1;
 140                 left_len = strlcpy(left, path + 1, sizeof(left));
 141         } else {
 142 #if !defined(VARIANT_DARWINEXTSN) && __DARWIN_UNIX03
 143                 /* 4447159: don't use GETPATH, so this will fail if */
 144                 /* if parent directories are not readable, as per POSIX */
 145                 if (__private_getcwd(resolved, PATH_MAX, 0) == NULL)
 146 #else /* VARIANT_DARWINEXTSN || !__DARWIN_UNIX03 */
 147                 if (__private_getcwd(resolved, PATH_MAX, 1) == NULL)
 148 #endif /* !VARIANT_DARWINEXTSN && __DARWIN_UNIX03 */
 149                 {
 150                         strlcpy(resolved, ".", PATH_MAX);
 151                         goto error_return;
 152                 }
 153                 resolved_len = strlen(resolved);
 154                 left_len = strlcpy(left, path, sizeof(left));
 155         }
 156         if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) {
 157                 errno = ENAMETOOLONG;
 158                 goto error_return;
 159         }
 160         if (resolved_len > 1) {
 161                 if (stat(resolved, &sb) < 0) {
 162                         goto error_return;
 163                 }
 164                 lastdev = sb.st_dev;
 165         } else
 166                 lastdev = rootdev;
 167
 168         /*
 169          * Iterate over path components in `left'.
 170          */
 171         while (left_len != 0) {
 172                 /*
 173                  * Extract the next path component and adjust `left'
 174                  * and its length.
 175                  */
 176                 p = strchr(left, '/');
 177                 next_token_len = p ? p - left : left_len;
 178                 memcpy(next_token, left, next_token_len);
 179                 next_token[next_token_len] = '\0';
 180
 181                 if (p != NULL) {
 182                         left_len -= next_token_len + 1;
 183                         memmove(left, p + 1, left_len + 1);
 184                 } else {
 185                         left[0] = '\0';
 186                         left_len = 0;
 187                 }
 188
 189                 if (resolved[resolved_len - 1] != '/') {
 190                         if (resolved_len + 1 >= PATH_MAX) {
 191                                 errno = ENAMETOOLONG;
 192                                 goto error_return;
 193                         }
 194                         resolved[resolved_len++] = '/';
 195                         resolved[resolved_len] = '\0';
 196                 }
 197                 if (next_token[0] == '\0') {
 198                         /* Handle consequential slashes. */
 199                         continue;
 200                 } else if (strcmp(next_token, ".") == 0) {
 201                         continue;
 202                 } else if (strcmp(next_token, "..") == 0) {
 203                         /*
 204                          * Strip the last path component except when we have
 205                          * single "/"
 206                          */
 207                         if (resolved_len > 1) {
 208                                 resolved[resolved_len - 1] = '\0';
 209                                 q = strrchr(resolved, '/') + 1;
 210                                 *q = '\0';
 211                                 resolved_len = q - resolved;
 212                         }
 213                         continue;
 214                 }
 215
 216                 /*
 217                  * Save resolved_len, so that we can later null out
 218                  * the the appended next_token, and replace with the
 219                  * real name (matters on case-insensitive filesystems).
 220                  */
 221                 save_resolved_len = resolved_len;
 222
 223                 /*
 224                  * Append the next path component and lstat() it. If
 225                  * lstat() fails we still can return successfully if
 226                  * there are no more path components left.
 227                  */
 228                 resolved_len = strlcat(resolved, next_token, PATH_MAX);
 229                 if (resolved_len >= PATH_MAX) {
 230                         errno = ENAMETOOLONG;
 231                         goto error_return;
 232                 }
 233                 if (getattrlist(resolved, (void *)&_rp_alist, &attrs, sizeof(attrs), FSOPT_NOFOLLOW) == 0) {
 234                         useattrs = 1;
 235                         islink = (attrs.type == VLNK);
 236                         dev = attrs.dev;
 237                         inode = attrs.id.fid_objno;
 238                 } else if (errno == ENOTSUP || errno == EINVAL) {
 239                         if ((useattrs = lstat(resolved, &sb)) == 0) {
 240                                 islink = S_ISLNK(sb.st_mode);
 241                                 dev = sb.st_dev;
 242                                 inode = sb.st_ino;
 243                         }
 244                 } else
 245                         useattrs = -1;
 246                 if (useattrs < 0) {
 247 #if !__DARWIN_UNIX03
 248                         if (errno == ENOENT && p == NULL) {
 249                                 errno = serrno;
 250                                 return (resolved);
 251                         }
 252 #endif /* !__DARWIN_UNIX03 */
 253                         goto error_return;
 254                 }
 255                 if (dev != lastdev) {
 256                         /*
 257                          * We have crossed a mountpoint.  For volumes like UDF
 258                          * the getattrlist name may not match the actual
 259                          * mountpoint, so we just copy the mountpoint directly.
 260                          * (3703138).  However, the mountpoint may not be
 261                          * accessible, as when chroot-ed, so check first.
 262                          * There may be a file on the chroot-ed volume with
 263                          * the same name as the mountpoint, so compare device
 264                          * and inode numbers.
 265                          */
 266                         lastdev = dev;
 267                         if (statfs(resolved, &sfs) == 0 && lstat(sfs.f_mntonname, &sb) == 0 && dev == sb.st_dev && inode == sb.st_ino) {
 268                                 /*
 269                                  * However, it's possible that the mountpoint
 270                                  * path matches, even though it isn't the real
 271                                  * path in the chroot-ed environment, so check
 272                                  * that each component of the mountpoint
 273                                  * is a directory (and not a symlink)
 274                                  */
 275                                 char temp[sizeof(sfs.f_mntonname)];
 276                                 char *cp;
 277                                 int ok = 1;
 278
 279                                 strcpy(temp, sfs.f_mntonname);
 280                                 for(;;) {
 281                                         if ((cp = strrchr(temp, '/')) == NULL) {
 282                                                 ok = 0;
 283                                                 break;
 284                                         }
 285                                         if (cp <= temp)
 286                                                 break;
 287                                         *cp = 0;
 288                                         if (lstat(temp, &sb) < 0 || (sb.st_mode & S_IFMT) != S_IFDIR) {
 289                                                 ok = 0;
 290                                                 break;
 291                                         }
 292                                 }
 293                                 if (ok) {
 294                                         resolved_len = strlcpy(resolved, sfs.f_mntonname, PATH_MAX);
 295                                         continue;
 296                                 }
 297                         }
 298                         /* if we fail, use the other methods. */
 299                 }
 300                 if (islink) {
 301                         if (symlinks++ > MAXSYMLINKS) {
 302                                 errno = ELOOP;
 303                                 goto error_return;
 304                         }
 305                         slen = readlink(resolved, symlink, sizeof(symlink));
 306                         if (slen <= 0 || slen >= sizeof(symlink)) {
 307                                 if (slen < 0)
 308                                         ; /* keep errno from readlink(2) call */
 309                                 else if (slen == 0)
 310                                         errno = ENOENT;
 311                                 else
 312                                         errno = ENAMETOOLONG;
 313                                 goto error_return;
 314                         }
 315                         symlink[slen] = '\0';
 316                         if (symlink[0] == '/') {
 317                                 resolved[1] = 0;
 318                                 resolved_len = 1;
 319                                 lastdev = rootdev;
 320                         } else {
 321                                 /* Strip the last path component. */
 322                                 q = strrchr(resolved, '/') + 1;
 323                                 *q = '\0';
 324                                 resolved_len = q - resolved;
 325                         }
 326
 327                         /*
 328                          * If there are any path components left, then
 329                          * append them to symlink. The result is placed
 330                          * in `left'.
 331                          */
 332                         if (p != NULL) {
 333                                 if (symlink[slen - 1] != '/') {
 334                                         if (slen + 1 >= sizeof(symlink)) {
 335                                                 errno = ENAMETOOLONG;
 336                                                 goto error_return;
 337                                         }
 338                                         symlink[slen] = '/';
 339                                         symlink[slen + 1] = 0;
 340                                 }
 341                                 left_len = strlcat(symlink, left, sizeof(symlink));
 342                                 if (left_len >= sizeof(symlink)) {
 343                                         errno = ENAMETOOLONG;
 344                                         goto error_return;
 345                                 }
 346                         }
 347                         left_len = strlcpy(left, symlink, sizeof(left));
 348                 } else if (useattrs) {
 349                         /*
 350                          * attrs already has the real name.
 351                          */
 352
 353                         resolved[save_resolved_len] = '\0';
 354                         resolved_len = strlcat(resolved, (const char *)&attrs.name + attrs.name.attr_dataoffset, PATH_MAX);
 355                         if (resolved_len >= PATH_MAX) {
 356                                 errno = ENAMETOOLONG;
 357                                 goto error_return;
 358                         }
 359                 }
 360                 /*
 361                  * For the case of useattrs == 0, we could scan the directory
 362                  * and try to match the inode.  There are many problems with
 363                  * this: (1) the directory may not be readable, (2) for multiple
 364                  * hard links, we would find the first, but not necessarily
 365                  * the one specified in the path, (3) we can't try to do
 366                  * a case-insensitive search to match the right one in (2),
 367                  * because the underlying filesystem may do things like
 368                  * decompose composed characters.  For most cases, doing
 369                  * nothing is the right thing when useattrs == 0, so we punt
 370                  * for now.
 371                  */
 372         }
 373
 374         /*
 375          * Remove trailing slash except when the resolved pathname
 376          * is a single "/".
 377          */
 378         if (resolved_len > 1 && resolved[resolved_len - 1] == '/')
 379                 resolved[resolved_len - 1] = '\0';
 380         return (resolved);
 381 }