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