lib/libc/gen/getcwd.c

   1 /*      $NetBSD: getcwd.c,v 1.53 2012/06/21 23:29:23 enami Exp $        */
   2
   3 /*
   4  * Copyright (c) 1989, 1991, 1993, 1995
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * This code is derived from software contributed to Berkeley by
   8  * Jan-Simon Pendry.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  * 3. Neither the name of the University nor the names of its contributors
  19  *    may be used to endorse or promote products derived from this software
  20  *    without specific prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  */
  34
  35 #include <sys/cdefs.h>
  36 #if defined(LIBC_SCCS) && !defined(lint)
  37 #if 0
  38 static char sccsid[] = "@(#)getcwd.c    8.5 (Berkeley) 2/7/95";
  39 #else
  40 __RCSID("$NetBSD: getcwd.c,v 1.53 2012/06/21 23:29:23 enami Exp $");
  41 #endif
  42 #endif /* LIBC_SCCS and not lint */
  43
  44 #include "namespace.h"
  45 #include <sys/param.h>
  46 #include <sys/stat.h>
  47
  48 #include <assert.h>
  49 #include <errno.h>
  50 #include <stdlib.h>
  51 #include <string.h>
  52 #include <unistd.h>
  53 #include <ssp/ssp.h>
  54
  55 #include "extern.h"
  56
  57 #ifdef __weak_alias
  58 __weak_alias(getcwd,_getcwd)
  59 __weak_alias(_sys_getcwd,_getcwd)
  60 __weak_alias(realpath,_realpath)
  61 #endif
  62
  63 /*
  64  * char *realpath(const char *path, char *resolved);
  65  *
  66  * Find the real name of path, by removing all ".", ".." and symlink
  67  * components.  Returns (resolved) on success, or (NULL) on failure,
  68  * in which case the path which caused trouble is left in (resolved).
  69  */
  70 char *
  71 realpath(const char * __restrict path, char * __restrict resolved)
  72 {
  73         struct stat sb;
  74         int idx = 0, nlnk = 0;
  75         const char *q;
  76         char *p, wbuf[2][MAXPATHLEN], *fres;
  77         size_t len;
  78         ssize_t n;
  79
  80         /* POSIX sez we must test for this */
  81         if (path == NULL) {
  82                 errno = EINVAL;
  83                 return NULL;
  84         }
  85
  86         if (resolved == NULL) {
  87                 fres = resolved = malloc(MAXPATHLEN);
  88                 if (resolved == NULL)
  89                         return NULL;
  90         } else
  91                 fres = NULL;
  92
  93
  94         /*
  95          * Build real path one by one with paying an attention to .,
  96          * .. and symbolic link.
  97          */
  98
  99         /*
 100          * `p' is where we'll put a new component with prepending
 101          * a delimiter.
 102          */
 103         p = resolved;
 104
 105         if (*path == '\0') {
 106                 *p = '\0';
 107                 errno = ENOENT;
 108                 goto out;
 109         }
 110
 111         /* If relative path, start from current working directory. */
 112         if (*path != '/') {
 113                 /* check for resolved pointer to appease coverity */
 114                 if (resolved && getcwd(resolved, MAXPATHLEN) == NULL) {
 115                         p[0] = '.';
 116                         p[1] = '\0';
 117                         goto out;
 118                 }
 119                 len = strlen(resolved);
 120                 if (len > 1)
 121                         p += len;
 122         }
 123
 124 loop:
 125         /* Skip any slash. */
 126         while (*path == '/')
 127                 path++;
 128
 129         if (*path == '\0') {
 130                 if (p == resolved)
 131                         *p++ = '/';
 132                 *p = '\0';
 133                 return resolved;
 134         }
 135
 136         /* Find the end of this component. */
 137         q = path;
 138         do
 139                 q++;
 140         while (*q != '/' && *q != '\0');
 141
 142         /* Test . or .. */
 143         if (path[0] == '.') {
 144                 if (q - path == 1) {
 145                         path = q;
 146                         goto loop;
 147                 }
 148                 if (path[1] == '.' && q - path == 2) {
 149                         /* Trim the last component. */
 150                         if (p != resolved)
 151                                 while (*--p != '/')
 152                                         continue;
 153                         path = q;
 154                         goto loop;
 155                 }
 156         }
 157
 158         /* Append this component. */
 159         if (p - resolved + 1 + q - path + 1 > MAXPATHLEN) {
 160                 errno = ENAMETOOLONG;
 161                 if (p == resolved)
 162                         *p++ = '/';
 163                 *p = '\0';
 164                 goto out;
 165         }
 166         p[0] = '/';
 167         memcpy(&p[1], path,
 168             /* LINTED We know q > path. */
 169             q - path);
 170         p[1 + q - path] = '\0';
 171
 172         /*
 173          * If this component is a symlink, toss it and prepend link
 174          * target to unresolved path.
 175          */
 176         if (lstat(resolved, &sb) == -1)
 177                 goto out;
 178
 179         if (S_ISLNK(sb.st_mode)) {
 180                 if (nlnk++ >= MAXSYMLINKS) {
 181                         errno = ELOOP;
 182                         goto out;
 183                 }
 184                 n = readlink(resolved, wbuf[idx], sizeof(wbuf[0]) - 1);
 185                 if (n < 0)
 186                         goto out;
 187                 if (n == 0) {
 188                         errno = ENOENT;
 189                         goto out;
 190                 }
 191
 192                 /* Append unresolved path to link target and switch to it. */
 193                 if (n + (len = strlen(q)) + 1 > sizeof(wbuf[0])) {
 194                         errno = ENAMETOOLONG;
 195                         goto out;
 196                 }
 197                 memcpy(&wbuf[idx][n], q, len + 1);
 198                 path = wbuf[idx];
 199                 idx ^= 1;
 200
 201                 /* If absolute symlink, start from root. */
 202                 if (*path == '/')
 203                         p = resolved;
 204                 goto loop;
 205         }
 206         if (*q == '/' && !S_ISDIR(sb.st_mode)) {
 207                 errno = ENOTDIR;
 208                 goto out;
 209         }
 210
 211         /* Advance both resolved and unresolved path. */
 212         p += 1 + q - path;
 213         path = q;
 214         goto loop;
 215 out:
 216         free(fres);
 217         return NULL;
 218 }
 219
 220 char *
 221 __ssp_real(getcwd)(char *pt, size_t size)
 222 {
 223         char *npt;
 224
 225         /*
 226          * If a buffer is specified, the size has to be non-zero.
 227          */
 228         if (pt != NULL) {
 229                 if (size == 0) {
 230                         /* __getcwd(pt, 0) results ERANGE. */
 231                         errno = EINVAL;
 232                         return (NULL);
 233                 }
 234                 if (__getcwd(pt, size) >= 0)
 235                         return (pt);
 236                 return (NULL);
 237         }
 238
 239         /*
 240          * If no buffer specified by the user, allocate one as necessary.
 241          */
 242         size = 1024 >> 1;
 243         do {
 244                 if ((npt = realloc(pt, size <<= 1)) == NULL)
 245                         break;
 246                 pt = npt;
 247                 if (__getcwd(pt, size) >= 0)
 248                         return (pt);
 249         } while (size <= MAXPATHLEN * 4 && errno == ERANGE);
 250
 251         free(pt);
 252         return (NULL);
 253 }