lib/libc/gen/getcwd.c

   1 /*      $NetBSD: getcwd.c,v 1.45 2007/10/26 19:48:14 christos 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 1.45 2007/10/26 19:48:14 christos 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
  54 #include "extern.h"
  55
  56 #ifdef __weak_alias
  57 __weak_alias(getcwd,_getcwd)
  58 __weak_alias(realpath,_realpath)
  59 #endif
  60
  61 /*
  62  * char *realpath(const char *path, char resolved[MAXPATHLEN]);
  63  *
  64  * Find the real name of path, by removing all ".", ".." and symlink
  65  * components.  Returns (resolved) on success, or (NULL) on failure,
  66  * in which case the path which caused trouble is left in (resolved).
  67  */
  68 char *
  69 realpath(const char *path, char *resolved)
  70 {
  71         struct stat sb;
  72         int idx = 0, n, nlnk = 0;
  73         const char *q;
  74         char *p, wbuf[2][MAXPATHLEN];
  75         size_t len;
  76
  77         _DIAGASSERT(resolved != NULL);
  78
  79         /* POSIX sez we must test for this */
  80         if (path == NULL) {
  81                 errno = EINVAL;
  82                 return NULL;
  83         }
  84
  85         /*
  86          * Build real path one by one with paying an attention to .,
  87          * .. and symbolic link.
  88          */
  89
  90         /*
  91          * `p' is where we'll put a new component with prepending
  92          * a delimiter.
  93          */
  94         p = resolved;
  95
  96         if (*path == 0) {
  97                 *p = 0;
  98                 errno = ENOENT;
  99                 return (NULL);
 100         }
 101
 102         /* If relative path, start from current working directory. */
 103         if (*path != '/') {
 104                 /* check for resolved pointer to appease coverity */
 105                 if (resolved && getcwd(resolved, MAXPATHLEN) == NULL) {
 106                         p[0] = '.';
 107                         p[1] = 0;
 108                         return (NULL);
 109                 }
 110                 len = strlen(resolved);
 111                 if (len > 1)
 112                         p += len;
 113         }
 114
 115 loop:
 116         /* Skip any slash. */
 117         while (*path == '/')
 118                 path++;
 119
 120         if (*path == 0) {
 121                 if (p == resolved)
 122                         *p++ = '/';
 123                 *p = 0;
 124                 return (resolved);
 125         }
 126
 127         /* Find the end of this component. */
 128         q = path;
 129         do
 130                 q++;
 131         while (*q != '/' && *q != 0);
 132
 133         /* Test . or .. */
 134         if (path[0] == '.') {
 135                 if (q - path == 1) {
 136                         path = q;
 137                         goto loop;
 138                 }
 139                 if (path[1] == '.' && q - path == 2) {
 140                         /* Trim the last component. */
 141                         if (p != resolved)
 142                                 while (*--p != '/')
 143                                         ;
 144                         path = q;
 145                         goto loop;
 146                 }
 147         }
 148
 149         /* Append this component. */
 150         if (p - resolved + 1 + q - path + 1 > MAXPATHLEN) {
 151                 errno = ENAMETOOLONG;
 152                 if (p == resolved)
 153                         *p++ = '/';
 154                 *p = 0;
 155                 return (NULL);
 156         }
 157         p[0] = '/';
 158         memcpy(&p[1], path,
 159             /* LINTED We know q > path. */
 160             q - path);
 161         p[1 + q - path] = 0;
 162
 163         /*
 164          * If this component is a symlink, toss it and prepend link
 165          * target to unresolved path.
 166          */
 167         if (lstat(resolved, &sb) == -1) {
 168                 return (NULL);
 169         }
 170         if (S_ISLNK(sb.st_mode)) {
 171                 if (nlnk++ >= MAXSYMLINKS) {
 172                         errno = ELOOP;
 173                         return (NULL);
 174                 }
 175                 n = readlink(resolved, wbuf[idx], sizeof(wbuf[0]) - 1);
 176                 if (n < 0)
 177                         return (NULL);
 178                 if (n == 0) {
 179                         errno = ENOENT;
 180                         return (NULL);
 181                 }
 182
 183                 /* Append unresolved path to link target and switch to it. */
 184                 if (n + (len = strlen(q)) + 1 > sizeof(wbuf[0])) {
 185                         errno = ENAMETOOLONG;
 186                         return (NULL);
 187                 }
 188                 memcpy(&wbuf[idx][n], q, len + 1);
 189                 path = wbuf[idx];
 190                 idx ^= 1;
 191
 192                 /* If absolute symlink, start from root. */
 193                 if (*path == '/')
 194                         p = resolved;
 195                 goto loop;
 196         }
 197         if (*q == '/' && !S_ISDIR(sb.st_mode)) {
 198                 errno = ENOTDIR;
 199                 return (NULL);
 200         }
 201
 202         /* Advance both resolved and unresolved path. */
 203         p += 1 + q - path;
 204         path = q;
 205         goto loop;
 206 }
 207
 208
 209 #if defined(_FORTIFY_SOURCE) && !defined(__lint__)
 210 #undef getcwd
 211 #define getcwd _getcwd
 212 #endif
 213
 214 char *
 215 getcwd(char *pt, size_t size)
 216 {
 217         char *npt;
 218
 219         /*
 220          * If a buffer is specified, the size has to be non-zero.
 221          */
 222         if (pt != NULL) {
 223                 if (size == 0) {
 224                         /* __getcwd(pt, 0) results ERANGE. */
 225                         errno = EINVAL;
 226                         return (NULL);
 227                 }
 228                 if (__getcwd(pt, size) >= 0)
 229                         return (pt);
 230                 return (NULL);
 231         }
 232
 233         /*
 234          * If no buffer specified by the user, allocate one as necessary.
 235          */
 236         size = 1024 >> 1;
 237         do {
 238                 if ((npt = realloc(pt, size <<= 1)) == NULL)
 239                         break;
 240                 pt = npt;
 241                 if (__getcwd(pt, size) >= 0)
 242                         return (pt);
 243         } while (size <= MAXPATHLEN * 4 && errno == ERANGE);
 244
 245         free(pt);
 246         return (NULL);
 247 }