lib/libc/gen/getcwd.c

   1 /*      $NetBSD: getcwd.c,v 1.47 2011/01/20 02:57:00 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 1.47 2011/01/20 02:57:00 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 #ifdef __minix
  58 __weak_alias(getcwd,_getcwd)
  59 #else
  60 __weak_alias(getcwd,_sys_getcwd)
  61 __weak_alias(_getcwd,_sys_getcwd)
  62 #endif
  63 __weak_alias(realpath,_realpath)
  64
  65 #if defined(_FORTIFY_SOURCE) && !defined(__lint__)
  66 #undef getcwd
  67 #define getcwd _sys_getcwd
  68 #endif
  69
  70 #endif
  71
  72 /*
  73  * char *realpath(const char *path, char resolved[MAXPATHLEN]);
  74  *
  75  * Find the real name of path, by removing all ".", ".." and symlink
  76  * components.  Returns (resolved) on success, or (NULL) on failure,
  77  * in which case the path which caused trouble is left in (resolved).
  78  */
  79 char *
  80 realpath(const char *path, char *resolved)
  81 {
  82         struct stat sb;
  83         int idx = 0, n, nlnk = 0;
  84         const char *q;
  85         char *p, wbuf[2][MAXPATHLEN];
  86         size_t len;
  87
  88         _DIAGASSERT(resolved != NULL);
  89
  90         /* POSIX sez we must test for this */
  91         if (path == NULL) {
  92                 errno = EINVAL;
  93                 return NULL;
  94         }
  95
  96         /*
  97          * Build real path one by one with paying an attention to .,
  98          * .. and symbolic link.
  99          */
 100
 101         /*
 102          * `p' is where we'll put a new component with prepending
 103          * a delimiter.
 104          */
 105         p = resolved;
 106
 107         if (*path == 0) {
 108                 *p = 0;
 109                 errno = ENOENT;
 110                 return (NULL);
 111         }
 112
 113         /* If relative path, start from current working directory. */
 114         if (*path != '/') {
 115                 /* check for resolved pointer to appease coverity */
 116                 if (resolved && getcwd(resolved, MAXPATHLEN) == NULL) {
 117                         p[0] = '.';
 118                         p[1] = 0;
 119                         return (NULL);
 120                 }
 121                 len = strlen(resolved);
 122                 if (len > 1)
 123                         p += len;
 124         }
 125
 126 loop:
 127         /* Skip any slash. */
 128         while (*path == '/')
 129                 path++;
 130
 131         if (*path == 0) {
 132                 if (p == resolved)
 133                         *p++ = '/';
 134                 *p = 0;
 135                 return (resolved);
 136         }
 137
 138         /* Find the end of this component. */
 139         q = path;
 140         do
 141                 q++;
 142         while (*q != '/' && *q != 0);
 143
 144         /* Test . or .. */
 145         if (path[0] == '.') {
 146                 if (q - path == 1) {
 147                         path = q;
 148                         goto loop;
 149                 }
 150                 if (path[1] == '.' && q - path == 2) {
 151                         /* Trim the last component. */
 152                         if (p != resolved)
 153                                 while (*--p != '/')
 154                                         ;
 155                         path = q;
 156                         goto loop;
 157                 }
 158         }
 159
 160         /* Append this component. */
 161         if (p - resolved + 1 + q - path + 1 > MAXPATHLEN) {
 162                 errno = ENAMETOOLONG;
 163                 if (p == resolved)
 164                         *p++ = '/';
 165                 *p = 0;
 166                 return (NULL);
 167         }
 168         p[0] = '/';
 169         memcpy(&p[1], path,
 170             /* LINTED We know q > path. */
 171             q - path);
 172         p[1 + q - path] = 0;
 173
 174         /*
 175          * If this component is a symlink, toss it and prepend link
 176          * target to unresolved path.
 177          */
 178         if (lstat(resolved, &sb) == -1) {
 179                 return (NULL);
 180         }
 181         if (S_ISLNK(sb.st_mode)) {
 182                 if (nlnk++ >= MAXSYMLINKS) {
 183                         errno = ELOOP;
 184                         return (NULL);
 185                 }
 186                 n = readlink(resolved, wbuf[idx], sizeof(wbuf[0]) - 1);
 187                 if (n < 0)
 188                         return (NULL);
 189                 if (n == 0) {
 190                         errno = ENOENT;
 191                         return (NULL);
 192                 }
 193
 194                 /* Append unresolved path to link target and switch to it. */
 195                 if (n + (len = strlen(q)) + 1 > sizeof(wbuf[0])) {
 196                         errno = ENAMETOOLONG;
 197                         return (NULL);
 198                 }
 199                 memcpy(&wbuf[idx][n], q, len + 1);
 200                 path = wbuf[idx];
 201                 idx ^= 1;
 202
 203                 /* If absolute symlink, start from root. */
 204                 if (*path == '/')
 205                         p = resolved;
 206                 goto loop;
 207         }
 208         if (*q == '/' && !S_ISDIR(sb.st_mode)) {
 209                 errno = ENOTDIR;
 210                 return (NULL);
 211         }
 212
 213         /* Advance both resolved and unresolved path. */
 214         p += 1 + q - path;
 215         path = q;
 216         goto loop;
 217 }
 218
 219 char *
 220 getcwd(char *pt, size_t size)
 221 {
 222         char *npt;
 223
 224         /*
 225          * If a buffer is specified, the size has to be non-zero.
 226          */
 227         if (pt != NULL) {
 228                 if (size == 0) {
 229                         /* __getcwd(pt, 0) results ERANGE. */
 230                         errno = EINVAL;
 231                         return (NULL);
 232                 }
 233                 if (__getcwd(pt, size) >= 0)
 234                         return (pt);
 235                 return (NULL);
 236         }
 237
 238         /*
 239          * If no buffer specified by the user, allocate one as necessary.
 240          */
 241         size = 1024 >> 1;
 242         do {
 243                 if ((npt = realloc(pt, size <<= 1)) == NULL)
 244                         break;
 245                 pt = npt;
 246                 if (__getcwd(pt, size) >= 0)
 247                         return (pt);
 248         } while (size <= MAXPATHLEN * 4 && errno == ERANGE);
 249
 250         free(pt);
 251         return (NULL);
 252 }