usr/src/lib/libc/port/gen/realpath.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 /*      Copyright (c) 1988 AT&T */
  28 /*        All Rights Reserved   */
  29
  30 #pragma ident   "%Z%%M% %I%     %E% SMI"
  31
  32 #include "lint.h"
  33 #include <sys/types.h>
  34 #include <dirent.h>
  35 #include <sys/param.h>
  36 #include <limits.h>
  37 #include <errno.h>
  38 #include <stdlib.h>
  39 #include <unistd.h>
  40 #include <string.h>
  41
  42 /*
  43  * Canonicalize the path given in file_name, resolving away all symbolic link
  44  * components.  Store the result into the buffer named by resolved_name, which
  45  * must be long enough (MAXPATHLEN bytes will suffice).  Returns NULL
  46  * on failure and resolved_name on success.  On failure, to maintain
  47  * compatibility with the past, the contents of file_name will be copied
  48  * into resolved_name.
  49  */
  50 char *
  51 realpath(const char *file_name, char *resolved_name)
  52 {
  53         char cwd[PATH_MAX];
  54         int len;
  55
  56         if (file_name == NULL || resolved_name == NULL) {
  57                 errno = EINVAL;
  58                 return (NULL);
  59         }
  60
  61         /*
  62          * Call resolvepath() to resolve all the symlinks in file_name,
  63          * eliminate embedded "." components, and collapse embedded ".."
  64          * components.  We may be left with leading ".." components.
  65          */
  66         if ((len = resolvepath(file_name, resolved_name, PATH_MAX)) < 0) {
  67                 (void) strlcpy(resolved_name, file_name, PATH_MAX);
  68                 return (NULL);          /* errno set by resolvepath() */
  69         }
  70
  71         if (len >= PATH_MAX)    /* "can't happen" */
  72                 len = PATH_MAX - 1;
  73         resolved_name[len] = '\0';
  74
  75         if (*resolved_name == '/')      /* nothing more to do */
  76                 return (resolved_name);
  77
  78         /*
  79          * Prepend the current working directory to the relative path.
  80          * If the relative path is not empty (or "."), collapse all of the
  81          * resulting embedded ".." components with trailing cwd components.
  82          * We know that getcwd() returns a path name free of symlinks.
  83          */
  84         if (getcwd(cwd, sizeof (cwd)) == NULL) {
  85                 (void) strlcpy(resolved_name, file_name, PATH_MAX);
  86                 return (NULL);          /* errno set by getcwd() */
  87         }
  88
  89         if (len != 0 && strcmp(resolved_name, ".") != 0) {
  90                 char *relpath = resolved_name;
  91                 char *endcwd = cwd + strlen(cwd);
  92
  93                 /*
  94                  * Eliminate ".." components from the relative path
  95                  * left-to-right, components from cwd right-to-left.
  96                  */
  97                 relpath[len++] = '/';
  98                 while (len >= 3 && strncmp(relpath, "../", 3) == 0) {
  99                         relpath += 3;
 100                         len -= 3;
 101                         while (*--endcwd != '/')
 102                                 continue;
 103                 }
 104                 if (len == 0) {
 105                         /* the relative path was all ".." components */
 106                         *endcwd = '\0';
 107                 } else {
 108                         /* there are non-null components on both sides */
 109                         relpath[--len] = '\0';
 110                         *endcwd++ = '/';
 111                         if (endcwd + len >= cwd + PATH_MAX) {
 112                                 (void) strlcpy(resolved_name,
 113                                     file_name, PATH_MAX);
 114                                 errno = ENAMETOOLONG;
 115                                 return (NULL);
 116                         }
 117                         (void) strcpy(endcwd, relpath);
 118                 }
 119         }
 120
 121         (void) strcpy(resolved_name, cwd);
 122         return (resolved_name);
 123 }