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 (c) 1989, 2010, Oracle and/or its affiliates. All rights reserved.
  24  */
  25
  26 /*      Copyright (c) 1988 AT&T */
  27 /*        All Rights Reserved   */
  28
  29 #include "lint.h"
  30 #include <sys/types.h>
  31 #include <dirent.h>
  32 #include <sys/param.h>
  33 #include <limits.h>
  34 #include <errno.h>
  35 #include <stdlib.h>
  36 #include <unistd.h>
  37 #include <string.h>
  38
  39 /*
  40  * Canonicalize the path given in file_name, resolving away all symbolic link
  41  * components.  Store the result into the buffer named by resolved_name, which
  42  * must be long enough (PATH_MAX bytes will suffice).  Returns NULL
  43  * on failure and resolved_name on success.  On failure, to maintain
  44  * compatibility with the past, the contents of file_name will be copied
  45  * into resolved_name.
  46  */
  47 static char *
  48 realpath_impl(const char *file_name, char *resolved_name)
  49 {
  50         char cwd[PATH_MAX];
  51         int len;
  52
  53         if (file_name == NULL) {
  54                 errno = EINVAL;
  55                 return (NULL);
  56         }
  57
  58         /*
  59          * Call resolvepath() to resolve all the symlinks in file_name,
  60          * eliminate embedded "." components, and collapse embedded ".."
  61          * components.  We may be left with leading ".." components.
  62          */
  63         if ((len = resolvepath(file_name, resolved_name, PATH_MAX)) < 0) {
  64                 (void) strlcpy(resolved_name, file_name, PATH_MAX);
  65                 return (NULL);          /* errno set by resolvepath() */
  66         }
  67
  68         if (len >= PATH_MAX)    /* "can't happen" */
  69                 len = PATH_MAX - 1;
  70         resolved_name[len] = '\0';
  71
  72         if (*resolved_name == '/')      /* nothing more to do */
  73                 return (resolved_name);
  74
  75         /*
  76          * Prepend the current working directory to the relative path.
  77          * If the relative path is not empty (or "."), collapse all of the
  78          * resulting embedded ".." components with trailing cwd components.
  79          * We know that getcwd() returns a path name free of symlinks.
  80          */
  81         if (getcwd(cwd, sizeof (cwd)) == NULL) {
  82                 (void) strlcpy(resolved_name, file_name, PATH_MAX);
  83                 return (NULL);          /* errno set by getcwd() */
  84         }
  85
  86         if (len != 0 && strcmp(resolved_name, ".") != 0) {
  87                 char *relpath = resolved_name;
  88                 char *endcwd = cwd + strlen(cwd);
  89
  90                 /*
  91                  * Eliminate ".." components from the relative path
  92                  * left-to-right, components from cwd right-to-left.
  93                  */
  94                 relpath[len++] = '/';
  95                 while (len >= 3 && strncmp(relpath, "../", 3) == 0) {
  96                         relpath += 3;
  97                         len -= 3;
  98                         while (*--endcwd != '/')
  99                                 continue;
 100                 }
 101                 if (len == 0) {
 102                         /* the relative path was all ".." components */
 103                         *endcwd = '\0';
 104                 } else {
 105                         /* there are non-null components on both sides */
 106                         relpath[--len] = '\0';
 107                         *endcwd++ = '/';
 108                         if (endcwd + len >= cwd + PATH_MAX) {
 109                                 (void) strlcpy(resolved_name,
 110                                     file_name, PATH_MAX);
 111                                 errno = ENAMETOOLONG;
 112                                 return (NULL);
 113                         }
 114                         (void) strcpy(endcwd, relpath);
 115                 }
 116         }
 117
 118         (void) strcpy(resolved_name, cwd);
 119         return (resolved_name);
 120 }
 121
 122 /*
 123  * Canonicalize the path given in file_name, resolving away all symbolic link
 124  * components.  If resolved_name is a null pointer, return a malloc()d
 125  * buffer containing the result, else store the result into resolved_name
 126  * and return resolved_name.  Return NULL on failure.
 127  */
 128 char *
 129 realpath(const char *file_name, char *resolved_name)
 130 {
 131         char buffer[PATH_MAX];
 132
 133         if (resolved_name != NULL)
 134                 return (realpath_impl(file_name, resolved_name));
 135
 136         if (realpath_impl(file_name, buffer) != NULL)
 137                 return (strdup(buffer));
 138
 139         return (NULL);
 140 }
 141
 142 /*
 143  * GNU extension.
 144  */
 145 char *
 146 canonicalize_file_name(const char *path)
 147 {
 148         return (realpath(path, NULL));
 149 }