crypto/openssh-3.8.1p1/openbsd-compat/realpath.c

   1 /* OPENBSD ORIGINAL: lib/libc/stdlib/realpath.c */
   2
   3 /*
   4  * Copyright (c) 1994
   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 "includes.h"
  36
  37 #if !defined(HAVE_REALPATH) || defined(BROKEN_REALPATH)
  38
  39 #if defined(LIBC_SCCS) && !defined(lint)
  40 static char *rcsid = "$OpenBSD: realpath.c,v 1.10 2003/08/01 21:04:59 millert Exp $";
  41 #endif /* LIBC_SCCS and not lint */
  42
  43 #include <sys/param.h>
  44 #include <sys/stat.h>
  45
  46 #include <errno.h>
  47 #include <fcntl.h>
  48 #include <stdlib.h>
  49 #include <string.h>
  50 #include <unistd.h>
  51
  52 /*
  53  * MAXSYMLINKS
  54  */
  55 #ifndef MAXSYMLINKS
  56 #define MAXSYMLINKS 5
  57 #endif
  58
  59 /*
  60  * char *realpath(const char *path, char resolved_path[MAXPATHLEN]);
  61  *
  62  * Find the real name of path, by removing all ".", ".." and symlink
  63  * components.  Returns (resolved) on success, or (NULL) on failure,
  64  * in which case the path which caused trouble is left in (resolved).
  65  */
  66 char *
  67 realpath(const char *path, char *resolved)
  68 {
  69         struct stat sb;
  70         int fd, n, needslash, serrno = 0;
  71         char *p, *q, wbuf[MAXPATHLEN], start[MAXPATHLEN];
  72         int symlinks = 0;
  73
  74         /* Save the starting point. */
  75         getcwd(start,MAXPATHLEN);
  76         if ((fd = open(".", O_RDONLY)) < 0) {
  77                 (void)strlcpy(resolved, ".", MAXPATHLEN);
  78                 return (NULL);
  79         }
  80         close(fd);
  81
  82         /* Convert "." -> "" to optimize away a needless lstat() and chdir() */
  83         if (path[0] == '.' && path[1] == '\0')
  84                 path = "";
  85
  86         /*
  87          * Find the dirname and basename from the path to be resolved.
  88          * Change directory to the dirname component.
  89          * lstat the basename part.
  90          *     if it is a symlink, read in the value and loop.
  91          *     if it is a directory, then change to that directory.
  92          * get the current directory name and append the basename.
  93          */
  94         strlcpy(resolved, path, MAXPATHLEN);
  95 loop:
  96         q = strrchr(resolved, '/');
  97         if (q != NULL) {
  98                 p = q + 1;
  99                 if (q == resolved)
 100                         q = "/";
 101                 else {
 102                         do {
 103                                 --q;
 104                         } while (q > resolved && *q == '/');
 105                         q[1] = '\0';
 106                         q = resolved;
 107                 }
 108                 if (chdir(q) < 0)
 109                         goto err1;
 110         } else
 111                 p = resolved;
 112
 113         /* Deal with the last component. */
 114         if (*p != '\0' && lstat(p, &sb) == 0) {
 115                 if (S_ISLNK(sb.st_mode)) {
 116                         if (++symlinks > MAXSYMLINKS) {
 117                                 serrno = ELOOP;
 118                                 goto err1;
 119                         }
 120                         n = readlink(p, resolved, MAXPATHLEN-1);
 121                         if (n < 0)
 122                                 goto err1;
 123                         resolved[n] = '\0';
 124                         goto loop;
 125                 }
 126                 if (S_ISDIR(sb.st_mode)) {
 127                         if (chdir(p) < 0)
 128                                 goto err1;
 129                         p = "";
 130                 }
 131         }
 132
 133         /*
 134          * Save the last component name and get the full pathname of
 135          * the current directory.
 136          */
 137         (void)strlcpy(wbuf, p, sizeof wbuf);
 138         if (getcwd(resolved, MAXPATHLEN) == 0)
 139                 goto err1;
 140
 141         /*
 142          * Join the two strings together, ensuring that the right thing
 143          * happens if the last component is empty, or the dirname is root.
 144          */
 145         if (resolved[0] == '/' && resolved[1] == '\0')
 146                 needslash = 0;
 147         else
 148                 needslash = 1;
 149
 150         if (*wbuf) {
 151                 if (strlen(resolved) + strlen(wbuf) + needslash >= MAXPATHLEN) {
 152                         serrno = ENAMETOOLONG;
 153                         goto err1;
 154                 }
 155                 if (needslash)
 156                         strlcat(resolved, "/", MAXPATHLEN);
 157                 strlcat(resolved, wbuf, MAXPATHLEN);
 158         }
 159
 160         /* Go back to where we came from. */
 161         if (chdir(start) < 0) {
 162                 serrno = errno;
 163                 goto err2;
 164         }
 165         return (resolved);
 166
 167 err1:   chdir(start);
 168 err2:   errno = serrno;
 169         return (NULL);
 170 }
 171 #endif /* !defined(HAVE_REALPATH) || defined(BROKEN_REALPATH) */