usr/src/cmd/ssh/libopenbsd-compat/common/realpath.c

   1 /*
   2  * Copyright (c) 1994
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Jan-Simon Pendry.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  */
  29
  30 #include "includes.h"
  31
  32 #if !defined(HAVE_REALPATH) || defined(BROKEN_REALPATH)
  33
  34 #if defined(LIBC_SCCS) && !defined(lint)
  35 static char *rcsid = "$OpenBSD: realpath.c,v 1.7 2002/05/24 21:22:37 deraadt Exp $";
  36 #endif /* LIBC_SCCS and not lint */
  37
  38 #include <sys/param.h>
  39 #include <sys/stat.h>
  40
  41 #include <errno.h>
  42 #include <fcntl.h>
  43 #include <stdlib.h>
  44 #include <string.h>
  45 #include <unistd.h>
  46
  47 /*
  48  * MAXSYMLINKS
  49  */
  50 #ifndef MAXSYMLINKS
  51 #define MAXSYMLINKS 5
  52 #endif
  53
  54 /*
  55  * char *realpath(const char *path, char resolved_path[MAXPATHLEN]);
  56  *
  57  * Find the real name of path, by removing all ".", ".." and symlink
  58  * components.  Returns (resolved) on success, or (NULL) on failure,
  59  * in which case the path which caused trouble is left in (resolved).
  60  */
  61 char *
  62 realpath(const char *path, char *resolved)
  63 {
  64         struct stat sb;
  65         int fd, n, rootd, serrno = 0;
  66         char *p, *q, wbuf[MAXPATHLEN], start[MAXPATHLEN];
  67         int symlinks = 0;
  68
  69         /* Save the starting point. */
  70         getcwd(start,MAXPATHLEN);
  71         if ((fd = open(".", O_RDONLY)) < 0) {
  72                 (void)strlcpy(resolved, ".", MAXPATHLEN);
  73                 return (NULL);
  74         }
  75         close(fd);
  76
  77         /* Convert "." -> "" to optimize away a needless lstat() and chdir() */
  78         if (path[0] == '.' && path[1] == '\0')
  79                 path = "";
  80
  81         /*
  82          * Find the dirname and basename from the path to be resolved.
  83          * Change directory to the dirname component.
  84          * lstat the basename part.
  85          *     if it is a symlink, read in the value and loop.
  86          *     if it is a directory, then change to that directory.
  87          * get the current directory name and append the basename.
  88          */
  89         strlcpy(resolved, path, MAXPATHLEN);
  90 loop:
  91         q = strrchr(resolved, '/');
  92         if (q != NULL) {
  93                 p = q + 1;
  94                 if (q == resolved)
  95                         q = "/";
  96                 else {
  97                         do {
  98                                 --q;
  99                         } while (q > resolved && *q == '/');
 100                         q[1] = '\0';
 101                         q = resolved;
 102                 }
 103                 if (chdir(q) < 0)
 104                         goto err1;
 105         } else
 106                 p = resolved;
 107
 108         /* Deal with the last component. */
 109         if (*p != '\0' && lstat(p, &sb) == 0) {
 110                 if (S_ISLNK(sb.st_mode)) {
 111                         if (++symlinks > MAXSYMLINKS) {
 112                                 serrno = ELOOP;
 113                                 goto err1;
 114                         }
 115                         n = readlink(p, resolved, MAXPATHLEN-1);
 116                         if (n < 0)
 117                                 goto err1;
 118                         resolved[n] = '\0';
 119                         goto loop;
 120                 }
 121                 if (S_ISDIR(sb.st_mode)) {
 122                         if (chdir(p) < 0)
 123                                 goto err1;
 124                         p = "";
 125                 }
 126         }
 127
 128         /*
 129          * Save the last component name and get the full pathname of
 130          * the current directory.
 131          */
 132         (void)strlcpy(wbuf, p, sizeof wbuf);
 133         if (getcwd(resolved, MAXPATHLEN) == 0)
 134                 goto err1;
 135
 136         /*
 137          * Join the two strings together, ensuring that the right thing
 138          * happens if the last component is empty, or the dirname is root.
 139          */
 140         if (resolved[0] == '/' && resolved[1] == '\0')
 141                 rootd = 1;
 142         else
 143                 rootd = 0;
 144
 145         if (*wbuf) {
 146                 if (strlen(resolved) + strlen(wbuf) + rootd + 1 > MAXPATHLEN) {
 147                         serrno = ENAMETOOLONG;
 148                         goto err1;
 149                 }
 150                 if (rootd == 0)
 151                         (void)strcat(resolved, "/");
 152                 (void)strcat(resolved, wbuf);
 153         }
 154
 155         /* Go back to where we came from. */
 156         if (chdir(start) < 0) {
 157                 serrno = errno;
 158                 goto err2;
 159         }
 160         return (resolved);
 161
 162 err1:   chdir(start);
 163 err2:   errno = serrno;
 164         return (NULL);
 165 }
 166 #endif /* !defined(HAVE_REALPATH) || defined(BROKEN_REALPATH) */
 167
 168 #pragma ident   "%Z%%M% %I%     %E% SMI"