lib/libssh/openbsd-compat/realpath.c

   1 /*      $OpenBSD: realpath.c,v 1.20 2015/10/13 20:55:37 millert Exp $ */
   2 /*
   3  * Copyright (c) 2003 Constantin S. Svintsoff <kostik@iclub.nsu.ru>
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. The names of the authors may not be used to endorse or promote
  14  *    products derived from this software without specific prior written
  15  *    permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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 /* OPENBSD ORIGINAL: lib/libc/stdlib/realpath.c */
  31
  32 #include "includes.h"
  33
  34 #if !defined(HAVE_REALPATH) || defined(BROKEN_REALPATH)
  35
  36 #include <sys/types.h>
  37 #include <sys/param.h>
  38 #include <sys/stat.h>
  39
  40 #include <errno.h>
  41 #include <stdlib.h>
  42 #include <stddef.h>
  43 #include <string.h>
  44 #include <unistd.h>
  45 #include <limits.h>
  46
  47 #ifndef SYMLOOP_MAX
  48 # define SYMLOOP_MAX 32
  49 #endif
  50
  51 /* A slightly modified copy of this file exists in libexec/ld.so */
  52
  53 /*
  54  * char *realpath(const char *path, char resolved[PATH_MAX]);
  55  *
  56  * Find the real name of path, by removing all ".", ".." and symlink
  57  * components.  Returns (resolved) on success, or (NULL) on failure,
  58  * in which case the path which caused trouble is left in (resolved).
  59  */
  60 char *
  61 realpath(const char *path, char *resolved)
  62 {
  63         struct stat sb;
  64         char *p, *q, *s;
  65         size_t left_len, resolved_len;
  66         unsigned symlinks;
  67         int serrno, slen, mem_allocated;
  68         char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX];
  69
  70         if (path[0] == '\0') {
  71                 errno = ENOENT;
  72                 return (NULL);
  73         }
  74
  75         serrno = errno;
  76
  77         if (resolved == NULL) {
  78                 resolved = malloc(PATH_MAX);
  79                 if (resolved == NULL)
  80                         return (NULL);
  81                 mem_allocated = 1;
  82         } else
  83                 mem_allocated = 0;
  84
  85         symlinks = 0;
  86         if (path[0] == '/') {
  87                 resolved[0] = '/';
  88                 resolved[1] = '\0';
  89                 if (path[1] == '\0')
  90                         return (resolved);
  91                 resolved_len = 1;
  92                 left_len = strlcpy(left, path + 1, sizeof(left));
  93         } else {
  94                 if (getcwd(resolved, PATH_MAX) == NULL) {
  95                         if (mem_allocated)
  96                                 free(resolved);
  97                         else
  98                                 strlcpy(resolved, ".", PATH_MAX);
  99                         return (NULL);
 100                 }
 101                 resolved_len = strlen(resolved);
 102                 left_len = strlcpy(left, path, sizeof(left));
 103         }
 104         if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) {
 105                 errno = ENAMETOOLONG;
 106                 goto err;
 107         }
 108
 109         /*
 110          * Iterate over path components in `left'.
 111          */
 112         while (left_len != 0) {
 113                 /*
 114                  * Extract the next path component and adjust `left'
 115                  * and its length.
 116                  */
 117                 p = strchr(left, '/');
 118                 s = p ? p : left + left_len;
 119                 if (s - left >= (ptrdiff_t)sizeof(next_token)) {
 120                         errno = ENAMETOOLONG;
 121                         goto err;
 122                 }
 123                 memcpy(next_token, left, s - left);
 124                 next_token[s - left] = '\0';
 125                 left_len -= s - left;
 126                 if (p != NULL)
 127                         memmove(left, s + 1, left_len + 1);
 128                 if (resolved[resolved_len - 1] != '/') {
 129                         if (resolved_len + 1 >= PATH_MAX) {
 130                                 errno = ENAMETOOLONG;
 131                                 goto err;
 132                         }
 133                         resolved[resolved_len++] = '/';
 134                         resolved[resolved_len] = '\0';
 135                 }
 136                 if (next_token[0] == '\0')
 137                         continue;
 138                 else if (strcmp(next_token, ".") == 0)
 139                         continue;
 140                 else if (strcmp(next_token, "..") == 0) {
 141                         /*
 142                          * Strip the last path component except when we have
 143                          * single "/"
 144                          */
 145                         if (resolved_len > 1) {
 146                                 resolved[resolved_len - 1] = '\0';
 147                                 q = strrchr(resolved, '/') + 1;
 148                                 *q = '\0';
 149                                 resolved_len = q - resolved;
 150                         }
 151                         continue;
 152                 }
 153
 154                 /*
 155                  * Append the next path component and lstat() it. If
 156                  * lstat() fails we still can return successfully if
 157                  * there are no more path components left.
 158                  */
 159                 resolved_len = strlcat(resolved, next_token, PATH_MAX);
 160                 if (resolved_len >= PATH_MAX) {
 161                         errno = ENAMETOOLONG;
 162                         goto err;
 163                 }
 164                 if (lstat(resolved, &sb) != 0) {
 165                         if (errno == ENOENT && p == NULL) {
 166                                 errno = serrno;
 167                                 return (resolved);
 168                         }
 169                         goto err;
 170                 }
 171                 if (S_ISLNK(sb.st_mode)) {
 172                         if (symlinks++ > SYMLOOP_MAX) {
 173                                 errno = ELOOP;
 174                                 goto err;
 175                         }
 176                         slen = readlink(resolved, symlink, sizeof(symlink) - 1);
 177                         if (slen < 0)
 178                                 goto err;
 179                         symlink[slen] = '\0';
 180                         if (symlink[0] == '/') {
 181                                 resolved[1] = 0;
 182                                 resolved_len = 1;
 183                         } else if (resolved_len > 1) {
 184                                 /* Strip the last path component. */
 185                                 resolved[resolved_len - 1] = '\0';
 186                                 q = strrchr(resolved, '/') + 1;
 187                                 *q = '\0';
 188                                 resolved_len = q - resolved;
 189                         }
 190
 191                         /*
 192                          * If there are any path components left, then
 193                          * append them to symlink. The result is placed
 194                          * in `left'.
 195                          */
 196                         if (p != NULL) {
 197                                 if (symlink[slen - 1] != '/') {
 198                                         if (slen + 1 >=
 199                                             (ptrdiff_t)sizeof(symlink)) {
 200                                                 errno = ENAMETOOLONG;
 201                                                 goto err;
 202                                         }
 203                                         symlink[slen] = '/';
 204                                         symlink[slen + 1] = 0;
 205                                 }
 206                                 left_len = strlcat(symlink, left, sizeof(symlink));
 207                                 if (left_len >= sizeof(symlink)) {
 208                                         errno = ENAMETOOLONG;
 209                                         goto err;
 210                                 }
 211                         }
 212                         left_len = strlcpy(left, symlink, sizeof(left));
 213                 }
 214         }
 215
 216         /*
 217          * Remove trailing slash except when the resolved pathname
 218          * is a single "/".
 219          */
 220         if (resolved_len > 1 && resolved[resolved_len - 1] == '/')
 221                 resolved[resolved_len - 1] = '\0';
 222         return (resolved);
 223
 224 err:
 225         if (mem_allocated)
 226                 free(resolved);
 227         return (NULL);
 228 }
 229 #endif /* !defined(HAVE_REALPATH) || defined(BROKEN_REALPATH) */