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fsmagic.c

/*
 * Copyright (c) Ian F. Darwin 1986-1995.
 * Software written by Ian F. Darwin and others;
 * maintained 1995-present by Christos Zoulas and others.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice immediately at the beginning of the file, without modification,
 *    this list of conditions, and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *  
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
/*
 * fsmagic - magic based on filesystem info - directory, special files, etc.
 */

#include "file.h"
#include "magic.h"
#include <string.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <stdlib.h>
#include <sys/stat.h>
/* Since major is a function on SVR4, we cannot use `ifndef major'.  */
#ifdef MAJOR_IN_MKDEV
# include <sys/mkdev.h>
# define HAVE_MAJOR
#endif
#ifdef MAJOR_IN_SYSMACROS
# include <sys/sysmacros.h>
# define HAVE_MAJOR
#endif
#ifdef major                  /* Might be defined in sys/types.h.  */
# define HAVE_MAJOR
#endif
  
#ifndef HAVE_MAJOR
# define major(dev)  (((dev) >> 8) & 0xff)
# define minor(dev)  ((dev) & 0xff)
#endif
#undef HAVE_MAJOR

#ifndef     lint
FILE_RCSID("@(#)$Id: fsmagic.c,v 1.45 2004/11/13 10:19:48 christos Exp $")
#endif      /* lint */

protected int
file_fsmagic(struct magic_set *ms, const char *fn, struct stat *sb)
{
      int ret = 0;
#ifdef      S_IFLNK
      char buf[BUFSIZ+4];
      int nch;
      struct stat tstatbuf;
#endif

      if (fn == NULL)
            return 0;

      /*
       * Fstat is cheaper but fails for files you don't have read perms on.
       * On 4.2BSD and similar systems, use lstat() to identify symlinks.
       */
#ifdef      S_IFLNK
      if ((ms->flags & MAGIC_SYMLINK) == 0)
            ret = lstat(fn, sb);
      else
#endif
      ret = stat(fn, sb);     /* don't merge into if; see "ret =" above */

      if (ret) {
            if (ms->flags & MAGIC_ERROR) {
                  file_error(ms, errno, "cannot stat `%s'", fn);
                  return -1;
            }
            if (file_printf(ms, "cannot open `%s' (%s)",
                fn, strerror(errno)) == -1)
                  return -1;
            ms->haderr++;
            return -1;
      }

      if ((ms->flags & MAGIC_MIME) != 0) {
            if ((sb->st_mode & S_IFMT) != S_IFREG) {
                  if (file_printf(ms, "application/x-not-regular-file")
                      == -1)
                        return -1;
                  return 1;
            }
      }
      else {
#ifdef S_ISUID
            if (sb->st_mode & S_ISUID) 
                  if (file_printf(ms, "setuid ") == -1)
                        return -1;
#endif
#ifdef S_ISGID
            if (sb->st_mode & S_ISGID) 
                  if (file_printf(ms, "setgid ") == -1)
                        return -1;
#endif
#ifdef S_ISVTX
            if (sb->st_mode & S_ISVTX) 
                  if (file_printf(ms, "sticky ") == -1)
                        return -1;
#endif
      }
      
      switch (sb->st_mode & S_IFMT) {
      case S_IFDIR:
            if (file_printf(ms, "directory") == -1)
                  return -1;
            return 1;
#ifdef S_IFCHR
      case S_IFCHR:
            /* 
             * If -s has been specified, treat character special files
             * like ordinary files.  Otherwise, just report that they
             * are block special files and go on to the next file.
             */
            if ((ms->flags & MAGIC_DEVICES) != 0)
                  break;
#ifdef HAVE_ST_RDEV
# ifdef dv_unit
            if (file_printf(ms, "character special (%d/%d/%d)",
                major(sb->st_rdev), dv_unit(sb->st_rdev),
                dv_subunit(sb->st_rdev)) == -1)
                  return -1;
# else
            if (file_printf(ms, "character special (%ld/%ld)",
                (long) major(sb->st_rdev), (long) minor(sb->st_rdev)) == -1)
                  return -1;
# endif
#else
            if (file_printf(ms, "character special") == -1)
                  return -1;
#endif
            return 1;
#endif
#ifdef S_IFBLK
      case S_IFBLK:
            /* 
             * If -s has been specified, treat block special files
             * like ordinary files.  Otherwise, just report that they
             * are block special files and go on to the next file.
             */
            if ((ms->flags & MAGIC_DEVICES) != 0)
                  break;
#ifdef HAVE_ST_RDEV
# ifdef dv_unit
            if (file_printf(ms, "block special (%d/%d/%d)",
                major(sb->st_rdev), dv_unit(sb->st_rdev),
                dv_subunit(sb->st_rdev)) == -1)
                  return -1;
# else
            if (file_printf(ms, "block special (%ld/%ld)",
                (long)major(sb->st_rdev), (long)minor(sb->st_rdev)) == -1)
                  return -1;
# endif
#else
            if (file_printf(ms, "block special") == -1)
                  return -1;
#endif
            return 1;
#endif
      /* TODO add code to handle V7 MUX and Blit MUX files */
#ifdef      S_IFIFO
      case S_IFIFO:
            if (file_printf(ms, "fifo (named pipe)") == -1)
                  return -1;
            return 1;
#endif
#ifdef      S_IFDOOR
      case S_IFDOOR:
            if (file_printf(ms, "door") == -1)
                  return -1;
            return 1;
#endif
#ifdef      S_IFLNK
      case S_IFLNK:
            if ((nch = readlink(fn, buf, BUFSIZ-1)) <= 0) {
                  if (ms->flags & MAGIC_ERROR) {
                      file_error(ms, errno, "unreadable symlink `%s'",
                        fn);
                      return -1;
                  }
                  if (file_printf(ms,
                      "unreadable symlink `%s' (%s)", fn,
                      strerror(errno)) == -1)
                        return -1;
                  return 1;
            }
            buf[nch] = '\0';  /* readlink(2) forgets this */

            /* If broken symlink, say so and quit early. */
            if (*buf == '/') {
                if (stat(buf, &tstatbuf) < 0) {
                      if (ms->flags & MAGIC_ERROR) {
                            file_error(ms, errno, 
                              "broken symbolic link to `%s'", buf);
                            return -1;
                      } 
                      if (file_printf(ms, "broken symbolic link to `%s'",
                        buf) == -1)
                            return -1;
                      return 1;
                }
            }
            else {
                  char *tmp;
                  char buf2[BUFSIZ+BUFSIZ+4];

                  if ((tmp = strrchr(fn,  '/')) == NULL) {
                        tmp = buf; /* in current directory anyway */
                  } else {
                        if (tmp - fn + 1 > BUFSIZ) {
                              if (ms->flags & MAGIC_ERROR) {
                                    file_error(ms, 0, 
                                        "path too long: `%s'", buf);
                                    return -1;
                              }
                              if (file_printf(ms,
                                  "path too long: `%s'", fn) == -1)
                                    return -1;
                              return 1;
                        }
                        (void)strcpy(buf2, fn);  /* take dir part */
                        buf2[tmp - fn + 1] = '\0';
                        (void)strcat(buf2, buf); /* plus (rel) link */
                        tmp = buf2;
                  }
                  if (stat(tmp, &tstatbuf) < 0) {
                        if (ms->flags & MAGIC_ERROR) {
                              file_error(ms, errno, 
                                  "broken symbolic link to `%s'",
                                  buf);
                              return -1;
                        }
                        if (file_printf(ms,
                            "broken symbolic link to `%s'", buf) == -1)
                              return -1;
                        return 1;
                  }
            }

            /* Otherwise, handle it. */
            if ((ms->flags & MAGIC_SYMLINK) != 0) {
                  const char *p;
                  ms->flags &= MAGIC_SYMLINK;
                  p = magic_file(ms, buf);
                  ms->flags |= MAGIC_SYMLINK;
                  return p != NULL ? 1 : -1;
            } else { /* just print what it points to */
                  if (file_printf(ms, "symbolic link to `%s'",
                      buf) == -1)
                        return -1;
            }
      return 1;
#endif
#ifdef      S_IFSOCK
#ifndef __COHERENT__
      case S_IFSOCK:
            if (file_printf(ms, "socket") == -1)
                  return -1;
            return 1;
#endif
#endif
      case S_IFREG:
            break;
      default:
            file_error(ms, 0, "invalid mode 0%o", sb->st_mode);
            return -1;
            /*NOTREACHED*/
      }

      /*
       * regular file, check next possibility
       *
       * If stat() tells us the file has zero length, report here that
       * the file is empty, so we can skip all the work of opening and 
       * reading the file.
       * But if the -s option has been given, we skip this optimization,
       * since on some systems, stat() reports zero size for raw disk
       * partitions.  (If the block special device really has zero length,
       * the fact that it is empty will be detected and reported correctly
       * when we read the file.)
       */
      if ((ms->flags & MAGIC_DEVICES) == 0 && sb->st_size == 0) {
            if (file_printf(ms, (ms->flags & MAGIC_MIME) ?
                "application/x-empty" : "empty") == -1)
                  return -1;
            return 1;
      }
      return 0;
}

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