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magic.c

/*
 * Copyright (c) Christos Zoulas 2003.
 * All Rights Reserved.
 * 
 * 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.
 */

#include "file.h"
#include "magic.h"

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/param.h>  /* for MAXPATHLEN */
#include <sys/stat.h>
#ifdef QUICK
#include <sys/mman.h>
#endif

#if defined(HAVE_UTIMES)
# include <sys/time.h>
#elif defined(HAVE_UTIME)
# if defined(HAVE_SYS_UTIME_H)
#  include <sys/utime.h>
# elif defined(HAVE_UTIME_H)
#  include <utime.h>
# endif
#endif

#ifdef HAVE_UNISTD_H
#include <unistd.h>     /* for read() */
#endif

#ifdef HAVE_LOCALE_H
#include <locale.h>
#endif

#include <netinet/in.h>       /* for byte swapping */

#include "patchlevel.h"

#ifndef     lint
FILE_RCSID("@(#)$Id: magic.c,v 1.32 2005/10/17 15:31:10 christos Exp $")
#endif      /* lint */

#ifdef __EMX__
private char *apptypeName = NULL;
protected int file_os2_apptype(struct magic_set *ms, const char *fn,
    const void *buf, size_t nb);
#endif /* __EMX__ */

private void free_mlist(struct mlist *);
private void close_and_restore(const struct magic_set *, const char *, int,
    const struct stat *);

#ifndef     STDIN_FILENO
#define     STDIN_FILENO      0
#endif

public struct magic_set *
magic_open(int flags)
{
      struct magic_set *ms;

      if ((ms = malloc(sizeof(struct magic_set))) == NULL)
            return NULL;

      if (magic_setflags(ms, flags) == -1) {
            errno = EINVAL;
            goto free1;
      }

      ms->o.ptr = ms->o.buf = malloc(ms->o.size = 1024);
      if (ms->o.buf == NULL)
            goto free1;

      ms->o.pbuf = malloc(ms->o.psize = 1024);
      if (ms->o.pbuf == NULL)
            goto free2;

      ms->c.off = malloc((ms->c.len = 10) * sizeof(*ms->c.off));
      if (ms->c.off == NULL)
            goto free3;
      
      ms->o.len = 0;
      ms->haderr = 0;
      ms->error = -1;
      ms->mlist = NULL;
      return ms;
free3:
      free(ms->o.pbuf);
free2:
      free(ms->o.buf);
free1:
      free(ms);
      return NULL;
}

private void
free_mlist(struct mlist *mlist)
{
      struct mlist *ml;

      if (mlist == NULL)
            return;

      for (ml = mlist->next; ml != mlist;) {
            struct mlist *next = ml->next;
            struct magic *mg = ml->magic;
            file_delmagic(mg, ml->mapped, ml->nmagic);
            free(ml);
            ml = next;
      }
      free(ml);
}

public void
magic_close(ms)
    struct magic_set *ms;
{
      free_mlist(ms->mlist);
      free(ms->o.pbuf);
      free(ms->o.buf);
      free(ms->c.off);
      free(ms);
}

/*
 * load a magic file
 */
public int
magic_load(struct magic_set *ms, const char *magicfile)
{
      struct mlist *ml = file_apprentice(ms, magicfile, FILE_LOAD);
      if (ml) {
            free_mlist(ms->mlist);
            ms->mlist = ml;
            return 0;
      }
      return -1;
}

public int
magic_compile(struct magic_set *ms, const char *magicfile)
{
      struct mlist *ml = file_apprentice(ms, magicfile, FILE_COMPILE);
      free_mlist(ml);
      return ml ? 0 : -1;
}

public int
magic_check(struct magic_set *ms, const char *magicfile)
{
      struct mlist *ml = file_apprentice(ms, magicfile, FILE_CHECK);
      free_mlist(ml);
      return ml ? 0 : -1;
}

private void
close_and_restore(const struct magic_set *ms, const char *name, int fd,
    const struct stat *sb)
{
      if (fd == STDIN_FILENO)
            return;
      (void) close(fd);

      if ((ms->flags & MAGIC_PRESERVE_ATIME) != 0) {
            /*
             * Try to restore access, modification times if read it.
             * This is really *bad* because it will modify the status
             * time of the file... And of course this will affect
             * backup programs
             */
#ifdef HAVE_UTIMES
            struct timeval  utsbuf[2];
            utsbuf[0].tv_sec = sb->st_atime;
            utsbuf[1].tv_sec = sb->st_mtime;

            (void) utimes(name, utsbuf); /* don't care if loses */
#elif defined(HAVE_UTIME_H) || defined(HAVE_SYS_UTIME_H)
            struct utimbuf  utbuf;

            utbuf.actime = sb->st_atime;
            utbuf.modtime = sb->st_mtime;
            (void) utime(name, &utbuf); /* don't care if loses */
#endif
      }
}

#ifndef COMPILE_ONLY
/*
 * find type of named file
 */
public const char *
magic_file(struct magic_set *ms, const char *inname)
{
      int   fd = 0;
      int   rv = -1;
      unsigned char *buf;
      struct stat sb;
      ssize_t nbytes = 0;     /* number of bytes read from a datafile */

      /*
       * one extra for terminating '\0', and
       * some overlapping space for matches near EOF
       */
#define SLOP (1 + sizeof(union VALUETYPE))
      if ((buf = malloc(HOWMANY + SLOP)) == NULL)
            return NULL;

      if (file_reset(ms) == -1)
            goto done;

      switch (file_fsmagic(ms, inname, &sb)) {
      case -1:
            goto done;
      case 0:
            break;
      default:
            rv = 0;
            goto done;
      }

      if (inname == NULL)
            fd = STDIN_FILENO;
      else if ((fd = open(inname, O_RDONLY|O_BINARY)) < 0) {
#ifdef __CYGWIN__
          char *tmp = alloca(strlen(inname) + 5);
          (void)strcat(strcpy(tmp, inname), ".exe");
          if ((fd = open(tmp, O_RDONLY|O_BINARY)) < 0) {
#endif
            /* We cannot open it, but we were able to stat it. */
            if (sb.st_mode & 0222)
                  if (file_printf(ms, "writable, ") == -1)
                        goto done;
            if (sb.st_mode & 0111)
                  if (file_printf(ms, "executable, ") == -1)
                        goto done;
            if (S_ISREG(sb.st_mode))
                  if (file_printf(ms, "regular file, ") == -1)
                        goto done;
            if (file_printf(ms, "no read permission") == -1)
                  goto done;
            rv = 0;
            goto done;
#ifdef __CYGWIN__
          }
#endif
      }

      /*
       * try looking at the first HOWMANY bytes
       */
      if ((nbytes = read(fd, (char *)buf, HOWMANY)) == -1) {
            file_error(ms, errno, "cannot read `%s'", inname);
            goto done;
      }

      if (nbytes == 0) {
            if (file_printf(ms, (ms->flags & MAGIC_MIME) ?
                "application/x-empty" : "empty") == -1)
                  goto done;
      } else if (nbytes == 1) {
            if (file_printf(ms, "very short file (no magic)") == -1)
                  goto done;
      } else {
            (void)memset(buf + nbytes, 0, SLOP); /* NUL terminate */
#ifdef __EMX__
            switch (file_os2_apptype(ms, inname, buf, nbytes)) {
            case -1:
                  goto done;
            case 0:
                  break;
            default:
                  rv = 0;
                  goto done;
            }
#endif
            if (file_buffer(ms, fd, buf, (size_t)nbytes) == -1)
                  goto done;
#ifdef BUILTIN_ELF
            if (nbytes > 5) {
                  /*
                   * We matched something in the file, so this *might*
                   * be an ELF file, and the file is at least 5 bytes
                   * long, so if it's an ELF file it has at least one
                   * byte past the ELF magic number - try extracting
                   * information from the ELF headers that cannot easily
                   * be extracted with rules in the magic file.
                   */
                  file_tryelf(ms, fd, buf, (size_t)nbytes);
            }
#endif
      }
      rv = 0;
done:
      free(buf);
      close_and_restore(ms, inname, fd, &sb);
      return rv == 0 ? file_getbuffer(ms) : NULL;
}


public const char *
magic_buffer(struct magic_set *ms, const void *buf, size_t nb)
{
      if (file_reset(ms) == -1)
            return NULL;
      /*
       * The main work is done here!
       * We have the file name and/or the data buffer to be identified. 
       */
      if (file_buffer(ms, -1, buf, nb) == -1) {
            return NULL;
      }
      return file_getbuffer(ms);
}
#endif

public const char *
magic_error(struct magic_set *ms)
{
      return ms->haderr ? ms->o.buf : NULL;
}

public int
magic_errno(struct magic_set *ms)
{
      return ms->haderr ? ms->error : 0;
}

public int
magic_setflags(struct magic_set *ms, int flags)
{
#if !defined(HAVE_UTIME) && !defined(HAVE_UTIMES)
      if (flags & MAGIC_PRESERVE_ATIME)
            return -1;
#endif
      ms->flags = flags;
      return 0;
}

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