file/src/magic.c

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/*
 * 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
#include <limits.h>     /* for PIPE_BUF */

#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("@(#)$File: magic.c,v 1.40 2007/03/01 22:14:55 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 *mlist)
        /*@globals fileSystem @*/
        /*@modifies mlist, fileSystem @*/;
private void close_and_restore(const struct magic_set *ms, /*@null@*/ const char *name,
    int fd, const struct stat *sb)
        /*@globals fileSystem, internalState @*/
        /*@modifies fileSystem, internalState @*/;
private int info_from_stat(struct magic_set *ms, mode_t md)
        /*@modifies ms @*/;

#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.left = 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.li = malloc((ms->c.len = 10) * sizeof(*ms->c.li));
        if (ms->c.li == NULL)
                goto free3;
        
        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);
}

private int
info_from_stat(struct magic_set *ms, mode_t md)
{
        /* We cannot open it, but we were able to stat it. */
        if (md & 0222)
                if (file_printf(ms, "writable, ") == -1)
                        return -1;
        if (md & 0111)
                if (file_printf(ms, "executable, ") == -1)
                        return -1;
        if (S_ISREG(md))
                if (file_printf(ms, "regular file, ") == -1)
                        return -1;
        if (file_printf(ms, "no read permission") == -1)
                return -1;
        return 0;
}

public void
magic_close(struct magic_set *ms)
{
        free_mlist(ms->mlist);
        free(ms->o.pbuf);
        free(ms->o.buf);
        free(ms->c.li);
        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 (name != NULL && (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, *st = &sb;
        ssize_t nbytes = 0;     /* number of bytes read from a datafile */
        int     ispipe = 0;

        /*
         * 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, st)) {
        case -1:                /* error */
                goto done;
        case 0:                 /* nothing found */
                break;
        default:                /* matched it and printed type */
                rv = 0;
                goto done;
        }

        if (inname == NULL) {
                fd = STDIN_FILENO;
                if (fstat(fd, &sb) == 0 && S_ISFIFO(sb.st_mode))
                        ispipe = 1;
        } else {
                int flags = O_RDONLY|O_BINARY;

                if (stat(inname, &sb) == 0 && S_ISFIFO(sb.st_mode)) {
                        flags |= O_NONBLOCK;
                        ispipe = 1;
                }

                errno = 0;
                if ((fd = open(inname, flags)) < 0) {
#ifdef __CYGWIN__
            char *tmp = alloca(strlen(inname) + 5);
            (void)strcat(strcpy(tmp, inname), ".exe");
                    if ((fd = open(tmp, flags)) < 0) {
#endif
                        if (info_from_stat(ms, sb.st_mode) == -1)
                        goto done;
                rv = 0;
                goto done;
#ifdef __CYGWIN__
            }
#endif
        }
#ifdef O_NONBLOCK
                if ((flags = fcntl(fd, F_GETFL)) != -1) {
                        flags &= ~O_NONBLOCK;
                        (void)fcntl(fd, F_SETFL, flags);
                }
#endif
        }

        /*
         * try looking at the first HOWMANY bytes
         */
        if (ispipe) {
                ssize_t r = 0;

                while ((r = sread(fd, (void *)&buf[nbytes],
                    (size_t)(HOWMANY - nbytes), 1)) > 0) {
                        nbytes += r;
                        if (r < PIPE_BUF) break;
                }

                if (nbytes == 0) {
                        /* We can not read it, but we were able to stat it. */
                        if (info_from_stat(ms, sb.st_mode) == -1)
                                goto done;
                        rv = 0;
                        goto done;
                }

        } else {
        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 */
                if (file_buffer(ms, fd, inname, buf, (size_t)nbytes) == -1)
                        goto done;
        }
        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, NULL, 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;
}

---