fsmagic.c

Go to the documentation of this file.

/*  $OpenBSD: fsmagic.c,v 1.14 2009/10/27 23:59:37 deraadt Exp $ */
/*
 * 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 <rz_userconf.h>
 
#if !USE_LIB_MAGIC
 
#include <rz_magic.h>
#include "file.h"
#include <string.h>
#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
 
static int bad_link(RzMagic *ms, int err, char *buf) {
#ifdef ELOOP
    const char *errfmt = (err == ELOOP) ? "symbolic link in a loop" : "broken symbolic link to `%s'";
#else
    const char *errfmt = "broken symbolic link to `%s'";
#endif
    if (ms->flags & RZ_MAGIC_ERROR) {
        file_error(ms, err, errfmt, buf);
        return -1;
    }
    if (file_printf(ms, errfmt, buf) == -1)
        return -1;
    return 1;
}
 
int file_fsmagic(struct rz_magic_set *ms, const char *fn, struct stat *sb) {
    int ret = 0;
    int mime = ms->flags & RZ_MAGIC_MIME;
#ifdef S_IFLNK
    char buf[BUFSIZ + 4];
    int nch;
    struct stat tstatbuf;
#endif
    if (!fn)
        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 & RZ_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 & RZ_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;
        return 1;
    }
 
    if (mime) {
        if ((sb->st_mode & S_IFMT) != S_IFREG) {
            if ((mime & RZ_MAGIC_MIME_TYPE) &&
                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 & RZ_MAGIC_DEVICES) != 0)
            break;
#ifdef HAVE_STAT_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 & RZ_MAGIC_DEVICES) != 0)
            break;
#ifdef HAVE_STAT_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 ((ms->flags & RZ_MAGIC_DEVICES) != 0)
            break;
        if (file_printf(ms, "fifo (named pipe)") == -1)
            return -1;
        return 1;
#endif
#ifdef S_IFDOOR
    case S_IFDOOR:
        return (file_printf(ms, "door") == -1) ? -1 : 1;
#endif
#ifdef S_IFLNK
    case S_IFLNK:
        if ((nch = readlink(fn, buf, BUFSIZ - 1)) <= 0) {
            if (ms->flags & RZ_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) does not do this */
 
        /* If broken symlink, say so and quit early. */
        if (*buf == '/') {
            if (stat(buf, &tstatbuf) < 0)
                return bad_link(ms, errno, buf);
        } else {
            char *tmp;
            char buf2[BUFSIZ + BUFSIZ + 4];
 
            if (!(tmp = strrchr(fn, '/'))) {
                tmp = buf; /* in current directory anyway */
            } else {
                if (tmp - fn + 1 > BUFSIZ) {
                    if (ms->flags & RZ_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;
                }
                snprintf(buf2, sizeof(buf2), "%s%s", fn, buf);
                tmp = buf2;
            }
            if (stat(tmp, &tstatbuf) < 0)
                return bad_link(ms, errno, buf);
        }
 
        /* Otherwise, handle it. */
        if ((ms->flags & RZ_MAGIC_SYMLINK) != 0) {
            const char *p;
            ms->flags &= RZ_MAGIC_SYMLINK;
            p = rz_magic_file(ms, buf);
            ms->flags |= RZ_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
    case S_IFSOCK:
        if (file_printf(ms, "socket") == -1)
            return -1;
        return 1;
#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 & RZ_MAGIC_DEVICES) == 0 && sb->st_size == 0) {
        if ((!mime || (mime & RZ_MAGIC_MIME_TYPE)) &&
            file_printf(ms, mime ? "application/x-empty" : "empty") == -1)
            return -1;
        return 1;
    }
    return 0;
}
#endif