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      1 /* ----------------------------------------------------------------------- *
      2  *
      3  *   Copyright 1998-2011 H. Peter Anvin - All Rights Reserved
      4  *   Copyright 2009-2011 Intel Corporation; author H. Peter Anvin
      5  *   Copyright 2011 Paulo Alcantara <pcacjr (at) gmail.com>
      6  *
      7  *   This program is free software; you can redistribute it and/or modify
      8  *   it under the terms of the GNU General Public License as published by
      9  *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
     10  *   Boston MA 02111-1307, USA; either version 2 of the License, or
     11  *   (at your option) any later version; incorporated herein by reference.
     12  *
     13  * ----------------------------------------------------------------------- */
     14 
     15 /*
     16  * fs.c - Generic sanity check for FAT/NTFS-based installers
     17  */
     18 
     19 #define _XOPEN_SOURCE 500	/* Required on glibc 2.x */
     20 #define _BSD_SOURCE
     21 /* glibc 2.20 deprecates _BSD_SOURCE in favour of _DEFAULT_SOURCE */
     22 #define _DEFAULT_SOURCE 1
     23 #include <stdio.h>
     24 #include <inttypes.h>
     25 #include <string.h>
     26 #include <stddef.h>
     27 #include <stdlib.h>
     28 
     29 #include "syslinux.h"
     30 #include "syslxint.h"
     31 #include "syslxcom.h"
     32 #include "syslxfs.h"
     33 
     34 void syslinux_make_bootsect(void *bs, int fs_type)
     35 {
     36     if (fs_type == VFAT) {
     37 	struct fat_boot_sector *bootsect = bs;
     38 	const struct fat_boot_sector *sbs =
     39 	    (const struct fat_boot_sector *)boot_sector;
     40 
     41 	memcpy(&bootsect->FAT_bsHead, &sbs->FAT_bsHead, FAT_bsHeadLen);
     42 	memcpy(&bootsect->FAT_bsCode, &sbs->FAT_bsCode, FAT_bsCodeLen);
     43     } else if (fs_type == NTFS) {
     44 	struct ntfs_boot_sector *bootsect = bs;
     45 	const struct ntfs_boot_sector *sbs =
     46 	    (const struct ntfs_boot_sector *)boot_sector;
     47 
     48 	memcpy(&bootsect->NTFS_bsHead, &sbs->NTFS_bsHead, NTFS_bsHeadLen);
     49 	memcpy(&bootsect->NTFS_bsCode, &sbs->NTFS_bsCode, NTFS_bsCodeLen);
     50     }
     51 }
     52 
     53 static const char *check_fat_bootsect(const void *bs, int *fs_type)
     54 {
     55     int sectorsize;
     56     const struct fat_boot_sector *sectbuf = bs;
     57     long long sectors, fatsectors, dsectors;
     58     long long clusters;
     59     int rootdirents, clustersize;
     60 
     61     sectorsize = get_16(&sectbuf->bsBytesPerSec);
     62 
     63     clustersize = get_8(&sectbuf->bsSecPerClust);
     64     if (clustersize == 0 || (clustersize & (clustersize - 1)))
     65 	return "impossible cluster size on an FAT volume";
     66 
     67     sectors = get_16(&sectbuf->bsSectors);
     68     sectors = sectors ? sectors : get_32(&sectbuf->bsHugeSectors);
     69 
     70     dsectors = sectors - get_16(&sectbuf->bsResSectors);
     71 
     72     fatsectors = get_16(&sectbuf->bsFATsecs);
     73     fatsectors = fatsectors ? fatsectors : get_32(&sectbuf->bs32.FATSz32);
     74     fatsectors *= get_8(&sectbuf->bsFATs);
     75     dsectors -= fatsectors;
     76 
     77     rootdirents = get_16(&sectbuf->bsRootDirEnts);
     78     dsectors -= (rootdirents + sectorsize / 32 - 1) / sectorsize;
     79 
     80     if (dsectors < 0)
     81 	return "negative number of data sectors on an FAT volume";
     82 
     83     clusters = dsectors / clustersize;
     84 
     85     fatsectors = get_16(&sectbuf->bsFATsecs);
     86     fatsectors = fatsectors ? fatsectors : get_32(&sectbuf->bs32.FATSz32);
     87     fatsectors *= get_8(&sectbuf->bsFATs);
     88 
     89     if (!fatsectors)
     90 	return "zero FAT sectors";
     91 
     92     if (clusters < 0xFFF5) {
     93 	/* FAT12 or FAT16 */
     94 	if (!get_16(&sectbuf->bsFATsecs))
     95 	    return "zero FAT sectors (FAT12/16)";
     96 
     97 	if (get_8(&sectbuf->bs16.BootSignature) == 0x29) {
     98 	    if (!memcmp(&sectbuf->bs16.FileSysType, "FAT12   ", 8)) {
     99 		if (clusters >= 0xFF5)
    100 		    return "more than 4084 clusters but claims FAT12";
    101 	    } else if (!memcmp(&sectbuf->bs16.FileSysType, "FAT16   ", 8)) {
    102 		if (clusters < 0xFF5)
    103 		    return "less than 4084 clusters but claims FAT16";
    104 	    } else if (!memcmp(&sectbuf->bs16.FileSysType, "FAT32   ", 8)) {
    105 		return "less than 65525 clusters but claims FAT32";
    106 	    } else if (memcmp(&sectbuf->bs16.FileSysType, "FAT     ", 8)) {
    107 		static char fserr[] = "filesystem type \"????????\" not "
    108 		    "supported";
    109 		memcpy(fserr + 17, &sectbuf->bs16.FileSysType, 8);
    110 		return fserr;
    111 	    }
    112 	}
    113     } else if (clusters < 0x0FFFFFF5) {
    114 	/*
    115 	 * FAT32...
    116 	 *
    117 	 * Moving the FileSysType and BootSignature was a lovely stroke
    118 	 * of M$ idiocy...
    119 	 */
    120 	if (get_8(&sectbuf->bs32.BootSignature) != 0x29 ||
    121 	    memcmp(&sectbuf->bs32.FileSysType, "FAT32   ", 8))
    122 	    return "missing FAT32 signature";
    123     } else {
    124 	return "impossibly large number of clusters on an FAT volume";
    125     }
    126 
    127     if (fs_type)
    128 	*fs_type = VFAT;
    129 
    130     return NULL;
    131 }
    132 
    133 static const char *check_ntfs_bootsect(const void *bs, int *fs_type)
    134 {
    135     const struct ntfs_boot_sector *sectbuf = bs;
    136 
    137     if (memcmp(&sectbuf->bsOemName, "NTFS    ", 8) &&
    138 	memcmp(&sectbuf->bsOemName, "MSWIN4.0", 8) &&
    139 	memcmp(&sectbuf->bsOemName, "MSWIN4.1", 8))
    140 	return "unknown OEM name but claims NTFS";
    141 
    142     if (fs_type)
    143 	*fs_type = NTFS;
    144 
    145     return NULL;
    146 }
    147 
    148 const char *syslinux_check_bootsect(const void *bs, int *fs_type)
    149 {
    150     uint8_t media_sig;
    151     int sectorsize;
    152     const struct fat_boot_sector *sectbuf = bs;
    153     const char *retval;
    154 
    155     media_sig = get_8(&sectbuf->bsMedia);
    156     /* Must be 0xF0 or 0xF8-0xFF for FAT/NTFS volumes */
    157     if (media_sig != 0xF0 && media_sig < 0xF8)
    158 	return "invalid media signature (not an FAT/NTFS volume?)";
    159 
    160     sectorsize = get_16(&sectbuf->bsBytesPerSec);
    161     if (sectorsize == SECTOR_SIZE) ;	/* ok */
    162     else if (sectorsize >= 512 && sectorsize <= 4096 &&
    163 	     (sectorsize & (sectorsize - 1)) == 0)
    164 	return "unsupported sectors size";
    165     else
    166 	return "impossible sector size";
    167 
    168     if (ntfs_check_zero_fields((struct ntfs_boot_sector *)bs))
    169 	retval = check_ntfs_bootsect(bs, fs_type);
    170     else
    171 	retval = check_fat_bootsect(bs, fs_type);
    172 
    173     return retval;
    174 }
    175