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@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
34void 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
53static 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
133static 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
148const 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