1/*	$NetBSD: msdosfs.c,v 1.1 2018/01/09 03:31:15 christos Exp $	*/
2
3/*-
4 * Copyright (c) 2017 The NetBSD Foundation, Inc.
5 * Copyright (c) 2016 The DragonFly Project
6 * Copyright (c) 2004 Pawel Jakub Dawidek <pjd@FreeBSD.org>
7 * Copyright (c) 2006 Tobias Reifenberger
8 * Copyright (c) 2014 The FreeBSD Foundation
9 * All rights reserved.
10 *
11 * This code is derived from software contributed to The NetBSD Foundation
12 * by Tomohiro Kusumi <kusumi.tomohiro@gmail.com>.
13 *
14 * This software was developed by Edward Tomasz Napierala under sponsorship
15 * from the FreeBSD Foundation.
16 *
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions
19 * are met:
20 * 1. Redistributions of source code must retain the above copyright
21 *    notice, this list of conditions and the following disclaimer.
22 * 2. Redistributions in binary form must reproduce the above copyright
23 *    notice, this list of conditions and the following disclaimer in the
24 *    documentation and/or other materials provided with the distribution.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * SUCH DAMAGE.
37 */
38#include <sys/cdefs.h>
39__RCSID("$NetBSD: msdosfs.c,v 1.1 2018/01/09 03:31:15 christos Exp $");
40
41#include <sys/param.h>
42#include <stdio.h>
43#include <stdlib.h>
44#include <string.h>
45
46#include "fstyp.h"
47#include "msdosfs.h"
48
49#define LABEL_NO_NAME		"NO NAME    "
50
51int
52fstyp_msdosfs(FILE *fp, char *label, size_t size)
53{
54	FAT_BSBPB *pfat_bsbpb;
55	FAT32_BSBPB *pfat32_bsbpb;
56	FAT_DES *pfat_entry;
57	uint8_t *sector0, *sector;
58
59	sector0 = NULL;
60	sector = NULL;
61
62	/* Load 1st sector with boot sector and boot parameter block. */
63	sector0 = read_buf(fp, 0, 512);
64	if (sector0 == NULL)
65		return 1;
66
67	/* Check for the FAT boot sector signature. */
68	if (sector0[510] != 0x55 || sector0[511] != 0xaa) {
69		goto error;
70	}
71
72	/*
73	 * Test if this is really a FAT volume and determine the FAT type.
74	 */
75
76	pfat_bsbpb = (FAT_BSBPB *)sector0;
77	pfat32_bsbpb = (FAT32_BSBPB *)sector0;
78
79	if (UINT16BYTES(pfat_bsbpb->BPB_FATSz16) != 0) {
80		/*
81		 * If the BPB_FATSz16 field is not zero and the string "FAT" is
82		 * at the right place, this should be a FAT12 or FAT16 volume.
83		 */
84		if (strncmp((char*)pfat_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
85			goto error;
86		}
87
88		/* A volume with no name should have "NO NAME    " as label. */
89		if (strncmp((char*)pfat_bsbpb->BS_VolLab, LABEL_NO_NAME,
90		    sizeof(pfat_bsbpb->BS_VolLab)) == 0) {
91			goto endofchecks;
92		}
93		strlcpy(label, (char*)pfat_bsbpb->BS_VolLab,
94		    MIN(size, sizeof(pfat_bsbpb->BS_VolLab) + 1));
95	} else if (UINT32BYTES(pfat32_bsbpb->BPB_FATSz32) != 0) {
96		uint32_t fat_FirstDataSector, fat_BytesPerSector, offset;
97
98		/*
99		 * If the BPB_FATSz32 field is not zero and the string "FAT" is
100		 * at the right place, this should be a FAT32 volume.
101		 */
102		if (strncmp((char*)pfat32_bsbpb->BS_FilSysType, "FAT", 3) != 0)
103		{
104			goto error;
105		}
106
107		/*
108		 * If the volume label is not "NO NAME    " we're done.
109		 */
110		if (strncmp((char*)pfat32_bsbpb->BS_VolLab, LABEL_NO_NAME,
111		    sizeof(pfat32_bsbpb->BS_VolLab)) != 0) {
112			strlcpy(label, (char*)pfat32_bsbpb->BS_VolLab,
113			    MIN(size, sizeof(pfat32_bsbpb->BS_VolLab) + 1));
114			goto endofchecks;
115		}
116
117		/*
118		 * If the volume label "NO NAME    " is in the boot sector, the
119		 * label of FAT32 volumes may be stored as a special entry in
120		 * the root directory.
121		 */
122		fat_FirstDataSector =
123		    UINT16BYTES(pfat32_bsbpb->BPB_RsvdSecCnt) +
124		    (pfat32_bsbpb->BPB_NumFATs *
125		     UINT32BYTES(pfat32_bsbpb->BPB_FATSz32));
126		fat_BytesPerSector = UINT16BYTES(pfat32_bsbpb->BPB_BytsPerSec);
127
128		//    fat_FirstDataSector, fat_BytesPerSector);
129
130		for (offset = fat_BytesPerSector * fat_FirstDataSector;;
131		    offset += fat_BytesPerSector) {
132			sector = read_buf(fp, offset, fat_BytesPerSector);
133			if (sector == NULL)
134				goto error;
135
136			pfat_entry = (FAT_DES *)sector;
137			do {
138				/* No more entries available. */
139				if (pfat_entry->DIR_Name[0] == 0) {
140					goto endofchecks;
141				}
142
143				/* Skip empty or long name entries. */
144				if (pfat_entry->DIR_Name[0] == 0xe5 ||
145				    (pfat_entry->DIR_Attr &
146				     FAT_DES_ATTR_LONG_NAME) ==
147				    FAT_DES_ATTR_LONG_NAME) {
148					continue;
149				}
150
151				/*
152				 * The name of the entry is the volume label if
153				 * ATTR_VOLUME_ID is set.
154				 */
155				if (pfat_entry->DIR_Attr &
156				    FAT_DES_ATTR_VOLUME_ID) {
157					strlcpy(label, (char*)pfat_entry->DIR_Name,
158					    MIN(size,
159					    sizeof(pfat_entry->DIR_Name) + 1));
160					goto endofchecks;
161				}
162			} while((uint8_t *)(++pfat_entry) <
163			    (uint8_t *)(sector + fat_BytesPerSector));
164			free(sector);
165		}
166	} else {
167		goto error;
168	}
169
170endofchecks:
171	rtrim(label, size);
172
173	free(sector0);
174	free(sector);
175
176	return (0);
177
178error:
179	free(sector0);
180	free(sector);
181
182	return (1);
183}
184