1/*-
2 * Copyright (c) 2004 Pawel Jakub Dawidek <pjd@FreeBSD.org>
3 * Copyright (c) 2006 Tobias Reifenberger
4 * Copyright (c) 2014 The FreeBSD Foundation
5 * All rights reserved.
6 *
7 * This software was developed by Edward Tomasz Napierala under sponsorship
8 * from the FreeBSD Foundation.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32#include <sys/cdefs.h>
33__FBSDID("$FreeBSD: releng/10.3/usr.sbin/fstyp/msdosfs.c 286193 2015-08-02 10:08:57Z trasz $");
34
35#include <stdio.h>
36#include <stdlib.h>
37#include <string.h>
38
39#include "fstyp.h"
40#include "msdosfs.h"
41
42#define LABEL_NO_NAME		"NO NAME    "
43
44int
45fstyp_msdosfs(FILE *fp, char *label, size_t size)
46{
47	FAT_BSBPB *pfat_bsbpb;
48	FAT32_BSBPB *pfat32_bsbpb;
49	FAT_DES *pfat_entry;
50	uint8_t *sector0, *sector;
51
52	sector0 = NULL;
53	sector = NULL;
54
55	/* Load 1st sector with boot sector and boot parameter block. */
56	sector0 = (uint8_t *)read_buf(fp, 0, 512);
57	if (sector0 == NULL)
58		return (1);
59
60	/* Check for the FAT boot sector signature. */
61	if (sector0[510] != 0x55 || sector0[511] != 0xaa) {
62		goto error;
63	}
64
65	/*
66	 * Test if this is really a FAT volume and determine the FAT type.
67	 */
68
69	pfat_bsbpb = (FAT_BSBPB *)sector0;
70	pfat32_bsbpb = (FAT32_BSBPB *)sector0;
71
72	if (UINT16BYTES(pfat_bsbpb->BPB_FATSz16) != 0) {
73		/*
74		 * If the BPB_FATSz16 field is not zero and the string "FAT" is
75		 * at the right place, this should be a FAT12 or FAT16 volume.
76		 */
77		if (strncmp(pfat_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
78			goto error;
79		}
80
81		/* A volume with no name should have "NO NAME    " as label. */
82		if (strncmp(pfat_bsbpb->BS_VolLab, LABEL_NO_NAME,
83		    sizeof(pfat_bsbpb->BS_VolLab)) == 0) {
84			goto endofchecks;
85		}
86		strlcpy(label, pfat_bsbpb->BS_VolLab,
87		    MIN(size, sizeof(pfat_bsbpb->BS_VolLab) + 1));
88	} else if (UINT32BYTES(pfat32_bsbpb->BPB_FATSz32) != 0) {
89		uint32_t fat_FirstDataSector, fat_BytesPerSector, offset;
90
91		/*
92		 * If the BPB_FATSz32 field is not zero and the string "FAT" is
93		 * at the right place, this should be a FAT32 volume.
94		 */
95		if (strncmp(pfat32_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
96			goto error;
97		}
98
99		/*
100		 * If the volume label is not "NO NAME    " we're done.
101		 */
102		if (strncmp(pfat32_bsbpb->BS_VolLab, LABEL_NO_NAME,
103		    sizeof(pfat32_bsbpb->BS_VolLab)) != 0) {
104			strlcpy(label, pfat32_bsbpb->BS_VolLab,
105			    MIN(size, sizeof(pfat32_bsbpb->BS_VolLab) + 1));
106			goto endofchecks;
107		}
108
109		/*
110		 * If the volume label "NO NAME    " is in the boot sector, the
111		 * label of FAT32 volumes may be stored as a special entry in
112		 * the root directory.
113		 */
114		fat_FirstDataSector =
115		    UINT16BYTES(pfat32_bsbpb->BPB_RsvdSecCnt) +
116		    (pfat32_bsbpb->BPB_NumFATs *
117		     UINT32BYTES(pfat32_bsbpb->BPB_FATSz32));
118		fat_BytesPerSector = UINT16BYTES(pfat32_bsbpb->BPB_BytsPerSec);
119
120		//    fat_FirstDataSector, fat_BytesPerSector);
121
122		for (offset = fat_BytesPerSector * fat_FirstDataSector;;
123		    offset += fat_BytesPerSector) {
124			sector = (uint8_t *)read_buf(fp, offset, fat_BytesPerSector);
125			if (sector == NULL)
126				goto error;
127
128			pfat_entry = (FAT_DES *)sector;
129			do {
130				/* No more entries available. */
131				if (pfat_entry->DIR_Name[0] == 0) {
132					goto endofchecks;
133				}
134
135				/* Skip empty or long name entries. */
136				if (pfat_entry->DIR_Name[0] == 0xe5 ||
137				    (pfat_entry->DIR_Attr &
138				     FAT_DES_ATTR_LONG_NAME) ==
139				    FAT_DES_ATTR_LONG_NAME) {
140					continue;
141				}
142
143				/*
144				 * The name of the entry is the volume label if
145				 * ATTR_VOLUME_ID is set.
146				 */
147				if (pfat_entry->DIR_Attr &
148				    FAT_DES_ATTR_VOLUME_ID) {
149					strlcpy(label, pfat_entry->DIR_Name,
150					    MIN(size,
151					    sizeof(pfat_entry->DIR_Name) + 1));
152					goto endofchecks;
153				}
154			} while((uint8_t *)(++pfat_entry) <
155			    (uint8_t *)(sector + fat_BytesPerSector));
156			free(sector);
157		}
158	} else {
159		goto error;
160	}
161
162endofchecks:
163	rtrim(label, size);
164
165	free(sector0);
166	free(sector);
167
168	return (0);
169
170error:
171	free(sector0);
172	free(sector);
173
174	return (1);
175}
176