1/*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2004 Pawel Jakub Dawidek <pjd@FreeBSD.org>
5 * Copyright (c) 2006 Tobias Reifenberger
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30#include <sys/cdefs.h>
31__FBSDID("$FreeBSD$");
32
33#include <sys/param.h>
34#include <sys/systm.h>
35#include <sys/kernel.h>
36#include <sys/malloc.h>
37
38#include <geom/geom.h>
39#include <geom/label/g_label.h>
40#include <geom/label/g_label_msdosfs.h>
41
42#define G_LABEL_MSDOSFS_DIR	"msdosfs"
43#define LABEL_NO_NAME		"NO NAME    "
44
45static void
46g_label_msdosfs_taste(struct g_consumer *cp, char *label, size_t size)
47{
48	struct g_provider *pp;
49	FAT_BSBPB *pfat_bsbpb;
50	FAT32_BSBPB *pfat32_bsbpb;
51	FAT_DES *pfat_entry;
52	uint8_t *sector0, *sector;
53
54	g_topology_assert_not();
55	pp = cp->provider;
56	sector0 = NULL;
57	sector = NULL;
58	bzero(label, size);
59
60	/* Check if the sector size of the medium is a valid FAT sector size. */
61	switch(pp->sectorsize) {
62	case 512:
63	case 1024:
64	case 2048:
65	case 4096:
66		break;
67	default:
68		G_LABEL_DEBUG(1, "MSDOSFS: %s: sector size %d not compatible.",
69		    pp->name, pp->sectorsize);
70		return;
71	}
72
73	/* Load 1st sector with boot sector and boot parameter block. */
74	sector0 = (uint8_t *)g_read_data(cp, 0, pp->sectorsize, NULL);
75	if (sector0 == NULL)
76		return;
77
78	/* Check for the FAT boot sector signature. */
79	if (sector0[510] != 0x55 || sector0[511] != 0xaa) {
80		G_LABEL_DEBUG(1, "MSDOSFS: %s: no FAT signature found.",
81		    pp->name);
82		goto error;
83	}
84
85
86	/*
87	 * Test if this is really a FAT volume and determine the FAT type.
88	 */
89
90	pfat_bsbpb = (FAT_BSBPB *)sector0;
91	pfat32_bsbpb = (FAT32_BSBPB *)sector0;
92
93	if (UINT16BYTES(pfat_bsbpb->BPB_FATSz16) != 0) {
94		/*
95		 * If the BPB_FATSz16 field is not zero and the string "FAT" is
96		 * at the right place, this should be a FAT12 or FAT16 volume.
97		 */
98		if (strncmp(pfat_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
99			G_LABEL_DEBUG(1,
100			    "MSDOSFS: %s: FAT12/16 volume not valid.",
101			    pp->name);
102			goto error;
103		}
104		G_LABEL_DEBUG(1, "MSDOSFS: %s: FAT12/FAT16 volume detected.",
105		    pp->name);
106
107		/* A volume with no name should have "NO NAME    " as label. */
108		if (strncmp(pfat_bsbpb->BS_VolLab, LABEL_NO_NAME,
109		    sizeof(pfat_bsbpb->BS_VolLab)) == 0) {
110			G_LABEL_DEBUG(1,
111			    "MSDOSFS: %s: FAT12/16 volume has no name.",
112			    pp->name);
113			goto error;
114		}
115		strlcpy(label, pfat_bsbpb->BS_VolLab,
116		    MIN(size, sizeof(pfat_bsbpb->BS_VolLab) + 1));
117	} else if (UINT32BYTES(pfat32_bsbpb->BPB_FATSz32) != 0) {
118		uint32_t fat_FirstDataSector, fat_BytesPerSector, offset;
119
120		/*
121		 * If the BPB_FATSz32 field is not zero and the string "FAT" is
122		 * at the right place, this should be a FAT32 volume.
123		 */
124		if (strncmp(pfat32_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
125			G_LABEL_DEBUG(1, "MSDOSFS: %s: FAT32 volume not valid.",
126			    pp->name);
127			goto error;
128		}
129		G_LABEL_DEBUG(1, "MSDOSFS: %s: FAT32 volume detected.",
130		    pp->name);
131
132		/*
133		 * If the volume label is not "NO NAME    " we're done.
134		 */
135		if (strncmp(pfat32_bsbpb->BS_VolLab, LABEL_NO_NAME,
136		    sizeof(pfat32_bsbpb->BS_VolLab)) != 0) {
137			strlcpy(label, pfat32_bsbpb->BS_VolLab,
138			    MIN(size, sizeof(pfat32_bsbpb->BS_VolLab) + 1));
139			goto endofchecks;
140		}
141
142		/*
143		 * If the volume label "NO NAME    " is in the boot sector, the
144		 * label of FAT32 volumes may be stored as a special entry in
145		 * the root directory.
146		 */
147		fat_FirstDataSector =
148		    UINT16BYTES(pfat32_bsbpb->BPB_RsvdSecCnt) +
149		    (pfat32_bsbpb->BPB_NumFATs *
150		     UINT32BYTES(pfat32_bsbpb->BPB_FATSz32));
151		fat_BytesPerSector = UINT16BYTES(pfat32_bsbpb->BPB_BytsPerSec);
152
153		G_LABEL_DEBUG(2,
154		    "MSDOSFS: FAT_FirstDataSector=0x%x, FAT_BytesPerSector=%d",
155		    fat_FirstDataSector, fat_BytesPerSector);
156
157		for (offset = fat_BytesPerSector * fat_FirstDataSector;;
158		    offset += fat_BytesPerSector) {
159			sector = (uint8_t *)g_read_data(cp, offset,
160			    fat_BytesPerSector, NULL);
161			if (sector == NULL)
162				goto error;
163
164			pfat_entry = (FAT_DES *)sector;
165			do {
166				/* No more entries available. */
167				if (pfat_entry->DIR_Name[0] == 0) {
168					G_LABEL_DEBUG(1, "MSDOSFS: %s: "
169					    "FAT32 volume has no name.",
170					    pp->name);
171					goto error;
172				}
173
174				/* Skip empty or long name entries. */
175				if (pfat_entry->DIR_Name[0] == 0xe5 ||
176				    (pfat_entry->DIR_Attr &
177				     FAT_DES_ATTR_LONG_NAME) ==
178				    FAT_DES_ATTR_LONG_NAME) {
179					continue;
180				}
181
182				/*
183				 * The name of the entry is the volume label if
184				 * ATTR_VOLUME_ID is set.
185				 */
186				if (pfat_entry->DIR_Attr &
187				    FAT_DES_ATTR_VOLUME_ID) {
188					strlcpy(label, pfat_entry->DIR_Name,
189					    MIN(size,
190					    sizeof(pfat_entry->DIR_Name) + 1));
191					goto endofchecks;
192				}
193			} while((uint8_t *)(++pfat_entry) <
194			    (uint8_t *)(sector + fat_BytesPerSector));
195			g_free(sector);
196		}
197	} else {
198		G_LABEL_DEBUG(1, "MSDOSFS: %s: no FAT volume detected.",
199		    pp->name);
200		goto error;
201	}
202
203endofchecks:
204	g_label_rtrim(label, size);
205
206error:
207	if (sector0 != NULL)
208		g_free(sector0);
209	if (sector != NULL)
210		g_free(sector);
211}
212
213struct g_label_desc g_label_msdosfs = {
214	.ld_taste = g_label_msdosfs_taste,
215	.ld_dir = G_LABEL_MSDOSFS_DIR,
216	.ld_enabled = 1
217};
218
219G_LABEL_INIT(msdosfs, g_label_msdosfs, "Create device nodes for MSDOSFS volumes");
220