1/*-
2 * SPDX-License-Identifier: BSD-2-Clause
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/param.h>
31#include <sys/systm.h>
32#include <sys/kernel.h>
33#include <sys/malloc.h>
34
35#include <geom/geom.h>
36#include <geom/geom_dbg.h>
37#include <geom/label/g_label.h>
38#include <geom/label/g_label_msdosfs.h>
39
40#define LABEL_NO_NAME		"NO NAME    "
41
42static void
43g_label_msdosfs_taste(struct g_consumer *cp, char *label, size_t size)
44{
45	struct g_provider *pp;
46	FAT_BSBPB *pfat_bsbpb;
47	FAT32_BSBPB *pfat32_bsbpb;
48	FAT_DES *pfat_entry;
49	uint8_t *sector0, *sector;
50	size_t copysize;
51
52	g_topology_assert_not();
53	pp = cp->provider;
54	sector0 = NULL;
55	sector = NULL;
56	bzero(label, size);
57
58	/* Check if the sector size of the medium is a valid FAT sector size. */
59	switch(pp->sectorsize) {
60	case 512:
61	case 1024:
62	case 2048:
63	case 4096:
64		break;
65	default:
66		G_LABEL_DEBUG(1, "MSDOSFS: %s: sector size %d not compatible.",
67		    pp->name, pp->sectorsize);
68		return;
69	}
70
71	/* Load 1st sector with boot sector and boot parameter block. */
72	sector0 = (uint8_t *)g_read_data(cp, 0, pp->sectorsize, NULL);
73	if (sector0 == NULL)
74		return;
75
76	/* Check for the FAT boot sector signature. */
77	if (sector0[510] != 0x55 || sector0[511] != 0xaa) {
78		G_LABEL_DEBUG(1, "MSDOSFS: %s: no FAT signature found.",
79		    pp->name);
80		goto error;
81	}
82
83	/*
84	 * Test if this is really a FAT volume and determine the FAT type.
85	 */
86
87	pfat_bsbpb = (FAT_BSBPB *)sector0;
88	pfat32_bsbpb = (FAT32_BSBPB *)sector0;
89
90	if (UINT16BYTES(pfat_bsbpb->BPB_FATSz16) != 0) {
91		/*
92		 * If the BPB_FATSz16 field is not zero and the string "FAT" is
93		 * at the right place, this should be a FAT12 or FAT16 volume.
94		 */
95		if (strncmp(pfat_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
96			G_LABEL_DEBUG(1,
97			    "MSDOSFS: %s: FAT12/16 volume not valid.",
98			    pp->name);
99			goto error;
100		}
101		G_LABEL_DEBUG(1, "MSDOSFS: %s: FAT12/FAT16 volume detected.",
102		    pp->name);
103
104		/* A volume with no name should have "NO NAME    " as label. */
105		if (strncmp(pfat_bsbpb->BS_VolLab, LABEL_NO_NAME,
106		    sizeof(pfat_bsbpb->BS_VolLab)) == 0) {
107			G_LABEL_DEBUG(1,
108			    "MSDOSFS: %s: FAT12/16 volume has no name.",
109			    pp->name);
110			goto error;
111		}
112		copysize = MIN(size - 1, sizeof(pfat_bsbpb->BS_VolLab));
113		memcpy(label, pfat_bsbpb->BS_VolLab, copysize);
114		label[copysize] = '\0';
115	} else if (UINT32BYTES(pfat32_bsbpb->BPB_FATSz32) != 0) {
116		uint32_t fat_FirstDataSector, fat_BytesPerSector, offset;
117
118		/*
119		 * If the BPB_FATSz32 field is not zero and the string "FAT" is
120		 * at the right place, this should be a FAT32 volume.
121		 */
122		if (strncmp(pfat32_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
123			G_LABEL_DEBUG(1, "MSDOSFS: %s: FAT32 volume not valid.",
124			    pp->name);
125			goto error;
126		}
127		G_LABEL_DEBUG(1, "MSDOSFS: %s: FAT32 volume detected.",
128		    pp->name);
129
130		/*
131		 * If the volume label is not "NO NAME    " we're done.
132		 */
133		if (strncmp(pfat32_bsbpb->BS_VolLab, LABEL_NO_NAME,
134		    sizeof(pfat32_bsbpb->BS_VolLab)) != 0) {
135			copysize = MIN(size - 1,
136			    sizeof(pfat32_bsbpb->BS_VolLab));
137			memcpy(label, pfat32_bsbpb->BS_VolLab, copysize);
138			label[copysize] = '\0';
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		if (fat_BytesPerSector == 0 ||
157		    fat_BytesPerSector % pp->sectorsize != 0) {
158			G_LABEL_DEBUG(1, "MSDOSFS: %s: corrupted BPB",
159			    pp->name);
160			goto error;
161		}
162
163		for (offset = fat_BytesPerSector * fat_FirstDataSector;;
164		    offset += fat_BytesPerSector) {
165			sector = (uint8_t *)g_read_data(cp, offset,
166			    fat_BytesPerSector, NULL);
167			if (sector == NULL)
168				goto error;
169
170			pfat_entry = (FAT_DES *)sector;
171			do {
172				/* No more entries available. */
173				if (pfat_entry->DIR_Name[0] == 0) {
174					G_LABEL_DEBUG(1, "MSDOSFS: %s: "
175					    "FAT32 volume has no name.",
176					    pp->name);
177					goto error;
178				}
179
180				/* Skip empty or long name entries. */
181				if (pfat_entry->DIR_Name[0] == 0xe5 ||
182				    (pfat_entry->DIR_Attr &
183				     FAT_DES_ATTR_LONG_NAME) ==
184				    FAT_DES_ATTR_LONG_NAME) {
185					continue;
186				}
187
188				/*
189				 * The name of the entry is the volume label if
190				 * ATTR_VOLUME_ID is set.
191				 */
192				if (pfat_entry->DIR_Attr &
193				    FAT_DES_ATTR_VOLUME_ID) {
194					copysize = MIN(size - 1,
195					    sizeof(pfat_entry->DIR_Name));
196					memcpy(label, pfat_entry->DIR_Name,
197					    copysize);
198					label[copysize] = '\0';
199					goto endofchecks;
200				}
201			} while((uint8_t *)(++pfat_entry) <
202			    (uint8_t *)(sector + fat_BytesPerSector));
203			g_free(sector);
204		}
205	} else {
206		G_LABEL_DEBUG(1, "MSDOSFS: %s: no FAT volume detected.",
207		    pp->name);
208		goto error;
209	}
210
211endofchecks:
212	g_label_rtrim(label, size);
213
214error:
215	g_free(sector0);
216	g_free(sector);
217}
218
219struct g_label_desc g_label_msdosfs = {
220	.ld_taste = g_label_msdosfs_taste,
221	.ld_dirprefix = "msdosfs/",
222	.ld_enabled = 1
223};
224
225G_LABEL_INIT(msdosfs, g_label_msdosfs, "Create device nodes for MSDOSFS volumes");
226