1 /*-
2 * Copyright (c) 2004 Pawel Jakub Dawidek <[email protected]>
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("$FreeBSD$");
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
44 /*
45 * XXX the signature 0x55 0xAA as the last two bytes of 512 is not required
46 * by specifications, but was historically required by fstyp. This check
47 * should be removed, with a more comprehensive BPB validation instead.
48 */
49 static bool
check_signature(uint8_t sector0[512])50 check_signature(uint8_t sector0[512])
51 {
52 /* Check for the FAT boot sector signature. */
53 if (sector0[510] == 0x55 && sector0[511] == 0xaa)
54 return (true);
55 /* Special case for Raspberry Pi Pico bootloader. */
56 if (sector0[510] == 0 && sector0[511] == 0 &&
57 sector0[0] == 0xeb && sector0[1] == 0x3c && sector0[2] == 0x90)
58 return (true);
59 return (false);
60 }
61
62 int
fstyp_msdosfs(FILE * fp,char * label,size_t size)63 fstyp_msdosfs(FILE *fp, char *label, size_t size)
64 {
65 FAT_BSBPB *pfat_bsbpb;
66 FAT32_BSBPB *pfat32_bsbpb;
67 FAT_DES *pfat_entry;
68 uint8_t *sector0, *sector;
69
70 sector0 = NULL;
71 sector = NULL;
72
73 /* Load 1st sector with boot sector and boot parameter block. */
74 sector0 = (uint8_t *)read_buf(fp, 0, 512);
75 if (sector0 == NULL)
76 return (1);
77
78 if (!check_signature(sector0)) {
79 goto error;
80 }
81
82 /*
83 * Test if this is really a FAT volume and determine the FAT type.
84 */
85
86 pfat_bsbpb = (FAT_BSBPB *)sector0;
87 pfat32_bsbpb = (FAT32_BSBPB *)sector0;
88
89 if (UINT16BYTES(pfat_bsbpb->BPB_FATSz16) != 0) {
90 /*
91 * If the BPB_FATSz16 field is not zero and the string "FAT" is
92 * at the right place, this should be a FAT12 or FAT16 volume.
93 */
94 if (strncmp(pfat_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
95 goto error;
96 }
97
98 /* A volume with no name should have "NO NAME " as label. */
99 if (strncmp(pfat_bsbpb->BS_VolLab, LABEL_NO_NAME,
100 sizeof(pfat_bsbpb->BS_VolLab)) == 0) {
101 goto endofchecks;
102 }
103 strlcpy(label, pfat_bsbpb->BS_VolLab,
104 MIN(size, sizeof(pfat_bsbpb->BS_VolLab) + 1));
105 } else if (UINT32BYTES(pfat32_bsbpb->BPB_FATSz32) != 0) {
106 uint32_t fat_FirstDataSector, fat_BytesPerSector, offset;
107
108 /*
109 * If the BPB_FATSz32 field is not zero and the string "FAT" is
110 * at the right place, this should be a FAT32 volume.
111 */
112 if (strncmp(pfat32_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
113 goto error;
114 }
115
116 /*
117 * If the volume label is not "NO NAME " we're done.
118 */
119 if (strncmp(pfat32_bsbpb->BS_VolLab, LABEL_NO_NAME,
120 sizeof(pfat32_bsbpb->BS_VolLab)) != 0) {
121 strlcpy(label, pfat32_bsbpb->BS_VolLab,
122 MIN(size, sizeof(pfat32_bsbpb->BS_VolLab) + 1));
123 goto endofchecks;
124 }
125
126 /*
127 * If the volume label "NO NAME " is in the boot sector, the
128 * label of FAT32 volumes may be stored as a special entry in
129 * the root directory.
130 */
131 fat_FirstDataSector =
132 UINT16BYTES(pfat32_bsbpb->BPB_RsvdSecCnt) +
133 (pfat32_bsbpb->BPB_NumFATs *
134 UINT32BYTES(pfat32_bsbpb->BPB_FATSz32));
135 fat_BytesPerSector = UINT16BYTES(pfat32_bsbpb->BPB_BytsPerSec);
136
137 // fat_FirstDataSector, fat_BytesPerSector);
138
139 for (offset = fat_BytesPerSector * fat_FirstDataSector;;
140 offset += fat_BytesPerSector) {
141 sector = (uint8_t *)read_buf(fp, offset, fat_BytesPerSector);
142 if (sector == NULL)
143 goto error;
144
145 pfat_entry = (FAT_DES *)sector;
146 do {
147 /* No more entries available. */
148 if (pfat_entry->DIR_Name[0] == 0) {
149 goto endofchecks;
150 }
151
152 /* Skip empty or long name entries. */
153 if (pfat_entry->DIR_Name[0] == 0xe5 ||
154 (pfat_entry->DIR_Attr &
155 FAT_DES_ATTR_LONG_NAME) ==
156 FAT_DES_ATTR_LONG_NAME) {
157 continue;
158 }
159
160 /*
161 * The name of the entry is the volume label if
162 * ATTR_VOLUME_ID is set.
163 */
164 if (pfat_entry->DIR_Attr &
165 FAT_DES_ATTR_VOLUME_ID) {
166 strlcpy(label, pfat_entry->DIR_Name,
167 MIN(size,
168 sizeof(pfat_entry->DIR_Name) + 1));
169 goto endofchecks;
170 }
171 } while((uint8_t *)(++pfat_entry) <
172 (uint8_t *)(sector + fat_BytesPerSector));
173 free(sector);
174 }
175 } else {
176 goto error;
177 }
178
179 endofchecks:
180 rtrim(label, size);
181
182 free(sector0);
183 free(sector);
184
185 return (0);
186
187 error:
188 free(sector0);
189 free(sector);
190
191 return (1);
192 }
193