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 #include <stdio.h>
34 #include <stdlib.h>
35 #include <string.h>
36
37 #include "fstyp.h"
38 #include "msdosfs.h"
39
40 #define LABEL_NO_NAME "NO NAME "
41
42 /*
43 * XXX the signature 0x55 0xAA as the last two bytes of 512 is not required
44 * by specifications, but was historically required by fstyp. This check
45 * should be removed, with a more comprehensive BPB validation instead.
46 */
47 static bool
check_signature(uint8_t sector0[512])48 check_signature(uint8_t sector0[512])
49 {
50 /* Check for the FAT boot sector signature. */
51 if (sector0[510] == 0x55 && sector0[511] == 0xaa)
52 return (true);
53 /* Special case for Raspberry Pi Pico bootloader. */
54 if (sector0[510] == 0 && sector0[511] == 0 &&
55 sector0[0] == 0xeb && sector0[1] == 0x3c && sector0[2] == 0x90)
56 return (true);
57 return (false);
58 }
59
60 int
fstyp_msdosfs(FILE * fp,char * label,size_t size)61 fstyp_msdosfs(FILE *fp, char *label, size_t size)
62 {
63 FAT_BSBPB *pfat_bsbpb;
64 FAT32_BSBPB *pfat32_bsbpb;
65 FAT_DES *pfat_entry;
66 uint8_t *sector0, *sector;
67 size_t copysize;
68
69 sector0 = NULL;
70 sector = NULL;
71
72 /* Load 1st sector with boot sector and boot parameter block. */
73 sector0 = (uint8_t *)read_buf(fp, 0, 512);
74 if (sector0 == NULL)
75 return (1);
76
77 if (!check_signature(sector0)) {
78 goto error;
79 }
80
81 /*
82 * Test if this is really a FAT volume and determine the FAT type.
83 */
84
85 pfat_bsbpb = (FAT_BSBPB *)sector0;
86 pfat32_bsbpb = (FAT32_BSBPB *)sector0;
87
88 if (UINT16BYTES(pfat_bsbpb->BPB_FATSz16) != 0) {
89 /*
90 * If the BPB_FATSz16 field is not zero and the string "FAT" is
91 * at the right place, this should be a FAT12 or FAT16 volume.
92 */
93 if (strncmp(pfat_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
94 goto error;
95 }
96
97 /* A volume with no name should have "NO NAME " as label. */
98 if (strncmp(pfat_bsbpb->BS_VolLab, LABEL_NO_NAME,
99 sizeof(pfat_bsbpb->BS_VolLab)) == 0) {
100 goto endofchecks;
101 }
102 copysize = MIN(size - 1, sizeof(pfat_bsbpb->BS_VolLab));
103 memcpy(label, pfat_bsbpb->BS_VolLab, copysize);
104 label[copysize] = '\0';
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 copysize = MIN(size - 1,
122 sizeof(pfat32_bsbpb->BS_VolLab));
123 memcpy(label, pfat32_bsbpb->BS_VolLab, copysize);
124 label[copysize] = '\0';
125 goto endofchecks;
126 }
127
128 /*
129 * If the volume label "NO NAME " is in the boot sector, the
130 * label of FAT32 volumes may be stored as a special entry in
131 * the root directory.
132 */
133 fat_FirstDataSector =
134 UINT16BYTES(pfat32_bsbpb->BPB_RsvdSecCnt) +
135 (pfat32_bsbpb->BPB_NumFATs *
136 UINT32BYTES(pfat32_bsbpb->BPB_FATSz32));
137 fat_BytesPerSector = UINT16BYTES(pfat32_bsbpb->BPB_BytsPerSec);
138
139 // fat_FirstDataSector, fat_BytesPerSector);
140
141 for (offset = fat_BytesPerSector * fat_FirstDataSector;;
142 offset += fat_BytesPerSector) {
143 sector = (uint8_t *)read_buf(fp, offset, fat_BytesPerSector);
144 if (sector == NULL)
145 goto error;
146
147 pfat_entry = (FAT_DES *)sector;
148 do {
149 /* No more entries available. */
150 if (pfat_entry->DIR_Name[0] == 0) {
151 goto endofchecks;
152 }
153
154 /* Skip empty or long name entries. */
155 if (pfat_entry->DIR_Name[0] == 0xe5 ||
156 (pfat_entry->DIR_Attr &
157 FAT_DES_ATTR_LONG_NAME) ==
158 FAT_DES_ATTR_LONG_NAME) {
159 continue;
160 }
161
162 /*
163 * The name of the entry is the volume label if
164 * ATTR_VOLUME_ID is set.
165 */
166 if (pfat_entry->DIR_Attr &
167 FAT_DES_ATTR_VOLUME_ID) {
168 copysize = MIN(size - 1,
169 sizeof(pfat_entry->DIR_Name));
170 memcpy(label, pfat_entry->DIR_Name,
171 copysize);
172 label[copysize] = '\0';
173 goto endofchecks;
174 }
175 } while((uint8_t *)(++pfat_entry) <
176 (uint8_t *)(sector + fat_BytesPerSector));
177 free(sector);
178 }
179 } else {
180 goto error;
181 }
182
183 endofchecks:
184 rtrim(label, size);
185
186 free(sector0);
187 free(sector);
188
189 return (0);
190
191 error:
192 free(sector0);
193 free(sector);
194
195 return (1);
196 }
197