1 /*
2  * Copyright (C) 1995, 1997 Wolfgang Solfrank
3  * Copyright (c) 1995 Martin Husemann
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. All advertising materials mentioning features or use of this software
14  *    must display the following acknowledgement:
15  *	This product includes software developed by Martin Husemann
16  *	and Wolfgang Solfrank.
17  * 4. Neither the name of the University nor the names of its contributors
18  *    may be used to endorse or promote products derived from this software
19  *    without specific prior written permission.
20  *
21  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
22  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
23  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
24  * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
26  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
30  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31  */
32 
33 
34 #include <sys/cdefs.h>
35 #ifndef lint
36 __RCSID("$NetBSD: boot.c,v 1.9 2003/07/24 19:25:46 ws Exp $");
37 static const char rcsid[] =
38   "$FreeBSD: src/sbin/fsck_msdosfs/boot.c,v 1.4.28.1 2009/04/15 03:14:26 kensmith Exp $";
39 #endif /* not lint */
40 
41 #include <stdlib.h>
42 #include <string.h>
43 #include <ctype.h>
44 #include <stdio.h>
45 #include <unistd.h>
46 
47 #include "ext.h"
48 #include "fsutil.h"
49 
50 int
readboot(dosfs,boot)51 readboot(dosfs, boot)
52 	int dosfs;
53 	struct bootblock *boot;
54 {
55 	u_char block[DOSBOOTBLOCKSIZE];
56 	u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
57 	u_char backup[DOSBOOTBLOCKSIZE];
58 	int ret = FSOK;
59 
60 	if (read(dosfs, block, sizeof block) < sizeof block) {
61 		perror("could not read boot block");
62                 exit(2);
63 	}
64 
65 	if (block[510] != 0x55 || block[511] != 0xaa) {
66 		pfatal("Invalid signature in boot block: %02x%02x", block[511], block[510]);
67                 exit(2);
68 	}
69 
70 	memset(boot, 0, sizeof *boot);
71 	boot->ValidFat = -1;
72 
73 	/* decode bios parameter block */
74 	boot->BytesPerSec = block[11] + (block[12] << 8);
75 	boot->SecPerClust = block[13];
76 	boot->ResSectors = block[14] + (block[15] << 8);
77 	boot->FATs = block[16];
78 	boot->RootDirEnts = block[17] + (block[18] << 8);
79 	boot->Sectors = block[19] + (block[20] << 8);
80 	boot->Media = block[21];
81 	boot->FATsmall = block[22] + (block[23] << 8);
82 	boot->SecPerTrack = block[24] + (block[25] << 8);
83 	boot->Heads = block[26] + (block[27] << 8);
84 	boot->HiddenSecs = block[28] + (block[29] << 8) + (block[30] << 16) + (block[31] << 24);
85 	boot->HugeSectors = block[32] + (block[33] << 8) + (block[34] << 16) + (block[35] << 24);
86 
87 	boot->FATsecs = boot->FATsmall;
88 
89 	if (!boot->RootDirEnts)
90 		boot->flags |= FAT32;
91 	if (boot->flags & FAT32) {
92 		boot->FATsecs = block[36] + (block[37] << 8)
93 				+ (block[38] << 16) + (block[39] << 24);
94 		if (block[40] & 0x80)
95 			boot->ValidFat = block[40] & 0x0f;
96 
97 		/* check version number: */
98 		if (block[42] || block[43]) {
99 			/* Correct?				XXX */
100 			pfatal("Unknown file system version: %x.%x",
101 			       block[43], block[42]);
102                         exit(2);
103 		}
104 		boot->RootCl = block[44] + (block[45] << 8)
105 			       + (block[46] << 16) + (block[47] << 24);
106 		boot->FSInfo = block[48] + (block[49] << 8);
107 		boot->Backup = block[50] + (block[51] << 8);
108 
109 		/* If the OEM Name field is EXFAT, it's not FAT32, so bail */
110 		if (!memcmp(&block[3], "EXFAT   ", 8)) {
111 			pfatal("exFAT filesystem is not supported.");
112 			return FSFATAL;
113 		}
114 
115 		/* check basic parameters */
116 		if ((boot->FSInfo == 0) ||
117 		    (boot->BytesPerSec % DOSBOOTBLOCKSIZE != 0) ||
118 		    (boot->BytesPerSec / DOSBOOTBLOCKSIZE == 0) ||
119 		    (boot->SecPerClust == 0)) {
120 			/*
121 			 * Either the BIOS Parameter Block has been corrupted,
122                          * or this is not a FAT32 filesystem, most likely an
123                          * exFAT filesystem.
124 			 */
125 			pfatal("Invalid FAT32 Extended BIOS Parameter Block");
126 			return FSFATAL;
127 		}
128 		if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
129 		    != boot->FSInfo * boot->BytesPerSec
130 		    || read(dosfs, fsinfo, sizeof fsinfo)
131 		    != sizeof fsinfo) {
132 			perror("could not read fsinfo block");
133 			return FSFATAL;
134 		}
135 		if (memcmp(fsinfo, "RRaA", 4)
136 		    || memcmp(fsinfo + 0x1e4, "rrAa", 4)
137 		    || fsinfo[0x1fc]
138 		    || fsinfo[0x1fd]
139 		    || fsinfo[0x1fe] != 0x55
140 		    || fsinfo[0x1ff] != 0xaa
141 		    || fsinfo[0x3fc]
142 		    || fsinfo[0x3fd]
143 		    || fsinfo[0x3fe] != 0x55
144 		    || fsinfo[0x3ff] != 0xaa) {
145 			pwarn("Invalid signature in fsinfo block\n");
146 			if (ask(1, "fix")) {
147 				memcpy(fsinfo, "RRaA", 4);
148 				memcpy(fsinfo + 0x1e4, "rrAa", 4);
149 				fsinfo[0x1fc] = fsinfo[0x1fd] = 0;
150 				fsinfo[0x1fe] = 0x55;
151 				fsinfo[0x1ff] = 0xaa;
152 				fsinfo[0x3fc] = fsinfo[0x3fd] = 0;
153 				fsinfo[0x3fe] = 0x55;
154 				fsinfo[0x3ff] = 0xaa;
155 				if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
156 				    != boot->FSInfo * boot->BytesPerSec
157 				    || write(dosfs, fsinfo, sizeof fsinfo)
158 				    != sizeof fsinfo) {
159 					perror("Unable to write FSInfo");
160 					return FSFATAL;
161 				}
162 				ret = FSBOOTMOD;
163 			} else
164 				boot->FSInfo = 0;
165 		}
166 		if (boot->FSInfo) {
167 			boot->FSFree = fsinfo[0x1e8] + (fsinfo[0x1e9] << 8)
168 				       + (fsinfo[0x1ea] << 16)
169 				       + (fsinfo[0x1eb] << 24);
170 			boot->FSNext = fsinfo[0x1ec] + (fsinfo[0x1ed] << 8)
171 				       + (fsinfo[0x1ee] << 16)
172 				       + (fsinfo[0x1ef] << 24);
173 		}
174 
175 		if (lseek(dosfs, boot->Backup * boot->BytesPerSec, SEEK_SET)
176 		    != boot->Backup * boot->BytesPerSec
177 		    || read(dosfs, backup, sizeof backup) != sizeof  backup) {
178 			perror("could not read backup bootblock");
179 			return FSFATAL;
180 		}
181 		backup[65] = block[65];				/* XXX */
182 		if (memcmp(block + 11, backup + 11, 79)) {
183                         char tmp[255];
184                         int i;
185 
186 			/*
187 			 * For now, lets not bail out if they don't match
188 			 * It seems a lot of sdcards are formatted with
189 			 * the backup either empty or containing garbage.
190 			 */
191 
192 			pwarn("Primary/Backup bootblock miscompare\n");
193 
194                         strcpy(tmp, "");
195                         pwarn("Primary:\n");
196 			for (i = 0; i < 79; i++) {
197 				char tmp2[16];
198                                 snprintf(tmp2, sizeof(tmp2), "%.2x ", block[11 + i]);
199 				strcat(tmp, tmp2);
200                         }
201                         pwarn("%s\n", tmp);
202 
203 			strcpy(tmp, "");
204                         pwarn("Backup:\n");
205 			for (i = 0; i < 79; i++) {
206 				char tmp2[16];
207                                 snprintf(tmp2, sizeof(tmp2), "%.2x ", backup[11 + i]);
208 				strcat(tmp, tmp2);
209                         }
210                         pwarn("%s\n", tmp);
211 		}
212 		/* Check backup FSInfo?					XXX */
213 	}
214 
215 	if (boot->BytesPerSec % DOSBOOTBLOCKSIZE != 0) {
216 		pfatal("Invalid sector size: %u", boot->BytesPerSec);
217 		return FSFATAL;
218 	}
219 	if (boot->SecPerClust == 0) {
220 		pfatal("Invalid cluster size: %u", boot->SecPerClust);
221 		return FSFATAL;
222 	}
223 	if (boot->BytesPerSec == 0) {
224 		pfatal("Invalid sector size: %u", boot->BytesPerSec);
225 		return FSFATAL;
226 	}
227 	if (boot->FATs == 0) {
228 		pfatal("Invalid number of FATs: %u", boot->FATs);
229 		return FSFATAL;
230 	}
231 	if (boot->Sectors) {
232 		boot->HugeSectors = 0;
233 		boot->NumSectors = boot->Sectors;
234 	} else
235 		boot->NumSectors = boot->HugeSectors;
236 
237 	boot->ClusterOffset = (boot->RootDirEnts * 32 + boot->BytesPerSec - 1)
238 	    / boot->BytesPerSec
239 	    + boot->ResSectors
240 	    + boot->FATs * boot->FATsecs
241 	    - CLUST_FIRST * boot->SecPerClust;
242 
243 	boot->NumClusters = (boot->NumSectors - boot->ClusterOffset) / boot->SecPerClust;
244 
245 	if (boot->flags&FAT32)
246 		boot->ClustMask = CLUST32_MASK;
247 	else if (boot->NumClusters < (CLUST_RSRVD&CLUST12_MASK))
248 		boot->ClustMask = CLUST12_MASK;
249 	else if (boot->NumClusters < (CLUST_RSRVD&CLUST16_MASK))
250 		boot->ClustMask = CLUST16_MASK;
251 	else {
252 		pfatal("Filesystem too big (%u clusters) for non-FAT32 partition",
253 		       boot->NumClusters);
254 		return FSFATAL;
255 	}
256 
257 	switch (boot->ClustMask) {
258 	case CLUST32_MASK:
259 		boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 4;
260 		break;
261 	case CLUST16_MASK:
262 		boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 2;
263 		break;
264 	default:
265 		boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec * 2) / 3;
266 		break;
267 	}
268 
269 	if (boot->NumFatEntries < boot->NumClusters) {
270 		pfatal("FAT size too small, %u entries won't fit into %u sectors\n",
271 		       boot->NumClusters, boot->FATsecs);
272 		return FSFATAL;
273 	}
274 	boot->ClusterSize = boot->BytesPerSec * boot->SecPerClust;
275 
276 	boot->NumFiles = 1;
277 	boot->NumFree = 0;
278 
279 	return ret;
280 }
281 
282 int
writefsinfo(dosfs,boot)283 writefsinfo(dosfs, boot)
284 	int dosfs;
285 	struct bootblock *boot;
286 {
287 	u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
288 
289 	if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
290 	    != boot->FSInfo * boot->BytesPerSec
291 	    || read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) {
292 		perror("could not read fsinfo block");
293 		return FSFATAL;
294 	}
295 	fsinfo[0x1e8] = (u_char)boot->FSFree;
296 	fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8);
297 	fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16);
298 	fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24);
299 	fsinfo[0x1ec] = (u_char)boot->FSNext;
300 	fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8);
301 	fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16);
302 	fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24);
303 	if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
304 	    != boot->FSInfo * boot->BytesPerSec
305 	    || write(dosfs, fsinfo, sizeof fsinfo)
306 	    != sizeof fsinfo) {
307 		perror("Unable to write FSInfo");
308 		return FSFATAL;
309 	}
310 	/*
311 	 * Technically, we should return FSBOOTMOD here.
312 	 *
313 	 * However, since Win95 OSR2 (the first M$ OS that has
314 	 * support for FAT32) doesn't maintain the FSINFO block
315 	 * correctly, it has to be fixed pretty often.
316 	 *
317 	 * Therefor, we handle the FSINFO block only informally,
318 	 * fixing it if necessary, but otherwise ignoring the
319 	 * fact that it was incorrect.
320 	 */
321 	return 0;
322 }
323