/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright (C) 1995, 1997 Wolfgang Solfrank
* Copyright (c) 1995 Martin Husemann
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: boot.c,v 1.22 2020/01/11 16:29:07 christos Exp $");
static const char rcsid[] =
"$FreeBSD$";
#endif /* not lint */
#include <sys/param.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include "ext.h"
#include "fsutil.h"
int
readboot(int dosfs, struct bootblock *boot)
{
u_char block[DOSBOOTBLOCKSIZE];
u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
int ret = FSOK;
if ((size_t)read(dosfs, block, sizeof block) != sizeof block) {
perr("could not read boot block");
return FSFATAL;
}
if (block[510] != 0x55 || block[511] != 0xaa) {
pfatal("Invalid signature in boot block: %02x%02x",
block[511], block[510]);
return FSFATAL;
}
memset(boot, 0, sizeof *boot);
boot->ValidFat = -1;
/* Decode BIOS Parameter Block */
/* Bytes per sector: can only be 512, 1024, 2048 and 4096. */
boot->bpbBytesPerSec = block[11] + (block[12] << 8);
if (boot->bpbBytesPerSec < DOSBOOTBLOCKSIZE_REAL ||
boot->bpbBytesPerSec > DOSBOOTBLOCKSIZE ||
!powerof2(boot->bpbBytesPerSec)) {
pfatal("Invalid sector size: %u", boot->bpbBytesPerSec);
return FSFATAL;
}
/* Sectors per cluster: can only be: 1, 2, 4, 8, 16, 32, 64, 128. */
boot->bpbSecPerClust = block[13];
if (boot->bpbSecPerClust == 0 || !powerof2(boot->bpbSecPerClust)) {
pfatal("Invalid cluster size: %u", boot->bpbSecPerClust);
return FSFATAL;
}
/* Reserved sectors: must be non-zero */
boot->bpbResSectors = block[14] + (block[15] << 8);
if (boot->bpbResSectors < 1) {
pfatal("Invalid reserved sectors: %u",
boot->bpbResSectors);
return FSFATAL;
}
/* Number of FATs */
boot->bpbFATs = block[16];
if (boot->bpbFATs == 0) {
pfatal("Invalid number of FATs: %u", boot->bpbFATs);
return FSFATAL;
}
/* Root directory entries for FAT12 and FAT16 */
boot->bpbRootDirEnts = block[17] + (block[18] << 8);
if (!boot->bpbRootDirEnts) {
/* bpbRootDirEnts = 0 suggests that we are FAT32 */
boot->flags |= FAT32;
}
/* Total sectors (16 bits) */
boot->bpbSectors = block[19] + (block[20] << 8);
if (boot->bpbSectors != 0 && (boot->flags & FAT32)) {
pfatal("Invalid 16-bit total sector count on FAT32: %u",
boot->bpbSectors);
return FSFATAL;
}
/* Media type: ignored */
boot->bpbMedia = block[21];
/* FAT12/FAT16: 16-bit count of sectors per FAT */
boot->bpbFATsmall = block[22] + (block[23] << 8);
if (boot->bpbFATsmall != 0 && (boot->flags & FAT32)) {
pfatal("Invalid 16-bit FAT sector count on FAT32: %u",
boot->bpbFATsmall);
return FSFATAL;
}
/* Legacy CHS geometry numbers: ignored */
boot->SecPerTrack = block[24] + (block[25] << 8);
boot->bpbHeads = block[26] + (block[27] << 8);
/* Hidden sectors: ignored */
boot->bpbHiddenSecs = block[28] + (block[29] << 8) +
(block[30] << 16) + (block[31] << 24);
/* Total sectors (32 bits) */
boot->bpbHugeSectors = block[32] + (block[33] << 8) +
(block[34] << 16) + (block[35] << 24);
if (boot->bpbHugeSectors == 0) {
if (boot->flags & FAT32) {
pfatal("FAT32 with sector count of zero");
return FSFATAL;
} else if (boot->bpbSectors == 0) {
pfatal("FAT with sector count of zero");
return FSFATAL;
}
boot->NumSectors = boot->bpbSectors;
} else {
if (boot->bpbSectors != 0) {
pfatal("Invalid FAT sector count");
return FSFATAL;
}
boot->NumSectors = boot->bpbHugeSectors;
}
if (boot->flags & FAT32) {
/* If the OEM Name field is EXFAT, it's not FAT32, so bail */
if (!memcmp(&block[3], "EXFAT ", 8)) {
pfatal("exFAT filesystem is not supported.");
return FSFATAL;
}
/* 32-bit count of sectors per FAT */
boot->FATsecs = block[36] + (block[37] << 8)
+ (block[38] << 16) + (block[39] << 24);
if (block[40] & 0x80)
boot->ValidFat = block[40] & 0x0f;
/* FAT32 version, bail out if not 0.0 */
if (block[42] || block[43]) {
pfatal("Unknown file system version: %x.%x",
block[43], block[42]);
return FSFATAL;
}
/*
* Cluster number of the first cluster of root directory.
*
* Should be 2 but do not require it.
*/
boot->bpbRootClust = block[44] + (block[45] << 8)
+ (block[46] << 16) + (block[47] << 24);
/* Sector number of the FSInfo structure, usually 1 */
boot->bpbFSInfo = block[48] + (block[49] << 8);
/* Sector number of the backup boot block, ignored */
boot->bpbBackup = block[50] + (block[51] << 8);
/* Check basic parameters */
if (boot->bpbFSInfo == 0) {
/*
* Either the BIOS Parameter Block has been corrupted,
* or this is not a FAT32 filesystem, most likely an
* exFAT filesystem.
*/
pfatal("Invalid FAT32 Extended BIOS Parameter Block");
return FSFATAL;
}
/* Read in and verify the FSInfo block */
if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec,
SEEK_SET) != boot->bpbFSInfo * boot->bpbBytesPerSec
|| read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) {
perr("could not read fsinfo block");
return FSFATAL;
}
if (memcmp(fsinfo, "RRaA", 4)
|| memcmp(fsinfo + 0x1e4, "rrAa", 4)
|| fsinfo[0x1fc]
|| fsinfo[0x1fd]
|| fsinfo[0x1fe] != 0x55
|| fsinfo[0x1ff] != 0xaa
|| fsinfo[0x3fc]
|| fsinfo[0x3fd]
|| fsinfo[0x3fe] != 0x55
|| fsinfo[0x3ff] != 0xaa) {
pwarn("Invalid signature in fsinfo block\n");
if (ask(0, "Fix")) {
memcpy(fsinfo, "RRaA", 4);
memcpy(fsinfo + 0x1e4, "rrAa", 4);
fsinfo[0x1fc] = fsinfo[0x1fd] = 0;
fsinfo[0x1fe] = 0x55;
fsinfo[0x1ff] = 0xaa;
fsinfo[0x3fc] = fsinfo[0x3fd] = 0;
fsinfo[0x3fe] = 0x55;
fsinfo[0x3ff] = 0xaa;
if (lseek(dosfs, boot->bpbFSInfo *
boot->bpbBytesPerSec, SEEK_SET)
!= boot->bpbFSInfo * boot->bpbBytesPerSec
|| write(dosfs, fsinfo, sizeof fsinfo)
!= sizeof fsinfo) {
perr("Unable to write bpbFSInfo");
return FSFATAL;
}
ret = FSBOOTMOD;
} else
boot->bpbFSInfo = 0;
} else {
/* We appear to have a valid FSInfo block, decode */
boot->FSFree = fsinfo[0x1e8] + (fsinfo[0x1e9] << 8)
+ (fsinfo[0x1ea] << 16)
+ (fsinfo[0x1eb] << 24);
boot->FSNext = fsinfo[0x1ec] + (fsinfo[0x1ed] << 8)
+ (fsinfo[0x1ee] << 16)
+ (fsinfo[0x1ef] << 24);
}
} else {
/* !FAT32: FAT12/FAT16 */
boot->FATsecs = boot->bpbFATsmall;
}
if (boot->FATsecs < 1 || boot->FATsecs > UINT32_MAX / boot->bpbFATs) {
pfatal("Invalid FATs(%u) with FATsecs(%zu)",
boot->bpbFATs, (size_t)boot->FATsecs);
return FSFATAL;
}
boot->FirstCluster = (boot->bpbRootDirEnts * 32 +
boot->bpbBytesPerSec - 1) / boot->bpbBytesPerSec +
boot->bpbResSectors + boot->bpbFATs * boot->FATsecs;
if (boot->FirstCluster + boot->bpbSecPerClust > boot->NumSectors) {
pfatal("Cluster offset too large (%u clusters)\n",
boot->FirstCluster);
return FSFATAL;
}
/*
* The number of clusters is derived from available data sectors,
* divided by sectors per cluster.
*/
boot->NumClusters =
(boot->NumSectors - boot->FirstCluster) / boot->bpbSecPerClust;
if (boot->flags & FAT32) {
if (boot->NumClusters > (CLUST_RSRVD & CLUST32_MASK)) {
pfatal("Filesystem too big (%u clusters) for FAT32 partition",
boot->NumClusters);
return FSFATAL;
}
if (boot->NumClusters < (CLUST_RSRVD & CLUST16_MASK)) {
pfatal("Filesystem too small (%u clusters) for FAT32 partition",
boot->NumClusters);
return FSFATAL;
}
boot->ClustMask = CLUST32_MASK;
if (boot->bpbRootClust < CLUST_FIRST ||
boot->bpbRootClust >= boot->NumClusters) {
pfatal("Root directory starts with cluster out of range(%u)",
boot->bpbRootClust);
return FSFATAL;
}
} else if (boot->NumClusters < (CLUST_RSRVD&CLUST12_MASK)) {
boot->ClustMask = CLUST12_MASK;
} else if (boot->NumClusters < (CLUST_RSRVD&CLUST16_MASK)) {
boot->ClustMask = CLUST16_MASK;
} else {
pfatal("Filesystem too big (%u clusters) for non-FAT32 partition",
boot->NumClusters);
return FSFATAL;
}
switch (boot->ClustMask) {
case CLUST32_MASK:
boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec) / 4;
break;
case CLUST16_MASK:
boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec) / 2;
break;
default:
boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec * 2) / 3;
break;
}
if (boot->NumFatEntries < boot->NumClusters) {
pfatal("FAT size too small, %u entries won't fit into %u sectors\n",
boot->NumClusters, boot->FATsecs);
return FSFATAL;
}
/*
* There are two reserved clusters. To avoid adding CLUST_FIRST every
* time we perform boundary checks, we increment the NumClusters by 2,
* which is CLUST_FIRST to denote the first out-of-range cluster number.
*/
boot->NumClusters += CLUST_FIRST;
boot->ClusterSize = boot->bpbBytesPerSec * boot->bpbSecPerClust;
boot->NumFiles = 1;
boot->NumFree = 0;
return ret;
}
int
writefsinfo(int dosfs, struct bootblock *boot)
{
u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec, SEEK_SET)
!= boot->bpbFSInfo * boot->bpbBytesPerSec
|| read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) {
perr("could not read fsinfo block");
return FSFATAL;
}
fsinfo[0x1e8] = (u_char)boot->FSFree;
fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8);
fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16);
fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24);
fsinfo[0x1ec] = (u_char)boot->FSNext;
fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8);
fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16);
fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24);
if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec, SEEK_SET)
!= boot->bpbFSInfo * boot->bpbBytesPerSec
|| write(dosfs, fsinfo, sizeof fsinfo)
!= sizeof fsinfo) {
perr("Unable to write bpbFSInfo");
return FSFATAL;
}
/*
* Technically, we should return FSBOOTMOD here.
*
* However, since Win95 OSR2 (the first M$ OS that has
* support for FAT32) doesn't maintain the FSINFO block
* correctly, it has to be fixed pretty often.
*
* Therefore, we handle the FSINFO block only informally,
* fixing it if necessary, but otherwise ignoring the
* fact that it was incorrect.
*/
return 0;
}
