/*-
* Copyright (c) 2004 Pawel Jakub Dawidek <pjd@FreeBSD.org>
* Copyright (c) 2006 Tobias Reifenberger
* Copyright (c) 2014 The FreeBSD Foundation
* All rights reserved.
*
* This software was developed by Edward Tomasz Napierala under sponsorship
* from the FreeBSD Foundation.
*
* 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 AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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>
__FBSDID("$FreeBSD$");
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "fstyp.h"
#include "msdosfs.h"
#define LABEL_NO_NAME "NO NAME "
/*
* XXX the signature 0x55 0xAA as the last two bytes of 512 is not required
* by specifications, but was historically required by fstyp. This check
* should be removed, with a more comprehensive BPB validation instead.
*/
static bool
check_signature(uint8_t sector0[512])
{
/* Check for the FAT boot sector signature. */
if (sector0[510] == 0x55 && sector0[511] == 0xaa)
return (true);
/* Special case for Raspberry Pi Pico bootloader. */
if (sector0[510] == 0 && sector0[511] == 0 &&
sector0[0] == 0xeb && sector0[1] == 0x3c && sector0[2] == 0x90)
return (true);
return (false);
}
int
fstyp_msdosfs(FILE *fp, char *label, size_t size)
{
FAT_BSBPB *pfat_bsbpb;
FAT32_BSBPB *pfat32_bsbpb;
FAT_DES *pfat_entry;
uint8_t *sector0, *sector;
size_t copysize;
sector0 = NULL;
sector = NULL;
/* Load 1st sector with boot sector and boot parameter block. */
sector0 = (uint8_t *)read_buf(fp, 0, 512);
if (sector0 == NULL)
return (1);
if (!check_signature(sector0)) {
goto error;
}
/*
* Test if this is really a FAT volume and determine the FAT type.
*/
pfat_bsbpb = (FAT_BSBPB *)sector0;
pfat32_bsbpb = (FAT32_BSBPB *)sector0;
if (UINT16BYTES(pfat_bsbpb->BPB_FATSz16) != 0) {
/*
* If the BPB_FATSz16 field is not zero and the string "FAT" is
* at the right place, this should be a FAT12 or FAT16 volume.
*/
if (strncmp(pfat_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
goto error;
}
/* A volume with no name should have "NO NAME " as label. */
if (strncmp(pfat_bsbpb->BS_VolLab, LABEL_NO_NAME,
sizeof(pfat_bsbpb->BS_VolLab)) == 0) {
goto endofchecks;
}
copysize = MIN(size - 1, sizeof(pfat_bsbpb->BS_VolLab));
memcpy(label, pfat_bsbpb->BS_VolLab, copysize);
label[copysize] = '\0';
} else if (UINT32BYTES(pfat32_bsbpb->BPB_FATSz32) != 0) {
uint32_t fat_FirstDataSector, fat_BytesPerSector, offset;
/*
* If the BPB_FATSz32 field is not zero and the string "FAT" is
* at the right place, this should be a FAT32 volume.
*/
if (strncmp(pfat32_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
goto error;
}
/*
* If the volume label is not "NO NAME " we're done.
*/
if (strncmp(pfat32_bsbpb->BS_VolLab, LABEL_NO_NAME,
sizeof(pfat32_bsbpb->BS_VolLab)) != 0) {
copysize = MIN(size - 1,
sizeof(pfat32_bsbpb->BS_VolLab));
memcpy(label, pfat32_bsbpb->BS_VolLab, copysize);
label[copysize] = '\0';
goto endofchecks;
}
/*
* If the volume label "NO NAME " is in the boot sector, the
* label of FAT32 volumes may be stored as a special entry in
* the root directory.
*/
fat_FirstDataSector =
UINT16BYTES(pfat32_bsbpb->BPB_RsvdSecCnt) +
(pfat32_bsbpb->BPB_NumFATs *
UINT32BYTES(pfat32_bsbpb->BPB_FATSz32));
fat_BytesPerSector = UINT16BYTES(pfat32_bsbpb->BPB_BytsPerSec);
// fat_FirstDataSector, fat_BytesPerSector);
for (offset = fat_BytesPerSector * fat_FirstDataSector;;
offset += fat_BytesPerSector) {
sector = (uint8_t *)read_buf(fp, offset, fat_BytesPerSector);
if (sector == NULL)
goto error;
pfat_entry = (FAT_DES *)sector;
do {
/* No more entries available. */
if (pfat_entry->DIR_Name[0] == 0) {
goto endofchecks;
}
/* Skip empty or long name entries. */
if (pfat_entry->DIR_Name[0] == 0xe5 ||
(pfat_entry->DIR_Attr &
FAT_DES_ATTR_LONG_NAME) ==
FAT_DES_ATTR_LONG_NAME) {
continue;
}
/*
* The name of the entry is the volume label if
* ATTR_VOLUME_ID is set.
*/
if (pfat_entry->DIR_Attr &
FAT_DES_ATTR_VOLUME_ID) {
copysize = MIN(size - 1,
sizeof(pfat_entry->DIR_Name));
memcpy(label, pfat_entry->DIR_Name,
copysize);
label[copysize] = '\0';
goto endofchecks;
}
} while((uint8_t *)(++pfat_entry) <
(uint8_t *)(sector + fat_BytesPerSector));
free(sector);
}
} else {
goto error;
}
endofchecks:
rtrim(label, size);
free(sector0);
free(sector);
return (0);
error:
free(sector0);
free(sector);
return (1);
}
