Volume labels, like directory entries, are padded with spaces and so have no NUL terminator. Whilst the MIN for the dsize argument to strlcpy ensures that the copy does not overflow the destination, strlcpy is defined to return the number of characters in the source string, regardless of the provided dsize, and so keeps reading until it finds a NUL, which likely exists somewhere within the following fields, but On CHERI with the subobject bounds enabled in the compiler this buffer overread will be detected and trap with a bounds violation. Found by: CHERI Reviewed by: imp Differential Revision: https://reviews.freebsd.org/D32579
182 lines
5.2 KiB
C
182 lines
5.2 KiB
C
/*-
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* Copyright (c) 2004 Pawel Jakub Dawidek <pjd@FreeBSD.org>
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* Copyright (c) 2006 Tobias Reifenberger
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* Copyright (c) 2014 The FreeBSD Foundation
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* All rights reserved.
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*
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* This software was developed by Edward Tomasz Napierala under sponsorship
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* from the FreeBSD Foundation.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "fstyp.h"
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#include "msdosfs.h"
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#define LABEL_NO_NAME "NO NAME "
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int
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fstyp_msdosfs(FILE *fp, char *label, size_t size)
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{
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FAT_BSBPB *pfat_bsbpb;
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FAT32_BSBPB *pfat32_bsbpb;
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FAT_DES *pfat_entry;
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uint8_t *sector0, *sector;
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size_t copysize;
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sector0 = NULL;
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sector = NULL;
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/* Load 1st sector with boot sector and boot parameter block. */
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sector0 = (uint8_t *)read_buf(fp, 0, 512);
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if (sector0 == NULL)
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return (1);
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/* Check for the FAT boot sector signature. */
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if (sector0[510] != 0x55 || sector0[511] != 0xaa) {
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goto error;
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}
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/*
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* Test if this is really a FAT volume and determine the FAT type.
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*/
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pfat_bsbpb = (FAT_BSBPB *)sector0;
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pfat32_bsbpb = (FAT32_BSBPB *)sector0;
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if (UINT16BYTES(pfat_bsbpb->BPB_FATSz16) != 0) {
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/*
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* If the BPB_FATSz16 field is not zero and the string "FAT" is
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* at the right place, this should be a FAT12 or FAT16 volume.
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*/
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if (strncmp(pfat_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
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goto error;
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}
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/* A volume with no name should have "NO NAME " as label. */
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if (strncmp(pfat_bsbpb->BS_VolLab, LABEL_NO_NAME,
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sizeof(pfat_bsbpb->BS_VolLab)) == 0) {
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goto endofchecks;
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}
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copysize = MIN(size - 1, sizeof(pfat_bsbpb->BS_VolLab));
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memcpy(label, pfat_bsbpb->BS_VolLab, copysize);
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label[copysize] = '\0';
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} else if (UINT32BYTES(pfat32_bsbpb->BPB_FATSz32) != 0) {
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uint32_t fat_FirstDataSector, fat_BytesPerSector, offset;
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/*
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* If the BPB_FATSz32 field is not zero and the string "FAT" is
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* at the right place, this should be a FAT32 volume.
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*/
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if (strncmp(pfat32_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
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goto error;
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}
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/*
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* If the volume label is not "NO NAME " we're done.
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*/
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if (strncmp(pfat32_bsbpb->BS_VolLab, LABEL_NO_NAME,
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sizeof(pfat32_bsbpb->BS_VolLab)) != 0) {
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copysize = MIN(size - 1,
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sizeof(pfat32_bsbpb->BS_VolLab) + 1);
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memcpy(label, pfat32_bsbpb->BS_VolLab, copysize);
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label[copysize] = '\0';
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goto endofchecks;
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}
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/*
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* If the volume label "NO NAME " is in the boot sector, the
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* label of FAT32 volumes may be stored as a special entry in
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* the root directory.
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*/
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fat_FirstDataSector =
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UINT16BYTES(pfat32_bsbpb->BPB_RsvdSecCnt) +
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(pfat32_bsbpb->BPB_NumFATs *
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UINT32BYTES(pfat32_bsbpb->BPB_FATSz32));
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fat_BytesPerSector = UINT16BYTES(pfat32_bsbpb->BPB_BytsPerSec);
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// fat_FirstDataSector, fat_BytesPerSector);
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for (offset = fat_BytesPerSector * fat_FirstDataSector;;
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offset += fat_BytesPerSector) {
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sector = (uint8_t *)read_buf(fp, offset, fat_BytesPerSector);
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if (sector == NULL)
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goto error;
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pfat_entry = (FAT_DES *)sector;
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do {
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/* No more entries available. */
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if (pfat_entry->DIR_Name[0] == 0) {
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goto endofchecks;
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}
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/* Skip empty or long name entries. */
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if (pfat_entry->DIR_Name[0] == 0xe5 ||
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(pfat_entry->DIR_Attr &
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FAT_DES_ATTR_LONG_NAME) ==
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FAT_DES_ATTR_LONG_NAME) {
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continue;
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}
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/*
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* The name of the entry is the volume label if
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* ATTR_VOLUME_ID is set.
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*/
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if (pfat_entry->DIR_Attr &
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FAT_DES_ATTR_VOLUME_ID) {
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copysize = MIN(size - 1,
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sizeof(pfat_entry->DIR_Name));
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memcpy(label, pfat_entry->DIR_Name,
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copysize);
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label[copysize] = '\0';
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goto endofchecks;
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}
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} while((uint8_t *)(++pfat_entry) <
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(uint8_t *)(sector + fat_BytesPerSector));
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free(sector);
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}
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} else {
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goto error;
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}
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endofchecks:
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rtrim(label, size);
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free(sector0);
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free(sector);
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return (0);
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error:
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free(sector0);
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free(sector);
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return (1);
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}
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