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When QEMU opens a backing store for a QCow2 file, it will normally auto-probe for the format of the backing store, rather than assuming it has the same format as the referencing file. There is a QCow2 extension that allows an explicit format for the backing store to be embedded in the referencing file. This closes the auto-probing security hole in QEMU. This backing store format can be useful for libvirt users of virStorageFileGetMetadata, so extract this data and report it. QEMU does not require disk image backing store files to be in the same format the file linkee. It will auto-probe the disk format for the backing store when opening it. If the backing store was intended to be a raw file this could be a security hole, because a guest may have written data into its disk that then makes the backing store look like a qcow2 file. If it can trick QEMU into thinking the raw file is a qcow2 file, it can access arbitrary files on the host by adding further backing store links. To address this, callers of virStorageFileGetMeta need to be told of the backing store format. If no format is declared, they can make a decision whether to allow format probing or not.
69 lines
2.0 KiB
C
69 lines
2.0 KiB
C
/*
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* storage_file.c: file utility functions for FS storage backend
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*
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* Copyright (C) 2007-2009 Red Hat, Inc.
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* Copyright (C) 2007-2008 Daniel P. Berrange
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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* Author: Daniel P. Berrange <berrange@redhat.com>
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*/
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#ifndef __VIR_STORAGE_FILE_H__
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# define __VIR_STORAGE_FILE_H__
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# include "util.h"
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# include <stdbool.h>
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enum virStorageFileFormat {
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VIR_STORAGE_FILE_AUTO = -1,
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VIR_STORAGE_FILE_RAW = 0,
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VIR_STORAGE_FILE_DIR,
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VIR_STORAGE_FILE_BOCHS,
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VIR_STORAGE_FILE_CLOOP,
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VIR_STORAGE_FILE_COW,
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VIR_STORAGE_FILE_DMG,
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VIR_STORAGE_FILE_ISO,
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VIR_STORAGE_FILE_QCOW,
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VIR_STORAGE_FILE_QCOW2,
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VIR_STORAGE_FILE_VMDK,
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VIR_STORAGE_FILE_VPC,
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VIR_STORAGE_FILE_LAST,
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};
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VIR_ENUM_DECL(virStorageFileFormat);
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typedef struct _virStorageFileMetadata {
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int format;
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char *backingStore;
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int backingStoreFormat;
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unsigned long long capacity;
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bool encrypted;
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} virStorageFileMetadata;
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# ifndef DEV_BSIZE
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# define DEV_BSIZE 512
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# endif
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int virStorageFileGetMetadata(const char *path,
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virStorageFileMetadata *meta);
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int virStorageFileGetMetadataFromFD(const char *path,
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int fd,
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virStorageFileMetadata *meta);
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int virStorageFileIsSharedFS(const char *path);
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#endif /* __VIR_STORAGE_FILE_H__ */
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