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DM configures a block device with various target specific attributes passed to it as a table. DM loads the table, and calls each target’s respective constructors with the attributes as input parameters. Some of these attributes are critical to ensure the device meets certain security bar. Thus, IMA should measure these attributes, to ensure they are not tampered with, during the lifetime of the device. So that the external services can have high confidence in the configuration of the block-devices on a given system. Some devices may have large tables. And a given device may change its state (table-load, suspend, resume, rename, remove, table-clear etc.) many times. Measuring these attributes each time when the device changes its state will significantly increase the size of the IMA logs. Further, once configured, these attributes are not expected to change unless a new table is loaded, or a device is removed and recreated. Therefore the clear-text of the attributes should only be measured during table load, and the hash of the active/inactive table should be measured for the remaining device state changes. Export IMA function ima_measure_critical_data() to allow measurement of DM device parameters, as well as target specific attributes, during table load. Compute the hash of the inactive table and store it for measurements during future state change. If a load is called multiple times, update the inactive table hash with the hash of the latest populated table. So that the correct inactive table hash is measured when the device transitions to different states like resume, remove, rename, etc. Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com> Signed-off-by: Colin Ian King <colin.king@canonical.com> # leak fix Signed-off-by: Mike Snitzer <snitzer@redhat.com>
59 lines
1.6 KiB
C
59 lines
1.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0
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*
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* Copyright (C) 2021 Microsoft Corporation
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*
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* Author: Tushar Sugandhi <tusharsu@linux.microsoft.com>
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*
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* File: dm-ima.h
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* Header file for device mapper IMA measurements.
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*/
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#ifndef DM_IMA_H
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#define DM_IMA_H
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#define DM_IMA_MEASUREMENT_BUF_LEN 4096
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#define DM_IMA_DEVICE_BUF_LEN 1024
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#define DM_IMA_TARGET_METADATA_BUF_LEN 128
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#define DM_IMA_TARGET_DATA_BUF_LEN 2048
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#ifdef CONFIG_IMA
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struct dm_ima_device_table_metadata {
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/*
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* Contains data specific to the device which is common across
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* all the targets in the table (e.g. name, uuid, major, minor, etc).
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* The values are stored in comma separated list of key1=val1,key2=val2;
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* pairs delimited by a semicolon at the end of the list.
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*/
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char *device_metadata;
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unsigned int device_metadata_len;
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unsigned int num_targets;
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/*
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* Contains the sha256 hashes of the IMA measurements of the target
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* attributes' key-value pairs from the active/inactive tables.
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*/
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char *hash;
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unsigned int hash_len;
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};
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/*
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* This structure contains device metadata, and table hash for
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* active and inactive tables for ima measurements.
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*/
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struct dm_ima_measurements {
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struct dm_ima_device_table_metadata active_table;
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struct dm_ima_device_table_metadata inactive_table;
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};
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void dm_ima_reset_data(struct mapped_device *md);
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void dm_ima_measure_on_table_load(struct dm_table *table, unsigned int status_flags);
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#else
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static inline void dm_ima_reset_data(struct mapped_device *md) {}
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static inline void dm_ima_measure_on_table_load(struct dm_table *table, unsigned int status_flags) {}
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#endif /* CONFIG_IMA */
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#endif /* DM_IMA_H */
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