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Subject: Re: [PATCH 1/3] dm: introduce audit event module for device mapper
To:     =?UTF-8?Q?Michael_Wei=c3=9f?= <michael.weiss@aisec.fraunhofer.de>
Cc:     Mike Snitzer <snitzer@redhat.com>, linux-kernel@vger.kernel.org,
        Eric Paris <eparis@redhat.com>, linux-raid@vger.kernel.org,
        Song Liu <song@kernel.org>, dm-devel@redhat.com,
        linux-audit@redhat.com, Alasdair Kergon <agk@redhat.com>
References: <20210812145748.4460-1-michael.weiss@aisec.fraunhofer.de>
 <20210812145748.4460-2-michael.weiss@aisec.fraunhofer.de>
From:   Casey Schaufler <casey@schaufler-ca.com>
Message-ID: <7f28b3b4-c0a2-cb03-09fd-e0705959576a@schaufler-ca.com>
Date:   Thu, 12 Aug 2021 10:08:57 -0700
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On 8/12/2021 7:57 AM, Michael Weiß wrote:
> To be able to send auditing events to user space, we introduce
> a generic dm-audit module. It provides helper functions to emit
> audit events through the kernel audit subsystem. We claim the
> AUDIT_DM type=1336 out of the audit event messages range in the
> corresponding userspace api in 'include/uapi/linux/audit.h' for
> those events.
>
> Following commits to device mapper targets actually will make
> use of this to emit those events in relevant cases.
>
> Signed-off-by: Michael Weiß <michael.weiss@aisec.fraunhofer.de>
> ---
>  drivers/md/Kconfig         | 10 +++++++
>  drivers/md/Makefile        |  4 +++
>  drivers/md/dm-audit.c      | 59 ++++++++++++++++++++++++++++++++++++++
>  drivers/md/dm-audit.h      | 33 +++++++++++++++++++++
>  include/uapi/linux/audit.h |  2 ++
>  5 files changed, 108 insertions(+)
>  create mode 100644 drivers/md/dm-audit.c
>  create mode 100644 drivers/md/dm-audit.h
>
> diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
> index 0602e82a9516..fd54c713a03e 100644
> --- a/drivers/md/Kconfig
> +++ b/drivers/md/Kconfig
> @@ -608,6 +608,7 @@ config DM_INTEGRITY
>  	select CRYPTO
>  	select CRYPTO_SKCIPHER
>  	select ASYNC_XOR
> +	select DM_AUDIT if AUDIT
>  	help
>  	  This device-mapper target emulates a block device that has
>  	  additional per-sector tags that can be used for storing
> @@ -640,4 +641,13 @@ config DM_ZONED
>  
>  	  If unsure, say N.
>  
> +config DM_AUDIT
> +	bool "DM audit events"
> +	depends on AUDIT
> +	help
> +	  Generate audit events for device-mapper.
> +
> +	  Enables audit loging of several security relevant events in the

s/loging/logging/

> +	  particular device-mapper targets, especially the integrity target.
> +
>  endif # MD
> diff --git a/drivers/md/Makefile b/drivers/md/Makefile
> index a74aaf8b1445..4cd47623c742 100644
> --- a/drivers/md/Makefile
> +++ b/drivers/md/Makefile
> @@ -103,3 +103,7 @@ endif
>  ifeq ($(CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG),y)
>  dm-verity-objs			+= dm-verity-verify-sig.o
>  endif
> +
> +ifeq ($(CONFIG_DM_AUDIT),y)
> +dm-mod-objs				+= dm-audit.o
> +endif
> diff --git a/drivers/md/dm-audit.c b/drivers/md/dm-audit.c
> new file mode 100644
> index 000000000000..c7e5824821bb
> --- /dev/null
> +++ b/drivers/md/dm-audit.c
> @@ -0,0 +1,59 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Creating audit records for mapped devices.
> + *
> + * Copyright (C) 2021 Fraunhofer AISEC. All rights reserved.
> + *
> + * Authors: Michael Weiß <michael.weiss@aisec.fraunhofer.de>
> + */
> +
> +#include <linux/audit.h>
> +#include <linux/module.h>
> +#include <linux/device-mapper.h>
> +#include <linux/bio.h>
> +#include <linux/blkdev.h>
> +
> +#include "dm-audit.h"
> +#include "dm-core.h"
> +
> +void dm_audit_log_bio(const char *dm_msg_prefix, const char *op,
> +		      struct bio *bio, sector_t sector, int result)
> +{
> +	struct audit_buffer *ab;
> +
> +	if (audit_enabled == AUDIT_OFF)
> +		return;
> +
> +	ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_DM);
> +	if (unlikely(!ab))
> +		return;
> +
> +	audit_log_format(ab, "module=%s dev=%d:%d op=%s sector=%llu res=%d",
> +			 dm_msg_prefix, MAJOR(bio->bi_bdev->bd_dev),
> +			 MINOR(bio->bi_bdev->bd_dev), op, sector, result);
> +	audit_log_end(ab);
> +}
> +EXPORT_SYMBOL_GPL(dm_audit_log_bio);
> +
> +void dm_audit_log_target(const char *dm_msg_prefix, const char *op,
> +			 struct dm_target *ti, int result)
> +{
> +	struct audit_buffer *ab;
> +	struct mapped_device *md = dm_table_get_md(ti->table);
> +
> +	if (audit_enabled == AUDIT_OFF)
> +		return;
> +
> +	ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_DM);
> +	if (unlikely(!ab))
> +		return;
> +
> +	audit_log_format(ab, "module=%s dev=%s op=%s",
> +			 dm_msg_prefix, dm_device_name(md), op);
> +
> +	if (!result && !strcmp("ctr", op))
> +		audit_log_format(ab, " error_msg='%s'", ti->error);
> +	audit_log_format(ab, " res=%d", result);
> +	audit_log_end(ab);
> +}
> +EXPORT_SYMBOL_GPL(dm_audit_log_target);
> diff --git a/drivers/md/dm-audit.h b/drivers/md/dm-audit.h
> new file mode 100644
> index 000000000000..9db4955d32e1
> --- /dev/null
> +++ b/drivers/md/dm-audit.h
> @@ -0,0 +1,33 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Creating audit records for mapped devices.
> + *
> + * Copyright (C) 2021 Fraunhofer AISEC. All rights reserved.
> + *
> + * Authors: Michael Weiß <michael.weiss@aisec.fraunhofer.de>
> + */
> +
> +#ifndef DM_AUDIT_H
> +#define DM_AUDIT_H
> +
> +#include <linux/device-mapper.h>
> +
> +#ifdef CONFIG_DM_AUDIT
> +void dm_audit_log_bio(const char *dm_msg_prefix, const char *op,
> +		      struct bio *bio, sector_t sector, int result);
> +void dm_audit_log_target(const char *dm_msg_prefix, const char *op,
> +			 struct dm_target *ti, int result);
> +#else
> +static inline void dm_audit_log_bio(const char *dm_msg_prefix, const char *op,
> +				    struct bio *bio, sector_t sector,
> +				    int result);
> +{
> +}
> +static inline void dm_audit_log_target(const char *dm_msg_prefix,
> +				       const char *op, struct dm_target *ti,
> +				       int result);
> +{
> +}
> +#endif
> +
> +#endif
> diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
> index daa481729e9b..9d766fcbcf62 100644
> --- a/include/uapi/linux/audit.h
> +++ b/include/uapi/linux/audit.h
> @@ -118,6 +118,7 @@
>  #define AUDIT_TIME_ADJNTPVAL	1333	/* NTP value adjustment */
>  #define AUDIT_BPF		1334	/* BPF subsystem */
>  #define AUDIT_EVENT_LISTENER	1335	/* Task joined multicast read socket */
> +#define AUDIT_DM		1336	/* Device Mapper events */
>  
>  #define AUDIT_AVC		1400	/* SE Linux avc denial or grant */
>  #define AUDIT_SELINUX_ERR	1401	/* Internal SE Linux Errors */
> @@ -140,6 +141,7 @@
>  #define AUDIT_MAC_CALIPSO_ADD	1418	/* NetLabel: add CALIPSO DOI entry */
>  #define AUDIT_MAC_CALIPSO_DEL	1419	/* NetLabel: del CALIPSO DOI entry */
>  
> +

Unnecessary additional whitespace.

>  #define AUDIT_FIRST_KERN_ANOM_MSG   1700
>  #define AUDIT_LAST_KERN_ANOM_MSG    1799
>  #define AUDIT_ANOM_PROMISCUOUS      1700 /* Device changed promiscuous mode */