Re: [PATCH 1/3] dm: introduce audit event module for device mapper

From: Casey Schaufler
Date: Thu Aug 12 2021 - 13:09:13 EST

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@xxxxxxxxxxxxxxxxxxx>
> ---
> 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@xxxxxxxxxxxxxxxxxxx>
> + */
> +
> +#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@xxxxxxxxxxxxxxxxxxx>
> + */
> +
> +#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 */