[dm-devel] [PATCH 1/3] dm: introduce audit event module for device mapper
Michael Weiß
michael.weiss at aisec.fraunhofer.de
Thu Aug 12 14:57:42 UTC 2021
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 at 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
+ 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 at 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 at 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 */
+
#define AUDIT_FIRST_KERN_ANOM_MSG 1700
#define AUDIT_LAST_KERN_ANOM_MSG 1799
#define AUDIT_ANOM_PROMISCUOUS 1700 /* Device changed promiscuous mode */
--
2.20.1
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