Hi Casey,
On Thu, 2021-08-12 at 10:08 -0700, Casey Schaufler wrote:
> 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);
> > +{
> > +}
kernel test robot spotted a syntax error if CONFIG_DM_AUDIT is
not set here, too. Will fix this in v2.
> > +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 */
Thanks for spotting the errors, I will fix them in v2.
Regards,
Michael
