diff mbox series

[v4,2/2] selinux: add basic filtering for audit trace events

Message ID 20200821140836.3707282-3-tweek@google.com (mailing list archive)
State Accepted
Headers show
Series selinux: add detailed tracepoint on audited events | expand

Commit Message

Thiébaud Weksteen Aug. 21, 2020, 2:08 p.m. UTC
From: Peter Enderborg <peter.enderborg@sony.com>

This patch adds further attributes to the event. These attributes are
helpful to understand the context of the message and can be used
to filter the events.

There are three common items. Source context, target context and tclass.
There are also items from the outcome of operation performed.

An event is similar to:
           <...>-1309  [002] ....  6346.691689: selinux_audited:
       requested=0x4000000 denied=0x4000000 audited=0x4000000
       result=-13
       scontext=system_u:system_r:cupsd_t:s0-s0:c0.c1023
       tcontext=system_u:object_r:bin_t:s0 tclass=file

With systems where many denials are occurring, it is useful to apply a
filter. The filtering is a set of logic that is inserted with
the filter file. Example:
 echo "tclass==\"file\" " > events/avc/selinux_audited/filter

This adds that we only get tclass=file.

The trace can also have extra properties. Adding the user stack
can be done with
   echo 1 > options/userstacktrace

Now the output will be
         runcon-1365  [003] ....  6960.955530: selinux_audited:
     requested=0x4000000 denied=0x4000000 audited=0x4000000
     result=-13
     scontext=system_u:system_r:cupsd_t:s0-s0:c0.c1023
     tcontext=system_u:object_r:bin_t:s0 tclass=file
          runcon-1365  [003] ....  6960.955560: <user stack trace>
 =>  <00007f325b4ce45b>
 =>  <00005607093efa57>

Signed-off-by: Peter Enderborg <peter.enderborg@sony.com>
Reviewed-by: Thiébaud Weksteen <tweek@google.com>
---
 include/trace/events/avc.h | 36 ++++++++++++++++++++++++++----------
 security/selinux/avc.c     | 28 +++++++++++++++-------------
 2 files changed, 41 insertions(+), 23 deletions(-)

Comments

Stephen Smalley Aug. 21, 2020, 3:35 p.m. UTC | #1
On Fri, Aug 21, 2020 at 10:09 AM Thiébaud Weksteen <tweek@google.com> wrote:
>
> From: Peter Enderborg <peter.enderborg@sony.com>
>
> This patch adds further attributes to the event. These attributes are
> helpful to understand the context of the message and can be used
> to filter the events.
>
> There are three common items. Source context, target context and tclass.
> There are also items from the outcome of operation performed.
>
> An event is similar to:
>            <...>-1309  [002] ....  6346.691689: selinux_audited:
>        requested=0x4000000 denied=0x4000000 audited=0x4000000
>        result=-13
>        scontext=system_u:system_r:cupsd_t:s0-s0:c0.c1023
>        tcontext=system_u:object_r:bin_t:s0 tclass=file
>
> With systems where many denials are occurring, it is useful to apply a
> filter. The filtering is a set of logic that is inserted with
> the filter file. Example:
>  echo "tclass==\"file\" " > events/avc/selinux_audited/filter
>
> This adds that we only get tclass=file.
>
> The trace can also have extra properties. Adding the user stack
> can be done with
>    echo 1 > options/userstacktrace
>
> Now the output will be
>          runcon-1365  [003] ....  6960.955530: selinux_audited:
>      requested=0x4000000 denied=0x4000000 audited=0x4000000
>      result=-13
>      scontext=system_u:system_r:cupsd_t:s0-s0:c0.c1023
>      tcontext=system_u:object_r:bin_t:s0 tclass=file
>           runcon-1365  [003] ....  6960.955560: <user stack trace>
>  =>  <00007f325b4ce45b>
>  =>  <00005607093efa57>
>
> Signed-off-by: Peter Enderborg <peter.enderborg@sony.com>
> Reviewed-by: Thiébaud Weksteen <tweek@google.com>

Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Paul Moore Aug. 21, 2020, 9:09 p.m. UTC | #2
On Fri, Aug 21, 2020 at 10:09 AM Thiébaud Weksteen <tweek@google.com> wrote:
>
> From: Peter Enderborg <peter.enderborg@sony.com>
>
> This patch adds further attributes to the event. These attributes are
> helpful to understand the context of the message and can be used
> to filter the events.
>
> There are three common items. Source context, target context and tclass.
> There are also items from the outcome of operation performed.
>
> An event is similar to:
>            <...>-1309  [002] ....  6346.691689: selinux_audited:
>        requested=0x4000000 denied=0x4000000 audited=0x4000000
>        result=-13
>        scontext=system_u:system_r:cupsd_t:s0-s0:c0.c1023
>        tcontext=system_u:object_r:bin_t:s0 tclass=file
>
> With systems where many denials are occurring, it is useful to apply a
> filter. The filtering is a set of logic that is inserted with
> the filter file. Example:
>  echo "tclass==\"file\" " > events/avc/selinux_audited/filter
>
> This adds that we only get tclass=file.
>
> The trace can also have extra properties. Adding the user stack
> can be done with
>    echo 1 > options/userstacktrace
>
> Now the output will be
>          runcon-1365  [003] ....  6960.955530: selinux_audited:
>      requested=0x4000000 denied=0x4000000 audited=0x4000000
>      result=-13
>      scontext=system_u:system_r:cupsd_t:s0-s0:c0.c1023
>      tcontext=system_u:object_r:bin_t:s0 tclass=file
>           runcon-1365  [003] ....  6960.955560: <user stack trace>
>  =>  <00007f325b4ce45b>
>  =>  <00005607093efa57>
>
> Signed-off-by: Peter Enderborg <peter.enderborg@sony.com>
> Reviewed-by: Thiébaud Weksteen <tweek@google.com>
> ---
>  include/trace/events/avc.h | 36 ++++++++++++++++++++++++++----------
>  security/selinux/avc.c     | 28 +++++++++++++++-------------
>  2 files changed, 41 insertions(+), 23 deletions(-)

... also merged into selinux/next, thanks everyone!
diff mbox series

Patch

diff --git a/include/trace/events/avc.h b/include/trace/events/avc.h
index 07c058a9bbcd..b55fda2e0773 100644
--- a/include/trace/events/avc.h
+++ b/include/trace/events/avc.h
@@ -1,6 +1,7 @@ 
 /* SPDX-License-Identifier: GPL-2.0 */
 /*
- * Author: Thiébaud Weksteen <tweek@google.com>
+ * Authors:	Thiébaud Weksteen <tweek@google.com>
+ *		Peter Enderborg <Peter.Enderborg@sony.com>
  */
 #undef TRACE_SYSTEM
 #define TRACE_SYSTEM avc
@@ -12,23 +13,38 @@ 
 
 TRACE_EVENT(selinux_audited,
 
-	TP_PROTO(struct selinux_audit_data *sad),
+	TP_PROTO(struct selinux_audit_data *sad,
+		char *scontext,
+		char *tcontext,
+		const char *tclass
+	),
 
-	TP_ARGS(sad),
+	TP_ARGS(sad, scontext, tcontext, tclass),
 
 	TP_STRUCT__entry(
-		__field(unsigned int, tclass)
-		__field(unsigned int, audited)
+		__field(u32, requested)
+		__field(u32, denied)
+		__field(u32, audited)
+		__field(int, result)
+		__string(scontext, scontext)
+		__string(tcontext, tcontext)
+		__string(tclass, tclass)
 	),
 
 	TP_fast_assign(
-		__entry->tclass = sad->tclass;
-		__entry->audited = sad->audited;
+		__entry->requested	= sad->requested;
+		__entry->denied		= sad->denied;
+		__entry->audited	= sad->audited;
+		__entry->result		= sad->result;
+		__assign_str(tcontext, tcontext);
+		__assign_str(scontext, scontext);
+		__assign_str(tclass, tclass);
 	),
 
-	TP_printk("tclass=%u audited=%x",
-		__entry->tclass,
-		__entry->audited)
+	TP_printk("requested=0x%x denied=0x%x audited=0x%x result=%d scontext=%s tcontext=%s tclass=%s",
+		__entry->requested, __entry->denied, __entry->audited, __entry->result,
+		__get_str(scontext), __get_str(tcontext), __get_str(tclass)
+	)
 );
 
 #endif
diff --git a/security/selinux/avc.c b/security/selinux/avc.c
index b0a0af778b70..3c05827608b6 100644
--- a/security/selinux/avc.c
+++ b/security/selinux/avc.c
@@ -705,35 +705,37 @@  static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
 {
 	struct common_audit_data *ad = a;
 	struct selinux_audit_data *sad = ad->selinux_audit_data;
-	char *scontext;
+	char *scontext = NULL;
+	char *tcontext = NULL;
+	const char *tclass = NULL;
 	u32 scontext_len;
+	u32 tcontext_len;
 	int rc;
 
-	trace_selinux_audited(sad);
-
 	rc = security_sid_to_context(sad->state, sad->ssid, &scontext,
 				     &scontext_len);
 	if (rc)
 		audit_log_format(ab, " ssid=%d", sad->ssid);
-	else {
+	else
 		audit_log_format(ab, " scontext=%s", scontext);
-		kfree(scontext);
-	}
 
-	rc = security_sid_to_context(sad->state, sad->tsid, &scontext,
-				     &scontext_len);
+	rc = security_sid_to_context(sad->state, sad->tsid, &tcontext,
+				     &tcontext_len);
 	if (rc)
 		audit_log_format(ab, " tsid=%d", sad->tsid);
-	else {
-		audit_log_format(ab, " tcontext=%s", scontext);
-		kfree(scontext);
-	}
+	else
+		audit_log_format(ab, " tcontext=%s", tcontext);
 
-	audit_log_format(ab, " tclass=%s", secclass_map[sad->tclass-1].name);
+	tclass = secclass_map[sad->tclass-1].name;
+	audit_log_format(ab, " tclass=%s", tclass);
 
 	if (sad->denied)
 		audit_log_format(ab, " permissive=%u", sad->result ? 0 : 1);
 
+	trace_selinux_audited(sad, scontext, tcontext, tclass);
+	kfree(tcontext);
+	kfree(scontext);
+
 	/* in case of invalid context report also the actual context string */
 	rc = security_sid_to_context_inval(sad->state, sad->ssid, &scontext,
 					   &scontext_len);