Messages in this thread | ![/](/images/icornerl.gif) | | Subject | Re: [PATCH v3 2/3] selinux: add basic filtering for audit trace events | From | Stephen Smalley <> | Date | Tue, 18 Aug 2020 10:36:12 -0400 |
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On 8/17/20 1:07 PM, Thiébaud Weksteen 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> > --- > diff --git a/security/selinux/avc.c b/security/selinux/avc.c > index b0a0af778b70..7de5cc5169af 100644 > --- a/security/selinux/avc.c > +++ b/security/selinux/avc.c > @@ -705,35 +705,39 @@ 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 { > audit_log_format(ab, " scontext=%s", scontext); > - kfree(scontext); > } I guess technically you should drop the { } above since it is reduced to a single statement body. > > - 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); > + audit_log_format(ab, " tcontext=%s", tcontext); > } Ditto.
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