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Age	Commit message (Collapse)	Author
2020-08-21	selinux: add basic filtering for audit trace events	Peter Enderborg
	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> Signed-off-by: Paul Moore <paul@paul-moore.com>
2020-08-21	selinux: add tracepoint on audited events	Thiébaud Weksteen
	The audit data currently captures which process and which target is responsible for a denial. There is no data on where exactly in the process that call occurred. Debugging can be made easier by being able to reconstruct the unified kernel and userland stack traces [1]. Add a tracepoint on the SELinux denials which can then be used by userland (i.e. perf). Although this patch could manually be added by each OS developer to trouble shoot a denial, adding it to the kernel streamlines the developers workflow. It is possible to use perf for monitoring the event: # perf record -e avc:selinux_audited -g -a ^C # perf report -g [...] 6.40% 6.40% audited=800000 tclass=4 \| __libc_start_main \| \|--4.60%--__GI___ioctl \| entry_SYSCALL_64 \| do_syscall_64 \| __x64_sys_ioctl \| ksys_ioctl \| binder_ioctl \| binder_set_nice \| can_nice \| capable \| security_capable \| cred_has_capability.isra.0 \| slow_avc_audit \| common_lsm_audit \| avc_audit_post_callback \| avc_audit_post_callback \| It is also possible to use the ftrace interface: # echo 1 > /sys/kernel/debug/tracing/events/avc/selinux_audited/enable # cat /sys/kernel/debug/tracing/trace tracer: nop entries-in-buffer/entries-written: 1/1 #P:8 [...] dmesg-3624 [001] 13072.325358: selinux_denied: audited=800000 tclass=4 The tclass value can be mapped to a class by searching security/selinux/flask.h. The audited value is a bit field of the permissions described in security/selinux/av_permissions.h for the corresponding class. [1] https://source.android.com/devices/tech/debug/native_stack_dump Signed-off-by: Thiébaud Weksteen <tweek@google.com> Suggested-by: Joel Fernandes <joelaf@google.com> Reviewed-by: Peter Enderborg <peter.enderborg@sony.com> Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com> Signed-off-by: Paul Moore <paul@paul-moore.com>