Re: [PATCH v1] perf tool: make Perf tool aware of SELinux access control

From: Alexey Budankov
Date: Fri Mar 20 2020 - 08:24:57 EST


On 19.03.2020 22:05, Arnaldo Carvalho de Melo wrote:
> Em Thu, Mar 19, 2020 at 04:01:26PM -0300, Arnaldo Carvalho de Melo escreveu:
<SNIP>
>
> So I'll try the steps below with/without your patch, and then... what
> are the steps that a tester needs to go thru to have that refpolicy in?
> Install some new SELinux package or library, spelling out in detail the
> steps one needs to go thru helps reviewing/testing,

Yes, sure. Steps to extend FC31 Targeted policy for testing perf_events access control:

* download selinux-policy srpm [1]: selinux-policy-3.14.4-48.fc31.src.rpm on my FC31

* install srpm - it creates rpmbuild dir:
[root@host ~]# rpm -Uhv selinux-policy-3.14.4-48.fc31.src.rpm

* get into rpmbuild/SPECS dir and unpack sources:
[root@host ~]# rpmbuild -bp selinux-policy.spec

* Place patch below at rpmbuild/BUILD/selinux-policy-b86eaaf4dbcf2d51dd4432df7185c0eaf3cbcc02
dir and apply it:
[root@host ~]# patch -p1 < selinux-policy-perf-events-perfmon.patch
patching file policy/flask/access_vectors
patching file policy/flask/security_classes
[root@host ~]# cat selinux-policy-perf-events-perfmon.patch
diff -Nura a/policy/flask/access_vectors b/policy/flask/access_vectors
--- a/policy/flask/access_vectors 2020-02-04 18:19:53.000000000 +0300
+++ b/policy/flask/access_vectors 2020-02-28 23:37:25.000000000 +0300
@@ -174,6 +174,7 @@
wake_alarm
block_suspend
audit_read
+ perfmon
}

#
@@ -1099,3 +1100,15 @@

class xdp_socket
inherits socket
+
+class perf_event
+{
+ open
+ cpu
+ kernel
+ tracepoint
+ read
+ write
+}
+
+
diff -Nura a/policy/flask/security_classes b/policy/flask/security_classes
--- a/policy/flask/security_classes 2020-02-04 18:19:53.000000000 +0300
+++ b/policy/flask/security_classes 2020-02-28 21:35:17.000000000 +0300
@@ -200,4 +200,6 @@

class xdp_socket

+class perf_event
+
# FLASK

[root@host ~]#

* get into rpmbuild/SPECS dir and build policy packages from patched sources:
[root@host ~]# rpmbuild --noclean --noprep -ba selinux-policy.spec
so you have this:
[root@host ~]# ls -alh rpmbuild/RPMS/noarch/
total 33M
drwxr-xr-x. 2 root root 4.0K Mar 20 12:16 .
drwxr-xr-x. 3 root root 4.0K Mar 20 12:16 ..
-rw-r--r--. 1 root root 112K Mar 20 12:16 selinux-policy-3.14.4-48.fc31.noarch.rpm
-rw-r--r--. 1 root root 1.2M Mar 20 12:17 selinux-policy-devel-3.14.4-48.fc31.noarch.rpm
-rw-r--r--. 1 root root 2.3M Mar 20 12:17 selinux-policy-doc-3.14.4-48.fc31.noarch.rpm
-rw-r--r--. 1 root root 12M Mar 20 12:17 selinux-policy-minimum-3.14.4-48.fc31.noarch.rpm
-rw-r--r--. 1 root root 4.5M Mar 20 12:16 selinux-policy-mls-3.14.4-48.fc31.noarch.rpm
-rw-r--r--. 1 root root 111K Mar 20 12:16 selinux-policy-sandbox-3.14.4-48.fc31.noarch.rpm
-rw-r--r--. 1 root root 14M Mar 20 12:17 selinux-policy-targeted-3.14.4-48.fc31.noarch.rpm

* install SELinux packages from FC repo [2], if not already done so, and
update with the patched rpms above:
[root@host ~]# rpm -Uhv rpmbuild/RPMS/noarch/selinux-policy-*

* there are also packages providing GUI interface and visualizing SELinux management
[root@host ~]# dnf install policycoreutils-gui

* enable SELinux Permissive mode for Targeted policy, if not already done so:
[root@host ~]# cat /etc/selinux/config
# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
# enforcing - SELinux security policy is enforced.
# permissive - SELinux prints warnings instead of enforcing.
# disabled - No SELinux policy is loaded.
SELINUX=permissive
# SELINUXTYPE= can take one of these three values:
# targeted - Targeted processes are protected,
# minimum - Modification of targeted policy. Only selected processes are protected.
# mls - Multi Level Security protection.
SELINUXTYPE=targeted

* enable filesystem SELinux labeling at the next reboot
[root@host ~]# touch /.autorelabel

* reboot machine and it will label filesystems and load Targeted policy into the kernel

* login and check that dmesg output doesn't mention that perf_event class is unknown to SELinux subsystem

* check that SELinux is enabled and in Permissive mode
[root@host ~]# getenforce
Permissive

* turn SELinux into Enforcing mode:
[root@host ~]# setenforce 1
[root@host ~]# getenforce
Enforcing

* Now the machine is enabled to test the patch

--- If something went wrong ---

* To turn SELinux into Permissive mode: setenforce 0
* To fully disable SELinux during kernel boot [3] set kernel command line parameter: selinux=0
* To remove SELinux labeling from local filesystems: find / -mount -print0 | xargs -0 setfattr -h -x security.selinux
* To fully turn SELinux off a machine set SELINUX=disabled at /etc/selinux/config file and reboot

~Alexey

[1] https://download-ib01.fedoraproject.org/pub/fedora/linux/updates/31/Everything/SRPMS/Packages/s/selinux-policy-3.14.4-49.fc31.src.rpm
[2] https://docs.fedoraproject.org/en-US/Fedora/11/html/Security-Enhanced_Linux/sect-Security-Enhanced_Linux-Working_with_SELinux-Enabling_and_Disabling_SELinux.html
[3] https://danwalsh.livejournal.com/10972.html