From:   Lukas Vrabec <lvrabec@redhat.com>
To:     selinux-refpolicy@vger.kernel.org
Cc:     Lukas Vrabec <lvrabec@redhat.com>
Subject: [PATCH] Label /sys/kernel/ns_last_pid as sysctl_kernel_ns_last_pid_t
Date:   Mon,  8 Apr 2019 18:19:07 +0200
Message-Id: <20190408161907.10322-1-lvrabec@redhat.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: selinux-refpolicy-owner@vger.kernel.org
Precedence: bulk

CRIU can influence the PID of the threads it wants to create.
CRIU uses /proc/sys/kernel/ns_last_pidto tell the kernel which
PID it wants for the next clone().
So it has to write to that file. This feels like a problematic as
it opens up the container writing to all sysctl_kernel_t.

Using new label container_t will just write to
sysctl_kernel_ns_last_pid_t instad writing to more generic
sysctl_kernel_t files.
---
 policy/modules/kernel/kernel.if | 60 +++++++++++++++++++++++++++++++++
 policy/modules/kernel/kernel.te |  7 ++++
 2 files changed, 67 insertions(+)

diff --git a/policy/modules/kernel/kernel.if b/policy/modules/kernel/kernel.if
index 1ad282aa..3f0a2dbe 100644
--- a/policy/modules/kernel/kernel.if
+++ b/policy/modules/kernel/kernel.if
@@ -2150,6 +2150,66 @@ interface(`kernel_mounton_kernel_sysctl_files',`
 	allow $1 sysctl_kernel_t:file { getattr mounton };
 ')
 
+########################################
+## <summary>
+##	Read kernel ns lastpid sysctls.
+## </summary>
+## <param name="domain">
+##	<summary>
+##	Domain allowed access.
+##	</summary>
+## </param>
+## <rolecap/>
+#
+interface(`kernel_read_kernel_ns_lastpid_sysctls',`
+	gen_require(`
+		type proc_t, sysctl_t, sysctl_kernel_ns_last_pid_t;
+	')
+
+	read_files_pattern($1, { proc_t sysctl_t sysctl_kernel_ns_last_pid_t }, sysctl_kernel_ns_last_pid_t)
+
+	list_dirs_pattern($1, { proc_t sysctl_t }, sysctl_kernel_ns_last_pid_t)
+')
+
+########################################
+## <summary>
+##	Do not audit attempts to write kernel ns lastpid sysctls.
+## </summary>
+## <param name="domain">
+##	<summary>
+##	Domain to not audit.
+##	</summary>
+## </param>
+#
+interface(`kernel_dontaudit_write_kernel_ns_lastpid_sysctl',`
+	gen_require(`
+		type sysctl_kernel_ns_last_pid_t;
+	')
+
+	dontaudit $1 sysctl_kernel_ns_last_pid_t:file write;
+')
+
+########################################
+## <summary>
+##	Read and write kernel ns lastpid sysctls.
+## </summary>
+## <param name="domain">
+##	<summary>
+##	Domain allowed access.
+##	</summary>
+## </param>
+## <rolecap/>
+#
+interface(`kernel_rw_kernel_ns_lastpid_sysctl',`
+	gen_require(`
+		type proc_t, sysctl_t, sysctl_kernel_ns_last_pid_t;
+	')
+
+	rw_files_pattern($1, { proc_t sysctl_t sysctl_kernel_ns_last_pid_t }, sysctl_kernel_ns_last_pid_t)
+
+	list_dirs_pattern($1, { proc_t sysctl_t }, sysctl_kernel_ns_last_pid_t)
+')
+
 ########################################
 ## <summary>
 ##	Search filesystem sysctl directories.
diff --git a/policy/modules/kernel/kernel.te b/policy/modules/kernel/kernel.te
index 8e958074..f5ec1c22 100644
--- a/policy/modules/kernel/kernel.te
+++ b/policy/modules/kernel/kernel.te
@@ -132,6 +132,11 @@ genfscon proc /sys/fs gen_context(system_u:object_r:sysctl_fs_t,s0)
 type sysctl_kernel_t, sysctl_type;
 genfscon proc /sys/kernel gen_context(system_u:object_r:sysctl_kernel_t,s0)
 
+# /sys/kernel/ns_last_pid file
+type sysctl_kernel_ns_last_pid_t, sysctl_type;
+fs_associate(sysctl_kernel_ns_last_pid_t)
+genfscon proc /sys/kernel/ns_last_pid gen_context(system_u:object_r:sysctl_kernel_ns_last_pid_t,s0)
+
 # /proc/sys/kernel/modprobe file
 type sysctl_modprobe_t, sysctl_type;
 genfscon proc /sys/kernel/modprobe gen_context(system_u:object_r:sysctl_modprobe_t,s0)
@@ -232,6 +237,8 @@ allow kernel_t sysctl_kernel_t:dir list_dir_perms;
 allow kernel_t sysctl_kernel_t:file read_file_perms;
 allow kernel_t sysctl_t:dir list_dir_perms;
 
+allow kernel_t sysctl_kernel_ns_last_pid_t:file read_file_perms;
+
 # Other possible mount points for the root fs are in files
 allow kernel_t unlabeled_t:dir mounton;
 # Kernel-generated traffic e.g., TCP resets on
-- 
2.20.1