Commit e37c1877 authored by Stephen Smalley's avatar Stephen Smalley Committed by Paul Moore
Browse files

scripts/selinux: modernize mdp 



Derived in part from a patch by Dominick Grift.

The MDP example no longer works on modern systems.  Fix it.
While we are at it, add MLS support and enable it.

NB This still does not work on systems using dbus-daemon instead of
dbus-broker because dbus-daemon does not yet gracefully handle unknown
classes/permissions.  This appears to be a deficiency in libselinux's
selinux_set_mapping() interface and underlying implementation,
which was never fully updated to deal with unknown classes/permissions
unlike the kernel.  The same problem also occurs with XSELinux.
Programs that instead use selinux_check_access() like dbus-broker
should not have this problem.

Changes to mdp:
Add support for devtmpfs, required by modern Linux distributions.
Add MLS support, with sample sensitivities, categories, and constraints.
Generate fs_use and genfscon rules based on kernel configuration.
Update list of filesystem types for fs_use and genfscon rules.
Use object_r for object contexts.

Changes to install_policy.sh:
Bail immediately on any errors.
Provide more helpful error messages when unable to find userspace tools.
Refuse to run if SELinux is already enabled.
Unconditionally move aside /etc/selinux/config and create a new one.
Build policy with -U allow so that userspace object managers do not break.
Build policy with MLS enabled by default.
Create seusers, failsafe_context, and default_contexts for use by
pam_selinux / libselinux.
Create x_contexts for the SELinux X extension.
Create virtual_domain_context and virtual_image_context for libvirtd.
Set to permissive mode rather than enforcing to permit initial autorelabel.
Update the list of filesystem types to be relabeled.
Write -F to /.autorelabel to cause a forced autorelabel on reboot.
Drop broken attempt to relabel the /dev mountpoint directory.

Signed-off-by: default avatarStephen Smalley <sds@tycho.nsa.gov>
Acked-by: default avatarDominick Grift <dominick.grift@defensec.nl>
Signed-off-by: default avatarPaul Moore <paul@paul-moore.com>
parent 9e98c678

scripts/selinux/install_policy.sh

+54 −38
Original line number Diff line number Diff line 
#!/bin/sh

# SPDX-License-Identifier: GPL-2.0

set -e

if [ `id -u` -ne 0 ]; then

	echo "$0: must be root to install the selinux policy"

	exit 1

fi



SF=`which setfiles`

if [ $? -eq 1 ]; then

	if [ -f /sbin/setfiles ]; then

		SF="/usr/setfiles"

	else

		echo "no selinux tools installed: setfiles"

	echo "Could not find setfiles"

	echo "Do you have policycoreutils installed?"

	exit 1

fi

fi



cd mdp



CP=`which checkpolicy`

if [ $? -eq 1 ]; then

	echo "Could not find checkpolicy"

	echo "Do you have checkpolicy installed?"

	exit 1

fi

VERS=`$CP -V | awk '{print $1}'`



./mdp policy.conf file_contexts

$CP -o policy.$VERS policy.conf

ENABLED=`which selinuxenabled`

if [ $? -eq 1 ]; then

	echo "Could not find selinuxenabled"

	echo "Do you have libselinux-utils installed?"

	exit 1

fi



if selinuxenabled; then

    echo "SELinux is already enabled"

    echo "This prevents safely relabeling all files."

    echo "Boot with selinux=0 on the kernel command-line or"

    echo "SELINUX=disabled in /etc/selinux/config."

    exit 1

fi



cd mdp

./mdp -m policy.conf file_contexts

$CP -U allow -M -o policy.$VERS policy.conf



mkdir -p /etc/selinux/dummy/policy

mkdir -p /etc/selinux/dummy/contexts/files



echo "__default__:user_u:s0" > /etc/selinux/dummy/seusers

echo "base_r:base_t:s0" > /etc/selinux/dummy/contexts/failsafe_context

echo "base_r:base_t:s0 base_r:base_t:s0" > /etc/selinux/dummy/default_contexts

cat > /etc/selinux/dummy/contexts/x_contexts <<EOF

client * user_u:base_r:base_t:s0

property * user_u:object_r:base_t:s0

extension * user_u:object_r:base_t:s0

selection * user_u:object_r:base_t:s0

event * user_u:object_r:base_t:s0

EOF

touch /etc/selinux/dummy/contexts/virtual_domain_context

touch /etc/selinux/dummy/contexts/virtual_image_context



cp file_contexts /etc/selinux/dummy/contexts/files

cp dbus_contexts /etc/selinux/dummy/contexts

cp policy.$VERS /etc/selinux/dummy/policy
@@ -33,37 +64,22 @@ FC_FILE=/etc/selinux/dummy/contexts/files/file_contexts 
if [ ! -d /etc/selinux ]; then

	mkdir -p /etc/selinux

fi

if [ ! -f /etc/selinux/config ]; then

if [ -f /etc/selinux/config ]; then

    echo "/etc/selinux/config exists, moving to /etc/selinux/config.bak."

    mv /etc/selinux/config /etc/selinux/config.bak

fi

echo "Creating new /etc/selinux/config for dummy policy."

cat > /etc/selinux/config << EOF

SELINUX=enforcing

SELINUX=permissive

SELINUXTYPE=dummy

EOF

else

	TYPE=`cat /etc/selinux/config | grep "^SELINUXTYPE" | tail -1 | awk -F= '{ print $2 '}`

	if [ "eq$TYPE" != "eqdummy" ]; then

		selinuxenabled

		if [ $? -eq 0 ]; then

			echo "SELinux already enabled with a non-dummy policy."

			echo "Exiting.  Please install policy by hand if that"

			echo "is what you REALLY want."

			exit 1

		fi

		mv /etc/selinux/config /etc/selinux/config.mdpbak

		grep -v "^SELINUXTYPE" /etc/selinux/config.mdpbak >> /etc/selinux/config

		echo "SELINUXTYPE=dummy" >> /etc/selinux/config

	fi

fi



cd /etc/selinux/dummy/contexts/files

$SF file_contexts /



mounts=`cat /proc/$$/mounts | egrep "ext2|ext3|xfs|jfs|ext4|ext4dev|gfs2" | awk '{ print $2 '}`

$SF file_contexts $mounts

$SF -F file_contexts /



mounts=`cat /proc/$$/mounts | \

	egrep "ext[234]|jfs|xfs|reiserfs|jffs2|gfs2|btrfs|f2fs|ocfs2" | \

	awk '{ print $2 '}`

$SF -F file_contexts $mounts



dodev=`cat /proc/$$/mounts | grep "/dev "`

if [ "eq$dodev" != "eq" ]; then

	mount --move /dev /mnt

	$SF file_contexts /dev

	mount --move /mnt /dev

fi
 
echo "-F" > /.autorelabel

scripts/selinux/mdp/mdp.c

+140 −25
Original line number Diff line number Diff line
@@ -33,6 +33,7 @@ 
#include <unistd.h>

#include <string.h>

#include <sys/socket.h>

#include <linux/kconfig.h>



static void usage(char *name)

{
@@ -95,10 +96,31 @@ int main(int argc, char *argv[]) 
	}

	fprintf(fout, "\n");



	/* NOW PRINT OUT MLS STUFF */

	/* print out mls declarations and constraints */

	if (mls) {

		printf("MLS not yet implemented\n");

		exit(1);

		fprintf(fout, "sensitivity s0;\n");

		fprintf(fout, "sensitivity s1;\n");

		fprintf(fout, "dominance { s0 s1 }\n");

		fprintf(fout, "category c0;\n");

		fprintf(fout, "category c1;\n");

		fprintf(fout, "level s0:c0.c1;\n");

		fprintf(fout, "level s1:c0.c1;\n");

#define SYSTEMLOW "s0"

#define SYSTEMHIGH "s1:c0.c1"

		for (i = 0; secclass_map[i].name; i++) {

			struct security_class_mapping *map = &secclass_map[i];



			fprintf(fout, "mlsconstrain %s {\n", map->name);

			for (j = 0; map->perms[j]; j++)

				fprintf(fout, "\t%s\n", map->perms[j]);

			/*

			 * This requires all subjects and objects to be

			 * single-level (l2 eq h2), and that the subject

			 * level dominate the object level (h1 dom h2)

			 * in order to have any permissions to it.

			 */

			fprintf(fout, "} (l2 eq h2 and h1 dom h2);\n\n");

		}

	}



	/* types, roles, and allows */
@@ -108,34 +130,127 @@ int main(int argc, char *argv[]) 
	for (i = 0; secclass_map[i].name; i++)

		fprintf(fout, "allow base_t base_t:%s *;\n",

			secclass_map[i].name);

	fprintf(fout, "user user_u roles { base_r };\n");

	fprintf(fout, "\n");

	fprintf(fout, "user user_u roles { base_r }");

	if (mls)

		fprintf(fout, " level %s range %s - %s", SYSTEMLOW,

			SYSTEMLOW, SYSTEMHIGH);

	fprintf(fout, ";\n");



#define SUBJUSERROLETYPE "user_u:base_r:base_t"

#define OBJUSERROLETYPE "user_u:object_r:base_t"



	/* default sids */

	for (i = 1; i < initial_sid_to_string_len; i++)

		fprintf(fout, "sid %s user_u:base_r:base_t\n", initial_sid_to_string[i]);

		fprintf(fout, "sid %s " SUBJUSERROLETYPE "%s\n",

			initial_sid_to_string[i], mls ? ":" SYSTEMLOW : "");

	fprintf(fout, "\n");



	fprintf(fout, "fs_use_xattr ext2 user_u:base_r:base_t;\n");

	fprintf(fout, "fs_use_xattr ext3 user_u:base_r:base_t;\n");

	fprintf(fout, "fs_use_xattr ext4 user_u:base_r:base_t;\n");

	fprintf(fout, "fs_use_xattr jfs user_u:base_r:base_t;\n");

	fprintf(fout, "fs_use_xattr xfs user_u:base_r:base_t;\n");

	fprintf(fout, "fs_use_xattr reiserfs user_u:base_r:base_t;\n");

	fprintf(fout, "fs_use_xattr jffs2 user_u:base_r:base_t;\n");

	fprintf(fout, "fs_use_xattr gfs2 user_u:base_r:base_t;\n");

#define FS_USE(behavior, fstype)			    \

	fprintf(fout, "fs_use_%s %s " OBJUSERROLETYPE "%s;\n", \

		behavior, fstype, mls ? ":" SYSTEMLOW : "")



	fprintf(fout, "fs_use_task eventpollfs user_u:base_r:base_t;\n");

	fprintf(fout, "fs_use_task pipefs user_u:base_r:base_t;\n");

	fprintf(fout, "fs_use_task sockfs user_u:base_r:base_t;\n");

	/*

	 * Filesystems whose inode labels can be fetched via getxattr.

	 */

#ifdef CONFIG_EXT2_FS_SECURITY

	FS_USE("xattr", "ext2");

#endif

#ifdef CONFIG_EXT4_FS_SECURITY

#ifdef CONFIG_EXT4_USE_FOR_EXT2

	FS_USE("xattr", "ext2");

#endif

	FS_USE("xattr", "ext3");

	FS_USE("xattr", "ext4");

#endif

#ifdef CONFIG_JFS_SECURITY

	FS_USE("xattr", "jfs");

#endif

#ifdef CONFIG_REISERFS_FS_SECURITY

	FS_USE("xattr", "reiserfs");

#endif

#ifdef CONFIG_JFFS2_FS_SECURITY

	FS_USE("xattr", "jffs2");

#endif

#ifdef CONFIG_XFS_FS

	FS_USE("xattr", "xfs");

#endif

#ifdef CONFIG_GFS2_FS

	FS_USE("xattr", "gfs2");

#endif

#ifdef CONFIG_BTRFS_FS

	FS_USE("xattr", "btrfs");

#endif

#ifdef CONFIG_F2FS_FS_SECURITY

	FS_USE("xattr", "f2fs");

#endif

#ifdef CONFIG_OCFS2_FS

	FS_USE("xattr", "ocsfs2");

#endif

#ifdef CONFIG_OVERLAY_FS

	FS_USE("xattr", "overlay");

#endif

#ifdef CONFIG_SQUASHFS_XATTR

	FS_USE("xattr", "squashfs");

#endif



	/*

	 * Filesystems whose inodes are labeled from allocating task.

	 */

	FS_USE("task", "pipefs");

	FS_USE("task", "sockfs");



	fprintf(fout, "fs_use_trans mqueue user_u:base_r:base_t;\n");

	fprintf(fout, "fs_use_trans devpts user_u:base_r:base_t;\n");

	fprintf(fout, "fs_use_trans hugetlbfs user_u:base_r:base_t;\n");

	fprintf(fout, "fs_use_trans tmpfs user_u:base_r:base_t;\n");

	fprintf(fout, "fs_use_trans shm user_u:base_r:base_t;\n");

	/*

	 * Filesystems whose inode labels are computed from both

	 * the allocating task and the superblock label.

	 */

#ifdef CONFIG_UNIX98_PTYS

	FS_USE("trans", "devpts");

#endif

#ifdef CONFIG_HUGETLBFS

	FS_USE("trans", "hugetlbfs");

#endif

#ifdef CONFIG_TMPFS

	FS_USE("trans", "tmpfs");

#endif

#ifdef CONFIG_DEVTMPFS

	FS_USE("trans", "devtmpfs");

#endif

#ifdef CONFIG_POSIX_MQUEUE

	FS_USE("trans", "mqueue");

#endif



#define GENFSCON(fstype, prefix)			     \

	fprintf(fout, "genfscon %s %s " OBJUSERROLETYPE "%s\n", \

		fstype, prefix, mls ? ":" SYSTEMLOW : "")



	fprintf(fout, "genfscon proc / user_u:base_r:base_t\n");

	/*

	 * Filesystems whose inodes are labeled from path prefix match

	 * relative to the filesystem root.  Depending on the filesystem,

	 * only a single label for all inodes may be supported.  Here

	 * we list the filesystem types for which per-file labeling is

	 * supported using genfscon; any other filesystem type can also

	 * be added by only with a single entry for all of its inodes.

	 */

#ifdef CONFIG_PROC_FS

	GENFSCON("proc", "/");

#endif

#ifdef CONFIG_SECURITY_SELINUX

	GENFSCON("selinuxfs", "/");

#endif

#ifdef CONFIG_SYSFS

	GENFSCON("sysfs", "/");

#endif

#ifdef CONFIG_DEBUG_FS

	GENFSCON("debugfs", "/");

#endif

#ifdef CONFIG_TRACING

	GENFSCON("tracefs", "/");

#endif

#ifdef CONFIG_PSTORE

	GENFSCON("pstore", "/");

#endif

	GENFSCON("cgroup", "/");

	GENFSCON("cgroup2", "/");



	fclose(fout);
@@ -144,8 +259,8 @@ int main(int argc, char *argv[]) 
		printf("Wrote policy, but cannot open %s for writing\n", ctxout);

		usage(argv[0]);

	}

	fprintf(fout, "/ user_u:base_r:base_t\n");

	fprintf(fout, "/.* user_u:base_r:base_t\n");

	fprintf(fout, "/ " OBJUSERROLETYPE "%s\n", mls ? ":" SYSTEMLOW : "");

	fprintf(fout, "/.* " OBJUSERROLETYPE "%s\n", mls ? ":" SYSTEMLOW : "");

	fclose(fout);



	return 0;

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