On Thu, Feb 21, 2019 at 01:42:13PM -0500, Stephen Smalley wrote:
> 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 is 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. Programs that instead use selinux_check_access()
> like dbus-broker do not have this problem.
>
> Other known issues:
> - Not everything appears to be relabeled, so some files are left with invalid
> contexts and remapped to the unlabeled SID/context.
> - X will fail due to lack of a x_contexts file
> - libvirtd will fail due to lack of a virtual_domain_context file
> - crond reports an error with "No security context"
>
> 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.
> Add default seusers mapping and failsafe context for use by
> pam_selinux / libselinux.
> Set to permissive mode rather than enforcing to permit initial autorelabel.
> Update the list of filesystem types to be relabeled.
> Create /.autorelabel to trigger an autorelabel on reboot.
> Drop broken attempt to relabel the /dev mountpoint directory.
>
> Signed-off-by: Stephen Smalley <sds@xxxxxxxxxxxxx>
> ---
> scripts/selinux/install_policy.sh | 82 ++++++++-------
> scripts/selinux/mdp/mdp.c | 164 +++++++++++++++++++++++++-----
> 2 files changed, 183 insertions(+), 63 deletions(-)
>
> diff --git a/scripts/selinux/install_policy.sh b/scripts/selinux/install_policy.sh
> index 0b86c47baf7d..09eab4d0da5c 100755
> --- a/scripts/selinux/install_policy.sh
> +++ b/scripts/selinux/install_policy.sh
> @@ -1,30 +1,51 @@
> #!/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"
> - exit 1
> - fi
> + echo "Could not find setfiles"
> + echo "Do you have policycoreutils installed?"
> + exit 1
> 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.$VERS policy.conf
>
> mkdir -p /etc/selinux/dummy/policy
> mkdir -p /etc/selinux/dummy/contexts/files
>
> +echo "__default__:user_u" > /etc/selinux/dummy/seusers
Should this be "__default__:user_u:s0-s0"?
> +echo "base_r:base_t" > /etc/selinux/dummy/contexts/failsafe_context
Should this be "base_r:base_t:s0"?
> +
> cp file_contexts /etc/selinux/dummy/contexts/files
> cp dbus_contexts /etc/selinux/dummy/contexts
> cp policy.$VERS /etc/selinux/dummy/policy
> @@ -33,37 +54,22 @@ 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
> - cat > /etc/selinux/config << EOF
> -SELINUX=enforcing
> +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=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 /
> +$SF -F file_contexts /
>
> -mounts=`cat /proc/$$/mounts | egrep "ext2|ext3|xfs|jfs|ext4|ext4dev|gfs2" | awk '{ print $2 '}`
> -$SF file_contexts $mounts
> +mounts=`cat /proc/$$/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
> +touch /.autorelabel
Probably best to instead: "echo "-F" > /.autorelabel"?
> diff --git a/scripts/selinux/mdp/mdp.c b/scripts/selinux/mdp/mdp.c
> index 073fe7537f6c..daad333c7252 100644
> --- a/scripts/selinux/mdp/mdp.c
> +++ b/scripts/selinux/mdp/mdp.c
> @@ -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 +130,126 @@ 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 : "")
> +
> + /*
> + * Filesystems whose inode labels can be fetched via getxattr.
> + */
> +#ifdef CONFIG_EXT2_FS_SECURITY
> + FS_USE("xattr", "ext2");
> +#endif
> +#ifdef CONFIG_EXT3_FS_SECURITY
> + FS_USE("xattr", "ext3");
> +#endif
> +#ifdef CONFIG_EXT4_FS_SECURITY
> + 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_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 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
>
> - 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");
> +#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 +258,8 @@ 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;
> --
> 2.20.1
>
--
Key fingerprint = 5F4D 3CDB D3F8 3652 FBD8 02D5 3B6C 5F1D 2C7B 6B02
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Dominick Grift
