platform_system_sepolicy/public/update_engine_common.te
David Anderson 09bb944221 Add sepolicy for starting the snapuserd daemon through init.
Restrict access to controlling snapuserd via ctl properties. Allow
update_engine to control snapuserd, and connect/write to its socket.

update_engine needs this access so it can create the appropriate dm-user
device (which sends queries to snapuserd), which is then used to build
the update snapshot.

This also fixes a bug where /dev/dm-user was not properly labelled. As a
result, snapuserd and update_engine have been granted r_dir_perms to
dm_user_device.

Bug: 168554689
Test: full ota with VABC enabled
Change-Id: I1f65ba9f16a83fe3e8ed41a594421939a256aec0
2020-11-19 21:03:30 +00:00

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3.8 KiB
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# update_engine payload application permissions. These are shared between the
# background daemon and the recovery tool to sideload an update.
# Allow update_engine to reach block devices in /dev/block.
allow update_engine_common block_device:dir search;
# Allow read/write on system and boot partitions.
allow update_engine_common boot_block_device:blk_file rw_file_perms;
allow update_engine_common system_block_device:blk_file rw_file_perms;
# Where ioctls are granted via standard allow rules to block devices,
# automatically allow common ioctls that are generally needed by
# update_engine.
allowxperm update_engine_common dev_type:blk_file ioctl {
BLKDISCARD
BLKDISCARDZEROES
BLKROGET
BLKROSET
BLKSECDISCARD
BLKZEROOUT
};
# Allow to set recovery options in the BCB. Used to trigger factory reset when
# the update to an older version (channel change) or incompatible version
# requires it.
allow update_engine_common misc_block_device:blk_file rw_file_perms;
# read fstab
allow update_engine_common rootfs:dir getattr;
allow update_engine_common rootfs:file r_file_perms;
# Allow update_engine_common to mount on the /postinstall directory and reset the
# labels on the mounted filesystem to postinstall_file.
allow update_engine_common postinstall_mnt_dir:dir { mounton getattr search };
allow update_engine_common postinstall_file:filesystem { mount unmount relabelfrom relabelto };
allow update_engine_common labeledfs:filesystem relabelfrom;
# Allow update_engine_common to read and execute postinstall_file.
allow update_engine_common postinstall_file:file rx_file_perms;
allow update_engine_common postinstall_file:lnk_file r_file_perms;
allow update_engine_common postinstall_file:dir r_dir_perms;
# install update.zip from cache
r_dir_file(update_engine_common, cache_file)
# A postinstall program is typically a shell script (with a #!), so we allow
# to execute those.
allow update_engine_common shell_exec:file rx_file_perms;
# Allow update_engine_common to suspend, resume and kill the postinstall program.
allow update_engine_common postinstall:process { signal sigstop sigkill };
# access /proc/cmdline
allow update_engine_common proc_cmdline:file r_file_perms;
# Read files in /sys/firmware/devicetree/base/firmware/android/
r_dir_file(update_engine_common, sysfs_dt_firmware_android)
# Needed because libdm reads sysfs to validate when a dm path is ready.
r_dir_file(update_engine_common, sysfs_dm)
# read / write on /dev/device-mapper to map / unmap devices
allow update_engine_common dm_device:chr_file rw_file_perms;
# apply / verify updates on devices mapped via device mapper
allow update_engine_common dm_device:blk_file rw_file_perms;
# read /dev/dm-user, so that we can inotify wait for control devices to be
# asynchronously created by ueventd.
allow update_engine dm_user_device:dir r_dir_perms;
# read / write metadata on super device to resize partitions
allow update_engine_common super_block_device_type:blk_file rw_file_perms;
# ioctl on super device to get block device alignment and alignment offset
allowxperm update_engine_common super_block_device_type:blk_file ioctl { BLKIOMIN BLKALIGNOFF };
# get physical block device to map logical partitions on device mapper
allow update_engine_common block_device:dir r_dir_perms;
# Allow update_engine_common to write to statsd socket.
unix_socket_send(update_engine_common, statsdw, statsd)
# Allow to read Virtual A/B feature flags.
get_prop(update_engine_common, virtual_ab_prop)
# Allow to read GKI related flags.
get_prop(update_engine_common, ab_update_gki_prop)
get_prop(update_engine_common, build_bootimage_prop)
# Allow to read/write/create OTA metadata files for snapshot status and COW file status.
allow update_engine_common metadata_file:dir search;
allow update_engine_common ota_metadata_file:dir rw_dir_perms;
allow update_engine_common ota_metadata_file:file create_file_perms;