android10/system/sepolicy/public/recovery.te

# recovery console (used in recovery init.rc for /sbin/recovery)

# Declare the domain unconditionally so we can always reference it
# in neverallow rules.
type recovery, domain;

# But the allow rules are only included in the recovery policy.
# Otherwise recovery is only allowed the domain rules.
recovery_only(`
  # Allow recovery to perform an update as update_engine would do.
  typeattribute recovery update_engine_common;
  # Recovery can only use HALs in passthrough mode
  passthrough_hal_client_domain(recovery, hal_bootctl)

  allow recovery self:global_capability_class_set {
    chown
    dac_override
    dac_read_search
    fowner
    setuid
    setgid
    sys_admin
    sys_tty_config
  };

  # Run helpers from / or /system without changing domain.
  r_dir_file(recovery, rootfs)
  allow recovery rootfs:file execute_no_trans;
  allow recovery system_file:file execute_no_trans;
  allow recovery toolbox_exec:file rx_file_perms;

  # Mount filesystems.
  allow recovery rootfs:dir mounton;
  allow recovery tmpfs:dir mounton;
  allow recovery fs_type:filesystem ~relabelto;
  allow recovery unlabeled:filesystem ~relabelto;
  allow recovery contextmount_type:filesystem relabelto;

  # We may be asked to set an SELinux label for a type not known to the
  # currently loaded policy. Allow it.
  allow recovery unlabeled:{ file lnk_file } { create_file_perms relabelfrom relabelto };
  allow recovery unlabeled:dir { create_dir_perms relabelfrom relabelto };

  # Get file contexts
  allow recovery file_contexts_file:file r_file_perms;

  # Write to /proc/sys/vm/drop_caches
  allow recovery proc_drop_caches:file w_file_perms;

  # Read /proc/swaps
  allow recovery proc_swaps:file r_file_perms;

  # Read kernel config through libvintf for OTA matching
  allow recovery config_gz:file { open read getattr };

  # Write to /sys/class/android_usb/android0/enable.
  r_dir_file(recovery, sysfs_android_usb)
  allow recovery sysfs_android_usb:file w_file_perms;

  # Write to /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq.
  allow recovery sysfs_devices_system_cpu:file w_file_perms;

  allow recovery sysfs_batteryinfo:file r_file_perms;

  # Read /sysfs/fs/ext4/features
  r_dir_file(recovery, sysfs_fs_ext4_features)

  # Read from /sys/class/leds/lcd-backlight/max_brightness and write to /s/c/l/l/brightness to
  # control backlight brightness.
  allow recovery sysfs_leds:dir r_dir_perms;
  allow recovery sysfs_leds:file rw_file_perms;
  allow recovery sysfs_leds:lnk_file read;

  allow recovery kernel:system syslog_read;

  # Access /dev/usb-ffs/adb/ep0
  allow recovery functionfs:dir search;
  allow recovery functionfs:file rw_file_perms;
  allowxperm recovery functionfs:file ioctl FUNCTIONFS_ENDPOINT_DESC;

  # Access to /sys/fs/selinux/policyvers for compatibility check
  allow recovery selinuxfs:file r_file_perms;

  # Required to e.g. wipe userdata/cache.
  allow recovery device:dir r_dir_perms;
  allow recovery block_device:dir r_dir_perms;
  allow recovery dev_type:blk_file rw_file_perms;
  allowxperm recovery { userdata_block_device metadata_block_device }:blk_file ioctl BLKPBSZGET;

  # GUI
  allow recovery graphics_device:chr_file rw_file_perms;
  allow recovery graphics_device:dir r_dir_perms;
  allow recovery input_device:dir r_dir_perms;
  allow recovery input_device:chr_file r_file_perms;
  allow recovery tty_device:chr_file rw_file_perms;

  # Create /tmp/recovery.log and execute /tmp/update_binary.
  allow recovery tmpfs:file { create_file_perms x_file_perms };
  allow recovery tmpfs:dir create_dir_perms;

  # Manage files on /cache and /cache/recovery
  allow recovery { cache_file cache_recovery_file }:dir create_dir_perms;
  allow recovery { cache_file cache_recovery_file }:file create_file_perms;

  # Read /sys/class/thermal/*/temp for thermal info.
  r_dir_file(recovery, sysfs_thermal)

  # Read files on /oem.
  r_dir_file(recovery, oemfs);

  # Reboot the device
  set_prop(recovery, powerctl_prop)

  # Read serial number of the device from system properties
  get_prop(recovery, serialno_prop)

  # Set sys.usb.ffs.ready when starting minadbd for sideload.
  set_prop(recovery, ffs_prop)
  set_prop(recovery, exported_ffs_prop)

  # Set sys.usb.config when switching into fastboot.
  set_prop(recovery, system_radio_prop)
  set_prop(recovery, exported_system_radio_prop)

  # Read ro.boot.bootreason
  get_prop(recovery, bootloader_boot_reason_prop)

  # Use setfscreatecon() to label files for OTA updates.
  allow recovery self:process setfscreate;

  # Allow recovery to create a fuse filesystem, and read files from it.
  allow recovery fuse_device:chr_file rw_file_perms;
  allow recovery fuse:dir r_dir_perms;
  allow recovery fuse:file r_file_perms;

  wakelock_use(recovery)

  # This line seems suspect, as it should not really need to
  # set scheduling parameters for a kernel domain task.
  allow recovery kernel:process setsched;

  # These are needed to update dynamic partitions in recovery.
  r_dir_file(recovery, sysfs_dm)
  allowxperm recovery super_block_device_type:blk_file ioctl { BLKIOMIN BLKALIGNOFF };
')

###
### neverallow rules
###

# Recovery should never touch /data.
#
# In particular, if /data is encrypted, it is not accessible
# to recovery anyway.
#
# For now, we only enforce write/execute restrictions, as domain.te
# contains a number of read-only rules that apply to all
# domains, including recovery.
#
# TODO: tighten this up further.
neverallow recovery {
   data_file_type
   -cache_file
   -cache_recovery_file
  with_native_coverage(`-method_trace_data_file')
}:file { no_w_file_perms no_x_file_perms };
neverallow recovery {
   data_file_type
   -cache_file
   -cache_recovery_file
  with_native_coverage(`-method_trace_data_file')
}:dir no_w_dir_perms;