platform_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, domain_deprecated;

# 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:capability { chown dac_override fowner fsetid setfcap setuid setgid sys_admin sys_tty_config };

  # Set security contexts on files that are not known to the loaded policy.
  allow recovery self:capability2 mac_admin;

  # Run helpers from / or /system without changing domain.
  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 fs_type:filesystem ~relabelto;
  allow recovery unlabeled:filesystem ~relabelto;
  allow recovery contextmount_type:filesystem relabelto;

  # Create and relabel files and directories under /system.
  allow recovery exec_type:{ file lnk_file } { create_file_perms relabelfrom relabelto };
  allow recovery { system_file }:{ file lnk_file } { create_file_perms relabelfrom relabelto };
  allow recovery system_file:dir { create_dir_perms relabelfrom 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;

  # 0eb17d944704b3eb140bb9dded299d3be3aed77e in build/ added SELinux
  # support to OTAs. However, that code has a bug. When an update occurs,
  # some directories are inappropriately labeled as exec_type. This is
  # only transient, and subsequent steps in the OTA script correct this
  # mistake. New devices are moving to block based OTAs, so this is not
  # worth fixing. b/15575013
  allow recovery exec_type:dir { create_dir_perms relabelfrom relabelto };

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

  # Write to /sys/class/android_usb/android0/enable.
  # TODO: create more specific label?
  allow recovery sysfs: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 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;

  # 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;

  # 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.
  allow recovery sysfs_thermal:dir search;
  allow recovery sysfs_thermal:file r_file_perms;

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

  # Reboot the device
  set_prop(recovery, powerctl_prop)

  # Start/stop adbd via ctl.start adbd
  set_prop(recovery, ctl_default_prop)

  # Read serial number of the device from system properties
  get_prop(recovery, serialno_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;
')

###
### 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:file { no_w_file_perms no_x_file_perms };
neverallow recovery data_file_type:dir no_w_dir_perms;