250 lines
9.8 KiB
Text
250 lines
9.8 KiB
Text
###
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### neverallow rules for untrusted app domains
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###
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define(`all_untrusted_apps',`{
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ephemeral_app
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isolated_app
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mediaprovider
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untrusted_app
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untrusted_app_25
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untrusted_app_all
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untrusted_v2_app
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}')
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# Receive or send uevent messages.
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neverallow all_untrusted_apps domain:netlink_kobject_uevent_socket *;
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# Receive or send generic netlink messages
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neverallow all_untrusted_apps domain:netlink_socket *;
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# Too much leaky information in debugfs. It's a security
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# best practice to ensure these files aren't readable.
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neverallow all_untrusted_apps debugfs_type:file read;
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# Do not allow untrusted apps to register services.
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# Only trusted components of Android should be registering
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# services.
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neverallow all_untrusted_apps service_manager_type:service_manager add;
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# Do not allow untrusted apps to use VendorBinder
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neverallow all_untrusted_apps vndbinder_device:chr_file *;
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neverallow all_untrusted_apps vndservice_manager_type:service_manager *;
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# Do not allow untrusted apps to connect to the property service
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# or set properties. b/10243159
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neverallow { all_untrusted_apps -mediaprovider } property_socket:sock_file write;
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neverallow { all_untrusted_apps -mediaprovider } init:unix_stream_socket connectto;
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neverallow { all_untrusted_apps -mediaprovider } property_type:property_service set;
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# Do not allow untrusted apps to be assigned mlstrustedsubject.
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# This would undermine the per-user isolation model being
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# enforced via levelFrom=user in seapp_contexts and the mls
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# constraints. As there is no direct way to specify a neverallow
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# on attribute assignment, this relies on the fact that fork
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# permission only makes sense within a domain (hence should
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# never be granted to any other domain within mlstrustedsubject)
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# and an untrusted app is allowed fork permission to itself.
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neverallow all_untrusted_apps mlstrustedsubject:process fork;
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# Do not allow untrusted apps to hard link to any files.
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# In particular, if an untrusted app links to other app data
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# files, installd will not be able to guarantee the deletion
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# of the linked to file. Hard links also contribute to security
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# bugs, so we want to ensure untrusted apps never have this
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# capability.
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neverallow all_untrusted_apps file_type:file link;
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# Do not allow untrusted apps to access network MAC address file
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neverallow all_untrusted_apps sysfs_mac_address:file no_rw_file_perms;
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# Do not allow any write access to files in /sys
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neverallow all_untrusted_apps sysfs_type:file no_w_file_perms;
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# Restrict socket ioctls. Either 1. disallow privileged ioctls, 2. disallow the
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# ioctl permission, or 3. disallow the socket class.
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neverallowxperm all_untrusted_apps domain:{ rawip_socket tcp_socket udp_socket } ioctl priv_sock_ioctls;
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neverallow all_untrusted_apps *:{ netlink_route_socket netlink_selinux_socket } ioctl;
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neverallow all_untrusted_apps *:{
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socket netlink_socket packet_socket key_socket appletalk_socket
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netlink_tcpdiag_socket netlink_nflog_socket
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netlink_xfrm_socket netlink_audit_socket
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netlink_dnrt_socket netlink_kobject_uevent_socket tun_socket
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netlink_iscsi_socket netlink_fib_lookup_socket netlink_connector_socket
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netlink_netfilter_socket netlink_generic_socket netlink_scsitransport_socket
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netlink_rdma_socket netlink_crypto_socket
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} *;
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# Do not allow untrusted apps access to /cache
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neverallow { all_untrusted_apps -mediaprovider } { cache_file cache_recovery_file }:dir ~{ r_dir_perms };
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neverallow { all_untrusted_apps -mediaprovider } { cache_file cache_recovery_file }:file ~{ read getattr };
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# Do not allow untrusted apps to create/unlink files outside of its sandbox,
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# internal storage or sdcard.
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# World accessible data locations allow application to fill the device
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# with unaccounted for data. This data will not get removed during
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# application un-installation.
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neverallow { all_untrusted_apps -mediaprovider } {
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fs_type
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-fuse # sdcard
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-sdcardfs # sdcard
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-vfat
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file_type
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-app_data_file # The apps sandbox itself
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-media_rw_data_file # Internal storage. Known that apps can
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# leave artfacts here after uninstall.
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-user_profile_data_file # Access to profile files
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userdebug_or_eng(`
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-method_trace_data_file # only on ro.debuggable=1
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-coredump_file # userdebug/eng only
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')
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}:dir_file_class_set { create unlink };
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# No untrusted component should be touching /dev/fuse
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neverallow all_untrusted_apps fuse_device:chr_file *;
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# Do not allow untrusted apps to directly open tun_device
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neverallow all_untrusted_apps tun_device:chr_file open;
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# Only allow appending to /data/anr/traces.txt (b/27853304, b/18340553)
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neverallow all_untrusted_apps anr_data_file:file ~{ open append };
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neverallow all_untrusted_apps anr_data_file:dir ~search;
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# Avoid reads from generically labeled /proc files
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# Create a more specific label if needed
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neverallow all_untrusted_apps {
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proc
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proc_asound
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proc_filesystems
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proc_kmsg
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proc_loadavg
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proc_mounts
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proc_pagetypeinfo
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proc_swaps
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proc_version
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proc_vmallocinfo
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}:file { no_rw_file_perms no_x_file_perms };
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# Avoid all access to kernel configuration
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neverallow all_untrusted_apps config_gz:file { no_rw_file_perms no_x_file_perms };
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# Do not allow untrusted apps access to preloads data files
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neverallow all_untrusted_apps preloads_data_file:file no_rw_file_perms;
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# Locking of files on /system could lead to denial of service attacks
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# against privileged system components
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neverallow all_untrusted_apps system_file:file lock;
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# Do not permit untrusted apps to perform actions on HwBinder service_manager
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# other than find actions for services listed below
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neverallow all_untrusted_apps *:hwservice_manager ~find;
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# Do not permit access from apps which host arbitrary code to HwBinder services,
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# except those considered sufficiently safe for access from such apps.
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# The two main reasons for this are:
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# 1. HwBinder servers do not perform client authentication because HIDL
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# currently does not expose caller UID information and, even if it did, many
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# HwBinder services either operate at a level below that of apps (e.g., HALs)
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# or must not rely on app identity for authorization. Thus, to be safe, the
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# default assumption is that every HwBinder service treats all its clients as
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# equally authorized to perform operations offered by the service.
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# 2. HAL servers (a subset of HwBinder services) contain code with higher
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# incidence rate of security issues than system/core components and have
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# access to lower layes of the stack (all the way down to hardware) thus
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# increasing opportunities for bypassing the Android security model.
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#
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# Safe services include:
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# - same process services: because they by definition run in the process
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# of the client and thus have the same access as the client domain in which
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# the process runs
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# - coredomain_hwservice: are considered safe because they do not pose risks
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# associated with reason #2 above.
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# - hal_configstore_ISurfaceFlingerConfigs: becuase it has specifically been
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# designed for use by any domain.
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# - hal_graphics_allocator_hwservice: because these operations are also offered
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# by surfaceflinger Binder service, which apps are permitted to access
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# - hal_omx_hwservice: because this is a HwBinder version of the mediacodec
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# Binder service which apps were permitted to access.
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neverallow all_untrusted_apps {
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hwservice_manager_type
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-same_process_hwservice
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-coredomain_hwservice
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-hal_configstore_ISurfaceFlingerConfigs
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-hal_graphics_allocator_hwservice
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-hal_omx_hwservice
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-hal_cas_hwservice
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-hal_neuralnetworks_hwservice
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-untrusted_app_visible_hwservice
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}:hwservice_manager find;
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# Make sure that the following services are never accessible by untrusted_apps
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neverallow all_untrusted_apps {
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default_android_hwservice
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hal_audio_hwservice
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hal_bluetooth_hwservice
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hal_bootctl_hwservice
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hal_camera_hwservice
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hal_confirmationui_hwservice
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hal_contexthub_hwservice
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hal_drm_hwservice
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hal_dumpstate_hwservice
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hal_fingerprint_hwservice
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hal_gatekeeper_hwservice
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hal_gnss_hwservice
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hal_graphics_composer_hwservice
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hal_health_hwservice
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hal_ir_hwservice
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hal_keymaster_hwservice
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hal_light_hwservice
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hal_memtrack_hwservice
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hal_nfc_hwservice
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hal_oemlock_hwservice
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hal_power_hwservice
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hal_secure_element_hwservice
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hal_sensors_hwservice
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hal_telephony_hwservice
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hal_thermal_hwservice
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hal_tv_cec_hwservice
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hal_tv_input_hwservice
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hal_usb_hwservice
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hal_vibrator_hwservice
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hal_vr_hwservice
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hal_weaver_hwservice
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hal_wifi_hwservice
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hal_wifi_offload_hwservice
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hal_wifi_supplicant_hwservice
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hidl_base_hwservice
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system_net_netd_hwservice
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thermalcallback_hwservice
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}:hwservice_manager find;
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# HwBinder services offered by core components (as opposed to vendor components)
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# are considered somewhat safer due to point #2 above.
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neverallow all_untrusted_apps {
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coredomain_hwservice
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-same_process_hwservice
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-hidl_allocator_hwservice # Designed for use by any domain
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-hidl_manager_hwservice # Designed for use by any domain
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-hidl_memory_hwservice # Designed for use by any domain
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-hidl_token_hwservice # Designed for use by any domain
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}:hwservice_manager find;
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# SELinux is not an API for untrusted apps to use
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neverallow all_untrusted_apps selinuxfs:file no_rw_file_perms;
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# Restrict *Binder access from apps to HAL domains. We can only do this on full
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# Treble devices where *Binder communications between apps and HALs are tightly
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# restricted.
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full_treble_only(`
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neverallow all_untrusted_apps {
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halserverdomain
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-coredomain
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-hal_configstore_server
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-hal_graphics_allocator_server
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-hal_cas_server
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-hal_neuralnetworks_server
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-binder_in_vendor_violators # TODO(b/35870313): Remove once all violations are gone
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-untrusted_app_visible_halserver
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}:binder { call transfer };
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')
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# Untrusted apps are not allowed to find mediaextractor update service.
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neverallow all_untrusted_apps mediaextractor_update_service:service_manager find;
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