private/untrusted_app.te

###
### Untrusted apps.
###
### This file defines the rules for untrusted apps.
### Apps are labeled based on mac_permissions.xml (maps signer and
### optionally package name to seinfo value) and seapp_contexts (maps UID
### and optionally seinfo value to domain for process and type for data
### directory).  The untrusted_app domain is the default assignment in
### seapp_contexts for any app with UID between APP_AID (10000)
### and AID_ISOLATED_START (99000) if the app has no specific seinfo
### value as determined from mac_permissions.xml.  In current AOSP, this
### domain is assigned to all non-system apps as well as to any system apps
### that are not signed by the platform key.  To move
### a system app into a specific domain, add a signer entry for it to
### mac_permissions.xml and assign it one of the pre-existing seinfo values
### or define and use a new seinfo value in both mac_permissions.xml and
### seapp_contexts.
###

app_domain(untrusted_app)
net_domain(untrusted_app)
bluetooth_domain(untrusted_app)

# Allow the allocation and use of ptys
# Used by: https://play.google.com/store/apps/details?id=jackpal.androidterm
create_pty(untrusted_app)

# Legacy text relocations
allow untrusted_app apk_data_file:file execmod;

# Some apps ship with shared libraries and binaries that they write out
# to their sandbox directory and then execute.
allow untrusted_app app_data_file:file { rx_file_perms execmod };

# ASEC
allow untrusted_app asec_apk_file:file r_file_perms;
allow untrusted_app asec_apk_file:dir r_dir_perms;
# Execute libs in asec containers.
allow untrusted_app asec_public_file:file { execute execmod };

# Used by Finsky / Android "Verify Apps" functionality when
# running "adb install foo.apk".
# TODO: Long term, we don't want apps probing into shell data files.
# Figure out a way to remove these rules.
allow untrusted_app shell_data_file:file r_file_perms;
allow untrusted_app shell_data_file:dir r_dir_perms;

# Read and write system app data files passed over Binder.
# Motivating case was /data/data/com.android.settings/cache/*.jpg for
# cropping or taking user photos.
allow untrusted_app system_app_data_file:file { read write getattr };

#
# Rules migrated from old app domains coalesced into untrusted_app.
# This includes what used to be media_app, shared_app, and release_app.
#

# Access to /data/media.
allow untrusted_app media_rw_data_file:dir create_dir_perms;
allow untrusted_app media_rw_data_file:file create_file_perms;

# Traverse into /mnt/media_rw for bypassing FUSE daemon
# TODO: narrow this to just MediaProvider
allow untrusted_app mnt_media_rw_file:dir search;

# allow cts to query all services
allow untrusted_app servicemanager:service_manager list;

allow untrusted_app audioserver_service:service_manager find;
allow untrusted_app cameraserver_service:service_manager find;
allow untrusted_app drmserver_service:service_manager find;
allow untrusted_app mediaserver_service:service_manager find;
allow untrusted_app mediaextractor_service:service_manager find;
allow untrusted_app mediacodec_service:service_manager find;
allow untrusted_app mediadrmserver_service:service_manager find;
allow untrusted_app nfc_service:service_manager find;
allow untrusted_app radio_service:service_manager find;
allow untrusted_app surfaceflinger_service:service_manager find;
allow untrusted_app app_api_service:service_manager find;

# Allow GMS core to access perfprofd output, which is stored
# in /data/misc/perfprofd/. GMS core will need to list all
# data stored in that directory to process them one by one.
userdebug_or_eng(`
  allow untrusted_app perfprofd_data_file:file r_file_perms;
  allow untrusted_app perfprofd_data_file:dir r_dir_perms;
')

# gdbserver for ndk-gdb ptrace attaches to app process.
allow untrusted_app self:process ptrace;

# Cts: HwRngTest
allow untrusted_app sysfs_hwrandom:dir search;
allow untrusted_app sysfs_hwrandom:file r_file_perms;

# Allow apps to view preloaded content
allow untrusted_app preloads_data_file:dir r_dir_perms;
allow untrusted_app preloads_data_file:file r_file_perms;

# Access to /proc/tty/drivers, to allow apps to determine if they
# are running in an emulated environment.
# b/33214085 b/33814662 b/33791054 b/33211769
# https://github.com/strazzere/anti-emulator/blob/master/AntiEmulator/src/diff/strazzere/anti/emulator/FindEmulator.java
allow untrusted_app proc_tty_drivers:file r_file_perms;

###
### neverallow rules
###

# Receive or send uevent messages.
neverallow untrusted_app domain:netlink_kobject_uevent_socket *;

# Receive or send generic netlink messages
neverallow untrusted_app domain:netlink_socket *;

# Too much leaky information in debugfs. It's a security
# best practice to ensure these files aren't readable.
neverallow untrusted_app debugfs_type:file read;

# Do not allow untrusted apps to register services.
# Only trusted components of Android should be registering
# services.
neverallow untrusted_app service_manager_type:service_manager add;

# Do not allow untrusted_apps to connect to the property service
# or set properties. b/10243159
neverallow untrusted_app property_socket:sock_file write;
neverallow untrusted_app init:unix_stream_socket connectto;
neverallow untrusted_app property_type:property_service set;

# Do not allow untrusted_app to be assigned mlstrustedsubject.
# This would undermine the per-user isolation model being
# enforced via levelFrom=user in seapp_contexts and the mls
# constraints.  As there is no direct way to specify a neverallow
# on attribute assignment, this relies on the fact that fork
# permission only makes sense within a domain (hence should
# never be granted to any other domain within mlstrustedsubject)
# and untrusted_app is allowed fork permission to itself.
neverallow untrusted_app mlstrustedsubject:process fork;

# Do not allow untrusted_app to hard link to any files.
# In particular, if untrusted_app links to other app data
# files, installd will not be able to guarantee the deletion
# of the linked to file. Hard links also contribute to security
# bugs, so we want to ensure untrusted_app never has this
# capability.
neverallow untrusted_app file_type:file link;

# Do not allow untrusted_app to access network MAC address file
neverallow untrusted_app sysfs_mac_address:file no_rw_file_perms;

# Restrict socket ioctls. Either 1. disallow privileged ioctls, 2. disallow the
# ioctl permission, or 3. disallow the socket class.
neverallowxperm untrusted_app domain:{ rawip_socket tcp_socket udp_socket } ioctl priv_sock_ioctls;
neverallow untrusted_app *:{ netlink_route_socket netlink_selinux_socket } ioctl;
neverallow untrusted_app *:{
  socket netlink_socket packet_socket key_socket appletalk_socket
  netlink_firewall_socket netlink_tcpdiag_socket netlink_nflog_socket
  netlink_xfrm_socket netlink_audit_socket netlink_ip6fw_socket
  netlink_dnrt_socket netlink_kobject_uevent_socket tun_socket
  netlink_iscsi_socket netlink_fib_lookup_socket netlink_connector_socket
  netlink_netfilter_socket netlink_generic_socket netlink_scsitransport_socket
  netlink_rdma_socket netlink_crypto_socket
} *;

# Do not allow untrusted_app access to /cache
neverallow untrusted_app { cache_file cache_recovery_file }:dir ~{ r_dir_perms };
neverallow untrusted_app { cache_file cache_recovery_file }:file ~{ read getattr };

# Do not allow untrusted_app to create/unlink files outside of its sandbox,
# internal storage or sdcard.
# World accessible data locations allow application to fill the device
# with unaccounted for data. This data will not get removed during
# application un-installation.
neverallow untrusted_app {
  fs_type
  -fuse                     # sdcard
  -sdcardfs                 # sdcard
  -vfat
  file_type
  -app_data_file            # The apps sandbox itself
  -media_rw_data_file       # Internal storage. Known that apps can
                            # leave artfacts here after uninstall.
  -user_profile_data_file   # Access to profile files
  -user_profile_foreign_dex_data_file   # Access to profile files
  userdebug_or_eng(`
    -method_trace_data_file # only on ro.debuggable=1
    -coredump_file          # userdebug/eng only
  ')
}:dir_file_class_set { create unlink };

# Do not allow untrusted_app to directly open tun_device
neverallow untrusted_app tun_device:chr_file open;

# Only allow appending to /data/anr/traces.txt (b/27853304, b/18340553)
neverallow untrusted_app anr_data_file:file ~{ open append };
neverallow untrusted_app anr_data_file:dir ~search;

# Avoid reads from generically labeled /proc files
# Create a more specific label if needed
neverallow untrusted_app proc:file { no_rw_file_perms no_x_file_perms };