app_neverallows.te revision 39fe4c715c061e84715fffd570c326f5bcf89c73 
1###
2### neverallow rules for untrusted app domains
3###
4
5define(`all_untrusted_apps',`{
6  ephemeral_app
7  isolated_app
8  mediaprovider
9  untrusted_app
10  untrusted_app_25
11  untrusted_app_all
12  untrusted_v2_app
13}')
14# Receive or send uevent messages.
15neverallow all_untrusted_apps domain:netlink_kobject_uevent_socket *;
16
17# Receive or send generic netlink messages
18neverallow all_untrusted_apps domain:netlink_socket *;
19
20# Too much leaky information in debugfs. It's a security
21# best practice to ensure these files aren't readable.
22neverallow all_untrusted_apps debugfs_type:file read;
23
24# Do not allow untrusted apps to register services.
25# Only trusted components of Android should be registering
26# services.
27neverallow all_untrusted_apps service_manager_type:service_manager add;
28
29# Do not allow untrusted apps to use VendorBinder
30neverallow all_untrusted_apps vndbinder_device:chr_file *;
31neverallow all_untrusted_apps vndservice_manager_type:service_manager *;
32
33# Do not allow untrusted apps to connect to the property service
34# or set properties. b/10243159
35neverallow { all_untrusted_apps -mediaprovider } property_socket:sock_file write;
36neverallow { all_untrusted_apps -mediaprovider } init:unix_stream_socket connectto;
37neverallow { all_untrusted_apps -mediaprovider } property_type:property_service set;
38
39# Do not allow untrusted apps to be assigned mlstrustedsubject.
40# This would undermine the per-user isolation model being
41# enforced via levelFrom=user in seapp_contexts and the mls
42# constraints.  As there is no direct way to specify a neverallow
43# on attribute assignment, this relies on the fact that fork
44# permission only makes sense within a domain (hence should
45# never be granted to any other domain within mlstrustedsubject)
46# and an untrusted app is allowed fork permission to itself.
47neverallow all_untrusted_apps mlstrustedsubject:process fork;
48
49# Do not allow untrusted apps to hard link to any files.
50# In particular, if an untrusted app links to other app data
51# files, installd will not be able to guarantee the deletion
52# of the linked to file. Hard links also contribute to security
53# bugs, so we want to ensure untrusted apps never have this
54# capability.
55neverallow all_untrusted_apps file_type:file link;
56
57# Do not allow untrusted apps to access network MAC address file
58neverallow all_untrusted_apps sysfs_mac_address:file no_rw_file_perms;
59
60# Restrict socket ioctls. Either 1. disallow privileged ioctls, 2. disallow the
61# ioctl permission, or 3. disallow the socket class.
62neverallowxperm all_untrusted_apps domain:{ rawip_socket tcp_socket udp_socket } ioctl priv_sock_ioctls;
63neverallow all_untrusted_apps *:{ netlink_route_socket netlink_selinux_socket } ioctl;
64neverallow all_untrusted_apps *:{
65  socket netlink_socket packet_socket key_socket appletalk_socket
66  netlink_tcpdiag_socket netlink_nflog_socket
67  netlink_xfrm_socket netlink_audit_socket
68  netlink_dnrt_socket netlink_kobject_uevent_socket tun_socket
69  netlink_iscsi_socket netlink_fib_lookup_socket netlink_connector_socket
70  netlink_netfilter_socket netlink_generic_socket netlink_scsitransport_socket
71  netlink_rdma_socket netlink_crypto_socket
72} *;
73
74# Do not allow untrusted apps access to /cache
75neverallow { all_untrusted_apps -mediaprovider } { cache_file cache_recovery_file }:dir ~{ r_dir_perms };
76neverallow { all_untrusted_apps -mediaprovider } { cache_file cache_recovery_file }:file ~{ read getattr };
77
78# Do not allow untrusted apps to create/unlink files outside of its sandbox,
79# internal storage or sdcard.
80# World accessible data locations allow application to fill the device
81# with unaccounted for data. This data will not get removed during
82# application un-installation.
83neverallow { all_untrusted_apps -mediaprovider } {
84  fs_type
85  -fuse                     # sdcard
86  -sdcardfs                 # sdcard
87  -vfat
88  file_type
89  -app_data_file            # The apps sandbox itself
90  -media_rw_data_file       # Internal storage. Known that apps can
91                            # leave artfacts here after uninstall.
92  -user_profile_data_file   # Access to profile files
93  userdebug_or_eng(`
94    -method_trace_data_file # only on ro.debuggable=1
95    -coredump_file          # userdebug/eng only
96  ')
97}:dir_file_class_set { create unlink };
98
99# No untrusted component should be touching /dev/fuse
100neverallow all_untrusted_apps fuse_device:chr_file *;
101
102# Do not allow untrusted apps to directly open tun_device
103neverallow all_untrusted_apps tun_device:chr_file open;
104
105# Only allow appending to /data/anr/traces.txt (b/27853304, b/18340553)
106neverallow all_untrusted_apps anr_data_file:file ~{ open append };
107neverallow all_untrusted_apps anr_data_file:dir ~search;
108
109# Avoid reads from generically labeled /proc files
110# Create a more specific label if needed
111neverallow all_untrusted_apps proc:file { no_rw_file_perms no_x_file_perms };
112
113# Avoid all access to kernel configuration
114neverallow all_untrusted_apps config_gz:file { no_rw_file_perms no_x_file_perms };
115
116# Do not allow untrusted apps access to preloads data files
117neverallow all_untrusted_apps preloads_data_file:file no_rw_file_perms;
118
119# Locking of files on /system could lead to denial of service attacks
120# against privileged system components
121neverallow all_untrusted_apps system_file:file lock;
122
123# Do not permit untrusted apps to perform actions on HwBinder service_manager
124# other than find actions for services listed below
125neverallow all_untrusted_apps *:hwservice_manager ~find;
126
127# Do not permit access from apps which host arbitrary code to HwBinder services,
128# except those considered sufficiently safe for access from such apps.
129# The two main reasons for this are:
130# 1. HwBinder servers do not perform client authentication because HIDL
131#    currently does not expose caller UID information and, even if it did, many
132#    HwBinder services either operate at a level below that of apps (e.g., HALs)
133#    or must not rely on app identity for authorization. Thus, to be safe, the
134#    default assumption is that every HwBinder service treats all its clients as
135#    equally authorized to perform operations offered by the service.
136# 2. HAL servers (a subset of HwBinder services) contain code with higher
137#    incidence rate of security issues than system/core components and have
138#    access to lower layes of the stack (all the way down to hardware) thus
139#    increasing opportunities for bypassing the Android security model.
140neverallow all_untrusted_apps {
141  hwservice_manager_type
142  # Same process services are safe because they by definition run in the process
143  # of the client and thus have the same access as the client domain in which
144  # the process runs
145  -same_process_hwservice
146  -coredomain_hwservice # neverallows for coredomain HwBinder services are below
147  -hal_configstore_ISurfaceFlingerConfigs # Designed for use by any domain
148  # These operations are also offered by surfaceflinger Binder service which
149  # apps are permitted to access
150  -hal_graphics_allocator_hwservice
151  # HwBinder version of mediacodec Binder service which apps were permitted to
152  # access
153  -hal_omx_hwservice
154  -hal_cas_hwservice
155}:hwservice_manager find;
156# HwBinder services offered by core components (as opposed to vendor components)
157# are considered somewhat safer due to point #2 above.
158neverallow all_untrusted_apps {
159  coredomain_hwservice
160  -same_process_hwservice
161  -hidl_allocator_hwservice # Designed for use by any domain
162  -hidl_manager_hwservice # Designed for use by any domain
163  -hidl_memory_hwservice # Designed for use by any domain
164  -hidl_token_hwservice # Designed for use by any domain
165}:hwservice_manager find;
166
167# SELinux is not an API for untrusted apps to use
168neverallow all_untrusted_apps selinuxfs:file no_rw_file_perms;
169
170# Restrict *Binder access from apps to HAL domains. We can only do this on full
171# Treble devices where *Binder communications between apps and HALs are tightly
172# restricted.
173full_treble_only(`
174  neverallow all_untrusted_apps {
175    halserverdomain
176    -coredomain
177    -hal_configstore_server
178    -hal_graphics_allocator_server
179    -hal_cas_server
180    -binder_in_vendor_violators # TODO(b/35870313): Remove once all violations are gone
181  }:binder { call transfer };
182')
183