f96cd6557e
Remove access from untrusted apps and instead grant it to platform_app (but on user builds as well as debug). Also restrict any app from creating a vsock_socket; using an already created one is fine. Bug: 193373841 Test: Microdroid demo app now gets a denial Test: Rebuild demo with certifcate: platform, adb install, no denial Change-Id: I7be011e05244767a42d4c56e26de792db4fe599d
253 lines
11 KiB
Text
253 lines
11 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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mediaprovider_app
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untrusted_app
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untrusted_app_25
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untrusted_app_27
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untrusted_app_29
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untrusted_app_30
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untrusted_app_all
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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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# Read or write kernel printk buffer
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neverallow all_untrusted_apps kmsg_device:chr_file no_rw_file_perms;
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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 -debugfs_kcov }:file read;
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neverallow {all_untrusted_apps userdebug_or_eng(`-domain')} debugfs_type:{ file lnk_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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# net.dns properties are not a public API. Disallow untrusted apps from reading this property.
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neverallow { all_untrusted_apps } net_dns_prop:file read;
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# Shared libraries created by trusted components within an app home
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# directory can be dlopen()ed. To maintain the W^X property, these files
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# must never be writable to the app.
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neverallow all_untrusted_apps app_exec_data_file:file
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{ append create link relabelfrom relabelto rename setattr write };
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# Block calling execve() on files in an apps home directory.
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# This is a W^X violation (loading executable code from a writable
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# home directory). For compatibility, allow for targetApi <= 28.
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# b/112357170
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neverallow {
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all_untrusted_apps
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-untrusted_app_25
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-untrusted_app_27
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-runas_app
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} { app_data_file privapp_data_file }:file execute_no_trans;
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# Do not allow untrusted apps to invoke dex2oat. This was historically required
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# by ART for compiling secondary dex files but has been removed in Q.
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# Exempt legacy apps (targetApi<=28) for compatibility.
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neverallow {
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all_untrusted_apps
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-untrusted_app_25
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-untrusted_app_27
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} dex2oat_exec:file no_x_file_perms;
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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_net: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 no_x_file_perms };
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# Apps may never access the default sysfs label.
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neverallow all_untrusted_apps sysfs:file no_rw_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:{ icmp_socket 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 sctp_socket
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ax25_socket ipx_socket netrom_socket atmpvc_socket x25_socket rose_socket decnet_socket
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atmsvc_socket rds_socket irda_socket pppox_socket llc_socket can_socket tipc_socket
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bluetooth_socket iucv_socket rxrpc_socket isdn_socket phonet_socket ieee802154_socket caif_socket
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alg_socket nfc_socket kcm_socket qipcrtr_socket smc_socket xdp_socket
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} *;
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# Apps can read/write an already open vsock (e.g. created by
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# virtualizationservice) but nothing more than that (e.g. creating a
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# new vsock, etc.)
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neverallow all_untrusted_apps *:vsock_socket ~{ getattr read write };
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# Disallow sending RTM_GETLINK messages on netlink sockets.
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neverallow all_untrusted_apps domain:netlink_route_socket { bind nlmsg_readpriv };
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# Disallow sending RTM_GETNEIGH{TBL} messages on netlink sockets.
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neverallow {
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all_untrusted_apps
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-untrusted_app_25
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-untrusted_app_27
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-untrusted_app_29
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-untrusted_app_30
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} domain:netlink_route_socket nlmsg_getneigh;
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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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-sdcard_type
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-fuse
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file_type
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-app_data_file # The apps sandbox itself
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-privapp_data_file
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-app_exec_data_file # stored within the app sandbox directory
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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 except mediaprovider_app should be touching /dev/fuse
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neverallow { all_untrusted_apps -mediaprovider_app } fuse_device:chr_file *;
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# Do not allow untrusted apps to directly open the tun_device
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neverallow all_untrusted_apps tun_device:chr_file open;
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# The tun_device ioctls below are not allowed, to prove equivalence
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# to the kernel patch at
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# https://android.googlesource.com/kernel/common/+/11cee2be0c2062ba88f04eb51196506f870a3b5d%5E%21
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neverallowxperm all_untrusted_apps tun_device:chr_file ioctl ~{ FIOCLEX FIONCLEX TUNGETIFF };
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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_kmsg
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proc_loadavg
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proc_mounts
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proc_pagetypeinfo
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proc_slabinfo
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proc_stat
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proc_swaps
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proc_uptime
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proc_version
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proc_vmallocinfo
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proc_vmstat
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}:file { no_rw_file_perms no_x_file_perms };
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# /proc/filesystems is accessible to mediaprovider_app only since it handles
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# external storage
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neverallow { all_untrusted_apps - mediaprovider_app } proc_filesystems: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 the protected services
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# The two main reasons for this are:
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# 1. Protected HwBinder servers do not perform client authentication because
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# vendor code does not have a way to understand apps or their relation to
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# caller UID information and, even if it did, those services either operate
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# at a level below that of apps (e.g., HALs) or must not rely on app identity
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# for authorization. Thus, to be safe, the default assumption for all added
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# vendor services is that they treat all their clients as equally authorized
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# to perform operations offered by the service.
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# 2. HAL servers contain code with higher incidence rate of security issues
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# than system/core components and have access to lower layes of the stack
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# (all the way down to hardware) thus increasing opportunities for bypassing
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# the Android security model.
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neverallow all_untrusted_apps protected_hwservice:hwservice_manager find;
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neverallow all_untrusted_apps protected_service:service_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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# Access to /proc/tty/drivers, to allow apps to determine if they
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# are running in an emulated environment.
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# b/33214085 b/33814662 b/33791054 b/33211769
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# https://github.com/strazzere/anti-emulator/blob/master/AntiEmulator/src/diff/strazzere/anti/emulator/FindEmulator.java
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# This will go away in a future Android release
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neverallow { all_untrusted_apps -untrusted_app_25 } proc_tty_drivers:file r_file_perms;
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neverallow all_untrusted_apps proc_tty_drivers:file ~r_file_perms;
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# Untrusted apps are not allowed to use cgroups.
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neverallow all_untrusted_apps cgroup:file *;
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neverallow all_untrusted_apps cgroup_v2:file *;
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# /mnt/sdcard symlink was supposed to have been removed in Gingerbread. Apps
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# must not use it.
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neverallow {
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all_untrusted_apps
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-untrusted_app_25
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-untrusted_app_27
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} mnt_sdcard_file:lnk_file *;
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# Only privileged apps may find the incident service
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neverallow all_untrusted_apps incident_service:service_manager find;
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