platform_system_sepolicy/domain.te

# Rules for all domains.

# Allow reaping by init.
allow domain init:process sigchld;

# Intra-domain accesses.
allow domain self:process {
    fork
    sigchld
    sigkill
    sigstop
    signull
    signal
    getsched
    setsched
    getsession
    getpgid
    setpgid
    getcap
    setcap
    getattr
    setrlimit
};
allow domain self:fd use;
allow domain proc:dir search;
allow domain self:dir r_dir_perms;
allow domain self:lnk_file r_file_perms;
allow domain self:{ fifo_file file } rw_file_perms;
allow domain self:unix_dgram_socket { create_socket_perms sendto };
allow domain self:unix_stream_socket { create_stream_socket_perms connectto };

# Inherit or receive open files from others.
allow domain init:fd use;

userdebug_or_eng(`
  # Same as adbd rules above, except allow su to do the same thing
  allow domain su:unix_stream_socket connectto;
  allow domain su:fd use;
  allow domain su:unix_stream_socket { getattr getopt read write shutdown };

  binder_call({ domain -init }, su)

  # Running something like "pm dump com.android.bluetooth" requires
  # fifo writes
  allow domain su:fifo_file { write getattr };

  # allow "gdbserver --attach" to work for su.
  allow domain su:process sigchld;

  # Allow writing coredumps to /cores/*
  allow domain coredump_file:file create_file_perms;
  allow domain coredump_file:dir ra_dir_perms;
')

###
### Talk to debuggerd.
###
allow domain debuggerd:process sigchld;
allow domain debuggerd:unix_stream_socket connectto;

# Root fs.
allow domain rootfs:dir search;
allow domain rootfs:lnk_file read;

# Device accesses.
allow domain device:dir search;
allow domain dev_type:lnk_file r_file_perms;
allow domain devpts:dir search;
allow domain socket_device:dir r_dir_perms;
allow domain owntty_device:chr_file rw_file_perms;
allow domain null_device:chr_file rw_file_perms;
allow domain zero_device:chr_file rw_file_perms;
allow domain ashmem_device:chr_file rw_file_perms;
allow domain binder_device:chr_file rw_file_perms;
allow domain ptmx_device:chr_file rw_file_perms;
allow domain alarm_device:chr_file r_file_perms;
allow domain urandom_device:chr_file rw_file_perms;
allow domain random_device:chr_file rw_file_perms;
allow domain properties_device:file r_file_perms;
allow domain init:key search;
allow domain vold:key search;

# logd access
write_logd(domain)

# System file accesses.
allow domain system_file:dir search;
allow domain system_file:file { execute read open getattr };
allow domain system_file:lnk_file read;

# files under /data.
allow domain system_data_file:dir { search getattr };

# required by the dynamic linker
allow domain proc:lnk_file read;

# toybox loads libselinux which stats /sys/fs/selinux/
allow domain selinuxfs:file getattr;
allow domain sysfs:dir search;
allow domain selinuxfs:filesystem getattr;

###
### neverallow rules
###

# Do not allow any domain other than init or recovery to create unlabeled files.
neverallow { domain -init -recovery } unlabeled:dir_file_class_set create;

# Limit ability to ptrace or read sensitive /proc/pid files of processes
# with other UIDs to these whitelisted domains.
neverallow {
  domain
  -debuggerd
  -vold
  -dumpstate
  -system_server
  userdebug_or_eng(`-perfprofd')
} self:capability sys_ptrace;

# Limit device node creation to these whitelisted domains.
neverallow {
  domain
  -kernel
  -init
  -ueventd
  -vold
  -recovery
} self:capability mknod;

# Limit raw I/O to these whitelisted domains.
neverallow { domain -kernel -init -recovery -ueventd -watchdogd -healthd -vold -uncrypt -tee } self:capability sys_rawio;

# No process can map low memory (< CONFIG_LSM_MMAP_MIN_ADDR).
neverallow domain self:memprotect mmap_zero;

# No domain needs mac_override as it is unused by SELinux.
neverallow domain self:capability2 mac_override;

# Only recovery needs mac_admin to set contexts not defined in current policy.
neverallow { domain -recovery } self:capability2 mac_admin;

# Only init should be able to load SELinux policies.
# The first load technically occurs while still in the kernel domain,
# but this does not trigger a denial since there is no policy yet.
# Policy reload requires allowing this to the init domain.
neverallow { domain -init } kernel:security load_policy;

# Only init and the system_server can set selinux.reload_policy 1
# to trigger a policy reload.
neverallow { domain -init -system_server } security_prop:property_service set;

# Only init and system_server can write to /data/security, where runtime
# policy updates live.
# Only init can relabel /data/security (for init.rc restorecon_recursive /data).
neverallow { domain -init } security_file:{ dir file lnk_file } { relabelfrom relabelto };
# Only init and system_server can create/setattr directories with this type.
# init is for init.rc mkdir /data/security.
# system_server is for creating subdirectories under /data/security.
neverallow { domain -init -system_server } security_file:dir { create setattr };
# Only system_server can create subdirectories and files under /data/security.
neverallow { domain -system_server } security_file:dir { rename write add_name remove_name rmdir };
neverallow { domain -system_server } security_file:file { create setattr write append unlink link rename };
neverallow { domain -system_server } security_file:lnk_file { create setattr unlink rename };

# Only init prior to switching context should be able to set enforcing mode.
# init starts in kernel domain and switches to init domain via setcon in
# the init.rc, so the setenforce occurs while still in kernel. After
# switching domains, there is never any need to setenforce again by init.
neverallow domain kernel:security setenforce;
neverallow { domain -kernel } kernel:security setcheckreqprot;

# No booleans in AOSP policy, so no need to ever set them.
neverallow domain kernel:security setbool;

# Adjusting the AVC cache threshold.
# Not presently allowed to anything in policy, but possibly something
# that could be set from init.rc.
neverallow { domain -init } kernel:security setsecparam;

# Only init, ueventd and system_server should be able to access HW RNG
neverallow { domain -init -system_server -ueventd } hw_random_device:chr_file *;

# Ensure that all entrypoint executables are in exec_type.
neverallow domain { file_type -exec_type }:file entrypoint;

# Ensure that nothing in userspace can access /dev/mem or /dev/kmem
neverallow { domain -kernel -ueventd -init } kmem_device:chr_file *;
neverallow domain kmem_device:chr_file ~{ create relabelto unlink setattr };

# Only init should be able to configure kernel usermodehelpers or
# security-sensitive proc settings.
neverallow { domain -init } usermodehelper:file { append write };
neverallow { domain -init } proc_security:file { append write };

# No domain should be allowed to ptrace init.
neverallow domain init:process ptrace;

# Init can't do anything with binder calls. If this neverallow rule is being
# triggered, it's probably due to a service with no SELinux domain.
neverallow domain init:binder *;

# Don't allow raw read/write/open access to block_device
# Rather force a relabel to a more specific type
neverallow { domain -kernel -init -recovery -uncrypt } block_device:blk_file { open read write };

# Don't allow raw read/write/open access to generic devices.
# Rather force a relabel to a more specific type.
# init is exempt from this as there are character devices that only it uses.
# ueventd is exempt from this, as it is managing these devices.
neverallow { domain -init -ueventd } device:chr_file { open read write };

# Limit what domains can mount filesystems or change their mount flags.
# sdcard_type / vfat is exempt as a larger set of domains need
# this capability, including device-specific domains.
neverallow { domain -kernel -init -recovery -vold -zygote } { fs_type -sdcard_type }:filesystem { mount remount relabelfrom relabelto };

#
# Assert that, to the extent possible, we're not loading executable content from
# outside the rootfs or /system partition except for a few whitelisted domains.
#
neverallow {
    domain
    -appdomain
    -dumpstate
    -shell
    userdebug_or_eng(`-su')
    -system_server
    -zygote
} { file_type -system_file -exec_type }:file execute;
neverallow {
    domain
    -appdomain # for oemfs
    -recovery # for /tmp/update_binary in tmpfs
} { fs_type -rootfs }:file execute;
# Files from cache should never be executed
neverallow domain { cache_file cache_backup_file }:file execute;

# Protect most domains from executing arbitrary content from /data.
neverallow {
  domain
  -untrusted_app
  -priv_app
  -shell
} {
  data_file_type
  -dalvikcache_data_file
  -system_data_file # shared libs in apks
  -apk_data_file
}:file no_x_file_perms;

neverallow { domain userdebug_or_eng(`-shell') } nativetest_data_file:file no_x_file_perms;

# Only the init property service should write to /data/property.
neverallow { domain -init } property_data_file:dir no_w_dir_perms;
neverallow { domain -init } property_data_file:file no_w_file_perms;

# Only recovery should be doing writes to /system
neverallow { domain -recovery } { system_file exec_type }:dir_file_class_set
    { create write setattr relabelfrom append unlink link rename };
neverallow { domain -recovery -kernel } { system_file exec_type }:dir_file_class_set relabelto;

# Don't allow mounting on top of /system files or directories
neverallow domain exec_type:dir_file_class_set mounton;
neverallow { domain -init } system_file:dir_file_class_set mounton;

# Nothing should be writing to files in the rootfs.
neverallow domain rootfs:file { create write setattr relabelto append unlink link rename };

# Restrict context mounts to specific types marked with
# the contextmount_type attribute.
neverallow domain {fs_type -contextmount_type}:filesystem relabelto;

# Ensure that context mount types are not writable, to ensure that
# the write to /system restriction above is not bypassed via context=
# mount to another type.
neverallow { domain -recovery } contextmount_type:dir_file_class_set
    { create write setattr relabelfrom relabelto append unlink link rename };

# Do not allow service_manager add for default_android_service.
# Instead domains should use a more specific type such as
# system_app_service rather than the generic type.
# New service_types are defined in service.te and new mappings
# from service name to service_type are defined in service_contexts.
neverallow domain default_android_service:service_manager add;

# Require that domains explicitly label unknown properties, and do not allow
# anyone but init to modify unknown properties.
neverallow { domain -init } default_prop:property_service set;

neverallow { domain -init -recovery -system_server } frp_block_device:blk_file rw_file_perms;

# No domain other than recovery and update_engine can write to system partition(s).
neverallow { domain -recovery -update_engine } system_block_device:blk_file write;

# No domains other than install_recovery or recovery can write to recovery.
neverallow { domain -install_recovery -recovery } recovery_block_device:blk_file write;

# Only servicemanager should be able to register with binder as the context manager
neverallow { domain -servicemanager } *:binder set_context_mgr;

# Only authorized processes should be writing to files in /data/dalvik-cache
neverallow {
  domain
  -init # TODO: limit init to relabelfrom for files
  -zygote
  -installd
  -dex2oat
} dalvikcache_data_file:file no_w_file_perms;

neverallow {
  domain
  -init
  -installd
  -dex2oat
  -zygote
} dalvikcache_data_file:dir no_w_dir_perms;

# Only system_server should be able to send commands via the zygote socket
neverallow { domain -zygote -system_server } zygote:unix_stream_socket connectto;
neverallow { domain -system_server } zygote_socket:sock_file write;

# Android does not support System V IPCs.
#
# The reason for this is due to the fact that, by design, they lead to global
# kernel resource leakage.
#
# For example, there is no way to automatically release a SysV semaphore
# allocated in the kernel when:
#
# - a buggy or malicious process exits
# - a non-buggy and non-malicious process crashes or is explicitly killed.
#
# Killing processes automatically to make room for new ones is an
# important part of Android's application lifecycle implementation. This means
# that, even assuming only non-buggy and non-malicious code, it is very likely
# that over time, the kernel global tables used to implement SysV IPCs will fill
# up.
neverallow domain domain:{ shm sem msg msgq } *;

# Do not mount on top of symlinks, fifos, or sockets.
# Feature parity with Chromium LSM.
neverallow domain { file_type fs_type dev_type }:{ lnk_file fifo_file sock_file } mounton;

# Nobody should be able to execute su on user builds.
# On userdebug/eng builds, only dumpstate, shell, and
# su itself execute su.
neverallow { domain userdebug_or_eng(`-dumpstate -shell -su') } su_exec:file no_x_file_perms;

# Do not allow the introduction of new execmod rules. Text relocations
# and modification of executable pages are unsafe.
# The only exceptions are for NDK text relocations associated with
# https://code.google.com/p/android/issues/detail?id=23203
# which, long term, need to go away.
neverallow domain {
  file_type
  -system_data_file
  -apk_data_file
  -app_data_file
  -asec_public_file
}:file execmod;

# Do not allow making the stack or heap executable.
# We would also like to minimize execmem but it seems to be
# required by some device-specific service domains.
neverallow domain self:process { execstack execheap };

# prohibit non-zygote spawned processes from using shared libraries
# with text relocations. b/20013628 .
neverallow { domain -appdomain } file_type:file execmod;

neverallow { domain -init } proc:{ file dir } mounton;

# Ensure that all types assigned to processes are included
# in the domain attribute, so that all allow and neverallow rules
# written on domain are applied to all processes.
# This is achieved by ensuring that it is impossible to transition
# from a domain to a non-domain type and vice versa.
neverallow domain ~domain:process { transition dyntransition };
neverallow ~domain domain:process { transition dyntransition };

#
# Only system_app and system_server should be creating or writing
# their files. The proper way to share files is to setup
# type transitions to a more specific type or assigning a type
# to its parent directory via a file_contexts entry.
# Example type transition:
#  mydomain.te:file_type_auto_trans(mydomain, system_data_file, new_file_type)
#
neverallow {
  domain
  -system_server
  -system_app
  -init
  -installd # for relabelfrom and unlink, check for this in explicit neverallow
} system_data_file:file no_w_file_perms;
# do not grant anything greater than r_file_perms and relabelfrom unlink
# to installd
neverallow installd system_data_file:file ~{ r_file_perms relabelfrom unlink };

#
# Only these domains should transition to shell domain. This domain is
# permissible for the "shell user". If you need a process to exec a shell
# script with differing privilege, define a domain and set up a transition.
#
neverallow {
  domain
  -adbd
  -init
  -runas
  -zygote
} shell:process { transition dyntransition };

# Minimize read access to shell- or app-writable symlinks.
# This is to prevent malicious symlink attacks.
neverallow {
  domain
  -appdomain
  -installd
  -uncrypt  # TODO: see if we can remove
} app_data_file:lnk_file read;

neverallow {
  domain
  -shell
  userdebug_or_eng(`-uncrypt')
  -installd
} shell_data_file:lnk_file read;

# In addition to the symlink reading restrictions above, restrict
# write access to shell owned directories. The /data/local/tmp
# directory is untrustworthy, and non-whitelisted domains should
# not be trusting any content in those directories.
neverallow {
  domain
  -adbd
  -dumpstate
  -installd
  -init
  -shell
  -vold
} shell_data_file:dir no_w_dir_perms;

neverallow {
  domain
  -adbd
  -appdomain
  -dumpstate
  -init
  -installd
  -system_server # why?
  userdebug_or_eng(`-uncrypt')
} shell_data_file:dir { open search };

# Same as above for /data/local/tmp files. We allow shell files
# to be passed around by file descriptor, but not directly opened.
neverallow {
  domain
  -adbd
  -appdomain
  -dumpstate
  -installd
  userdebug_or_eng(`-uncrypt')
} shell_data_file:file open;

# servicemanager is the only process which handles list request
neverallow domain ~servicemanager:service_manager list;

# only service_manager_types can be added to service_manager
neverallow domain ~service_manager_type:service_manager { add find };

# logpersist is only allowed on userdebug/eng builds
neverallow { domain userdebug_or_eng(`-logd -shell') } misc_logd_file:file rw_file_perms;

# Prevent assigning non property types to properties
neverallow domain ~property_type:property_service set;

# Domain types should never be assigned to any files other
# than the /proc/pid files associated with a process. The
# executable file used to enter a domain should be labeled
# with its own _exec type, not with the domain type.
# Conventionally, this looks something like:
# $ cat mydaemon.te
# type mydaemon, domain;
# type mydaemon_exec, exec_type, file_type;
# init_daemon_domain(mydaemon)
# $ grep mydaemon file_contexts
# /system/bin/mydaemon -- u:object_r:mydaemon_exec:s0
neverallow domain domain:file { execute execute_no_trans entrypoint };