private/dexopt_chroot_setup.te

# A service that sets up the chroot environment for Pre-reboot Dexopt.
type dexopt_chroot_setup, domain, coredomain;
type dexopt_chroot_setup_exec, system_file_type, exec_type, file_type;
type dexopt_chroot_setup_tmpfs, file_type;

# Allow dexopt_chroot_setup to publish a binder service and make binder calls.
binder_use(dexopt_chroot_setup)
add_service(dexopt_chroot_setup, dexopt_chroot_setup_service)
allow dexopt_chroot_setup dumpstate:fifo_file { getattr write };
allow dexopt_chroot_setup dumpstate:fd use;

init_daemon_domain(dexopt_chroot_setup)

# Use tmpfs_domain() which will give tmpfs files created by dexopt_chroot_setup
# their own label, which differs from other labels created by other processes.
# This allows to distinguish in policy files created by dexopt_chroot_setup vs
# other processes.
tmpfs_domain(dexopt_chroot_setup)

# libart (mark_compact.cc) has some intialization code that touches the cache
# info file and userfaultfd.
allow dexopt_chroot_setup apex_module_data_file:dir { getattr search };
r_dir_file(dexopt_chroot_setup, apex_art_data_file)
userfaultfd_use(dexopt_chroot_setup)

# Allow getting root capabilities to bypass permission checks.
# - "sys_admin" is for performing mount and umount.
# - "sys_chroot" is for performing chroot.
allow dexopt_chroot_setup self:global_capability_class_set { sys_admin sys_chroot };

# Allow managing its own files.
# The root of the temp dir that dexopt_chroot_setup uses is labeled
# pre_reboot_dexopt_file.
allow dexopt_chroot_setup pre_reboot_dexopt_file:dir create_dir_perms;
allow dexopt_chroot_setup pre_reboot_dexopt_file:file create_file_perms;

# Allow accessing /proc/filesystems.
allow dexopt_chroot_setup proc_filesystems:file r_file_perms;

# Allow accessing block devices (/dev/block/...).
allow dexopt_chroot_setup block_device:dir { getattr search };

# Allow mounting file systems, to create a chroot environment.
allow dexopt_chroot_setup {
  apex_mnt_dir
  binderfs
  cgroup
  cgroup_v2
  debugfs_tracing_debug
  device
  devpts
  fs_bpf
  functionfs
  fusectlfs
  linkerconfig_file
  metadata_file
  mnt_expand_file
  pre_reboot_dexopt_file
  proc
  pstorefs
  rootfs
  selinuxfs
  sysfs
  system_data_file
  system_data_root_file
  system_file
  tmpfs
  vendor_file
}:dir mounton;

allow dexopt_chroot_setup { tmpfs labeledfs }:filesystem mount;

allow dexopt_chroot_setup {
  binderfs
  cgroup
  cgroup_v2
  debugfs_tracing_debug
  devpts
  fs_bpf
  functionfs
  fusectlfs
  labeledfs
  proc
  pstorefs
  selinuxfs
  sysfs
  tmpfs
}:filesystem unmount;

# Allow reading /apex in chroot.
r_dir_file(dexopt_chroot_setup, apex_mnt_dir)
allow dexopt_chroot_setup apex_info_file:file r_file_perms;

# Allow writing an empty linker config in chroot to suppress linker warnings.
# The empty linker config is used until linkerconfig has run.
# In chroot, we're reusing the type outside the chroot, to reuse all the rules
# for it for other domains, even though we're not changing the real linker
# config outside the chroot.
allow dexopt_chroot_setup linkerconfig_file:dir { write add_name };
allow dexopt_chroot_setup linkerconfig_file:file { create write };

# Allow using the `rootcontext=` option when mounting tmpfs, so we can give the
# right labels to /apex, /linkerconfig, /mnt/artd_tmp in chroot.
# Combined with `allow file_type tmpfs:filesystem associate;`, this allows
# giving any labels to any tmpfs filesystems as soon as they are mounted.
# Note that those tmpfs filesystems are known to be empty at the time where the
# labels are given, and this rule doesn't allow relabeling any existing tmpfs.
allow dexopt_chroot_setup tmpfs:filesystem relabelfrom;

# Allow executing art_exec_exec without a domain transition because it is a thin
# wrapper that executes other binaries on behalf of dexopt_chroot_setup. Domain
# transition will take place as soon as art_exec_exec executes other binaries.
allow dexopt_chroot_setup art_exec_exec:file rx_file_perms;

# Allow running other binaries in their own domains.
domain_auto_trans(dexopt_chroot_setup, apexd_exec, apexd)
domain_auto_trans(dexopt_chroot_setup, linkerconfig_exec, linkerconfig)

# Allow running snapshotctl through init, to map and unmap block devices.
set_prop(dexopt_chroot_setup, snapshotctl_prop)

# Neverallow rules.

# Never allow running other binaries without a domain transition.
# The exception for art_exec_exec is explained above.
neverallow dexopt_chroot_setup ~{art_exec_exec}:file execute_no_trans;

# Given how powerful this domain is, it shouldn't be used for other purposes.
neverallow { domain -init } dexopt_chroot_setup:process transition;
neverallow * dexopt_chroot_setup:process dyntransition;

# Never allow other processes to access the temp dirs for Pre-reboot Dexopt.
neverallow {
  domain
  -art_exec
  -artd
  -dexopt_chroot_setup
  -init
  -system_server
  -vendor_init
} pre_reboot_dexopt_file:dir *;