platform_system_sepolicy/private/app.te
Nick Kralevich 0eb0a16fbd bless app created renderscript files
When an app uses renderscript to compile a Script instance,
renderscript compiles and links the script using /system/bin/bcc and
/system/bin/ld.mc, then places the resulting shared library into the
application's code_cache directory. The application then dlopen()s the
resulting shared library.

Currently, this executable code is writable to the application. This
violates the W^X property (https://en.wikipedia.org/wiki/W%5EX), which
requires any executable code be immutable.

This change introduces a new label "rs_data_file". Files created by
/system/bin/bcc and /system/bin/ld.mc in the application's home
directory assume this label. This allows us to differentiate in
security policy between app created files, and files created by
renderscript on behalf of the application.

Apps are allowed to delete these files, but cannot create or write these
files. This is enforced through a neverallow compile time assertion.

Several exceptions are added to Treble neverallow assertions to support
this functionality. However, because renderscript was previously invoked
from an application context, this is not a Treble separation regression.

This change is needed to support blocking dlopen() for non-renderscript
/data/data files, which will be submitted in a followup change.

Bug: 112357170
Test: cts-tradefed run cts -m CtsRenderscriptTestCases
Change-Id: Ie38bbd94d26db8a418c2a049c24500a5463698a3
2018-12-12 13:20:22 -08:00

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1.1 KiB
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# TODO: deal with tmpfs_domain pub/priv split properly
# Read system properties managed by zygote.
allow appdomain zygote_tmpfs:file read;
# Read from (but not create) system_server buffers transferred through
# ashmem, e.g. battery stats.
allow appdomain system_server_tmpfs:file read;
# Get info from priv_app through ashmem, such as contact
# info etc.
allow appdomain priv_app_tmpfs:file read;
neverallow appdomain system_server:udp_socket {
accept append bind create ioctl listen lock name_bind
relabelfrom relabelto setattr shutdown };
# Transition to a non-app domain.
# Exception for the shell and su domains, can transition to runas, etc.
# Exception for crash_dump to allow for app crash reporting.
# Exception for renderscript binaries (/system/bin/bcc, /system/bin/ld.mc)
# to allow renderscript to create privileged executable files.
neverallow { appdomain -shell userdebug_or_eng(`-su') }
{ domain -appdomain -crash_dump -rs }:process { transition };
neverallow { appdomain -shell userdebug_or_eng(`-su') }
{ domain -appdomain }:process { dyntransition };