Enforce execve() restrictions for API > 28
untrusted_app: Remove the ability to run execve() on files within an
application's home directory. Executing code from a writable /home
directory is a W^X violation (https://en.wikipedia.org/wiki/W%5EX).
Additionally, loading code from application home directories violates a
security requirement that all executable code mapped into memory must
come from signed sources, or be derived from signed sources.
Note: this change does *not* remove the ability to load executable code
through other mechanisms, such as mmap(PROT_EXEC) of a file descriptor
from the app's home directory. In particular, functionality like
dlopen() on files in an app's home directory continues to work even
after this change.
untrusted_app_25 and untrusted_app_27: For backwards compatibility,
continue to allow these domains to execve() files from the
application's home directory.
seapp_contexts: Bump the minimum API level required to enter the
untrusted_app domain. This will run API level 27-28 processes in
the API level 27 sandbox. API level 28 will continue to run with
levelFrom=all, and API level 27 will continue to run with
levelFrom=user.
Bug: 112357170
Test: Device boots and no obvious problems.
Test: See CTS test at https://android-review.googlesource.com/c/platform/cts/+/804228
Change-Id: Ief9ae3a227d16ab5792f43bacbb577c1e70185a0
diff --git a/private/untrusted_app_27.te b/private/untrusted_app_27.te
index 79c7762..7b9060d 100644
--- a/private/untrusted_app_27.te
+++ b/private/untrusted_app_27.te
@@ -2,7 +2,7 @@
### Untrusted_27.
###
### This file defines the rules for untrusted apps running with
-### 25 < targetSdkVersion <= 27.
+### 25 < targetSdkVersion <= 28.
###
### This file defines the rules for untrusted apps.
### Apps are labeled based on mac_permissions.xml (maps signer and
@@ -26,3 +26,7 @@
untrusted_app_domain(untrusted_app_27)
net_domain(untrusted_app_27)
bluetooth_domain(untrusted_app_27)
+
+# The ability to call exec() on files in the apps home directories
+# for targetApi 26, 27, and 28.
+allow untrusted_app_27 app_data_file:file execute_no_trans;