From c78f53cd0e9ce68cc52a851584b6ce5b34baef7d Mon Sep 17 00:00:00 2001
From: Chavi Weingarten <chaviw@google.com>
Date: Fri, 14 Apr 2023 18:50:53 +0000
Subject: Cleaned up transaction sanitize calls

Exposed a way for a client to invoke sanitize with a uid and pid to
ensure we don't remove states when the process that added it was
privileged.

Added a helper function to get the permission ints based on the String
permission values so SF and clients can call the same API.

In SF, call sanitize as soon as setTransactionState is called since
that's the point where the Transaction has been passed over binder so we
can identify the calling uid. This allows us to remove the permission
values passed to applyTransactionState and unifies the places that were
calling sanitize.

Test: CredentialsTest
Bug: 267794530
Change-Id: I30c1800f0fee43df1cee82464139db7b56a7d911
---
 libs/gui/LayerStatePermissions.cpp | 58 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 libs/gui/LayerStatePermissions.cpp

(limited to 'libs/gui/LayerStatePermissions.cpp')

diff --git a/libs/gui/LayerStatePermissions.cpp b/libs/gui/LayerStatePermissions.cpp
new file mode 100644
index 0000000000..28697ca953
--- /dev/null
+++ b/libs/gui/LayerStatePermissions.cpp
@@ -0,0 +1,58 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <binder/IPCThreadState.h>
+#include <gui/LayerStatePermissions.h>
+#include <private/android_filesystem_config.h>
+#ifndef __ANDROID_VNDK__
+#include <binder/PermissionCache.h>
+#endif // __ANDROID_VNDK__
+#include <gui/LayerState.h>
+
+namespace android {
+std::unordered_map<std::string, int> LayerStatePermissions::mPermissionMap = {
+        // If caller has ACCESS_SURFACE_FLINGER, they automatically get ROTATE_SURFACE_FLINGER
+        // permission, as well
+        {"android.permission.ACCESS_SURFACE_FLINGER",
+         layer_state_t::Permission::ACCESS_SURFACE_FLINGER |
+                 layer_state_t::Permission::ROTATE_SURFACE_FLINGER},
+        {"android.permission.ROTATE_SURFACE_FLINGER",
+         layer_state_t::Permission::ROTATE_SURFACE_FLINGER},
+        {"android.permission.INTERNAL_SYSTEM_WINDOW",
+         layer_state_t::Permission::INTERNAL_SYSTEM_WINDOW},
+};
+
+static bool callingThreadHasPermission(const std::string& permission __attribute__((unused)),
+                                       int pid __attribute__((unused)),
+                                       int uid __attribute__((unused))) {
+#ifndef __ANDROID_VNDK__
+    return uid == AID_GRAPHICS || uid == AID_SYSTEM ||
+            PermissionCache::checkPermission(String16(permission.c_str()), pid, uid);
+#endif // __ANDROID_VNDK__
+    return false;
+}
+
+uint32_t LayerStatePermissions::getTransactionPermissions(int pid, int uid) {
+    uint32_t permissions = 0;
+    for (auto [permissionName, permissionVal] : mPermissionMap) {
+        if (callingThreadHasPermission(permissionName, pid, uid)) {
+            permissions |= permissionVal;
+        }
+    }
+
+    return permissions;
+}
+} // namespace android
-- 
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