Add script for modifying privapp permission allowlists

This script will be used to change the package that is being allowed to
use privileged permissions.

Test: python scripts/modify_permissions_allowlist.py
Bug: 242509786
(cherry picked from https://android-review.googlesource.com/q/commit:580f7b0094bd98d3769b6cdeaaab6a9748621253)
Merged-In: I1d7cb3c906ad39aef42ad4394953251db40d1bf1
Change-Id: I1d7cb3c906ad39aef42ad4394953251db40d1bf1

scripts/modify_permissions_allowlist_test.py

@@ -0,0 +1,76 @@
+#!/usr/bin/env python
+#
+# Copyright (C) 2022 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.
+#
+"""Unit tests for modify_permissions_allowlist.py."""
+
+from __future__ import print_function
+
+import unittest
+
+from xml.dom import minidom
+
+from modify_permissions_allowlist import InvalidRootNodeException, InvalidNumberOfPrivappPermissionChildren, modify_allowlist
+
+
+class ModifyPermissionsAllowlistTest(unittest.TestCase):
+
+  def test_invalid_root(self):
+    xml_data = '<foo></foo>'
+    xml_dom = minidom.parseString(xml_data)
+    self.assertRaises(InvalidRootNodeException, modify_allowlist, xml_dom, 'x')
+
+  def test_no_packages(self):
+    xml_data = '<permissions></permissions>'
+    xml_dom = minidom.parseString(xml_data)
+    self.assertRaises(
+        InvalidNumberOfPrivappPermissionChildren, modify_allowlist, xml_dom, 'x'
+    )
+
+  def test_multiple_packages(self):
+    xml_data = (
+        '<permissions>'
+        '  <privapp-permissions package="foo.bar"></privapp-permissions>'
+        '  <privapp-permissions package="bar.baz"></privapp-permissions>'
+        '</permissions>'
+    )
+    xml_dom = minidom.parseString(xml_data)
+    self.assertRaises(
+        InvalidNumberOfPrivappPermissionChildren, modify_allowlist, xml_dom, 'x'
+    )
+
+  def test_modify_package_name(self):
+    xml_data = (
+        '<permissions>'
+        '  <privapp-permissions package="foo.bar">'
+        '    <permission name="myperm1"/>'
+        '  </privapp-permissions>'
+        '</permissions>'
+    )
+    xml_dom = minidom.parseString(xml_data)
+    modify_allowlist(xml_dom, 'bar.baz')
+    expected_data = (
+        '<?xml version="1.0" ?>'
+        '<permissions>'
+        '  <privapp-permissions package="bar.baz">'
+        '    <permission name="myperm1"/>'
+        '  </privapp-permissions>'
+        '</permissions>'
+    )
+    self.assertEqual(expected_data, xml_dom.toxml())
+
+
+if __name__ == '__main__':
+  unittest.main(verbosity=2)