Add script to verify priv-app permission allowlists

* TODO: Implement this with CI/CD

cicd/verify-permissions.py

@@ -0,0 +1,123 @@
+#!/usr/bin/python3
+#
+# Copyright (C) 2021 Paul Keith <javelinanddart@gmail.com>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 and
+# only version 2 as published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+import errno
+from glob import glob
+import subprocess
+import sys
+from xml.etree import ElementTree
+
+# Get external packages
+try:
+    import requests
+except ImportError:
+    print('Please install the "requests" package via pip3.')
+    exit(errno.ENOPKG)
+
+# Definitions for privileged permissions
+ANDROID_MANIFEST_XML = \
+        'https://raw.githubusercontent.com/LineageOS/android_frameworks_base/lineage-19.0/core/res/AndroidManifest.xml'
+ANDROID_XML_NS = '{http://schemas.android.com/apk/res/android}'
+privileged_permissions = set()
+privileged_permission_mask = {'privileged', 'signature'}
+
+# Get AndroidManifest.xml
+req = requests.get(ANDROID_MANIFEST_XML)
+
+# Parse AndroidManifest.xml to get signature|privileged permissions
+root = ElementTree.fromstring(req.text)
+for perm in root.findall('permission'):
+    # Get name of permission
+    name = perm.get('{}name'.format(ANDROID_XML_NS))
+    # Get the protection levels on the permission
+    levels = set(perm.get('{}protectionLevel'.format(ANDROID_XML_NS)).split('|'))
+    # Check if the protections include signature and privileged
+    levels_masked = levels & privileged_permission_mask
+    if len(levels_masked) > 0:
+        privileged_permissions.add(name)
+
+# Definitions for privapp-permissions
+# Dictionary with structure:
+#     package_name : (set(allowed_permissions), set(requested_permissions))
+privapp_permissions_dict = {}
+
+# Definitions for privapp-permission allowlists
+GLOB_XML_STR = '../*/proprietary/*/etc/permissions/privapp-permissions*.xml'
+
+# Parse allowlists to extract allowed privileged permissions
+for allowlist in glob(GLOB_XML_STR):
+    # Get root of XML
+    tree = ElementTree.parse(allowlist)
+    root = tree.getroot()
+    # Loop through and find packages
+    for package in root.findall('privapp-permissions'):
+        name = package.get('package')
+        # Create empty entry if it's not in the dictionary
+        if name not in privapp_permissions_dict:
+            privapp_permissions_dict[name] = (set(), set())
+        # Get all permissions and add them to dictionary
+        for permission in package.findall('permission'):
+            privapp_permissions_dict[name][0].add(permission.get('name'))
+        for permission in package.findall('deny-permission'):
+            privapp_permissions_dict[name][0].add(permission.get('name'))
+
+# Definitions for parsing APKs
+GLOB_APK_STR = '../*/proprietary/*/priv-app/*/*.apk'
+AAPT_CMD = ['aapt', 'd', 'permissions']
+
+# Extract requested privileged permissions from all priv-app APKs
+for apk in glob(GLOB_APK_STR):
+    # Run 'aapt d permissions' on APK
+    aapt_output = subprocess.check_output(AAPT_CMD + [apk],
+            stderr=subprocess.STDOUT).decode(encoding='UTF-8')
+    lines = aapt_output.split('\n')
+    # Extract package name from the output
+    # Output looks like:
+    #     package: my.package.name
+    package_name = lines[0].replace('package: ', '')
+    # Create empty entry if package is not in dic
+    if package_name not in privapp_permissions_dict:
+        privapp_permissions_dict[package_name] = (set(), set())
+    # Extract 'uses-permission' lines from the rest of the output
+    # Relevant output looks like:
+    #     uses-permission: name='permission'
+    for line in lines[1:]:
+        if line.startswith('uses-permission'):
+            # Extract permission name and add it to the dictionary if it's
+            # one of the privileged permissions we extracted earlier
+            perm_name = line.replace('uses-permission: name=', '') \
+                .replace('\'', '')
+            if perm_name in privileged_permissions:
+                privapp_permissions_dict[package_name][1].add(perm_name)
+
+# Keep track of exit code
+rc = 0
+
+# Loop through all the packages and compare permission sets
+for package in privapp_permissions_dict:
+    # Get the sets of permissions
+    # Format is (allowed, requested)
+    perm_sets = privapp_permissions_dict[package]
+    # Compute the set difference requested - allowed
+    # This gives us all the permissions requested that were not allowed
+    perm_diff = perm_sets[1] - perm_sets[0]
+    # If any permissions are left, set exit code to EPERM and print output
+    if len(perm_diff) > 0:
+        rc = errno.EPERM
+        sys.stderr.write("Package {} is missing these permissions:\n"
+                .format(package))
+        for perm in perm_diff:
+            sys.stderr.write(" - {}\n".format(perm))
+
+# Exit program
+exit(rc)