new: featureFlags support for SDK 35 apps (#3706)

* new: featureFlags support for SDK 35 apps

This records all featureFlag attrs that were enabled when the APK was originally built.
This is now required by AAPT2 to pass these flags and their enabled/disabled state if
they are used in AndroidManifest.xml.
The flags are recorded to apktool.yml and can be configured, if so desired.
In normal usage, all flags should remain set to true (i.e. enabled).
Sample APK sourced from AOSP Android 15.

https://drive.google.com/file/d/1av7Ih7-YUXi73Hf0E3xlPv-V-nE_sXdt/view

* test: adapt testapp for featureFlag

brut.apktool/apktool-lib/src/main/java/brut/androlib/AaptInvoker.java

@@ -189,6 +189,15 @@ public class AaptInvoker {
             cmd.add("-x");
         }
 
+        if (!mApkInfo.featureFlags.isEmpty()) {
+            List<String> featureFlags = new ArrayList<>();
+            for (Map.Entry<String, Boolean> entry : mApkInfo.featureFlags.entrySet()) {
+                featureFlags.add(entry.getKey() + "=" + entry.getValue());
+            }
+            cmd.add("--feature-flags");
+            cmd.add(String.join(",", featureFlags));
+        }
+
         if (include != null) {
             for (File file : include) {
                 cmd.add("-I");

brut.apktool/apktool-lib/src/main/java/brut/androlib/ApkDecoder.java

@@ -21,6 +21,7 @@ import brut.androlib.exceptions.InFileNotFoundException;
 import brut.androlib.exceptions.OutDirExistsException;
 import brut.androlib.apk.ApkInfo;
 import brut.androlib.res.ResourcesDecoder;
+import brut.androlib.res.xml.ResXmlPatcher;
 import brut.androlib.src.SmaliDecoder;
 import brut.directory.Directory;
 import brut.directory.ExtFile;
@@ -321,6 +322,15 @@ public class ApkDecoder {
             mApkInfo.setMinSdkVersion(Integer.toString(mMinSdkVersion));
         }
 
+        // record feature flags
+        File manifest = new File(outDir, "AndroidManifest.xml");
+        List<String> featureFlags = ResXmlPatcher.pullManifestFeatureFlags(manifest);
+        if (featureFlags != null) {
+            for (String flag : featureFlags) {
+                mApkInfo.addFeatureFlag(flag, true);
+            }
+        }
+
         // record uncompressed files
         try {
             Map<String, String> resFileMapping = mResDecoder.getResFileMapping();

brut.apktool/apktool-lib/src/main/java/brut/androlib/apk/ApkInfo.java

@@ -48,6 +48,7 @@ public class ApkInfo implements YamlSerializable {
     public Map<String, String> sdkInfo = new LinkedHashMap<>();
     public PackageInfo packageInfo = new PackageInfo();
     public VersionInfo versionInfo = new VersionInfo();
+    public Map<String, Boolean> featureFlags = new LinkedHashMap<>();
     public boolean sharedLibrary;
     public boolean sparseResources;
     public List<String> doNotCompress = new ArrayList<>();
@@ -185,6 +186,10 @@ public class ApkInfo implements YamlSerializable {
         }
     }
 
+    public void addFeatureFlag(String flag, boolean value) {
+        featureFlags.put(flag, value);
+    }
+
     public void save(File file) throws AndrolibException {
         try (YamlWriter writer = new YamlWriter(new FileOutputStream(file))) {
             write(writer);
@@ -235,7 +240,7 @@ public class ApkInfo implements YamlSerializable {
             }
             case "sdkInfo": {
                 sdkInfo.clear();
-                reader.readMap(sdkInfo);
+                reader.readStringMap(sdkInfo);
                 break;
             }
             case "packageInfo": {
@@ -248,6 +253,11 @@ public class ApkInfo implements YamlSerializable {
                 reader.readObject(versionInfo);
                 break;
             }
+            case "featureFlags": {
+                featureFlags.clear();
+                reader.readBoolMap(featureFlags);
+                break;
+            }
             case "sharedLibrary": {
                 sharedLibrary = line.getValueBool();
                 break;
@@ -270,9 +280,12 @@ public class ApkInfo implements YamlSerializable {
         writer.writeString("apkFileName", apkFileName);
         writer.writeBool("isFrameworkApk", isFrameworkApk);
         writer.writeObject("usesFramework", usesFramework);
-        writer.writeStringMap("sdkInfo", sdkInfo);
+        writer.writeMap("sdkInfo", sdkInfo);
         writer.writeObject("packageInfo", packageInfo);
         writer.writeObject("versionInfo", versionInfo);
+        if (!featureFlags.isEmpty()) {
+            writer.writeMap("featureFlags", featureFlags);
+        }
         writer.writeBool("sharedLibrary", sharedLibrary);
         writer.writeBool("sparseResources", sparseResources);
         if (!doNotCompress.isEmpty()) {

brut.apktool/apktool-lib/src/main/java/brut/androlib/apk/YamlReader.java

@@ -203,7 +203,7 @@ public class YamlReader {
         readList(list, (items, reader) -> items.add(reader.getLine().getValueInt()));
     }
 
-    public void readMap(Map<String, String> map) throws AndrolibException {
+    public void readStringMap(Map<String, String> map) throws AndrolibException {
         readObject(map,
             line -> line.hasColon,
             (items, reader) -> {
@@ -211,4 +211,13 @@ public class YamlReader {
                 items.put(line.getKey(), line.getValue());
             });
     }
+
+    public void readBoolMap(Map<String, Boolean> map) throws AndrolibException {
+        readObject(map,
+            line -> line.hasColon,
+            (items, reader) -> {
+                YamlLine line = reader.getLine();
+                items.put(line.getKey(), line.getValueBool());
+            });
+    }
 }

brut.apktool/apktool-lib/src/main/java/brut/androlib/apk/YamlWriter.java

@@ -95,7 +95,7 @@ public class YamlWriter implements Closeable {
         }
     }
 
-    public void writeStringMap(String key, Map<String, String> map) {
+    public <T> void writeMap(String key, Map<String, T> map) {
         if (Objects.isNull(map)) {
             return;
         }
@@ -103,7 +103,7 @@ public class YamlWriter implements Closeable {
         mWriter.println(escape(key) + ":");
         nextIndent();
         for (String mapKey : map.keySet()) {
-            writeString(mapKey, map.get(mapKey));
+            writeString(mapKey, String.valueOf(map.get(mapKey)));
         }
         prevIndent();
     }

brut.apktool/apktool-lib/src/main/java/brut/androlib/res/xml/ResXmlPatcher.java

@@ -30,6 +30,7 @@ import javax.xml.transform.dom.DOMSource;
 import javax.xml.transform.stream.StreamResult;
 import javax.xml.xpath.*;
 import java.io.*;
+import java.util.*;
 import java.util.logging.Logger;
 
 public final class ResXmlPatcher {
@@ -357,6 +358,42 @@ public final class ResXmlPatcher {
         }
     }
 
+    /**
+     * Finds all feature flags set on permissions in AndroidManifest.xml.
+     *
+     * @param file File for AndroidManifest.xml
+     */
+    public static List<String> pullManifestFeatureFlags(File file) {
+        if (!file.exists()) {
+            return null;
+        }
+        try {
+            Document doc = loadDocument(file);
+            XPath xPath = XPathFactory.newInstance().newXPath();
+            XPathExpression expression = xPath.compile("/manifest/permission");
+
+            Object result = expression.evaluate(doc, XPathConstants.NODESET);
+            NodeList nodes = (NodeList) result;
+
+            List<String> featureFlags = new ArrayList<>();
+
+            for (int i = 0; i < nodes.getLength(); i++) {
+                Node node = nodes.item(i);
+                NamedNodeMap attrs = node.getAttributes();
+                Node featureFlagAttr = attrs.getNamedItem("android:featureFlag");
+
+                if (featureFlagAttr != null) {
+                    featureFlags.add(featureFlagAttr.getNodeValue());
+                }
+            }
+
+            return featureFlags;
+
+        } catch (SAXException | ParserConfigurationException | IOException | XPathExpressionException ignored) {
+            return null;
+        }
+    }
+
     /**
      *
      * @param file File to load into Document

brut.apktool/apktool-lib/src/test/resources/aapt2/testapp/AndroidManifest.xml

@@ -11,4 +11,5 @@
         <meta-data name="test_int" value="12345" />
     </application>
     <uses-permission android:name="android.permission.BLUETOOTH_SCAN" android:usesPermissionFlags="neverForLocation" />
+    <permission android:featureFlag="brut.feature.flag" android:label="Test Permission" android:name="brut.permission.TEST" android:permissionGroup="android.permission-group.UNDEFINED" android:protectionLevel="signature"/>
 </manifest>

brut.apktool/apktool-lib/src/test/resources/aapt2/testapp/apktool.yml

@@ -9,6 +9,8 @@ packageInfo:
 versionInfo:
   versionCode: '1'
   versionName: '1.0'
+featureFlags:
+  brut.feature.flag: true
 doNotCompress:
 - assets/0byte_file.jpg
 sparseResources: false