DP-3T · jeffallen · May 25, 2020 · May 25, 2020
diff --git a/calibration-app/app/build.gradle b/calibration-app/app/build.gradle
@@ -28,7 +28,7 @@ android {
 
 	defaultConfig {
 		applicationId "org.dpppt.android.calibration"
-		minSdkVersion 23
+		minSdkVersion 21
 		targetSdkVersion 29
 		versionCode 2
 		versionName "0.2"

diff --git a/...ration-app/app/src/main/java/org/dpppt/android/calibration/controls/ControlsFragment.java b/...ration-app/app/src/main/java/org/dpppt/android/calibration/controls/ControlsFragment.java
@@ -311,7 +311,7 @@ private SpannableString formatStatusString(TracingStatus status) {
 			for (TracingStatus.ErrorState error : errors) {
 				builder.append("\n").append(error.getErrorString(getContext()));
 			}
-			builder.setSpan(new ForegroundColorSpan(getResources().getColor(R.color.red, null)),
+			builder.setSpan(new ForegroundColorSpan(getResources().getColor(R.color.red)),
 					start, builder.length(), Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
 		}
 

diff --git a/calibration-app/app/src/main/java/org/dpppt/android/calibration/util/RequirementsUtil.java b/calibration-app/app/src/main/java/org/dpppt/android/calibration/util/RequirementsUtil.java
@@ -12,6 +12,7 @@
 
 import android.bluetooth.BluetoothAdapter;
 import android.content.Context;
+import android.os.Build;
 import android.os.PowerManager;
 
 public class RequirementsUtil {
@@ -25,8 +26,13 @@ public static boolean isBluetoothEnabled() {
 	}
 
 	public static boolean isBatteryOptimizationDeactivated(Context context) {
-		PowerManager powerManager = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
-		return powerManager.isIgnoringBatteryOptimizations(context.getPackageName());
+		if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
+			PowerManager powerManager = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
+			return powerManager.isIgnoringBatteryOptimizations(context.getPackageName());
+		} else {
+			// this phone is too old to turn them off, so we lie and say we did.
+			return true;
+		}
 	}
 
 }
diff --git a/dp3t-sdk/sdk/build.gradle b/dp3t-sdk/sdk/build.gradle
@@ -18,7 +18,7 @@ android {
 	compileSdkVersion 29
 
 	defaultConfig {
-		minSdkVersion 23
+		minSdkVersion 21
 		targetSdkVersion 29
 		versionCode 50
 		versionName "0.5.0"

diff --git a/dp3t-sdk/sdk/src/main/AndroidManifest.xml b/dp3t-sdk/sdk/src/main/AndroidManifest.xml
@@ -9,8 +9,11 @@
   -->
 
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:tools="http://schemas.android.com/tools"
 	package="org.dpppt.android.sdk">
 
+	<uses-sdk tools:overrideLibrary="androidx.security"/>
+
 	<uses-permission android:name="android.permission.INTERNET" />
 	<uses-permission android:name="android.permission.BLUETOOTH" />
 	<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />

diff --git a/dp3t-sdk/sdk/src/main/java/org/dpppt/android/sdk/internal/ErrorHelper.java b/dp3t-sdk/sdk/src/main/java/org/dpppt/android/sdk/internal/ErrorHelper.java
@@ -46,8 +46,14 @@ public static Collection<ErrorState> checkTracingErrorStatus(Context context, Ap
 		}
 
 		PowerManager powerManager = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
-		boolean batteryOptimizationsDeactivated =
-				powerManager == null || powerManager.isIgnoringBatteryOptimizations(context.getPackageName());
+		boolean batteryOptimizationsDeactivated;
+		if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.M) {
+			batteryOptimizationsDeactivated = powerManager == null ||
+					powerManager.isIgnoringBatteryOptimizations(context.getPackageName());
+		} else {
+			// This phone is too old to do it, so we lie and say they did.
+			batteryOptimizationsDeactivated = true;
+		}
 		if (!batteryOptimizationsDeactivated) {
 			errors.add(ErrorState.BATTERY_OPTIMIZER_ENABLED);
 		}

diff --git a/dp3t-sdk/sdk/src/main/java/org/dpppt/android/sdk/internal/ExposureDayStorage.java b/dp3t-sdk/sdk/src/main/java/org/dpppt/android/sdk/internal/ExposureDayStorage.java
@@ -11,6 +11,8 @@
 
 import android.content.Context;
 import android.content.SharedPreferences;
+import android.os.Build;
+
 import androidx.security.crypto.EncryptedSharedPreferences;
 import androidx.security.crypto.MasterKeys;
 
@@ -33,7 +35,7 @@ public class ExposureDayStorage {
 
 	private static ExposureDayStorage instance;
 
-	private SharedPreferences esp;
+	private SharedPreferences sp;
 
 	public static synchronized ExposureDayStorage getInstance(Context context) {
 		if (instance == null) {
@@ -44,20 +46,39 @@ public static synchronized ExposureDayStorage getInstance(Context context) {
 
 	private ExposureDayStorage(Context context) {
 		try {
-			String KEY_ALIAS = MasterKeys.getOrCreate(MasterKeys.AES256_GCM_SPEC);
-			esp = EncryptedSharedPreferences.create("dp3t_exposuredays_store",
-					KEY_ALIAS,
-					context,
-					EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
-					EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM);
+			if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
+				String KEY_ALIAS = MasterKeys.getOrCreate(MasterKeys.AES256_GCM_SPEC);
+				sp = EncryptedSharedPreferences.create("dp3t_exposuredays_store",
+						KEY_ALIAS,
+						context,
+						EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
+						EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM);
+
+				// See if there's data from API < 23 to migrate to secure storage.
+				SharedPreferences spOld = context.getSharedPreferences("dp3t_exposuredays_store_not_encrypted", Context.MODE_PRIVATE);
+				boolean needClear = false;
+				if (spOld.contains(PREF_KEY_LAST_ID)) {
+					sp.edit().putString(PREF_KEY_LAST_ID, spOld.getString(PREF_KEY_LAST_ID, "")).apply();
+					needClear = true;
+				}
+				if (spOld.contains(PREF_KEY_EEXPOSURE_DAYS)) {
+					sp.edit().putString(PREF_KEY_EEXPOSURE_DAYS, spOld.getString(PREF_KEY_EEXPOSURE_DAYS, "")).apply();
+					needClear = true;
+				}
+				if (needClear) {
+					spOld.edit().clear().apply();
+				}
+			} else {
+				sp = context.getSharedPreferences("dp3t_exposuredays_store_not_encrypted", Context.MODE_PRIVATE);
+			}
 		} catch (GeneralSecurityException | IOException ex) {
 			ex.printStackTrace();
 		}
 	}
 
 	private ExposureDayList getExposureDaysInternal() {
 		ExposureDayList list =
-				Json.safeFromJson(esp.getString(PREF_KEY_EEXPOSURE_DAYS, "[]"), ExposureDayList.class, ExposureDayList::new);
+				Json.safeFromJson(sp.getString(PREF_KEY_EEXPOSURE_DAYS, "[]"), ExposureDayList.class, ExposureDayList::new);
 
 		DayDate maxAgeForExposureDay = new DayDate().subtractDays(NUMBER_OF_DAYS_TO_KEEP_EXPOSED_DAYS);
 		Iterator<ExposureDay> iterator = list.iterator();
@@ -91,10 +112,10 @@ public void addExposureDay(Context context, ExposureDay exposureDay) {
 			}
 		}
 
-		int id = esp.getInt(PREF_KEY_LAST_ID, 0) + 1;
+		int id = sp.getInt(PREF_KEY_LAST_ID, 0) + 1;
 		exposureDay.setId(id);
 		previousExposureDays.add(exposureDay);
-		esp.edit()
+		sp.edit()
 				.putInt(PREF_KEY_LAST_ID, id)
 				.putString(PREF_KEY_EEXPOSURE_DAYS, Json.toJson(previousExposureDays))
 				.apply();
@@ -107,13 +128,13 @@ public void resetExposureDays() {
 		for (ExposureDay previousExposureDay : previousExposureDays) {
 			previousExposureDay.setDeleted(true);
 		}
-		esp.edit()
+		sp.edit()
 				.putString(PREF_KEY_EEXPOSURE_DAYS, Json.toJson(previousExposureDays))
 				.apply();
 	}
 
 	public void clear() {
-		esp.edit()
+		sp.edit()
 				.putString(PREF_KEY_EEXPOSURE_DAYS, Json.toJson(new ExposureDayList()))
 				.apply();
 	}

diff --git a/dp3t-sdk/sdk/src/main/java/org/dpppt/android/sdk/internal/PendingKeyUploadStorage.java b/dp3t-sdk/sdk/src/main/java/org/dpppt/android/sdk/internal/PendingKeyUploadStorage.java
@@ -11,6 +11,8 @@
 
 import android.content.Context;
 import android.content.SharedPreferences;
+import android.os.Build;
+
 import androidx.security.crypto.EncryptedSharedPreferences;
 import androidx.security.crypto.MasterKeys;
 
@@ -27,7 +29,7 @@ public class PendingKeyUploadStorage {
 
 	private static PendingKeyUploadStorage instance;
 
-	private SharedPreferences esp;
+	private SharedPreferences sp;
 
 	public static synchronized PendingKeyUploadStorage getInstance(Context context) {
 		if (instance == null) {
@@ -38,24 +40,35 @@ public static synchronized PendingKeyUploadStorage getInstance(Context context)
 
 	private PendingKeyUploadStorage(Context context) {
 		try {
-			String KEY_ALIAS = MasterKeys.getOrCreate(MasterKeys.AES256_GCM_SPEC);
-			esp = EncryptedSharedPreferences.create("dp3t_pendingkeyupload_store",
-					KEY_ALIAS,
-					context,
-					EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
-					EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM);
+			if ( Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
+				String KEY_ALIAS = MasterKeys.getOrCreate(MasterKeys.AES256_GCM_SPEC);
+				sp = EncryptedSharedPreferences.create("dp3t_pendingkeyupload_store",
+						KEY_ALIAS,
+						context,
+						EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
+						EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM);
+
+				// Check if there are values in old pref file that need to be migrated to secure storage.
+				SharedPreferences spOld = context.getSharedPreferences("dp3t_pendingkeyupload_store_not_encrypted", Context.MODE_PRIVATE);
+				if (spOld.contains(PREF_KEY_PENDING_KEYS)) {
+					sp.edit().putString(PREF_KEY_PENDING_KEYS, spOld.getString(PREF_KEY_PENDING_KEYS, "")).apply();
+					spOld.edit().clear().apply();
+				}
+			} else {
+				sp = context.getSharedPreferences("dp3t_pendingkeyupload_store_not_encrypted", Context.MODE_PRIVATE);
+			}
 		} catch (GeneralSecurityException | IOException ex) {
 			ex.printStackTrace();
 		}
 	}
 
 	private PendingKeyList getPendingKeys() {
-		return Json.fromJson(esp.getString(PREF_KEY_PENDING_KEYS, "[]"), PendingKeyList.class);
+		return Json.fromJson(sp.getString(PREF_KEY_PENDING_KEYS, "[]"), PendingKeyList.class);
 	}
 
 	private void setPendingKeys(PendingKeyList list) {
 		Collections.sort(list, (a, b) -> Integer.compare(a.getRollingStartNumber(), b.getRollingStartNumber()));
-		esp.edit().putString(PREF_KEY_PENDING_KEYS, Json.toJson(list)).apply();
+		sp.edit().putString(PREF_KEY_PENDING_KEYS, Json.toJson(list)).apply();
 	}
 
 	public int peekRollingStartNumber() {
@@ -89,7 +102,7 @@ public void addPendingKey(PendingKey key) {
 	}
 
 	public void clear() {
-		esp.edit().clear().apply();
+		sp.edit().clear().apply();
 	}
 
 	public static class PendingKey {