Reduce minSDKVersion to 21

The Google Exposure Notification service works down to API 21, so the SDK should as well. Handle the missing EncryptedSharedPreferences by simply writing the preferences in cleartext when it is not available. Fixes #16.
DP-3T · May 25, 2020 · a78bb72 · a78bb72
1 parent 3eec9b9
commit a78bb72
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Showing 8 changed files with 56 additions and 29 deletions.
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 +46,24 @@ 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);
+			} 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 +97,10 @@ 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 +113,13 @@ 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 +40,28 @@ 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);
+			} 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 +95,7 @@ public void addPendingKey(PendingKey key) {
 	}
 
 	public void clear() {
-		esp.edit().clear().apply();
+		sp.edit().clear().apply();
 	}
 
 	public static class PendingKey {