raise minimum OS version to Android 10

Android 11 is the oldest version receiving official security support but
the Android 10 end-of-life was relatively recent.

app/build.gradle.kts

@@ -45,7 +45,7 @@ android {
 
     defaultConfig {
         applicationId = "app.attestation.auditor"
-        minSdk = 26
+        minSdk = 29
         targetSdk = 33
         versionCode = 69
         versionName = versionCode.toString()

app/src/main/java/app/attestation/auditor/AttestationProtocol.java

@@ -243,7 +243,7 @@ class AttestationProtocol {
     private static final byte AUDITOR_APP_VARIANT_PLAY = 1;
     private static final byte AUDITOR_APP_VARIANT_DEBUG = 2;
     private static final int AUDITOR_APP_MINIMUM_VERSION = 47;
-    private static final int OS_VERSION_MINIMUM = 80000;
+    private static final int OS_VERSION_MINIMUM = 100000;
     private static final int OS_PATCH_LEVEL_MINIMUM = 201801;
     private static final int VENDOR_PATCH_LEVEL_MINIMUM = 201808;
     private static final int BOOT_PATCH_LEVEL_MINIMUM = 201809;
@@ -1362,11 +1362,6 @@ static class AttestationResult {
         }
     }
 
-    @TargetApi(28)
-    static void enableStrongBox(final KeyGenParameterSpec.Builder builder) {
-        builder.setIsStrongBoxBacked(true);
-    }
-
     @TargetApi(31)
     static void setAttestKeyAlias(final KeyGenParameterSpec.Builder builder, final String alias) {
         builder.setAttestKeyAlias(alias);
@@ -1384,7 +1379,7 @@ static KeyGenParameterSpec.Builder getKeyBuilder(final String alias, final int p
             builder.setKeyValidityEnd(new Date(startTime.getTime() + EXPIRE_OFFSET_MS));
         }
         if (useStrongBox) {
-            enableStrongBox(builder);
+            builder.setIsStrongBoxBacked(true);
         }
         return builder;
     }

app/src/main/java/app/attestation/auditor/RemoteVerifyJob.java

@@ -88,9 +88,8 @@ static void schedule(final Context context, int interval) {
         final long intervalMillis = interval * 1000;
         final long flexMillis = intervalMillis / 10;
         if (jobInfo != null &&
-                (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P &&
-                        jobInfo.getEstimatedNetworkDownloadBytes() == ESTIMATED_DOWNLOAD_BYTES &&
-                        jobInfo.getEstimatedNetworkUploadBytes() == ESTIMATED_UPLOAD_BYTES) &&
+                jobInfo.getEstimatedNetworkDownloadBytes() == ESTIMATED_DOWNLOAD_BYTES &&
+                jobInfo.getEstimatedNetworkUploadBytes() == ESTIMATED_UPLOAD_BYTES &&
                 jobInfo.getIntervalMillis() == intervalMillis &&
                 jobInfo.getFlexMillis() == flexMillis) {
             Log.d(TAG, "job already registered");
@@ -100,10 +99,8 @@ static void schedule(final Context context, int interval) {
         if (jobInfo == null) {
             final JobInfo.Builder builder = new JobInfo.Builder(FIRST_RUN_JOB_ID, serviceName)
                     .setPersisted(true)
-                    .setRequiredNetworkType(JobInfo.NETWORK_TYPE_ANY);
-            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
-                builder.setEstimatedNetworkBytes(ESTIMATED_DOWNLOAD_BYTES, ESTIMATED_UPLOAD_BYTES);
-            }
+                    .setRequiredNetworkType(JobInfo.NETWORK_TYPE_ANY)
+                    .setEstimatedNetworkBytes(ESTIMATED_DOWNLOAD_BYTES, ESTIMATED_UPLOAD_BYTES);
             if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
                 builder.setExpedited(true);
             }
@@ -117,10 +114,8 @@ static void schedule(final Context context, int interval) {
         final JobInfo.Builder builder = new JobInfo.Builder(PERIODIC_JOB_ID, serviceName)
                 .setPeriodic(intervalMillis, flexMillis)
                 .setPersisted(true)
-                .setRequiredNetworkType(JobInfo.NETWORK_TYPE_ANY);
-        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
-            builder.setEstimatedNetworkBytes(ESTIMATED_DOWNLOAD_BYTES, ESTIMATED_UPLOAD_BYTES);
-        }
+                .setRequiredNetworkType(JobInfo.NETWORK_TYPE_ANY)
+                .setEstimatedNetworkBytes(ESTIMATED_DOWNLOAD_BYTES, ESTIMATED_UPLOAD_BYTES);
         if (scheduler.schedule(builder.build()) == JobScheduler.RESULT_FAILURE) {
             throw new RuntimeException("job schedule failed");
         }

app/src/main/java/app/attestation/auditor/SubmitSampleJob.java

@@ -63,10 +63,8 @@ static void schedule(final Context context) {
         final JobScheduler scheduler = context.getSystemService(JobScheduler.class);
         final JobInfo.Builder builder = new JobInfo.Builder(JOB_ID, serviceName)
                 .setPersisted(true)
-                .setRequiredNetworkType(JobInfo.NETWORK_TYPE_ANY);
-        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
-            builder.setEstimatedNetworkBytes(ESTIMATED_DOWNLOAD_BYTES, ESTIMATED_UPLOAD_BYTES);
-        }
+                .setRequiredNetworkType(JobInfo.NETWORK_TYPE_ANY)
+                .setEstimatedNetworkBytes(ESTIMATED_DOWNLOAD_BYTES, ESTIMATED_UPLOAD_BYTES);
         if (scheduler.schedule(builder.build()) == JobScheduler.RESULT_FAILURE) {
             throw new RuntimeException("job schedule failed");
         }
@@ -96,17 +94,15 @@ public boolean onStartJob(final JobParameters params) {
                 keyStore.deleteEntry(KEYSTORE_ALIAS_SAMPLE);
 
                 Certificate[] strongBoxCerts = null;
-                if (Build.VERSION.SDK_INT >= 28) {
-                    try {
-                        builder.setIsStrongBoxBacked(true);
-                        AttestationProtocol.generateKeyPair(builder.build());
-                        strongBoxCerts = keyStore.getCertificateChain(KEYSTORE_ALIAS_SAMPLE);
-                        keyStore.deleteEntry(KEYSTORE_ALIAS_SAMPLE);
-                    } catch (final StrongBoxUnavailableException ignored) {
-                    } catch (final IOException e) {
-                        if (!(e.getCause() instanceof StrongBoxUnavailableException)) {
-                            throw e;
-                        }
+                try {
+                    builder.setIsStrongBoxBacked(true);
+                    AttestationProtocol.generateKeyPair(builder.build());
+                    strongBoxCerts = keyStore.getCertificateChain(KEYSTORE_ALIAS_SAMPLE);
+                    keyStore.deleteEntry(KEYSTORE_ALIAS_SAMPLE);
+                } catch (final StrongBoxUnavailableException ignored) {
+                } catch (final IOException e) {
+                    if (!(e.getCause() instanceof StrongBoxUnavailableException)) {
+                        throw e;
                     }
                 }
 

app/src/main/res/values/strings.xml

@@ -1,6 +1,6 @@
 <resources>
     <string name="app_name">Auditor</string>
-    <string name="introduction">Two devices are needed to perform verification:\n\n- The device to be verified (Auditee), which needs to be one of the supported devices launched with Android 8.0+.\n\n- An Android 8.0+ device to perform the verification (Auditor).\n\nThe verification process requires sending data between the devices by scanning QR codes.</string>
+    <string name="introduction">Two devices with Android 10 or higher are needed to perform verification:\n\n- The device to be verified (Auditee), which needs to be one of the supported devices.\n\n- An Android device to perform the verification (Auditor).\n\nThe verification process requires sending data between the devices by scanning QR codes.</string>
     <string name="unsupported_auditee">Device is not one of the supported models.</string>
     <string name="camera_permission_denied">Camera permission is required to scan QR codes.</string>
     <string name="auditee_button">Auditee (device being verified)</string>