SafetyNet Implementation (EXPOSUREAPP-4754) (#2242)

* First safetynet draft.
TODO: Additional integrity checks.

* Add nonce and APK check.
Move JWS data access helpers up to the wrapper.

* Add device time and time_since_onboarding check.

* Increase test coverage, check for null jwsResults.

* Add data donation test menu.
(Currently only shows SafetyNet JWS)

* Improve exception message.

* Additional test cases for different JSON fields.
Log optional error message that may be returned.

* Fix test regression due to missing mock

* Address Lukas PR comments.

* Add attestation max timeout (30s) + test.

Co-authored-by: harambasicluka <64483219+harambasicluka@users.noreply.github.com>
Co-authored-by: chris-cwa <69595386+chris-cwa@users.noreply.github.com>

Corona-Warn-App/src/deviceForTesters/java/de/rki/coronawarnapp/test/datadonation/ui/DataDonationTestFragment.kt

+package de.rki.coronawarnapp.test.datadonation.ui
+
+import android.annotation.SuppressLint
+import android.os.Bundle
+import android.view.View
+import android.widget.Toast
+import androidx.core.app.ShareCompat
+import androidx.fragment.app.Fragment
+import de.rki.coronawarnapp.R
+import de.rki.coronawarnapp.databinding.FragmentTestDatadonationBinding
+import de.rki.coronawarnapp.test.menu.ui.TestMenuItem
+import de.rki.coronawarnapp.util.di.AutoInject
+import de.rki.coronawarnapp.util.ui.observe2
+import de.rki.coronawarnapp.util.ui.viewBindingLazy
+import de.rki.coronawarnapp.util.viewmodel.CWAViewModelFactoryProvider
+import de.rki.coronawarnapp.util.viewmodel.cwaViewModels
+import org.json.JSONObject
+import javax.inject.Inject
+
+@SuppressLint("SetTextI18n")
+class DataDonationTestFragment : Fragment(R.layout.fragment_test_datadonation), AutoInject {
+
+    @Inject lateinit var viewModelFactory: CWAViewModelFactoryProvider.Factory
+    private val vm: DataDonationTestFragmentViewModel by cwaViewModels { viewModelFactory }
+
+    private val binding: FragmentTestDatadonationBinding by viewBindingLazy()
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        super.onViewCreated(view, savedInstanceState)
+
+        vm.currentReport.observe2(this) {
+            binding.safetynetBody.text = it?.body?.toString()?.let { json ->
+                JSONObject(json).toString(4)
+            }
+        }
+
+        binding.apply {
+            safetynetCreateReport.setOnClickListener { vm.createSafetyNetReport() }
+            safetynetCopyJws.setOnClickListener { vm.copyJWS() }
+        }
+
+        vm.copyJWSEvent.observe2(this) { jws ->
+            val intent = ShareCompat.IntentBuilder.from(requireActivity()).apply {
+                setType("text/plain")
+                setSubject("JWS")
+                setText(jws)
+            }.createChooserIntent()
+            startActivity(intent)
+        }
+
+        vm.errorEvents.observe2(this) {
+            Toast.makeText(requireContext(), it.toString(), Toast.LENGTH_LONG).show()
+        }
+    }
+
+    companion object {
+        val MENU_ITEM = TestMenuItem(
+            title = "Data Donation",
+            description = "SafetyNet, Analytics, Surveys et al.",
+            targetId = R.id.test_datadonation_fragment
+        )
+    }
+}

Corona-Warn-App/src/deviceForTesters/java/de/rki/coronawarnapp/test/datadonation/ui/DataDonationTestFragmentModule.kt

+package de.rki.coronawarnapp.test.datadonation.ui
+
+import dagger.Binds
+import dagger.Module
+import dagger.multibindings.IntoMap
+import de.rki.coronawarnapp.util.viewmodel.CWAViewModel
+import de.rki.coronawarnapp.util.viewmodel.CWAViewModelFactory
+import de.rki.coronawarnapp.util.viewmodel.CWAViewModelKey
+
+@Module
+abstract class DataDonationTestFragmentModule {
+    @Binds
+    @IntoMap
+    @CWAViewModelKey(DataDonationTestFragmentViewModel::class)
+    abstract fun dataDonation(
+        factory: DataDonationTestFragmentViewModel.Factory
+    ): CWAViewModelFactory<out CWAViewModel>
+}

Corona-Warn-App/src/deviceForTesters/java/de/rki/coronawarnapp/test/datadonation/ui/DataDonationTestFragmentViewModel.kt

+package de.rki.coronawarnapp.test.datadonation.ui
+
+import androidx.lifecycle.asLiveData
+import dagger.assisted.AssistedFactory
+import dagger.assisted.AssistedInject
+import de.rki.coronawarnapp.datadonation.safetynet.SafetyNetClientWrapper
+import de.rki.coronawarnapp.util.coroutine.DispatcherProvider
+import de.rki.coronawarnapp.util.ui.SingleLiveEvent
+import de.rki.coronawarnapp.util.viewmodel.CWAViewModel
+import de.rki.coronawarnapp.util.viewmodel.SimpleCWAViewModelFactory
+import kotlinx.coroutines.flow.MutableStateFlow
+import timber.log.Timber
+import java.security.SecureRandom
+
+class DataDonationTestFragmentViewModel @AssistedInject constructor(
+    dispatcherProvider: DispatcherProvider,
+    private val safetyNetClientWrapper: SafetyNetClientWrapper,
+    private val secureRandom: SecureRandom
+) : CWAViewModel(dispatcherProvider = dispatcherProvider) {
+
+    private val currentReportInternal = MutableStateFlow<SafetyNetClientWrapper.Report?>(null)
+    val currentReport = currentReportInternal.asLiveData(context = dispatcherProvider.Default)
+    val errorEvents = SingleLiveEvent<Throwable>()
+    val copyJWSEvent = SingleLiveEvent<String>()
+
+    fun createSafetyNetReport() {
+        launch {
+            val nonce = ByteArray(16)
+            secureRandom.nextBytes(nonce)
+            try {
+                val report = safetyNetClientWrapper.attest(nonce)
+                currentReportInternal.value = report
+            } catch (e: Exception) {
+                Timber.e(e, "attest() failed.")
+                errorEvents.postValue(e)
+            }
+        }
+    }
+
+    fun copyJWS() {
+        launch {
+            val value = currentReport.value?.jwsResult ?: ""
+            copyJWSEvent.postValue(value)
+        }
+    }
+
+    @AssistedFactory
+    interface Factory : SimpleCWAViewModelFactory<DataDonationTestFragmentViewModel>
+}

Corona-Warn-App/src/deviceForTesters/java/de/rki/coronawarnapp/test/menu/ui/TestMenuFragmentViewModel.kt

@@ -7,6 +7,7 @@ import de.rki.coronawarnapp.miscinfo.MiscInfoFragment
 import de.rki.coronawarnapp.test.appconfig.ui.AppConfigTestFragment
 import de.rki.coronawarnapp.test.contactdiary.ui.ContactDiaryTestFragment
 import de.rki.coronawarnapp.test.crash.ui.SettingsCrashReportFragment
+import de.rki.coronawarnapp.test.datadonation.ui.DataDonationTestFragment
 import de.rki.coronawarnapp.test.debugoptions.ui.DebugOptionsFragment
 import de.rki.coronawarnapp.test.keydownload.ui.KeyDownloadTestFragment
 import de.rki.coronawarnapp.test.risklevel.ui.TestRiskLevelCalculationFragment
@@ -28,7 +29,8 @@ class TestMenuFragmentViewModel @AssistedInject constructor() : CWAViewModel() {
             SubmissionTestFragment.MENU_ITEM,
             SettingsCrashReportFragment.MENU_ITEM,
             MiscInfoFragment.MENU_ITEM,
-            ContactDiaryTestFragment.MENU_ITEM
+            ContactDiaryTestFragment.MENU_ITEM,
+            DataDonationTestFragment.MENU_ITEM
         ).let { MutableLiveData(it) }
     }
     val showTestScreenEvent = SingleLiveEvent<TestMenuItem>()

Corona-Warn-App/src/deviceForTesters/java/de/rki/coronawarnapp/ui/main/MainActivityTestModule.kt

@@ -8,6 +8,8 @@ import de.rki.coronawarnapp.test.appconfig.ui.AppConfigTestFragment
 import de.rki.coronawarnapp.test.appconfig.ui.AppConfigTestFragmentModule
 import de.rki.coronawarnapp.test.contactdiary.ui.ContactDiaryTestFragment
 import de.rki.coronawarnapp.test.contactdiary.ui.ContactDiaryTestFragmentModule
+import de.rki.coronawarnapp.test.datadonation.ui.DataDonationTestFragment
+import de.rki.coronawarnapp.test.datadonation.ui.DataDonationTestFragmentModule
 import de.rki.coronawarnapp.test.debugoptions.ui.DebugOptionsFragment
 import de.rki.coronawarnapp.test.debugoptions.ui.DebugOptionsFragmentModule
 import de.rki.coronawarnapp.test.keydownload.ui.KeyDownloadTestFragment
@@ -50,4 +52,7 @@ abstract class MainActivityTestModule {
 
     @ContributesAndroidInjector(modules = [ContactDiaryTestFragmentModule::class])
     abstract fun contactDiaryTest(): ContactDiaryTestFragment
+
+    @ContributesAndroidInjector(modules = [DataDonationTestFragmentModule::class])
+    abstract fun dataDonation(): DataDonationTestFragment
 }

Corona-Warn-App/src/deviceForTesters/res/layout/fragment_test_datadonation.xml

+<?xml version="1.0" encoding="utf-8"?>
+<layout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    tools:ignore="HardcodedText">
+
+    <androidx.core.widget.NestedScrollView
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:fillViewport="true">
+
+        <LinearLayout
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_margin="@dimen/spacing_tiny"
+            android:orientation="vertical">
+
+            <androidx.constraintlayout.widget.ConstraintLayout
+                android:id="@+id/debug_container"
+                style="@style/Card"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:layout_margin="@dimen/spacing_tiny">
+
+                <TextView
+                    android:id="@+id/safetynet_title"
+                    style="@style/headline6"
+                    android:layout_width="0dp"
+                    android:layout_height="wrap_content"
+                    android:layout_marginEnd="8dp"
+                    android:text="SafetyNet Report"
+                    app:layout_constraintEnd_toEndOf="parent"
+                    app:layout_constraintStart_toStartOf="parent"
+                    app:layout_constraintTop_toTopOf="parent" />
+
+                <TextView
+                    android:id="@+id/safetynet_body"
+                    android:layout_width="match_parent"
+                    android:textIsSelectable="true"
+                    android:layout_height="wrap_content"
+                    android:layout_marginTop="@dimen/spacing_tiny"
+                    app:layout_constraintEnd_toEndOf="parent"
+                    app:layout_constraintStart_toStartOf="parent"
+                    app:layout_constraintTop_toBottomOf="@+id/safetynet_title"
+                    tools:text="Body" />
+
+                <Button
+                    android:id="@+id/safetynet_copy_jws"
+                    android:layout_width="0dp"
+                    android:layout_height="wrap_content"
+                    android:layout_marginTop="8dp"
+                    android:text="Copy JWS"
+                    app:layout_constraintEnd_toStartOf="@+id/safetynet_create_report"
+                    app:layout_constraintStart_toStartOf="parent"
+                    app:layout_constraintTop_toBottomOf="@id/safetynet_body" />
+
+                <Button
+                    android:id="@+id/safetynet_create_report"
+                    android:layout_width="0dp"
+                    android:layout_height="wrap_content"
+                    android:layout_marginTop="8dp"
+                    android:text="Create"
+                    app:layout_constraintEnd_toEndOf="parent"
+                    app:layout_constraintStart_toEndOf="@id/safetynet_copy_jws"
+                    app:layout_constraintTop_toBottomOf="@id/safetynet_body" />
+            </androidx.constraintlayout.widget.ConstraintLayout>
+
+
+        </LinearLayout>
+    </androidx.core.widget.NestedScrollView>
+</layout>

Corona-Warn-App/src/deviceForTesters/res/navigation/test_nav_graph.xml

@@ -37,6 +37,9 @@
         <action
             android:id="@+id/action_test_menu_fragment_to_contactDiaryTestFragment"
             app:destination="@id/test_contact_diary_fragment" />
+        <action
+            android:id="@+id/action_test_menu_fragment_to_dataDonationFragment"
+            app:destination="@id/test_datadonation_fragment" />
     </fragment>
 
     <fragment
@@ -100,5 +103,10 @@
         android:name="de.rki.coronawarnapp.test.contactdiary.ui.ContactDiaryTestFragment"
         android:label="ContactDiaryTestFragment"
         tools:layout="@layout/fragment_test_contact_diary" />
+    <fragment
+        android:id="@+id/test_datadonation_fragment"
+        tools:layout="@layout/fragment_test_datadonation"
+        android:name="de.rki.coronawarnapp.test.datadonation.ui.DataDonationTestFragment"
+        android:label="DataDonationFragment" />
 
 </navigation>

Corona-Warn-App/src/main/java/de/rki/coronawarnapp/appconfig/ConfigData.kt

@@ -29,6 +29,8 @@ interface ConfigData : ConfigMapping {
      */
     val isDeviceTimeCorrect: Boolean
 
+    val deviceTimeState: DeviceTimeState
+
     /**
      * Returns the type config this is.
      */
@@ -57,6 +59,23 @@ interface ConfigData : ConfigMapping {
      */
     fun isValid(nowUTC: Instant): Boolean
 
+    enum class DeviceTimeState(val key: String) {
+        /**
+         * Device time was compared against server time and deemed correct
+         */
+        CORRECT("CORRECT"),
+
+        /**
+         * Device time was not compared against server time for various reasons
+         */
+        ASSUMED_CORRECT("ASSUMED_CORRECT"),
+
+        /**
+         * Device time was compared against server time and deemed incorrect
+         */
+        INCORRECT("INCORRECT")
+    }
+
     companion object {
         val DEVICE_TIME_GRACE_RANGE: Duration = Duration.standardHours(2)
     }

Corona-Warn-App/src/main/java/de/rki/coronawarnapp/appconfig/internal/AppConfigSource.kt

@@ -2,12 +2,14 @@ package de.rki.coronawarnapp.appconfig.internal
 
 import dagger.Reusable
 import de.rki.coronawarnapp.appconfig.ConfigData
+import de.rki.coronawarnapp.appconfig.ConfigData.DeviceTimeState.CORRECT
 import de.rki.coronawarnapp.appconfig.sources.fallback.DefaultAppConfigSource
 import de.rki.coronawarnapp.appconfig.sources.local.LocalAppConfigSource
 import de.rki.coronawarnapp.appconfig.sources.remote.RemoteAppConfigSource
 import de.rki.coronawarnapp.main.CWASettings
 import de.rki.coronawarnapp.util.TimeStamper
 import org.joda.time.Duration
+import org.joda.time.Instant
 import timber.log.Timber
 import javax.inject.Inject
 
@@ -49,6 +51,20 @@ class AppConfigSource @Inject constructor(
                     Timber.tag(TAG).i("Resetting previous incorrect device time acknowledgement.")
                     cwaSettings.wasDeviceTimeIncorrectAcknowledged = false
                 }
+                if (remoteConfig.deviceTimeState == CORRECT && cwaSettings.firstReliableDeviceTime == Instant.EPOCH) {
+                    Timber.tag(TAG).i("Setting firstReliableDeviceTime to NOW (UTC). ")
+                    cwaSettings.firstReliableDeviceTime = timeStamper.nowUTC
+                }
+                if (remoteConfig.deviceTimeState != cwaSettings.lastDeviceTimeStateChangeState) {
+                    Timber.tag(TAG).i(
+                        "New device time state, saving timestamp (old=%s(%s), new=%s#)",
+                        cwaSettings.lastDeviceTimeStateChangeState,
+                        cwaSettings.lastDeviceTimeStateChangeAt,
+                        remoteConfig.deviceTimeState
+                    )
+                    cwaSettings.lastDeviceTimeStateChangeState = remoteConfig.deviceTimeState
+                    cwaSettings.lastDeviceTimeStateChangeAt = timeStamper.nowUTC
+                }
                 remoteConfig
             }
             localConfig != null -> {

Corona-Warn-App/src/main/java/de/rki/coronawarnapp/appconfig/internal/ConfigDataContainer.kt

@@ -15,7 +15,14 @@ data class ConfigDataContainer(
 ) : ConfigData, ConfigMapping by mappedConfig {
 
     override val isDeviceTimeCorrect: Boolean
-        get() = !isDeviceTimeCheckEnabled || localOffset.abs() < ConfigData.DEVICE_TIME_GRACE_RANGE
+        get() = deviceTimeState != ConfigData.DeviceTimeState.INCORRECT
+
+    override val deviceTimeState: ConfigData.DeviceTimeState
+        get() = when {
+            !isDeviceTimeCheckEnabled -> ConfigData.DeviceTimeState.ASSUMED_CORRECT
+            localOffset.abs() < ConfigData.DEVICE_TIME_GRACE_RANGE -> ConfigData.DeviceTimeState.CORRECT
+            else -> ConfigData.DeviceTimeState.INCORRECT
+        }
 
     override val updatedAt: Instant = serverTime.plus(localOffset)
 

Corona-Warn-App/src/main/java/de/rki/coronawarnapp/datadonation/safetynet/AttestationContainer.kt

+package de.rki.coronawarnapp.datadonation.safetynet
+
+import de.rki.coronawarnapp.appconfig.SafetyNetRequirements
+import de.rki.coronawarnapp.datadonation.safetynet.SafetyNetException.Type
+import de.rki.coronawarnapp.server.protocols.internal.ppdd.PpacAndroid
+import okio.ByteString.Companion.toByteString
+
+internal data class AttestationContainer(
+    private val ourSalt: ByteArray,
+    private val report: SafetyNetClientWrapper.Report
+) : DeviceAttestation.Result {
+    override val accessControlProtoBuf: PpacAndroid.PPACAndroid
+        get() = PpacAndroid.PPACAndroid.newBuilder().apply {
+            salt = ourSalt.toByteString().base64()
+            safetyNetJws = report.jwsResult
+        }.build()
+
+    override fun requirePass(reqs: SafetyNetRequirements) {
+        if (reqs.requireBasicIntegrity && !report.basicIntegrity) {
+            throw SafetyNetException(
+                Type.BASIC_INTEGRITY_REQUIRED,
+                "Requirement 'basicIntegrity' not met (${report.advice})."
+            )
+        }
+
+        if (reqs.requireCTSProfileMatch && !report.ctsProfileMatch) {
+            throw SafetyNetException(
+                Type.CTS_PROFILE_MATCH_REQUIRED,
+                "Requirement 'ctsProfileMatch' not met (${report.advice})."
+            )
+        }
+
+        if (reqs.requireBasicIntegrity && !report.evaluationTypes.contains("BASIC")) {
+            throw SafetyNetException(
+                Type.EVALUATION_TYPE_BASIC_REQUIRED,
+                "Evaluation type 'BASIC' not met (${report.advice})."
+            )
+        }
+
+        if (reqs.requireEvaluationTypeHardwareBacked && !report.evaluationTypes.contains("HARDWARE_BACKED")) {
+            throw SafetyNetException(
+                Type.EVALUATION_TYPE_HARDWARE_BACKED_REQUIRED,
+                "Evaluation type 'HARDWARE_BACKED' not met (${report.advice})."
+            )
+        }
+    }
+
+    override fun equals(other: Any?): Boolean {
+        if (this === other) return true
+        if (javaClass != other?.javaClass) return false
+
+        other as AttestationContainer
+
+        if (!ourSalt.contentEquals(other.ourSalt)) return false
+        if (report != other.report) return false
+
+        return true
+    }
+
+    override fun hashCode(): Int {
+        var result = ourSalt.contentHashCode()
+        result = 31 * result + report.hashCode()
+        return result
+    }
+}

Corona-Warn-App/src/main/java/de/rki/coronawarnapp/datadonation/safetynet/CWASafetyNet.kt

 package de.rki.coronawarnapp.datadonation.safetynet
 
-import de.rki.coronawarnapp.appconfig.SafetyNetRequirements
-import de.rki.coronawarnapp.server.protocols.internal.ppdd.PpacAndroid
+import android.content.Context
+import androidx.annotation.VisibleForTesting
+import de.rki.coronawarnapp.appconfig.AppConfigProvider
+import de.rki.coronawarnapp.appconfig.ConfigData
+import de.rki.coronawarnapp.datadonation.safetynet.SafetyNetException.Type
+import de.rki.coronawarnapp.main.CWASettings
+import de.rki.coronawarnapp.util.HashExtensions.toSHA256
+import de.rki.coronawarnapp.util.TimeStamper
+import de.rki.coronawarnapp.util.di.AppContext
+import de.rki.coronawarnapp.util.gplay.GoogleApiVersion
+import org.joda.time.Duration
+import org.joda.time.Instant
+import timber.log.Timber
+import java.security.SecureRandom
 import javax.inject.Inject
 import javax.inject.Singleton
 
 @Singleton
-class CWASafetyNet @Inject constructor() : DeviceAttestation {
+class CWASafetyNet @Inject constructor(
+    @AppContext private val context: Context,
+    private val client: SafetyNetClientWrapper,
+    private val secureRandom: SecureRandom,
+    private val appConfigProvider: AppConfigProvider,
+    private val googleApiVersion: GoogleApiVersion,
+    private val cwaSettings: CWASettings,
+    private val timeStamper: TimeStamper
+) : DeviceAttestation {
+
+    @VisibleForTesting(otherwise = VisibleForTesting.PRIVATE)
+    fun generateSalt(): ByteArray = ByteArray(16).apply {
+        secureRandom.nextBytes(this)
+    }
+
+    @VisibleForTesting(otherwise = VisibleForTesting.PRIVATE)
+    fun calculateNonce(salt: ByteArray, payload: ByteArray): String {
+        val concat = salt + payload
+        return concat.toSHA256()
+    }
+
     override suspend fun attest(request: DeviceAttestation.Request): DeviceAttestation.Result {
-        return object : DeviceAttestation.Result {
-            override val accessControlProtoBuf: PpacAndroid.PPACAndroid = PpacAndroid.PPACAndroid.getDefaultInstance()
+        if (!googleApiVersion.isPlayServicesVersionAvailable(13000000)) {
+            throw SafetyNetException(Type.PLAY_SERVICES_VERSION_MISMATCH, "Google Play Services too old.")
+        }
 
-            override fun requirePass(requirements: SafetyNetRequirements) {
-                // Passed
+        appConfigProvider.getAppConfig().apply {
+            if (deviceTimeState == ConfigData.DeviceTimeState.ASSUMED_CORRECT) {
+                throw SafetyNetException(Type.DEVICE_TIME_UNVERIFIED, "Device time is unverified")
+            }
+            if (deviceTimeState == ConfigData.DeviceTimeState.INCORRECT) {
+                throw SafetyNetException(Type.DEVICE_TIME_INCORRECT, "Device time is incorrect")
             }
         }
+
+        val firstReliableTimeStamp = cwaSettings.firstReliableDeviceTime
+        if (firstReliableTimeStamp == Instant.EPOCH) {
+            throw SafetyNetException(Type.TIME_SINCE_ONBOARDING_UNVERIFIED, "No first reliable timestamp available")
+        } else if (Duration(firstReliableTimeStamp, timeStamper.nowUTC) < Duration.standardHours(24)) {
+            throw SafetyNetException(Type.TIME_SINCE_ONBOARDING_UNVERIFIED, "Time since first reliable timestamp <24h")
+        }
+
+        val salt = generateSalt()
+        val nonce = calculateNonce(salt = salt, payload = request.scenarioPayload)
+        Timber.tag(TAG).d("With salt=%s and payload=%s, we created nonce=%s", salt, request.scenarioPayload, nonce)
+
+        val report = client.attest(nonce.toByteArray())
+
+        report.error?.let {
+            Timber.tag(TAG).w("SafetyNet Response has an error message: %s", it)
+        }
+
+        if (nonce != report.nonce) {
+            throw SafetyNetException(
+                Type.NONCE_MISMATCH,
+                "Request nonce doesn't match response ($nonce != ${report.nonce})"
+            )
+        }
+
+        if (context.packageName != report.apkPackageName) {
+            throw SafetyNetException(
+                Type.APK_PACKAGE_NAME_MISMATCH,
+                "Our APK name doesn't match response (${context.packageName} != ${report.apkPackageName})"
+            )
+        }
+
+        return AttestationContainer(salt, report)
+    }
+
+    companion object {
+        private const val TAG = "CWASafetyNet"
     }
 }

Corona-Warn-App/src/main/java/de/rki/coronawarnapp/datadonation/safetynet/SafetyNetClientWrapper.kt

+package de.rki.coronawarnapp.datadonation.safetynet
+
+import com.google.android.gms.common.api.ApiException
+import com.google.android.gms.common.api.CommonStatusCodes
+import com.google.android.gms.safetynet.SafetyNetApi
+import com.google.android.gms.safetynet.SafetyNetClient
+import com.google.gson.JsonObject
+import com.google.gson.JsonParser
+import dagger.Reusable
+import de.rki.coronawarnapp.datadonation.safetynet.SafetyNetException.Type
+import de.rki.coronawarnapp.environment.EnvironmentSetup
+import kotlinx.coroutines.TimeoutCancellationException
+import kotlinx.coroutines.withTimeout
+import okio.ByteString.Companion.decodeBase64
+import timber.log.Timber
+import javax.inject.Inject
+import kotlin.coroutines.resume
+import kotlin.coroutines.resumeWithException
+import kotlin.coroutines.suspendCoroutine
+
+@Reusable
+class SafetyNetClientWrapper @Inject constructor(
+    private val safetyNetClient: SafetyNetClient,
+    private val environmentSetup: EnvironmentSetup
+) {
+
+    suspend fun attest(nonce: ByteArray): Report {
+        val response = try {
+            withTimeout(30 * 1000L) { callClient(nonce) }
+        } catch (e: TimeoutCancellationException) {
+            throw SafetyNetException(Type.ATTESTATION_FAILED, "Attestation timeout.", e)
+        }
+
+        val jwsResult = response.jwsResult ?: throw SafetyNetException(
+            Type.ATTESTATION_FAILED,
+            "JWS was null"
+        )
+
+        val components = jwsResult.split(".")
+        if (components.size != 3) throw SafetyNetException(
+            Type.ATTESTATION_FAILED,
+            "Invalid JWS: Components are missing."
+        )
+
+        val header = try {
+            components[0].decodeBase64Json()
+        } catch (e: Exception) {
+            throw SafetyNetException(Type.ATTESTATION_FAILED, "Failed to decode JWS header.", e)
+        }
+        val body = try {
+            components[1].decodeBase64Json()
+        } catch (e: Exception) {
+            throw SafetyNetException(Type.ATTESTATION_FAILED, "Failed to decode JWS body.", e)
+        }
+
+        val signature = try {
+            components[2].decodeBase64()!!.toByteArray()
+        } catch (e: Exception) {
+            throw SafetyNetException(Type.ATTESTATION_FAILED, "Failed to decode JWS signature.", e)
+        }
+
+        return Report(
+            jwsResult = jwsResult,
+            header = header,
+            body = body,
+            signature = signature
+        )
+    }
+
+    private fun String.decodeBase64Json(): JsonObject {
+        val rawJson = decodeBase64()!!.string(Charsets.UTF_8)
+        return JsonParser.parseString(rawJson).asJsonObject
+    }
+
+    private suspend fun callClient(nonce: ByteArray): SafetyNetApi.AttestationResponse = suspendCoroutine { cont ->
+        safetyNetClient.attest(nonce, environmentSetup.safetyNetApiKey)
+            .addOnSuccessListener {
+                Timber.tag(TAG).v("Attestation finished with %s", it)
+                cont.resume(it)
+            }
+            .addOnFailureListener {
+                Timber.tag(TAG).w(it, "Attestation failed.")
+                val wrappedError = if (it is ApiException && it.statusCode == CommonStatusCodes.NETWORK_ERROR) {
+                    SafetyNetException(Type.ATTESTATION_REQUEST_FAILED, "Network error", it)
+                } else {
+                    SafetyNetException(Type.ATTESTATION_FAILED, "SafetyNet client returned an error.", it)
+                }
+                cont.resumeWithException(wrappedError)
+            }
+    }
+
+    data class Report(
+        val jwsResult: String,
+        val header: JsonObject,
+        val body: JsonObject,
+        val signature: ByteArray
+    ) {
+        val nonce: String? = body.get("nonce")?.asString
+
+        val apkPackageName: String? = body.get("apkPackageName")?.asString
+
+        val basicIntegrity: Boolean = body.get("basicIntegrity")?.asBoolean == true
+        val ctsProfileMatch = body.get("ctsProfileMatch")?.asBoolean == true
+
+        val evaluationTypes = body.get("evaluationType")?.asString
+            ?.split(",")?.map { it.trim() } ?: emptyList()
+
+        val error: String? = body.get("error")?.asString
+        val advice: String? = body.get("advice")?.asString
+
+        override fun equals(other: Any?): Boolean {
+            if (this === other) return true
+            if (javaClass != other?.javaClass) return false
+            other as Report
+            if (jwsResult != other.jwsResult) return false
+            return true
+        }
+
+        override fun hashCode(): Int = jwsResult.hashCode()
+    }
+
+    companion object {
+        private const val TAG = "SafetyNetWrapper"
+    }
+}

Corona-Warn-App/src/main/java/de/rki/coronawarnapp/datadonation/safetynet/SafetyNetException.kt

 package de.rki.coronawarnapp.datadonation.safetynet
 
 class SafetyNetException constructor(
-    message: String?,
+    val type: Type,
+    message: String,
     cause: Throwable? = null
-) : Exception(message, cause)
+) : Exception("$type: $message", cause) {
+
+    enum class Type {
+        // TRY_AGAIN_LATER (Text Key)
+        APK_PACKAGE_NAME_MISMATCH,
+        ATTESTATION_FAILED,
+        ATTESTATION_REQUEST_FAILED,
+        DEVICE_TIME_UNVERIFIED,
+        NONCE_MISMATCH,
+
+        // DEVICE_NOT_TRUSTED (Text Key)
+        BASIC_INTEGRITY_REQUIRED,
+        CTS_PROFILE_MATCH_REQUIRED,
+        EVALUATION_TYPE_BASIC_REQUIRED,
+        EVALUATION_TYPE_HARDWARE_BACKED_REQUIRED,
+
+        // CHANGE_DEVICE_TIME (Text Key)
+        DEVICE_TIME_INCORRECT,
+
+        // UPDATE_PLAY_SERVICES (Text Key)
+        PLAY_SERVICES_VERSION_MISMATCH,
+
+        // TIME_SINCE_ONBOARDING_UNVERIFIED (Text Key)
+        TIME_SINCE_ONBOARDING_UNVERIFIED
+    }
+}

Corona-Warn-App/src/main/java/de/rki/coronawarnapp/main/CWASettings.kt

@@ -2,9 +2,11 @@ package de.rki.coronawarnapp.main
 
 import android.content.Context
 import androidx.core.content.edit
+import de.rki.coronawarnapp.appconfig.ConfigData
 import de.rki.coronawarnapp.util.di.AppContext
 import de.rki.coronawarnapp.util.preferences.clearAndNotify
 import de.rki.coronawarnapp.util.preferences.createFlowPreference
+import org.joda.time.Instant
 import javax.inject.Inject
 
 /**
@@ -25,6 +27,21 @@ class CWASettings @Inject constructor(
         get() = prefs.getBoolean(PKEY_DEVICE_TIME_INCORRECT_ACK, false)
         set(value) = prefs.edit { putBoolean(PKEY_DEVICE_TIME_INCORRECT_ACK, value) }
 
+    var firstReliableDeviceTime: Instant
+        get() = Instant.ofEpochMilli(prefs.getLong(PKEY_DEVICE_TIME_FIRST_RELIABLE, 0L))
+        set(value) = prefs.edit { putLong(PKEY_DEVICE_TIME_FIRST_RELIABLE, value.millis) }
+
+    var lastDeviceTimeStateChangeAt: Instant
+        get() = Instant.ofEpochMilli(prefs.getLong(PKEY_DEVICE_TIME_LAST_STATE_CHANGE_TIME, 0L))
+        set(value) = prefs.edit { putLong(PKEY_DEVICE_TIME_LAST_STATE_CHANGE_TIME, value.millis) }
+
+    var lastDeviceTimeStateChangeState: ConfigData.DeviceTimeState
+        get() = prefs.getString(
+            PKEY_DEVICE_TIME_LAST_STATE_CHANGE_STATE,
+            ConfigData.DeviceTimeState.INCORRECT.key
+        ).let { raw -> ConfigData.DeviceTimeState.values().single { it.key == raw } }
+        set(value) = prefs.edit { putString(PKEY_DEVICE_TIME_LAST_STATE_CHANGE_STATE, value.key) }
+
     val lastChangelogVersion = prefs.createFlowPreference(
         key = LAST_CHANGELOG_VERSION,
         defaultValue = DEFAULT_APP_VERSION
@@ -36,6 +53,9 @@ class CWASettings @Inject constructor(
 
     companion object {
         private const val PKEY_DEVICE_TIME_INCORRECT_ACK = "devicetime.incorrect.acknowledged"
+        private const val PKEY_DEVICE_TIME_FIRST_RELIABLE = "devicetime.correct.first"
+        private const val PKEY_DEVICE_TIME_LAST_STATE_CHANGE_TIME = "devicetime.laststatechange.timestamp"
+        private const val PKEY_DEVICE_TIME_LAST_STATE_CHANGE_STATE = "devicetime.laststatechange.state"
         private const val LAST_CHANGELOG_VERSION = "update.changelog.lastversion"
         private const val DEFAULT_APP_VERSION = 1L
     }

Corona-Warn-App/src/main/java/de/rki/coronawarnapp/util/di/AndroidModule.kt

@@ -12,6 +12,8 @@ import androidx.lifecycle.LifecycleOwner
 import androidx.lifecycle.ProcessLifecycleOwner
 import androidx.navigation.NavDeepLinkBuilder
 import androidx.work.WorkManager
+import com.google.android.gms.safetynet.SafetyNet
+import com.google.android.gms.safetynet.SafetyNetClient
 import dagger.Module
 import dagger.Provides
 import de.rki.coronawarnapp.CoronaWarnApplication
@@ -70,4 +72,8 @@ class AndroidModule {
     @Singleton
     @ProcessLifecycle
     fun procressLifecycleOwner(): LifecycleOwner = ProcessLifecycleOwner.get()
+
+    @Provides
+    @Singleton
+    fun safetyNet(@AppContext context: Context): SafetyNetClient = SafetyNet.getClient(context)
 }

Corona-Warn-App/src/main/java/de/rki/coronawarnapp/util/di/ApplicationComponent.kt

@@ -37,6 +37,7 @@ import de.rki.coronawarnapp.util.coroutine.CoroutineModule
 import de.rki.coronawarnapp.util.device.DeviceModule
 import de.rki.coronawarnapp.util.security.EncryptedPreferencesFactory
 import de.rki.coronawarnapp.util.security.EncryptionErrorResetTool
+import de.rki.coronawarnapp.util.security.SecurityModule
 import de.rki.coronawarnapp.util.serialization.SerializationModule
 import de.rki.coronawarnapp.util.worker.WorkerBinder
 import de.rki.coronawarnapp.verification.VerificationModule
@@ -70,7 +71,8 @@ import javax.inject.Singleton
         SerializationModule::class,
         WorkerBinder::class,
         StatisticsModule::class,
-        DataDonationModule::class
+        DataDonationModule::class,
+        SecurityModule::class
     ]
 )
 interface ApplicationComponent : AndroidInjector<CoronaWarnApplication> {

Corona-Warn-App/src/main/java/de/rki/coronawarnapp/util/gplay/GoogleApiVersion.kt

+package de.rki.coronawarnapp.util.gplay
+
+import android.content.Context
+import com.google.android.gms.common.ConnectionResult
+import com.google.android.gms.common.GoogleApiAvailability
+import dagger.Reusable
+import de.rki.coronawarnapp.util.di.AppContext
+import javax.inject.Inject
+
+@Reusable
+class GoogleApiVersion @Inject constructor(
+    @AppContext private val context: Context
+) {
+
+    private val apiAvailability = GoogleApiAvailability.getInstance()
+
+    fun isPlayServicesVersionAvailable(requiredVersion: Int): Boolean {
+        return apiAvailability.isGooglePlayServicesAvailable(context, requiredVersion) == ConnectionResult.SUCCESS
+    }
+}

Corona-Warn-App/src/main/java/de/rki/coronawarnapp/util/security/SecurityHelper.kt

@@ -2,7 +2,6 @@ package de.rki.coronawarnapp.util.security
 
 import android.annotation.SuppressLint
 import android.content.SharedPreferences
-import android.os.Build
 import android.util.Base64
 import androidx.annotation.VisibleForTesting
 import de.rki.coronawarnapp.exception.CwaSecurityException
@@ -14,7 +13,6 @@ import de.rki.coronawarnapp.util.security.SecurityConstants.DB_PASSWORD_MAX_LENG
 import de.rki.coronawarnapp.util.security.SecurityConstants.DB_PASSWORD_MIN_LENGTH
 import de.rki.coronawarnapp.util.security.SecurityConstants.ENCRYPTED_SHARED_PREFERENCES_FILE
 import timber.log.Timber
-import java.security.SecureRandom
 
 /**
  * Key Store and Password Access
@@ -78,11 +76,7 @@ object SecurityHelper {
     }
 
     private fun generateDBPassword(): ByteArray {
-        val secureRandom = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
-            SecureRandom.getInstanceStrong()
-        } else {
-            SecureRandom()
-        }
+        val secureRandom = SecurityModule().secureRandom()
         val max = DB_PASSWORD_MAX_LENGTH
         val min = DB_PASSWORD_MIN_LENGTH
         val passwordLength = secureRandom.nextInt(max - min + 1) + min

Corona-Warn-App/src/main/java/de/rki/coronawarnapp/util/security/SecurityModule.kt

+package de.rki.coronawarnapp.util.security
+
+import android.os.Build
+import dagger.Module
+import dagger.Provides
+import java.security.SecureRandom
+
+@Module
+class SecurityModule {
+
+    @Provides
+    fun secureRandom(): SecureRandom = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+        SecureRandom.getInstanceStrong()
+    } else {
+        SecureRandom()
+    }
+}