Add U2F support to the connected mode

2025-10-06 03:50:23 +02:00 · 2022-09-19 02:00:00 +02:00 · 2022-09-19 02:00:00 +02:00 · d8b492e2e3
commit d8b492e2e3
parent f804f421ff
26 changed files with 505 additions and 173 deletions
--- a/app/src/main/java/io/timelimit/android/crypto/DH.kt
+++ b/app/src/main/java/io/timelimit/android/crypto/DH.kt
@ -27,7 +27,10 @@ import javax.crypto.KeyAgreement
 import javax.crypto.spec.GCMParameterSpec
 import javax.crypto.spec.SecretKeySpec

-data class DHHandshake(val keyVersion: String, val ownPublicKey: ByteArray, val sharedSecret: ByteArray) {
+data class DHHandshake(
+    val keyVersion: String, val otherPublicKey: ByteArray,
+    val ownPublicKey: ByteArray, val sharedSecret: ByteArray
+) {
    companion object {
        private const val SHARED_SECRET_LENGTH = 32
        private const val AES_KEY_SIZE = 16
@ -51,6 +54,7 @@ data class DHHandshake(val keyVersion: String, val ownPublicKey: ByteArray, val

            return DHHandshake(
                keyVersion = serverDhKey.version,
+                otherPublicKey = serverDhKey.key,
                ownPublicKey = ownPublicKey,
                sharedSecret = sharedSecret
            )
--- a/app/src/main/java/io/timelimit/android/data/dao/ConfigDao.kt
+++ b/app/src/main/java/io/timelimit/android/data/dao/ConfigDao.kt
@ -379,4 +379,12 @@ abstract class ConfigDao {
        updateValueSync(ConfigurationItemType.DhKeyVersion, key.version)
        updateValueSync(ConfigurationItemType.DhKey, key.key.base64())
    }
+
+    fun getU2fVersionSync(): String? {
+        return getValueOfKeySync(ConfigurationItemType.U2fListVersion)
+    }
+
+    fun setU2fListVersionSync(version: String?) {
+        updateValueSync(ConfigurationItemType.U2fListVersion, version)
+    }
 }
--- a/app/src/main/java/io/timelimit/android/data/dao/U2FDao.kt
+++ b/app/src/main/java/io/timelimit/android/data/dao/U2FDao.kt
@ -35,6 +35,9 @@ interface U2FDao {
    @Query("SELECT * FROM user_u2f_key WHERE user_id = :userId")
    fun getByUserLive(userId: String): LiveData<List<UserU2FKey>>

+    @Query("SELECT * FROM user_u2f_key WHERE key_id = :keyId")
+    fun getByClientKeyIdLive(keyId: Long): LiveData<UserU2FKey?>
+
    @Query("UPDATe user_u2f_key SET next_counter = :counter + 1 WHERE user_id = :parentUserId AND key_handle = :keyHandle AND public_key = :publicKey AND :counter >= next_counter")
    fun updateCounter(parentUserId: String, keyHandle: ByteArray, publicKey: ByteArray, counter: Long): Int
 }
--- a/app/src/main/java/io/timelimit/android/data/model/ConfigurationItem.kt
+++ b/app/src/main/java/io/timelimit/android/data/model/ConfigurationItem.kt
@ -105,7 +105,8 @@ enum class ConfigurationItemType {
    LastServerKeyRequestSequence,
    LastKeyResponseSequence,
    DhKey,
-    DhKeyVersion
+    DhKeyVersion,
+    U2fListVersion
 }

 object ConfigurationItemTypeUtil {
@ -140,6 +141,7 @@ object ConfigurationItemTypeUtil {
    private const val LAST_SERVER_KEY_RESPONSE_SEQUENCE = 30
    private const val DH_KEY = 31
    private const val DH_KEY_VERSION = 32
+    private const val U2F_LIST_VERSION = 33

    val TYPES = listOf(
            ConfigurationItemType.OwnDeviceId,
@ -172,7 +174,8 @@ object ConfigurationItemTypeUtil {
            ConfigurationItemType.LastServerKeyRequestSequence,
            ConfigurationItemType.LastKeyResponseSequence,
            ConfigurationItemType.DhKey,
-            ConfigurationItemType.DhKeyVersion
+            ConfigurationItemType.DhKeyVersion,
+            ConfigurationItemType.U2fListVersion
    )

    fun serialize(value: ConfigurationItemType) = when(value) {
@ -207,6 +210,7 @@ object ConfigurationItemTypeUtil {
        ConfigurationItemType.LastKeyResponseSequence -> LAST_SERVER_KEY_RESPONSE_SEQUENCE
        ConfigurationItemType.DhKey -> DH_KEY
        ConfigurationItemType.DhKeyVersion -> DH_KEY_VERSION
+        ConfigurationItemType.U2fListVersion -> U2F_LIST_VERSION
    }

    fun parse(value: Int) = when(value) {
@ -241,6 +245,7 @@ object ConfigurationItemTypeUtil {
        LAST_SERVER_KEY_RESPONSE_SEQUENCE -> ConfigurationItemType.LastKeyResponseSequence
        DH_KEY -> ConfigurationItemType.DhKey
        DH_KEY_VERSION -> ConfigurationItemType.DhKeyVersion
+        U2F_LIST_VERSION -> ConfigurationItemType.U2fListVersion
        else -> throw IllegalArgumentException()
    }
 }
--- a/app/src/main/java/io/timelimit/android/data/model/UserU2FKey.kt
+++ b/app/src/main/java/io/timelimit/android/data/model/UserU2FKey.kt
@ -16,6 +16,9 @@
 package io.timelimit.android.data.model

 import androidx.room.*
+import io.timelimit.android.extensions.base64
+import io.timelimit.android.extensions.toByteArray
+import java.security.MessageDigest

@Entity(
    tableName = "user_u2f_key",
@ -49,4 +52,14 @@ data class UserU2FKey (
    val publicKey: ByteArray,
    @ColumnInfo(name = "next_counter")
    val nextCounter: Long
-)
+) {
+    fun calculateServerKeyIdSync() = MessageDigest.getInstance("SHA256").also {
+        it.update(keyHandle.size.toByteArray())
+        it.update(keyHandle)
+
+        it.update(publicKey.size.toByteArray())
+        it.update(publicKey)
+    }.digest()
+        .sliceArray(0 until 6)
+        .base64()
+}
--- a/app/src/main/java/io/timelimit/android/extensions/Numbers.kt
+++ b/app/src/main/java/io/timelimit/android/extensions/Numbers.kt
@ -0,0 +1,29 @@
+/*
+ * TimeLimit Copyright <C> 2019 - 2022 Jonas Lochmann
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+package io.timelimit.android.extensions
+
+import okio.ByteString.Companion.toByteString
+import java.nio.ByteBuffer
+
+fun Int.toByteArray() = ByteBuffer.allocate(Int.SIZE_BYTES).also {
+    it.putInt(this)
+    it.rewind()
+}.toByteString().toByteArray()
+
+fun Long.toByteArray() = ByteBuffer.allocate(Long.SIZE_BYTES).also {
+    it.putLong(this)
+    it.rewind()
+}.toByteString().toByteArray()
--- a/app/src/main/java/io/timelimit/android/sync/ApplyServerDataStatus.kt
+++ b/app/src/main/java/io/timelimit/android/sync/ApplyServerDataStatus.kt
@ -614,6 +614,42 @@ object ApplyServerDataStatus {
                }
            }

+            status.u2f?.also { u2f ->
+                database.config().setU2fListVersionSync(u2f.version)
+
+                val savedKeys = database.u2f().getAllSync().toMutableList()
+
+                u2f.data.forEach { newKey ->
+                    val oldKey = savedKeys.find {
+                        it.keyHandle.contentEquals(newKey.keyHandle) &&
+                                it.publicKey.contentEquals(newKey.publicKey)
+                    }
+
+                    if (oldKey != null) {
+                        savedKeys.remove(oldKey)
+                    } else {
+                        database.u2f().addKey(
+                            UserU2FKey(
+                                keyId = 0,
+                                userId = newKey.userId,
+                                addedAt = newKey.addedAt,
+                                keyHandle = newKey.keyHandle,
+                                publicKey = newKey.publicKey,
+                                nextCounter = 0
+                            )
+                        )
+                    }
+                }
+
+                savedKeys.forEach { key ->
+                    database.u2f().deleteKey(
+                        parentUserId = key.userId,
+                        keyHandle = key.keyHandle,
+                        publicKey = key.publicKey
+                    )
+                }
+            }
+
            Result(
                newDeviceTitles = newDeviceTitles,
                didCreateNewActions = didCreateNewActions
--- a/app/src/main/java/io/timelimit/android/sync/actions/Actions.kt
+++ b/app/src/main/java/io/timelimit/android/sync/actions/Actions.kt
@ -2122,6 +2122,18 @@ data class RemoveParentU2FKey(val publicKey: ByteArray, val keyHandle: ByteArray
    }
 }

+object ReportU2fLoginAction: ParentAction() {
+    const val TYPE_VALUE = "REPORT_U2F_LOGIN"
+
+    override fun serialize(writer: JsonWriter) {
+        writer.beginObject()
+
+        writer.name(TYPE).value(TYPE_VALUE)
+
+        writer.endObject()
+    }
+}
+
 // child actions
 object ChildSignInAction: ChildAction() {
    private const val TYPE_VALUE = "CHILD_SIGN_IN"
--- a/app/src/main/java/io/timelimit/android/sync/actions/apply/ApplyAction.kt
+++ b/app/src/main/java/io/timelimit/android/sync/actions/apply/ApplyAction.kt
@ -25,15 +25,21 @@ import io.timelimit.android.data.Database
 import io.timelimit.android.data.model.PendingSyncAction
 import io.timelimit.android.data.model.PendingSyncActionType
 import io.timelimit.android.data.model.UserType
+import io.timelimit.android.extensions.base64
+import io.timelimit.android.extensions.toByteArray
 import io.timelimit.android.integration.platform.PlatformIntegration
 import io.timelimit.android.logic.AppLogic
+import io.timelimit.android.logic.ServerApiLevelLogic
 import io.timelimit.android.sync.SyncUtil
 import io.timelimit.android.sync.actions.*
 import io.timelimit.android.sync.actions.dispatch.LocalDatabaseAppLogicActionDispatcher
 import io.timelimit.android.sync.actions.dispatch.LocalDatabaseChildActionDispatcher
 import io.timelimit.android.sync.actions.dispatch.LocalDatabaseParentActionDispatcher
+import io.timelimit.android.ui.main.AuthenticatedUser
 import org.json.JSONObject
 import java.io.StringWriter
+import javax.crypto.Mac
+import javax.crypto.spec.SecretKeySpec

 object ApplyActionUtil {
    private const val LOG_TAG = "ApplyActionUtil"
@ -192,7 +198,13 @@ object ApplyActionUtil {
        }
    }

-    suspend fun applyParentAction(action: ParentAction, database: Database, authentication: ApplyActionParentAuthentication, syncUtil: SyncUtil, platformIntegration: PlatformIntegration) {
+    suspend fun applyParentAction(
+        action: ParentAction,
+        database: Database,
+        authentication: ApplyActionParentAuthentication,
+        syncUtil: SyncUtil,
+        platformIntegration: PlatformIntegration
+    ) {
        Threads.database.executeAndWait {
            database.runInTransaction {
                val deviceUserIdBeforeDispatchingForDeviceAuth = if (authentication is ApplyActionParentDeviceAuthentication || authentication is ApplyActionChildAddLimitAuthentication) {
@ -226,7 +238,7 @@ object ApplyActionUtil {
                        database = database,
                        fromChildSelfLimitAddChildUserId = if (authentication is ApplyActionChildAddLimitAuthentication) deviceUserIdBeforeDispatchingForDeviceAuth else null,
                        parentUserId = when (authentication) {
-                            is ApplyActionParentPasswordAuthentication -> authentication.parentUserId
+                            is ApplyActionUserAuthentication -> authentication.user.userId
                            is ApplyActionParentDeviceAuthentication -> deviceUserIdBeforeDispatchingForDeviceAuth
                            is ApplyActionChildAddLimitAuthentication -> null
                        }
@ -249,27 +261,62 @@ object ApplyActionUtil {

                    val sequenceNumber = database.config().getNextSyncActionSequenceActionAndIncrementIt()

+                    fun mac(secret: ByteArray) = Mac.getInstance("HmacSHA256").also {
+                        val binaryDeviceId = database.config().getOwnDeviceIdSync()!!.toByteArray(Charsets.UTF_8)
+                        val binaryAction = serializedAction.toByteArray(Charsets.UTF_8)
+
+                        it.init(SecretKeySpec(secret, "HmacSHA256"))
+
+                        it.update(sequenceNumber.toByteArray())
+
+                        it.update(binaryDeviceId.size.toByteArray())
+                        it.update(binaryDeviceId)
+
+                        it.update(binaryAction.size.toByteArray())
+                        it.update(binaryAction)
+                    }.doFinal()
+
                    val pendingAction = when (authentication) {
-                        is ApplyActionParentPasswordAuthentication -> {
-                            val integrityData = sequenceNumber.toString() +
-                                    database.config().getOwnDeviceIdSync() +
-                                    authentication.secondPasswordHash +
-                                    serializedAction
+                        is ApplyActionUserAuthentication -> {
+                            val integrity = when (authentication.user) {
+                                is AuthenticatedUser.Password -> {
+                                    val serverLevel = ServerApiLevelLogic.getSync(database)

-                            val hashedIntegrityData = Sha512.hashSync(integrityData)
+                                    if (serverLevel.hasLevelOrIsOffline(6)) {
+                                        val mac = mac(authentication.user.secondPasswordHash.toByteArray(Charsets.UTF_8))

-                            if (BuildConfig.DEBUG) {
-                                Log.d(LOG_TAG, "integrity data: $integrityData")
-                                Log.d(LOG_TAG, "integrity hash: $hashedIntegrityData")
+                                        "password:${mac.base64()}"
+                                    } else {
+                                        val integrityData = sequenceNumber.toString() +
+                                                database.config().getOwnDeviceIdSync() +
+                                                authentication.user.secondPasswordHash +
+                                                serializedAction
+
+                                        val hashedIntegrityData = Sha512.hashSync(integrityData)
+
+                                        if (BuildConfig.DEBUG) {
+                                            Log.d(LOG_TAG, "integrity data: $integrityData")
+                                            Log.d(LOG_TAG, "integrity hash: $hashedIntegrityData")
+                                        }
+
+                                        hashedIntegrityData
+                                    }
+                                }
+                                is AuthenticatedUser.U2fSigned -> {
+                                    val mac = mac(authentication.user.dh.sharedSecret)
+
+                                    constructU2fIntegrityString(authentication.user, mac)
+                                }
+                                is AuthenticatedUser.LocalAuth -> throw IllegalStateException()
                            }

                            PendingSyncAction(
-                                    sequenceNumber = sequenceNumber,
-                                    encodedAction = serializedAction,
-                                    integrity = hashedIntegrityData,
-                                    scheduledForUpload = false,
-                                    type = PendingSyncActionType.Parent,
-                                    userId = authentication.parentUserId
+                                sequenceNumber = sequenceNumber,
+                                encodedAction = serializedAction,
+                                integrity = integrity,
+                                scheduledForUpload = false,
+                                type = PendingSyncActionType.Parent,
+                                userId = authentication.user.userId
                            )
                        }
                        ApplyActionParentDeviceAuthentication -> {
@ -353,6 +400,10 @@ object ApplyActionUtil {
        }
    }

+    fun constructU2fIntegrityString(authentication: AuthenticatedUser.U2fSigned, mac: ByteArray): String {
+        return "u2f:${authentication.dh.keyVersion}.${authentication.dh.ownPublicKey.base64()}.${authentication.u2fServerKeyId}.${authentication.signature.raw.base64()}.${mac.base64()}"
+    }
+
    private fun isSyncEnabled(database: Database): Boolean {
        return database.config().getDeviceAuthTokenSync() != ""
    }
@ -361,6 +412,34 @@ object ApplyActionUtil {
 sealed class ApplyActionParentAuthentication
 object ApplyActionParentDeviceAuthentication: ApplyActionParentAuthentication()
 object ApplyActionChildAddLimitAuthentication: ApplyActionParentAuthentication()
-data class ApplyActionParentPasswordAuthentication(val parentUserId: String, val secondPasswordHash: String): ApplyActionParentAuthentication()
-
+data class ApplyActionUserAuthentication(val user: AuthenticatedUser): ApplyActionParentAuthentication()
 data class ApplyActionChildAuthentication(val childUserId: String, val secondPasswordHash: String)
+
+data class ApplyDirectCallAuthentication (
+    val parentUserId: String,
+    val parentPasswordSecondHash: String
+) {
+    companion object {
+        fun from(auth: ApplyActionParentAuthentication) = when (auth) {
+            ApplyActionParentDeviceAuthentication -> ApplyDirectCallAuthentication(
+                parentUserId = "",
+                parentPasswordSecondHash = "device"
+            )
+            is ApplyActionUserAuthentication -> ApplyDirectCallAuthentication(
+                parentUserId = auth.user.userId,
+                parentPasswordSecondHash = when (auth.user) {
+                    is AuthenticatedUser.Password -> auth.user.secondPasswordHash
+                    is AuthenticatedUser.U2fSigned -> ApplyActionUtil.constructU2fIntegrityString(
+                        auth.user,
+                        Mac.getInstance("HmacSHA256").also {
+                            it.init(SecretKeySpec(auth.user.dh.sharedSecret, "HmacSHA256"))
+                            it.update("direct action".toByteArray(Charsets.UTF_8))
+                        }.doFinal()
+                    )
+                    is AuthenticatedUser.LocalAuth -> throw RuntimeException("authentication does not support that")
+                }
+            )
+            is ApplyActionChildAddLimitAuthentication -> throw RuntimeException("child can not do that")
+        }
+    }
+}
--- a/app/src/main/java/io/timelimit/android/sync/actions/apply/UploadActionsUtil.kt
+++ b/app/src/main/java/io/timelimit/android/sync/actions/apply/UploadActionsUtil.kt
@ -1,5 +1,5 @@
 /*
- * TimeLimit Copyright <C> 2019 - 2020 Jonas Lochmann
+ * TimeLimit Copyright <C> 2019 - 2022 Jonas Lochmann
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
@ -30,6 +30,7 @@ class UploadActionsUtil(private val database: Database, private val syncConflict
            database.runInTransaction {
                database.config().setUserListVersionSync("")
                database.config().setDeviceListVersionSync("")
+                database.config().setU2fListVersionSync(null)
                database.device().deleteAllInstalledAppsVersions()
                database.category().deleteAllCategoriesVersionNumbers()
                database.cryptContainer().deleteAllServerVersionNumbers()
--- a/app/src/main/java/io/timelimit/android/sync/actions/dispatch/ParentAction.kt
+++ b/app/src/main/java/io/timelimit/android/sync/actions/dispatch/ParentAction.kt
@ -922,6 +922,7 @@ object LocalDatabaseParentActionDispatcher {
                        publicKey = action.publicKey
                    )
                }
+                is ReportU2fLoginAction -> null // nothing to do
            }.let { }
        }
    }
--- a/app/src/main/java/io/timelimit/android/sync/network/ClientDataStatus.kt
+++ b/app/src/main/java/io/timelimit/android/sync/network/ClientDataStatus.kt
@ -26,7 +26,8 @@ data class ClientDataStatus(
        val userListVersion: String,
        val lastKeyRequestServerSequence: Long?,
        val lastKeyResponseServerSequence: Long?,
-        val dhKeyVersion: String?
+        val dhKeyVersion: String?,
+        val u2fVersion: String?
 ) {
    companion object {
        private const val DEVICES = "devices"
@ -38,7 +39,8 @@ data class ClientDataStatus(
        private const val LAST_KEY_REQUEST_SEQUENCE = "kri"
        private const val LAST_KEY_RESPONSE_SEQUENCE = "kr"
        private const val DH = "dh"
-        private const val CLIENT_LEVEL_VALUE = 5
+        private const val U2F = "u2f"
+        private const val CLIENT_LEVEL_VALUE = 6

        val empty = ClientDataStatus(
            deviceListVersion = "",
@ -48,7 +50,8 @@ data class ClientDataStatus(
            userListVersion = "",
            lastKeyRequestServerSequence = null,
            lastKeyResponseServerSequence = null,
-            dhKeyVersion = null
+            dhKeyVersion = null,
+            u2fVersion = null
        )

        fun getClientDataStatusSync(database: Database): ClientDataStatus {
@ -87,7 +90,8 @@ data class ClientDataStatus(
                    userListVersion = database.config().getUserListVersionSync(),
                    lastKeyRequestServerSequence = database.config().getLastServerKeyRequestSequenceSync(),
                    lastKeyResponseServerSequence = database.config().getLastServerKeyResponseSequenceSync(),
-                    dhKeyVersion = database.config().getLastDhKeySync()?.version
+                    dhKeyVersion = database.config().getLastDhKeySync()?.version,
+                    u2fVersion = database.config().getU2fVersionSync()
                )
            }
        }
@ -128,6 +132,7 @@ data class ClientDataStatus(
        lastKeyRequestServerSequence?.let { writer.name(LAST_KEY_REQUEST_SEQUENCE).value(it) }
        lastKeyResponseServerSequence?.let { writer.name(LAST_KEY_RESPONSE_SEQUENCE).value(it) }
        dhKeyVersion?.let { writer.name(DH).value(it) }
+        u2fVersion?.let { writer.name(U2F).value(it) }

        writer.endObject()
    }
--- a/app/src/main/java/io/timelimit/android/sync/network/ServerDataStatus.kt
+++ b/app/src/main/java/io/timelimit/android/sync/network/ServerDataStatus.kt
@ -47,6 +47,7 @@ data class ServerDataStatus(
        val pendingKeyRequests: List<ServerKeyRequest>,
        val keyResponses: List<ServerKeyResponse>,
        val dh: ServerDhKey?,
+        val u2f: ServerU2fData?,
        val fullVersionUntil: Long,
        val message: String?,
        val apiLevel: Int
@ -65,6 +66,7 @@ data class ServerDataStatus(
        private const val PENDING_KEY_REQUESTS = "krq"
        private const val KEY_RESPONSES = "kr"
        private const val DH = "dh"
+        private const val U2F = "u2f"
        private const val FULL_VERSION_UNTIL = "fullVersion"
        private const val MESSAGE = "message"
        private const val API_LEVEL = "apiLevel"
@ -83,6 +85,7 @@ data class ServerDataStatus(
            var pendingKeyRequests = emptyList<ServerKeyRequest>()
            var keyResponses = emptyList<ServerKeyResponse>()
            var dh: ServerDhKey? = null
+            var u2f: ServerU2fData? = null
            var fullVersionUntil: Long? = null
            var message: String? = null
            var apiLevel = 0
@ -103,6 +106,7 @@ data class ServerDataStatus(
                    PENDING_KEY_REQUESTS -> pendingKeyRequests = ServerKeyRequest.parseList(reader)
                    KEY_RESPONSES -> keyResponses = ServerKeyResponse.parseList(reader)
                    DH -> dh = ServerDhKey.parse(reader)
+                    U2F -> u2f = ServerU2fData.parse(reader)
                    FULL_VERSION_UNTIL -> fullVersionUntil = reader.nextLong()
                    MESSAGE -> message = reader.nextString()
                    API_LEVEL -> apiLevel = reader.nextInt()
@ -125,6 +129,7 @@ data class ServerDataStatus(
                pendingKeyRequests = pendingKeyRequests,
                keyResponses = keyResponses,
                dh = dh,
+                u2f = u2f,
                fullVersionUntil = fullVersionUntil!!,
                message = message,
                apiLevel = apiLevel
@ -1297,3 +1302,75 @@ data class ServerDhKey(val version: String, val key: ByteArray) {
        }
    }
 }
+
+data class ServerU2fData(
+    val version: String,
+    val data: List<ServerU2fItem>
+) {
+    companion object {
+        private const val VERSION = "v"
+        private const val DATA = "d"
+
+        fun parse(reader: JsonReader): ServerU2fData {
+            var version: String? = null
+            var data: List<ServerU2fItem>? = null
+
+            reader.beginObject()
+            while (reader.hasNext()) {
+                when (reader.nextName()) {
+                    VERSION -> version = reader.nextString()
+                    DATA -> data = ServerU2fItem.parseList(reader)
+                    else -> reader.skipValue()
+                }
+            }
+            reader.endObject()
+
+            return ServerU2fData(
+                version = version!!,
+                data = data!!
+            )
+        }
+    }
+}
+
+data class ServerU2fItem(
+    val userId: String,
+    val addedAt: Long,
+    val keyHandle: ByteArray,
+    val publicKey: ByteArray
+) {
+    companion object {
+        private const val USER_ID = "u"
+        private const val ADDED_AT = "a"
+        private const val KEY_HANDLE = "h"
+        private const val PUBLIC_KEY = "p"
+
+        fun parseList(reader: JsonReader) = parseJsonArray(reader) { parse(reader) }
+
+        fun parse(reader: JsonReader): ServerU2fItem {
+            var userId: String? = null
+            var addedAt: Long? = null
+            var keyHandle: ByteArray? = null
+            var publicKey: ByteArray? = null
+
+            reader.beginObject()
+            while (reader.hasNext()) {
+                when (reader.nextName()) {
+                    USER_ID -> userId = reader.nextString()
+                    ADDED_AT -> addedAt = reader.nextLong()
+                    KEY_HANDLE -> keyHandle = reader.nextString().parseBase64()
+                    PUBLIC_KEY -> publicKey = reader.nextString().parseBase64()
+                    else -> reader.skipValue()
+                }
+            }
+            reader.endObject()
+
+            return ServerU2fItem(
+                userId = userId!!,
+                addedAt = addedAt!!,
+                keyHandle = keyHandle!!,
+                publicKey = publicKey!!
+            )
+        }
+    }
+}
--- a/app/src/main/java/io/timelimit/android/u2f/protocol/U2FResponse.kt
+++ b/app/src/main/java/io/timelimit/android/u2f/protocol/U2FResponse.kt
@ -48,6 +48,16 @@ object U2FResponse {
        val counter: UInt,
        val signature: ByteArray
    ) {
+        val raw by lazy {
+            byteArrayOf(
+                flags,
+                counter.shr(24).toUByte().toByte(),
+                counter.shr(16).toUByte().toByte(),
+                counter.shr(8).toUByte().toByte(),
+                counter.toUByte().toByte(),
+            ) + signature
+        }
+
        companion object {
            fun parse(rawResponse: U2fRawResponse): Login {
                if (rawResponse.payload.size < 5) throw U2FException.InvalidDataException()
--- a/app/src/main/java/io/timelimit/android/ui/login/AuthTokenLoginProcessor.kt
+++ b/app/src/main/java/io/timelimit/android/ui/login/AuthTokenLoginProcessor.kt
@ -22,6 +22,10 @@ import io.timelimit.android.R
 import io.timelimit.android.async.Threads
 import io.timelimit.android.coroutines.executeAndWait
 import io.timelimit.android.coroutines.runAsync
+import io.timelimit.android.crypto.DHHandshake
+import io.timelimit.android.extensions.toByteArray
+import io.timelimit.android.livedata.waitForNonNullValue
+import io.timelimit.android.sync.actions.ReportU2fLoginAction
 import io.timelimit.android.u2f.U2FApplicationId
 import io.timelimit.android.u2f.U2FSignatureValidation
 import io.timelimit.android.u2f.protocol.U2FDevice
@ -31,7 +35,7 @@ import io.timelimit.android.u2f.util.U2FException
 import io.timelimit.android.u2f.util.U2FThread
 import io.timelimit.android.ui.main.ActivityViewModel
 import io.timelimit.android.ui.main.AuthenticatedUser
-import io.timelimit.android.ui.main.AuthenticationMethod
+import java.security.MessageDigest
 import java.security.SecureRandom

 object AuthTokenLoginProcessor {
@ -45,18 +49,52 @@ object AuthTokenLoginProcessor {

        runAsync {
            try {
+                val hasFullVersion = model.logic.fullVersion.shouldProvideFullVersionFunctions.waitForNonNullValue()
+
+                if (!hasFullVersion) {
+                    toast(R.string.update_primary_device_toast_requires_full_version)
+
+                    return@runAsync
+                }
+
                device.connect().use { session ->
-                    val keys = Threads.database.executeAndWait { model.logic.database.u2f().getAllSync() }
-                    val random = SecureRandom()
+                    val (keys, serverDhKey) = Threads.database.executeAndWait {
+                        model.logic.database.runInTransaction {
+                            val u2f = model.logic.database.u2f().getAllSync()
+                            val dh = model.logic.database.config().getLastDhKeySync()
+
+                            u2f to dh
+                        }
+                    }
+
+                    val dhHandshake = serverDhKey?.let {
+                        Threads.crypto.executeAndWait {
+                            DHHandshake.fromServerKey(it)
+                        }
+                    }
+
                    val applicationId = U2FApplicationId.fromUrl(U2FApplicationId.URL)
+                    val challenge = if (dhHandshake == null) ByteArray(32).also { SecureRandom().nextBytes(it) }
+                    else {
+                        val binaryDhKey = dhHandshake.keyVersion.toByteArray(Charsets.UTF_8)
+
+                        MessageDigest.getInstance("SHA256").also {
+                            it.update(binaryDhKey.size.toByteArray())
+                            it.update(binaryDhKey)
+
+                            it.update(dhHandshake.otherPublicKey.size.toByteArray())
+                            it.update(dhHandshake.otherPublicKey)
+
+                            it.update(dhHandshake.ownPublicKey.size.toByteArray())
+                            it.update(dhHandshake.ownPublicKey)
+                        }.digest()
+                    }

                    for (key in keys) {
                        if (BuildConfig.DEBUG) {
                            Log.d(LOG_TAG, "try key $key")
                        }

-                        val challenge = ByteArray(32).also { random.nextBytes(it) }
-
                        try {
                            val response = session.login(
                                U2FRequest.Login(
@ -121,13 +159,28 @@ object AuthTokenLoginProcessor {
                                return@runAsync
                            }

-                            model.setAuthenticatedUser(
-                                AuthenticatedUser(
+                            val authenticatedUser = if (dhHandshake == null) {
+                                AuthenticatedUser.LocalAuth.U2f(userId = key.userId)
+                            } else {
+                                val serverKeyId = Threads.crypto.executeAndWait {
+                                    key.calculateServerKeyIdSync()
+                                }
+
+                                AuthenticatedUser.U2fSigned(
                                    userId = key.userId,
-                                    authenticatedBy = AuthenticationMethod.KeyCode,
-                                    firstPasswordHash = userEntry.password,
-                                    secondPasswordHash = "u2f"
+                                    u2fServerKeyId = serverKeyId,
+                                    u2fClientKeyId = key.keyId,
+                                    signature = response,
+                                    dh = dhHandshake
                                )
+                            }
+
+                            model.setAuthenticatedUser(authenticatedUser)
+
+                            ActivityViewModel.dispatchWithoutCheckOrCatching(
+                                action = ReportU2fLoginAction,
+                                authenticatedUser = authenticatedUser,
+                                logic = model.logic
                            )

                            return@runAsync // no need to try more
--- a/app/src/main/java/io/timelimit/android/ui/login/LoginDialogFragmentModel.kt
+++ b/app/src/main/java/io/timelimit/android/ui/login/LoginDialogFragmentModel.kt
@ -39,7 +39,6 @@ import io.timelimit.android.sync.actions.apply.ApplyActionChildAuthentication
 import io.timelimit.android.sync.actions.apply.ApplyActionUtil
 import io.timelimit.android.ui.main.ActivityViewModel
 import io.timelimit.android.ui.main.AuthenticatedUser
-import io.timelimit.android.ui.main.AuthenticationMethod
 import io.timelimit.android.ui.manage.parent.key.ScannedKey
 import kotlinx.coroutines.sync.Mutex
 import kotlinx.coroutines.sync.withLock
@ -210,11 +209,10 @@ class LoginDialogFragmentModel(application: Application): AndroidViewModel(appli
                    }

                    if (shouldSignIn) {
-                        model.setAuthenticatedUser(AuthenticatedUser(
+                        model.setAuthenticatedUser(AuthenticatedUser.Password(
                                userId = user.id,
                                firstPasswordHash = user.password,
-                                secondPasswordHash = Threads.crypto.executeAndWait { PasswordHashing.hashSyncWithSalt("", user.secondPasswordSalt) },
-                                authenticatedBy = AuthenticationMethod.Password
+                                secondPasswordHash = Threads.crypto.executeAndWait { PasswordHashing.hashSyncWithSalt("", user.secondPasswordSalt) }
                        ))

                        isLoginDone.value = true
@ -278,11 +276,8 @@ class LoginDialogFragmentModel(application: Application): AndroidViewModel(appli

                    if (shouldSignIn) {
                        // this feature is limited to the local mode
-                        model.setAuthenticatedUser(AuthenticatedUser(
-                                userId = user.id,
-                                firstPasswordHash = user.password,
-                                secondPasswordHash = "device",
-                                authenticatedBy = AuthenticationMethod.Password
+                        model.setAuthenticatedUser(AuthenticatedUser.LocalAuth.ScanCode(
+                            userId = user.id
                        ))

                        isLoginDone.value = true
@ -326,11 +321,10 @@ class LoginDialogFragmentModel(application: Application): AndroidViewModel(appli

                    val secondPasswordHash = Threads.crypto.executeAndWait { PasswordHashing.hashSyncWithSalt(password, userEntry.secondPasswordSalt) }

-                    val authenticatedUser = AuthenticatedUser(
+                    val authenticatedUser = AuthenticatedUser.Password(
                            userId = userEntry.id,
                            firstPasswordHash = userEntry.password,
-                            secondPasswordHash = secondPasswordHash,
-                            authenticatedBy = AuthenticationMethod.Password
+                            secondPasswordHash = secondPasswordHash
                    )

                    val allowLoginStatus = Threads.database.executeAndWait {
--- a/app/src/main/java/io/timelimit/android/ui/main/ActivityViewModel.kt
+++ b/app/src/main/java/io/timelimit/android/ui/main/ActivityViewModel.kt
@ -21,19 +21,19 @@ import android.widget.Toast
 import androidx.lifecycle.AndroidViewModel
 import androidx.lifecycle.LiveData
 import androidx.lifecycle.MutableLiveData
+import androidx.lifecycle.map
 import io.timelimit.android.BuildConfig
 import io.timelimit.android.R
 import io.timelimit.android.coroutines.runAsync
+import io.timelimit.android.crypto.DHHandshake
 import io.timelimit.android.data.model.User
 import io.timelimit.android.data.model.UserType
-import io.timelimit.android.livedata.ignoreUnchanged
-import io.timelimit.android.livedata.liveDataFromNullableValue
-import io.timelimit.android.livedata.map
-import io.timelimit.android.livedata.switchMap
+import io.timelimit.android.livedata.*
 import io.timelimit.android.logic.AppLogic
 import io.timelimit.android.logic.DefaultAppLogic
 import io.timelimit.android.sync.actions.ParentAction
 import io.timelimit.android.sync.actions.apply.*
+import io.timelimit.android.u2f.protocol.U2FResponse

 class ActivityViewModel(application: Application): AndroidViewModel(application) {
    companion object {
@ -47,10 +47,7 @@ class ActivityViewModel(application: Application): AndroidViewModel(application)
            ApplyActionUtil.applyParentAction(
                    action = action,
                    database = logic.database,
-                    authentication = ApplyActionParentPasswordAuthentication(
-                            parentUserId = authenticatedUser.userId,
-                            secondPasswordHash = authenticatedUser.secondPasswordHash
-                    ),
+                    authentication = ApplyActionUserAuthentication(authenticatedUser),
                    syncUtil = logic.syncUtil,
                    platformIntegration = logic.platformIntegration
            )
@ -79,41 +76,45 @@ class ActivityViewModel(application: Application): AndroidViewModel(application)
        }
    }.ignoreUnchanged()

-    private val authenticatedChild: LiveData<Pair<ApplyActionParentAuthentication, User>?> = deviceUser.map { user ->
+    private val authenticatedUserChecked = authenticatedUserMetadata.switchMap { user ->
+        val userEntryLive =
+            if (user == null) liveDataFromNullableValue(null)
+            else database.user().getUserByIdLive(user.userId)
+
+        userEntryLive.switchMap { userEntry ->
+            if (userEntry == null) liveDataFromNullableValue(null)
+            else {
+                val stillValid = when (user) {
+                    is AuthenticatedUser.Password -> liveDataFromNonNullValue( user.firstPasswordHash == userEntry.password)
+                    is AuthenticatedUser.U2fSigned -> logic.database.u2f().getByClientKeyIdLive(user.u2fClientKeyId).map { keyEntry ->
+                        keyEntry != null && keyEntry.userId == user.userId
+                    }
+                    is AuthenticatedUser.LocalAuth -> logic.fullVersion.isLocalMode
+                    null -> liveDataFromNonNullValue(false)
+                }
+
+                stillValid.map { valid ->
+                    if (valid && user != null) ApplyActionUserAuthentication(user) to userEntry
+                    else null
+                }
+            }
+        }
+    }
+
+    private val authenticatedChildChecked: LiveData<Pair<ApplyActionParentAuthentication, User>?> = deviceUser.map { user ->
        if (user?.type == UserType.Child && user.allowSelfLimitAdding) {
            ApplyActionChildAddLimitAuthentication as ApplyActionParentAuthentication to user
        } else null
    }

-    val authenticatedUserOrChild: LiveData<Pair<ApplyActionParentAuthentication, User>?> = userWhichIsKeptSignedIn.switchMap { signedInUser ->
-        if (signedInUser != null) {
-            liveDataFromNullableValue(
-                    (ApplyActionParentDeviceAuthentication to signedInUser)
-                            as Pair<ApplyActionParentAuthentication, User>?
-            )
-        } else {
-            authenticatedUserMetadata.switchMap {
-                authenticatedUser ->
-
-                if (authenticatedUser == null) {
-                    authenticatedChild
-                } else {
-                    database.user().getUserByIdLive(authenticatedUser.userId).switchMap {
-                        if (it == null || it.password != authenticatedUser.firstPasswordHash) {
-                            authenticatedChild
-                        } else {
-                            liveDataFromNullableValue(
-                                    (ApplyActionParentPasswordAuthentication(
-                                            parentUserId = authenticatedUser.userId,
-                                            secondPasswordHash = authenticatedUser.secondPasswordHash
-                                    ) to it) as Pair<ApplyActionParentAuthentication, User>?
-                            )
-                        }
-                    }
-                }
+    val authenticatedUserOrChild: LiveData<Pair<ApplyActionParentAuthentication, User>?> =
+        mergeLiveDataWaitForValues(userWhichIsKeptSignedIn, authenticatedChildChecked, authenticatedUserChecked)
+            .map { (keptSignedIn, localChild, authenticatedUser) ->
+                keptSignedIn?.let {
+                    ApplyActionParentDeviceAuthentication to it
+                } ?: authenticatedUser ?: localChild
            }
-        }
-    }
+            .ignoreUnchanged()

    val authenticatedUser = authenticatedUserOrChild.map { if (it?.second?.type != UserType.Parent) null else it }

@ -198,13 +199,25 @@ class ActivityViewModel(application: Application): AndroidViewModel(application)
    }
 }

-data class AuthenticatedUser (
-        val userId: String,
-        val firstPasswordHash: String,
-        val secondPasswordHash: String,
-        val authenticatedBy: AuthenticationMethod
-)
+sealed class AuthenticatedUser {
+    abstract val userId: String

-enum class AuthenticationMethod {
-    Password, KeyCode
+    data class Password(
+        override val userId: String,
+        val firstPasswordHash: String,
+        val secondPasswordHash: String
+    ): AuthenticatedUser()
+
+    data class U2fSigned(
+        override val userId: String,
+        val u2fServerKeyId: String,
+        val u2fClientKeyId: Long,
+        val signature: U2FResponse.Login,
+        val dh: DHHandshake
+    ): AuthenticatedUser()
+
+    sealed class LocalAuth: AuthenticatedUser() {
+        data class U2f(override val userId: String): LocalAuth()
+        data class ScanCode(override val userId: String): LocalAuth()
+    }
 }
--- a/app/src/main/java/io/timelimit/android/ui/manage/device/add/AddDeviceModel.kt
+++ b/app/src/main/java/io/timelimit/android/ui/manage/device/add/AddDeviceModel.kt
@ -1,5 +1,5 @@
 /*
- * TimeLimit Copyright <C> 2019 Jonas Lochmann
+ * TimeLimit Copyright <C> 2019 - 2022 Jonas Lochmann
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
@ -23,9 +23,7 @@ import io.timelimit.android.livedata.castDown
 import io.timelimit.android.livedata.waitForNonNullValue
 import io.timelimit.android.livedata.waitUntilValueMatches
 import io.timelimit.android.logic.DefaultAppLogic
-import io.timelimit.android.sync.actions.apply.ApplyActionChildAddLimitAuthentication
-import io.timelimit.android.sync.actions.apply.ApplyActionParentDeviceAuthentication
-import io.timelimit.android.sync.actions.apply.ApplyActionParentPasswordAuthentication
+import io.timelimit.android.sync.actions.apply.ApplyDirectCallAuthentication
 import io.timelimit.android.ui.main.ActivityViewModel
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.withContext
@ -65,21 +63,13 @@ class AddDeviceModel(application: Application): AndroidViewModel(application) {
                statusInternal.value = Failed
            } else {
                try {
-                    val auth = user.first
+                    val auth = ApplyDirectCallAuthentication.from(user.first)

-                    val response = when (auth) {
-                        ApplyActionParentDeviceAuthentication -> server.api.createAddDeviceToken(
-                                deviceAuthToken = server.deviceAuthToken,
-                                parentUserId = "",
-                                parentPasswordSecondHash = "device"
-                        )
-                        is ApplyActionParentPasswordAuthentication -> server.api.createAddDeviceToken(
-                                deviceAuthToken = server.deviceAuthToken,
-                                parentUserId = auth.parentUserId,
-                                parentPasswordSecondHash = auth.secondPasswordHash
-                        )
-                        is ApplyActionChildAddLimitAuthentication -> throw RuntimeException("child can not do that")
-                    }
+                    val response = server.api.createAddDeviceToken(
+                        deviceAuthToken = server.deviceAuthToken,
+                        parentUserId = auth.parentUserId,
+                        parentPasswordSecondHash = auth.parentPasswordSecondHash
+                    )

                    statusInternal.value = ShowingToken(response.token)

--- a/app/src/main/java/io/timelimit/android/ui/manage/device/remove/RemoveDeviceModel.kt
+++ b/app/src/main/java/io/timelimit/android/ui/manage/device/remove/RemoveDeviceModel.kt
@ -25,9 +25,7 @@ import io.timelimit.android.R
 import io.timelimit.android.coroutines.runAsync
 import io.timelimit.android.livedata.castDown
 import io.timelimit.android.logic.DefaultAppLogic
-import io.timelimit.android.sync.actions.apply.ApplyActionChildAddLimitAuthentication
-import io.timelimit.android.sync.actions.apply.ApplyActionParentDeviceAuthentication
-import io.timelimit.android.sync.actions.apply.ApplyActionParentPasswordAuthentication
+import io.timelimit.android.sync.actions.apply.ApplyDirectCallAuthentication
 import io.timelimit.android.ui.main.ActivityViewModel

 class RemoveDeviceModel(application: Application): AndroidViewModel(application) {
@ -54,28 +52,18 @@ class RemoveDeviceModel(application: Application): AndroidViewModel(application)
                if (!server.hasAuthToken) {
                    Toast.makeText(getApplication(), R.string.remove_device_local_mode, Toast.LENGTH_LONG).show()
                } else {
-                    val parent = activityViewModel.authenticatedUser.value?.first
+                    val auth = activityViewModel.authenticatedUser.value?.first?.let {
+                        ApplyDirectCallAuthentication.from(it)
+                    }

-                    if (parent != null) {
+                    if (auth != null) {
                        try {
-                            when (parent) {
-                                ApplyActionParentDeviceAuthentication -> server.api.removeDevice(
-                                        deviceAuthToken = server.deviceAuthToken,
-                                        parentUserId = "",
-                                        parentPasswordSecondHash = "device",
-                                        deviceId = deviceId
-                                )
-                                is ApplyActionParentPasswordAuthentication -> server.api.removeDevice(
-                                        deviceAuthToken = server.deviceAuthToken,
-                                        parentUserId = parent.parentUserId,
-                                        parentPasswordSecondHash = parent.secondPasswordHash,
-                                        deviceId = deviceId
-                                )
-                                is ApplyActionChildAddLimitAuthentication -> {
-                                    // caught below
-                                    throw IllegalStateException()
-                                }
-                            }
+                            server.api.removeDevice(
+                                deviceAuthToken = server.deviceAuthToken,
+                                parentUserId = auth.parentUserId,
+                                parentPasswordSecondHash = auth.parentPasswordSecondHash,
+                                deviceId = deviceId
+                            )
                        } catch (ex: Exception) {
                            if (BuildConfig.DEBUG) {
                                Log.w(LOG_TAG, "removing device failed", ex)
--- a/app/src/main/java/io/timelimit/android/ui/manage/parent/ManageParentFragment.kt
+++ b/app/src/main/java/io/timelimit/android/ui/manage/parent/ManageParentFragment.kt
@ -1,5 +1,5 @@
 /*
- * TimeLimit Copyright <C> 2019 - 2021 Jonas Lochmann
+ * TimeLimit Copyright <C> 2019 - 2022 Jonas Lochmann
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
@ -95,6 +95,11 @@ class ManageParentFragment : Fragment(), FragmentWithCustomTitle {
            binding.isUsingLocalMode = isLocalMode
        })

+        logic.serverApiLevelLogic.infoLive
+            .map { it.hasLevelOrIsOffline(6) }
+            .observe(viewLifecycleOwner)
+            { binding.hasU2fSupport = it }
+
        DeleteParentView.bind(
                view = binding.deleteParent,
                lifecycleOwner = this,
--- a/app/src/main/java/io/timelimit/android/ui/manage/parent/password/change/ChangeParentPasswordViewModel.kt
+++ b/app/src/main/java/io/timelimit/android/ui/manage/parent/password/change/ChangeParentPasswordViewModel.kt
@ -29,9 +29,10 @@ import io.timelimit.android.livedata.castDown
 import io.timelimit.android.livedata.waitForNullableValue
 import io.timelimit.android.logic.DefaultAppLogic
 import io.timelimit.android.sync.actions.ChangeParentPasswordAction
-import io.timelimit.android.sync.actions.apply.ApplyActionParentPasswordAuthentication
+import io.timelimit.android.sync.actions.apply.ApplyActionUserAuthentication
 import io.timelimit.android.sync.actions.apply.ApplyActionUtil
 import io.timelimit.android.sync.network.ParentPassword
+import io.timelimit.android.ui.main.AuthenticatedUser
 import java.nio.charset.Charset
 import javax.crypto.Cipher
 import javax.crypto.spec.IvParameterSpec
@ -155,14 +156,17 @@ class ChangeParentPasswordViewModel(application: Application): AndroidViewModel(
                }

                ApplyActionUtil.applyParentAction(
-                        action,
-                        logic.database,
-                        ApplyActionParentPasswordAuthentication(
-                                parentUserId = parentUserId,
-                                secondPasswordHash = oldPasswordSecondHash
-                        ),
-                        logic.syncUtil,
-                        logic.platformIntegration
+                    action,
+                    logic.database,
+                    ApplyActionUserAuthentication(
+                        AuthenticatedUser.Password(
+                            userId = parentUserId,
+                            firstPasswordHash = userEntry.password,
+                            secondPasswordHash = oldPasswordSecondHash
+                        )
+                    ),
+                    logic.syncUtil,
+                    logic.platformIntegration
                )

                if (BuildConfig.DEBUG) {
--- a/app/src/main/java/io/timelimit/android/ui/manage/parent/u2fkey/ManageParentU2FKeyFragment.kt
+++ b/app/src/main/java/io/timelimit/android/ui/manage/parent/u2fkey/ManageParentU2FKeyFragment.kt
@ -77,14 +77,17 @@ class ManageParentU2FKeyFragment : Fragment(), FragmentWithCustomTitle {

            override fun onRemoveClicked(keyItem: U2FKeyListItem.KeyItem) {
                if (isAuthValidOrShowMessage()) {
-                    if (activityModel.getAuthenticatedUser()?.authenticatedBy == AuthenticationMethod.Password) {
+                    if (
+                        activityModel.getAuthenticatedUser() is AuthenticatedUser.U2fSigned ||
+                        activityModel.getAuthenticatedUser() is AuthenticatedUser.LocalAuth.U2f
+                    ) {
+                        U2FRequiresPasswordForRemovalDialogFragment.newInstance().show(parentFragmentManager)
+                    } else {
                        RemoveU2FKeyDialogFragment.newInstance(
                            userId = params.userId,
                            keyHandle = keyItem.item.keyHandle,
                            publicKey = keyItem.item.publicKey
                        ).show(parentFragmentManager)
-                    } else {
-                        U2FRequiresPasswordForRemovalDialogFragment.newInstance().show(parentFragmentManager)
                    }
                }
            }
--- a/app/src/main/java/io/timelimit/android/ui/payment/PurchaseModel.kt
+++ b/app/src/main/java/io/timelimit/android/ui/payment/PurchaseModel.kt
@ -25,9 +25,7 @@ import io.timelimit.android.extensions.BillingNotSupportedException
 import io.timelimit.android.livedata.castDown
 import io.timelimit.android.logic.AppLogic
 import io.timelimit.android.logic.DefaultAppLogic
-import io.timelimit.android.sync.actions.apply.ApplyActionChildAddLimitAuthentication
-import io.timelimit.android.sync.actions.apply.ApplyActionParentDeviceAuthentication
-import io.timelimit.android.sync.actions.apply.ApplyActionParentPasswordAuthentication
+import io.timelimit.android.sync.actions.apply.ApplyDirectCallAuthentication
 import io.timelimit.android.sync.network.CanDoPurchaseStatus
 import io.timelimit.android.sync.network.api.NotFoundHttpError
 import io.timelimit.android.ui.main.ActivityViewModel
@ -78,25 +76,16 @@ class PurchaseModel(application: Application): AndroidViewModel(application) {

                    if (!BuildConfig.storeCompilant) {
                        if (auth.isParentAuthenticated()) {
-                            val authData = auth.authenticatedUser.value?.first
-
                            try {
-                                val token = when (authData) {
-                                    ApplyActionParentDeviceAuthentication -> server.api.createIdentityToken(
-                                        deviceAuthToken = server.deviceAuthToken,
-                                        parentUserId = "",
-                                        parentPasswordSecondHash = "device"
-                                    )
-                                    is ApplyActionParentPasswordAuthentication -> server.api.createIdentityToken(
-                                        deviceAuthToken = server.deviceAuthToken,
-                                        parentUserId = authData.parentUserId,
-                                        parentPasswordSecondHash = authData.secondPasswordHash
-                                    )
-                                    is ApplyActionChildAddLimitAuthentication -> throw RuntimeException(
-                                        "child can not do that"
-                                    )
-                                    null -> throw RuntimeException("missing user")
-                                }
+                                val authData = ApplyDirectCallAuthentication.from(
+                                    auth.authenticatedUser.value?.first!!
+                                )
+
+                                val token = server.api.createIdentityToken(
+                                    deviceAuthToken = server.deviceAuthToken,
+                                    parentUserId = authData.parentUserId,
+                                    parentPasswordSecondHash = authData.parentPasswordSecondHash
+                                )

                                statusInternal.value = Status.ReadyToken(token)
                            } catch (ex: NotFoundHttpError) {
--- a/app/src/main/res/layout/fragment_manage_parent.xml
+++ b/app/src/main/res/layout/fragment_manage_parent.xml
@ -30,6 +30,10 @@
            name="isUsingLocalMode"
            type="Boolean" />

+        <variable
+            name="hasU2fSupport"
+            type="boolean" />
+
        <variable
            name="handlers"
            type="io.timelimit.android.ui.manage.parent.ManageParentFragmentHandlers" />
@ -158,7 +162,7 @@
                    layout="@layout/manage_parent_notifications" />

                <androidx.cardview.widget.CardView
-                    android:visibility="@{isUsingLocalMode ? View.VISIBLE : View.GONE}"
+                    android:visibility="@{hasU2fSupport ? View.VISIBLE : View.GONE}"
                    android:onClick="@{() -> handlers.onManageU2FClicked()}"
                    android:foreground="?selectableItemBackground"
                    app:cardUseCompatPadding="true"
@ -182,6 +186,12 @@
                            android:layout_width="match_parent"
                            android:layout_height="wrap_content" />

+                        <TextView
+                            android:textAppearance="?android:textAppearanceSmall"
+                            android:text="@string/purchase_required_info_local_mode_free"
+                            android:layout_width="match_parent"
+                            android:layout_height="wrap_content" />
+
                    </LinearLayout>
                </androidx.cardview.widget.CardView>

--- a/app/src/main/res/values-de/strings.xml
+++ b/app/src/main/res/values-de/strings.xml
@ -1688,7 +1688,7 @@
    <string name="manage_parent_u2f_status_done">Das Gerät wurde verknüpft</string>

    <string name="manage_parent_u2f_remove_key_text">Möchten sich diesen Schlüssel wirklich entfernen?</string>
-    <string name="manage_parent_u2f_remove_key_requires_password">Schlüssel können nur nach einer Anmeldung mittels Passwort entfernt werden</string>
+    <string name="manage_parent_u2f_remove_key_requires_password">Schlüssel können nur nach einer Anmeldung ohne Schlüssel entfernt werden</string>

    <string name="manage_parent_u2f_err_wrong_user">Nur der Benutzer selbst kann seine U2F-Schlüssel verwalten</string>

--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@ -1735,7 +1735,7 @@
    <string name="manage_parent_u2f_status_done">The Device was linked</string>

    <string name="manage_parent_u2f_remove_key_text">Would you like to remove this key?</string>
-    <string name="manage_parent_u2f_remove_key_requires_password">You can only remove keys after signing in by password</string>
+    <string name="manage_parent_u2f_remove_key_requires_password">You can only remove keys after signing in without a key</string>

    <string name="manage_parent_u2f_err_wrong_user">Only the user itself can manage its U2F Keys</string>