Add USB U2F support

app/src/main/AndroidManifest.xml

@@ -43,6 +43,7 @@
     <uses-feature android:name="android.software.leanback" android:required="false" />
     <uses-feature android:name="android.hardware.touchscreen" android:required="false" />
     <uses-feature android:name="android.hardware.nfc" android:required="false" />
+    <uses-feature android:name="android.hardware.usb.host" android:required="false" />
 
     <application
         android:banner="@drawable/banner"

app/src/main/java/io/timelimit/android/extensions/Collection.kt

@@ -0,0 +1,23 @@
+/*
+ * 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
+
+inline fun <T> Collection<T>.some(predicate: (T) -> Boolean): Boolean {
+    for (element in this) if (predicate(element)) return true
+
+    return false
+}

app/src/main/java/io/timelimit/android/integration/platform/android/Notification.kt

@@ -236,6 +236,7 @@ object PendingIntentIds {
     const val UPDATE_STATUS = 5
     const val OPEN_UPDATER = 6
     const val U2F_NFC_DISCOVERY = 7
+    const val U2F_USB_RESPONSE = 8
     val DYNAMIC_NOTIFICATION_RANGE = 100..10000
 
     val PENDING_INTENT_FLAGS = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {

app/src/main/java/io/timelimit/android/u2f/U2fManager.kt

@@ -19,6 +19,7 @@ import android.content.Context
 import androidx.fragment.app.FragmentActivity
 import io.timelimit.android.u2f.nfc.NFCU2FManager
 import io.timelimit.android.u2f.protocol.U2FDevice
+import io.timelimit.android.u2f.usb.UsbU2FManager
 
 class U2fManager (context: Context) {
     companion object {
@@ -41,6 +42,7 @@ class U2fManager (context: Context) {
     }
 
     private val nfc = NFCU2FManager(this, context)
+    private val usb = UsbU2FManager(this, context)
 
     private val deviceFoundListeners = mutableListOf<DeviceFoundListener>()
 

app/src/main/java/io/timelimit/android/u2f/nfc/NFCU2FManager.kt

@@ -32,11 +32,11 @@ import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.LifecycleEventObserver
 import androidx.lifecycle.LiveData
 import io.timelimit.android.BuildConfig
-import io.timelimit.android.data.IdGenerator
 import io.timelimit.android.integration.platform.android.PendingIntentIds
 import io.timelimit.android.livedata.liveDataFromFunction
 import io.timelimit.android.livedata.liveDataFromNonNullValue
 import io.timelimit.android.u2f.U2fManager
+import io.timelimit.android.u2f.util.U2FId
 
 class NFCU2FManager (val parent: U2fManager, context: Context) {
     companion object {
@@ -48,17 +48,23 @@ class NFCU2FManager (val parent: U2fManager, context: Context) {
 
     private val nfcReceiver = object: BroadcastReceiver() {
         override fun onReceive(p0: Context?, intent: Intent?) {
-            val tagFromIntent: Tag = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU)
-                intent?.getParcelableExtra(NfcAdapter.EXTRA_TAG, Tag::class.java) ?: return
-            else
-                intent?.getParcelableExtra(NfcAdapter.EXTRA_TAG) ?: return
+            try {
+                val tagFromIntent: Tag = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU)
+                    intent?.getParcelableExtra(NfcAdapter.EXTRA_TAG, Tag::class.java) ?: return
+                else
+                    intent?.getParcelableExtra(NfcAdapter.EXTRA_TAG) ?: return
 
-            val isoDep: IsoDep = IsoDep.get(tagFromIntent) ?: return
+                val isoDep: IsoDep = IsoDep.get(tagFromIntent) ?: return
 
-            parent.dispatchDeviceFound(NfcU2FDevice(isoDep))
+                parent.dispatchDeviceFound(NfcU2FDevice(isoDep))
+            } catch (ex: Exception) {
+                if (BuildConfig.DEBUG) {
+                    Log.d(LOG_TAG, "could not handle nfc broadcast", ex)
+                }
+            }
         }
     }
-    private val nfcReceiverAction = (0..6).map { IdGenerator.generateId() }.joinToString()
+    private val nfcReceiverAction = U2FId.generate()
     private val nfcReceiverIntent = PendingIntent.getBroadcast(
         context,
         PendingIntentIds.U2F_NFC_DISCOVERY,

app/src/main/java/io/timelimit/android/u2f/nfc/NfcU2FDeviceSession.kt

@@ -20,7 +20,6 @@ import android.nfc.tech.IsoDep
 import android.util.Log
 import io.timelimit.android.BuildConfig
 import io.timelimit.android.coroutines.executeAndWait
-import io.timelimit.android.u2f.*
 import io.timelimit.android.u2f.protocol.U2FDeviceSession
 import io.timelimit.android.u2f.protocol.U2FRequest
 import io.timelimit.android.u2f.protocol.U2fRawResponse
@@ -35,7 +34,7 @@ class NfcU2FDeviceSession(private val tag: IsoDep): U2FDeviceSession {
 
     override suspend fun execute(request: U2FRequest): U2fRawResponse = U2FThread.nfc.executeAndWait {
         try {
-            var response = U2fRawResponse.decode(tag.transceive(request.encode()))
+            var response = U2fRawResponse.decode(tag.transceive(request.encodeShort()))
             var fullPayload = response.payload
 
             // https://fidoalliance.org/specs/fido-u2f-v1.2-ps-20170411/fido-u2f-nfc-protocol-v1.2-ps-20170411.html
@@ -60,9 +59,7 @@ class NfcU2FDeviceSession(private val tag: IsoDep): U2FDeviceSession {
 
             response = response.copy(payload = fullPayload)
 
-            if (response.status == 0x6A80.toUShort()) throw U2FException.BadKeyHandleException()
-            if (response.status == 0x6985.toUShort()) throw U2FException.UserInteractionRequired()
-            if (response.status != 0x9000.toUShort()) throw U2FException.DeviceException()
+            response.throwIfNoSuccess()
 
             response
         } catch (ex: TagLostException) {
@@ -75,4 +72,14 @@ class NfcU2FDeviceSession(private val tag: IsoDep): U2FDeviceSession {
             throw U2FException.CommunicationException()
         }
     }
+
+    override fun close() {
+        U2FThread.nfc.submit {
+            try {
+                tag.close()
+            } catch (ex: IOException) {
+                // ignore
+            }
+        }
+    }
 }

app/src/main/java/io/timelimit/android/u2f/protocol/U2FDeviceSession.kt

@@ -15,7 +15,9 @@
  */
 package io.timelimit.android.u2f.protocol
 
-interface U2FDeviceSession {
+import java.io.Closeable
+
+interface U2FDeviceSession: Closeable {
     suspend fun execute(request: U2FRequest): U2fRawResponse
 }
 

app/src/main/java/io/timelimit/android/u2f/protocol/U2FRequest.kt

@@ -23,7 +23,7 @@ sealed class U2FRequest {
     abstract val p2: Byte
     abstract val payload: ByteArray
 
-    fun encode(): ByteArray {
+    fun encodeShort(): ByteArray {
         val cla: Byte = 0
 
         if (payload.size > 255) {
@@ -39,6 +39,23 @@ sealed class U2FRequest {
         ) + payload + byteArrayOf(0)
     }
 
+    fun encodeExtended(): ByteArray {
+        val cla: Byte = 0
+
+        if (payload.size > 65535) {
+            throw U2FException.CommunicationException()
+        }
+
+        return byteArrayOf(
+            cla,
+            ins,
+            p1,
+            p2,
+            0,
+            payload.size.ushr(8).toByte(),
+            payload.size.toByte()
+        ) + payload + byteArrayOf(1, 0)
+    }
     data class Register(
         val challenge: ByteArray,
         val applicationId: ByteArray

app/src/main/java/io/timelimit/android/u2f/protocol/U2fRawResponse.kt

@@ -31,4 +31,11 @@ data class U2fRawResponse (
             )
         }
     }
+
+    fun throwIfNoSuccess() {
+        if (status == 0x6A80.toUShort()) throw U2FException.BadKeyHandleException()
+        if (status == 0x6985.toUShort()) throw U2FException.UserInteractionRequired()
+        if (status == 0x6700.toUShort()) throw U2FException.BadRequestLength()
+        if (status != 0x9000.toUShort()) throw U2FException.DeviceException(status)
+    }
 }

app/src/main/java/io/timelimit/android/u2f/usb/DisconnectReporter.kt

@@ -0,0 +1,24 @@
+/*
+ * 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.u2f.usb
+
+class DisconnectReporter {
+    private var didDisconnectInternal = false
+
+    val didDisconnect get() = didDisconnectInternal
+
+    fun reportDisconnect() { didDisconnectInternal = true }
+}

app/src/main/java/io/timelimit/android/u2f/usb/UsbException.kt

@@ -0,0 +1,23 @@
+/*
+ * 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.u2f.usb
+
+sealed class UsbException(message: String): RuntimeException(message) {
+    class InvalidDescriptorLengthException: UsbException("invalid descriptor length")
+    class InvalidDescriptorTypeException: UsbException("invalid descriptor type")
+    class WrongCounterException(type: String, expected: Int, found: Int): UsbException("expected $expected but found $found $type")
+    class InvalidIndexException: UsbException("invalid index")
+}

app/src/main/java/io/timelimit/android/u2f/usb/UsbExtensions.kt

@@ -0,0 +1,32 @@
+/*
+ * 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.u2f.usb
+
+import android.content.Intent
+import android.hardware.usb.*
+import android.os.Build
+
+val Intent.usbDevice
+    get() = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU)
+        this.getParcelableExtra(UsbManager.EXTRA_DEVICE, UsbDevice::class.java)!!
+    else
+        this.getParcelableExtra(UsbManager.EXTRA_DEVICE)!!
+
+val UsbDevice.interfaces
+    get() = (0 until this.interfaceCount).map { this.getInterface(it) }
+
+val UsbInterface.endpoints
+    get() = (0 until this.endpointCount).map { this.getEndpoint(it) }

app/src/main/java/io/timelimit/android/u2f/usb/UsbPermissionRequestManager.kt

@@ -0,0 +1,54 @@
+/*
+ * 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.u2f.usb
+
+import android.hardware.usb.UsbDevice
+import kotlinx.coroutines.CancellableContinuation
+import kotlinx.coroutines.suspendCancellableCoroutine
+import kotlin.coroutines.resume
+
+class UsbPermissionRequestManager (
+    private val sendRequest: (UsbDevice) -> Unit
+) {
+    private val pendingRequests = mutableMapOf<String, MutableList<CancellableContinuation<Boolean>>>()
+
+    fun reportResult(device: UsbDevice, granted: Boolean) {
+        synchronized(pendingRequests) { pendingRequests.remove(device.deviceName) }
+            ?.forEach { it.resume(granted) }
+    }
+
+    suspend fun requestPermission(device: UsbDevice): Boolean {
+        return suspendCancellableCoroutine { continuation ->
+            continuation.invokeOnCancellation { removePendingRequest(device, continuation) }
+
+            addPendingRequest(device, continuation)
+
+            sendRequest(device)
+        }
+    }
+
+    private fun addPendingRequest(device: UsbDevice, listener: CancellableContinuation<Boolean>) = synchronized(pendingRequests) {
+        pendingRequests.getOrPut(device.deviceName) { mutableListOf() }.add(listener)
+    }
+
+    private fun removePendingRequest(device: UsbDevice, listener: CancellableContinuation<Boolean>) = synchronized(pendingRequests) {
+        pendingRequests[device.deviceName]?.remove(listener)
+
+        if (pendingRequests[device.deviceName]?.isEmpty() == true) {
+            pendingRequests.remove(device.deviceName)
+        }
+    }
+}

app/src/main/java/io/timelimit/android/u2f/usb/UsbU2FDevice.kt

@@ -0,0 +1,204 @@
+/*
+ * 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.u2f.usb
+
+import android.hardware.usb.UsbConstants
+import android.hardware.usb.UsbDevice
+import android.hardware.usb.UsbManager
+import android.util.Log
+import io.timelimit.android.BuildConfig
+import io.timelimit.android.coroutines.executeAndWait
+import io.timelimit.android.extensions.some
+import io.timelimit.android.u2f.protocol.U2FDevice
+import io.timelimit.android.u2f.protocol.U2FDeviceSession
+import io.timelimit.android.u2f.usb.descriptors.DeviceDescriptor
+import io.timelimit.android.u2f.usb.descriptors.ReportDescriptor
+import io.timelimit.android.u2f.util.U2FException
+import io.timelimit.android.u2f.util.U2FThread
+
+data class UsbU2FDevice (
+    val device: UsbDevice,
+    val permissionRequestManager: UsbPermissionRequestManager,
+    val usbManager: UsbManager,
+    val disconnectReporter: DisconnectReporter
+): U2FDevice {
+    companion object {
+        private const val LOG_TAG = "UsbU2FDevice"
+        private const val CLASS_HID = 3
+        private const val ATTRIBUTES_INTERRUPT = 3
+        private const val ATTRIBUTES_INTERRUPT_MASK = 3
+
+        // https://fidoalliance.org/specs/fido-u2f-v1.0-ps-20141009/fido-u2f-hid-protocol-ps-20141009.html
+        // http://esd.cs.ucr.edu/webres/usb11.pdf
+        // https://www.usb.org/sites/default/files/documents/hid1_11.pdf
+        fun from(
+            device: UsbDevice,
+            permissionRequestManager: UsbPermissionRequestManager,
+            usbManager: UsbManager,
+            disconnectReporter: DisconnectReporter
+        ): UsbU2FDevice? {
+            for (usbInterface in device.interfaces) {
+                // according to the U2F spec, there must be a input and output endpoint
+                // according to the HID spec, the endpoints must be data interrupt endpoints
+                // it looks like the U2F spec wants no subclass and protocol that is not zero
+                // it looks like the HID spec does not allow more than one endpoint per type
+                if (
+                    usbInterface.interfaceClass != CLASS_HID ||
+                    usbInterface.interfaceSubclass != 0 ||
+                    usbInterface.interfaceProtocol != 0 ||
+                    usbInterface.endpointCount != 2
+                ) continue
+
+                val hasInputEndpoint = usbInterface.endpoints.some {
+                    it.attributes and ATTRIBUTES_INTERRUPT_MASK == ATTRIBUTES_INTERRUPT &&
+                    it.direction == UsbConstants.USB_DIR_IN
+                }
+
+                val hasOutputEndpoint = usbInterface.endpoints.some {
+                    it.attributes and ATTRIBUTES_INTERRUPT_MASK == ATTRIBUTES_INTERRUPT &&
+                    it.direction == UsbConstants.USB_DIR_OUT
+                }
+
+                if (hasInputEndpoint && hasOutputEndpoint) {
+                    return UsbU2FDevice(
+                        device = device,
+                        permissionRequestManager = permissionRequestManager,
+                        usbManager = usbManager,
+                        disconnectReporter = disconnectReporter
+                    )
+                }
+            }
+
+            return null
+        }
+    }
+
+    override suspend fun connect(): U2FDeviceSession {
+        if (!permissionRequestManager.requestPermission(device)) {
+            throw U2FException.CommunicationException()
+        }
+
+        val connection = usbManager.openDevice(device)
+
+        try {
+            val descriptors = DeviceDescriptor.parse(connection.rawDescriptors)
+
+            for (configuration in descriptors.configurations) {
+                for (usbInterface in configuration.interfaces) {
+                    // same as above
+                    if (
+                        usbInterface.interfaceClass != CLASS_HID ||
+                        usbInterface.interfaceSubclass != 0 ||
+                        usbInterface.interfaceProtocol != 0 ||
+                        usbInterface.endpoints.size != 2 ||
+                        usbInterface.hid == null
+                    ) continue
+
+                    val inputEndpoint = usbInterface.endpoints.find {
+                        it.attributes and ATTRIBUTES_INTERRUPT_MASK == ATTRIBUTES_INTERRUPT &&
+                                it.address and UsbConstants.USB_ENDPOINT_DIR_MASK == UsbConstants.USB_DIR_IN
+                    }
+
+                    val outputEndpoint = usbInterface.endpoints.find {
+                        it.attributes and ATTRIBUTES_INTERRUPT_MASK == ATTRIBUTES_INTERRUPT &&
+                                it.address and UsbConstants.USB_ENDPOINT_DIR_MASK == UsbConstants.USB_DIR_OUT
+                    }
+
+                    if (inputEndpoint == null || outputEndpoint == null) continue
+
+                    val inputEndpointIndex = usbInterface.endpoints.indexOf(inputEndpoint)
+                    val outputEndpointIndex = usbInterface.endpoints.indexOf(outputEndpoint)
+
+                    val hidDescriptorRaw = U2FThread.usb.executeAndWait {
+                        val buffer = ByteArray(usbInterface.hid.reportDescriptorSize)
+
+                        if (!connection.claimInterface(
+                                device.getInterface(usbInterface.index),
+                                true
+                            )
+                        ) {
+                            throw U2FException.CommunicationException()
+                        }
+
+                        val size = connection.controlTransfer(
+                            1 /* interface */ or 0x80 /* data from device to host */,
+                            6, /* GET_DESCRIPTOR */
+                            0x2200, /* first report descriptor (there is always a single one) */
+                            usbInterface.index, /* interface index */
+                            buffer, /* data */
+                            buffer.size, /* length */
+                            100 /* timeout */
+                        )
+
+                        if (size != buffer.size)
+                            throw U2FException.CommunicationException()
+
+                        buffer
+                    }
+
+                    val hidDescriptor = ReportDescriptor.parse(hidDescriptorRaw)
+
+                    if (BuildConfig.DEBUG) {
+                        Log.d(
+                            LOG_TAG,
+                            "found device: $hidDescriptor; isU2F = ${hidDescriptor.isU2F}"
+                        )
+                    }
+
+                    if (!hidDescriptor.isU2F) continue
+
+                    val u2FConnection = UsbU2FDeviceConnection(
+                        inputEndpoint = device.getInterface(usbInterface.index)
+                            .getEndpoint(inputEndpointIndex),
+                        outputEndpoint = device.getInterface(usbInterface.index)
+                            .getEndpoint(outputEndpointIndex),
+                        connection = connection,
+                        disconnectReporter = disconnectReporter
+                    )
+
+                    try {
+                        if (BuildConfig.DEBUG) {
+                            Log.d(LOG_TAG, "created connection")
+                        }
+
+                        u2FConnection.ping(16)
+                        u2FConnection.ping(128)
+
+                        if (BuildConfig.DEBUG) {
+                            Log.d(LOG_TAG, "pings worked")
+                        }
+
+                        return u2FConnection
+                    } catch (ex: Exception) {
+                        u2FConnection.cancelPendingRequests()
+
+                        throw ex
+                    }
+                }
+
+                break // does not support multiple configurations yet
+            }
+
+            throw U2FException.CommunicationException()
+        } catch (ex: UsbException) {
+            throw U2FException.CommunicationException()
+        } catch (ex: Exception) {
+            connection.close()
+
+            throw ex
+        }
+    }
+}

app/src/main/java/io/timelimit/android/u2f/usb/UsbU2FDeviceConnection.kt

@@ -0,0 +1,361 @@
+/*
+ * 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.u2f.usb
+
+import android.hardware.usb.UsbDeviceConnection
+import android.hardware.usb.UsbEndpoint
+import android.hardware.usb.UsbRequest
+import android.os.SystemClock
+import android.util.Log
+import io.timelimit.android.BuildConfig
+import io.timelimit.android.coroutines.executeAndWait
+import io.timelimit.android.crypto.HexString
+import io.timelimit.android.u2f.protocol.U2FDeviceSession
+import io.timelimit.android.u2f.protocol.U2FRequest
+import io.timelimit.android.u2f.protocol.U2fRawResponse
+import io.timelimit.android.u2f.util.U2FException
+import io.timelimit.android.u2f.util.U2FThread
+import java.nio.ByteBuffer
+import java.util.*
+
+class UsbU2FDeviceConnection (
+    private val inputEndpoint: UsbEndpoint,
+    private val outputEndpoint: UsbEndpoint,
+    private val connection: UsbDeviceConnection,
+    private val disconnectReporter: DisconnectReporter
+): U2FDeviceSession {
+    companion object {
+        private const val LOG_TAG = "UsbU2FDeviceConnection"
+        private const val CHANNEL_BROADCAST = -1
+        private const val CMD_PING = 1.toByte()
+        private const val CMD_MSG = 3.toByte()
+        private const val CMD_INIT = 6.toByte()
+        private const val CMD_ERROR = 0x3f.toByte()
+        private const val TIMEOUT = 3000L
+    }
+
+    internal data class ReceiveRequestClientData(val buffer: ByteBuffer)
+
+    private var channelId: Int? = null
+    private val pendingRequests = mutableListOf<UsbRequest>()
+
+    init { for (i in 0..8) enqueueReceivePacketRequest() }
+
+    fun cancelPendingRequests() {
+        synchronized(pendingRequests) {
+            pendingRequests.forEach { it.close() }
+            pendingRequests.clear()
+        }
+    }
+
+    private fun enqueueSendPacket(data: ByteArray) {
+        if (BuildConfig.DEBUG) {
+            Log.d(LOG_TAG, "send packet: ${HexString.toHex(data)}")
+        }
+
+        UsbRequest().also {
+            synchronized(pendingRequests) { pendingRequests.add(it) }
+
+            it.initialize(connection, outputEndpoint)
+            it.queue(ByteBuffer.wrap(data))
+        }
+    }
+
+    private fun enqueueReceivePacketRequest() {
+        UsbRequest().also {
+            synchronized(pendingRequests) { pendingRequests.add(it) }
+
+            val request = ReceiveRequestClientData(ByteBuffer.allocate(inputEndpoint.maxPacketSize))
+
+            it.initialize(connection, inputEndpoint)
+            it.clientData = request
+            it.queue(request.buffer)
+        }
+    }
+
+    private suspend fun receiveResponsePacket(timeout: Long): ByteArray? {
+        val end = SystemClock.uptimeMillis() + timeout
+
+        while (true) {
+            if (BuildConfig.DEBUG) {
+                Log.d(LOG_TAG, "receiveResponsePacket()")
+            }
+
+            if (disconnectReporter.didDisconnect) throw U2FException.DisconnectedException()
+
+            val remaining = end - SystemClock.uptimeMillis(); if (remaining < 0) break
+            val response = U2FThread.usb.executeAndWait { connection.requestWait(remaining) } ?: continue
+
+            synchronized(pendingRequests) { pendingRequests.remove(response) }
+
+            response.clientData.let { request ->
+                if (request is ReceiveRequestClientData) {
+                    enqueueReceivePacketRequest()
+
+                    request.buffer.rewind()
+
+                    return ByteArray(request.buffer.remaining())
+                        .also { request.buffer.get(it) }
+                        .also {
+                            if (BuildConfig.DEBUG) {
+                                Log.d(LOG_TAG, "got response packet: ${HexString.toHex(it)}")
+                            }
+                        }
+                }
+            }
+        }
+
+        return null
+    }
+
+    private fun sendRequest(
+        channelId: Int,
+        command: Byte,
+        payload: ByteArray
+    ) {
+        if (payload.size >= UShort.MAX_VALUE.toInt()) throw U2FException.CommunicationException()
+
+        val messageSize = outputEndpoint.maxPacketSize; if (messageSize < 8) throw IllegalStateException()
+        val maxPayloadSize = messageSize - 7 + 128 * (messageSize - 5)
+
+        if (payload.size > maxPayloadSize) throw U2FException.CommunicationException()
+
+        var payloadOffset = 0
+
+        kotlin.run { // initial package
+            val buffer = ByteArray(messageSize)
+
+            buffer[0] = channelId.ushr(24).toByte()
+            buffer[1] = channelId.ushr(16).toByte()
+            buffer[2] = channelId.ushr(8).toByte()
+            buffer[3] = channelId.toByte()
+
+            buffer[4] = (command.toInt() or 0x80).toByte() // add init flag
+
+            buffer[5] = payload.size.ushr(8).toByte()
+            buffer[6] = payload.size.toByte()
+
+            payloadOffset = (messageSize - 7).coerceAtMost(payload.size)
+
+            payload.copyInto(
+                destination = buffer,
+                destinationOffset = 7,
+                startIndex = 0,
+                endIndex = payloadOffset
+            )
+
+            enqueueSendPacket(buffer)
+        }
+
+        var sequenceCounter = 0; while (payloadOffset < payload.size) {
+            val buffer = ByteArray(messageSize)
+
+            buffer[0] = channelId.ushr(24).toByte()
+            buffer[1] = channelId.ushr(16).toByte()
+            buffer[2] = channelId.ushr(8).toByte()
+            buffer[3] = channelId.toByte()
+
+            if (sequenceCounter < 0 || sequenceCounter > 0x7f) throw IllegalStateException()
+            buffer[4] = sequenceCounter++.toByte()
+
+            val consumedBytes = (messageSize - 5).coerceAtMost(payload.size - payloadOffset)
+
+            payload.copyInto(
+                destination = buffer,
+                destinationOffset = 5,
+                startIndex = payloadOffset,
+                endIndex = payloadOffset + consumedBytes
+            )
+
+            payloadOffset += consumedBytes
+
+            enqueueSendPacket(buffer)
+        }
+    }
+
+    internal data class Response(val channelId: Int, val command: Byte, val payload: ByteArray)
+
+    private suspend fun receiveResponse(timeout: Long): Response? {
+        val end = SystemClock.uptimeMillis() + timeout
+
+        val remaining1 = end - SystemClock.uptimeMillis(); if (remaining1 < 0) return null
+        val response = receiveResponsePacket(remaining1) ?: return null
+
+        if (response.size < 8) throw U2FException.CommunicationException()
+
+        val maxPayloadSize = response.size - 7 + 128 * (response.size - 5)
+
+        val channelId =
+            (response[3].toUByte().toUInt() or
+                    response[2].toUByte().toUInt().shl(8) or
+                    response[1].toUByte().toUInt().shl(16) or
+                    response[0].toUByte().toUInt().shl(24)
+                    ).toInt()
+
+        val command = response[4].toUByte().toInt()
+        val payloadSize = response[6].toUByte().toInt() or response[5].toUByte().toInt().shl(8)
+
+        if (command and 0x80 != 0x80) return null // not at the start of a reponse
+        if (payloadSize > maxPayloadSize) throw U2FException.CommunicationException()
+
+        val payload = ByteArray(payloadSize)
+        var payloadOffset = (response.size - 7).coerceAtMost(payloadSize)
+
+        response.copyInto(
+            destination = payload,
+            destinationOffset = 0,
+            startIndex = 7,
+            endIndex = response.size.coerceAtMost(payloadSize + 7)
+        )
+
+        var sequenceCounter = 0; while (payloadOffset < payload.size) {
+            val remaining2 = end - SystemClock.uptimeMillis(); if (remaining2 < 0) return null
+            val response2 = receiveResponsePacket(remaining2) ?: return null
+
+            if (response2.size != response.size) throw U2FException.CommunicationException()
+
+            val channelId2 =
+                (response2[3].toUByte().toUInt() or
+                        response2[2].toUByte().toUInt().shl(8) or
+                        response2[1].toUByte().toUInt().shl(16) or
+                        response2[0].toUByte().toUInt().shl(24)
+                        ).toInt()
+
+            val command2 = response2[4].toUByte().toInt()
+
+            if (sequenceCounter < 0 || sequenceCounter > 0x7f) throw IllegalStateException()
+            val decodedSequenceCounterr = response2[4].toUByte().toInt()
+
+            if (channelId != channelId2) continue
+            if (command2 and 0x80 == 0x80) return null // not at a continuation
+            if (sequenceCounter++ != decodedSequenceCounterr) return null // broken sequence
+
+            val consumedBytes = (response.size - 5).coerceAtMost(payloadSize - payloadOffset)
+
+            response2.copyInto(
+                destination = payload,
+                destinationOffset = payloadOffset,
+                startIndex = 5,
+                endIndex = response.size.coerceAtMost(consumedBytes + 5)
+            )
+
+            payloadOffset += consumedBytes
+        }
+
+        return Response(
+            channelId = channelId,
+            command = (command xor 0x80).toByte(),
+            payload = payload
+        ).also {
+            if (BuildConfig.DEBUG) {
+                Log.d(LOG_TAG, "got response: $it")
+            }
+        }
+    }
+
+    private suspend fun sendRequestAndGetResponse(
+        channelId: Int,
+        command: Byte,
+        payload: ByteArray,
+        timeout: Long
+    ): Response? {
+        val end = SystemClock.uptimeMillis() + timeout
+
+        sendRequest(channelId = channelId, command = command, payload = payload)
+
+        while (true) {
+            val remaining = end - SystemClock.uptimeMillis(); if (remaining < 0) return null
+            val response = receiveResponse(remaining) ?: continue
+            if (response.channelId != channelId) continue
+
+            return response
+        }
+    }
+
+    private suspend fun allocateChannelId(): Int {
+        val end = SystemClock.uptimeMillis() + TIMEOUT
+        val nonce = ByteArray(8).also { Random().nextBytes(it) }
+
+        sendRequest(
+            channelId = CHANNEL_BROADCAST,
+            command = CMD_INIT,
+            payload = nonce
+        )
+
+        while (true) {
+            val remaining = end - SystemClock.uptimeMillis(); if (remaining < 0) throw U2FException.CommunicationException()
+            val response = receiveResponse(remaining) ?: continue
+
+            if (response.channelId != CHANNEL_BROADCAST) continue
+            if (response.command != CMD_INIT) continue
+            if (response.payload.size < 17) continue
+            if (!response.payload.sliceArray(0 until 8).contentEquals(nonce)) continue
+
+            val channelId =
+                (response.payload[11].toUByte().toUInt() or
+                        response.payload[10].toUByte().toUInt().shl(8) or
+                        response.payload[9].toUByte().toUInt().shl(16) or
+                        response.payload[8].toUByte().toUInt().shl(24)
+                        ).toInt()
+
+            if (channelId == CHANNEL_BROADCAST) throw U2FException.CommunicationException()
+
+            return channelId
+        }
+    }
+
+    private suspend fun getOwnChannelId(): Int {
+        channelId?.let { return it }
+
+        allocateChannelId().let { channelId = it; return it }
+    }
+
+    suspend fun ping(payload: ByteArray) {
+        val response = sendRequestAndGetResponse(
+            channelId = getOwnChannelId(),
+            command = CMD_PING,
+            payload = payload,
+            timeout = TIMEOUT
+        ) ?: throw U2FException.CommunicationException()
+
+        if (response.command != CMD_PING) throw U2FException.CommunicationException()
+        if (!response.payload.contentEquals(payload)) throw U2FException.CommunicationException()
+    }
+
+    suspend fun ping(length: Int) = ByteArray(length).also {
+        Random().nextBytes(it)
+
+        ping(it)
+    }
+
+    override suspend fun execute(request: U2FRequest): U2fRawResponse {
+        val response = sendRequestAndGetResponse(
+            channelId = getOwnChannelId(),
+            command = CMD_MSG,
+            payload = request.encodeExtended(),
+            timeout = TIMEOUT
+        ) ?: throw U2FException.CommunicationException()
+
+        if (response.command != CMD_MSG) throw U2FException.CommunicationException()
+
+        return U2fRawResponse.decode(response.payload).also { it.throwIfNoSuccess() }
+    }
+
+    override fun close() {
+        cancelPendingRequests()
+        connection.close()
+    }
+}

app/src/main/java/io/timelimit/android/u2f/usb/UsbU2FManager.kt

@@ -0,0 +1,117 @@
+/*
+ * 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.u2f.usb
+
+import android.app.PendingIntent
+import android.content.BroadcastReceiver
+import android.content.Context
+import android.content.Intent
+import android.content.IntentFilter
+import android.hardware.usb.UsbDevice
+import android.hardware.usb.UsbManager
+import android.util.Log
+import androidx.core.content.getSystemService
+import io.timelimit.android.BuildConfig
+import io.timelimit.android.integration.platform.android.PendingIntentIds
+import io.timelimit.android.u2f.U2fManager
+import io.timelimit.android.u2f.util.U2FId
+
+class UsbU2FManager (val parent: U2fManager, context: Context) {
+    companion object {
+        private const val LOG_TAG = "UsbU2FManager"
+    }
+
+    private val usbManager = context.getSystemService<UsbManager>()
+    private val disconnectReporters = mutableMapOf<String, DisconnectReporter>()
+
+    private val usbConnectionListener = object: BroadcastReceiver() {
+        override fun onReceive(context: Context, intent: Intent) {
+            try {
+                if (intent.action == UsbManager.ACTION_USB_DEVICE_ATTACHED) handleAddedDevice(intent.usbDevice)
+                else if (intent.action == UsbManager.ACTION_USB_DEVICE_DETACHED) handleRemovedDevice(intent.usbDevice)
+            } catch (ex: Exception) {
+                if (BuildConfig.DEBUG) {
+                    Log.w(LOG_TAG, "error handling new/removed device", ex)
+                }
+            }
+        }
+    }
+
+    private val permissionResponseAction = U2FId.generate()
+
+    private val permissionResponseListener = object: BroadcastReceiver() {
+        override fun onReceive(context: Context, intent: Intent) {
+            try {
+                if (intent.action == permissionResponseAction) {
+                    val device = intent.usbDevice
+                    val granted = intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false)
+
+                    if (BuildConfig.DEBUG) {
+                        Log.d(LOG_TAG, "got permission $granted for $device")
+                    }
+
+                    permissionRequestManager.reportResult(device, granted)
+                }
+            } catch (ex: Exception) {
+                if (BuildConfig.DEBUG) {
+                    Log.w(LOG_TAG, "error handling permission response", ex)
+                }
+            }
+        }
+    }
+
+    private val permissionResponseIntent = PendingIntent.getBroadcast(
+        context,
+        PendingIntentIds.U2F_USB_RESPONSE,
+        Intent(permissionResponseAction),
+        PendingIntent.FLAG_MUTABLE
+    )
+
+    private val permissionRequestManager = UsbPermissionRequestManager(sendRequest = {
+        usbManager?.requestPermission(it, permissionResponseIntent)
+    })
+
+    init {
+        context.registerReceiver(usbConnectionListener, IntentFilter(UsbManager.ACTION_USB_DEVICE_ATTACHED))
+        context.registerReceiver(usbConnectionListener, IntentFilter(UsbManager.ACTION_USB_DEVICE_DETACHED))
+        context.registerReceiver(permissionResponseListener, IntentFilter(permissionResponseAction))
+    }
+
+    private fun handleAddedDevice(device: UsbDevice) {
+        if (BuildConfig.DEBUG) {
+            Log.d(LOG_TAG, "new device $device")
+        }
+
+        val disconnectReporter = DisconnectReporter().also { disconnectReporters[device.deviceName] = it }
+
+        val u2FDevice = UsbU2FDevice.from(device, permissionRequestManager, usbManager!!, disconnectReporter)
+
+        if (BuildConfig.DEBUG) {
+            Log.d(LOG_TAG, "found u2f device $u2FDevice")
+        }
+
+        u2FDevice?.also { parent.dispatchDeviceFound(it) }
+    }
+
+    private fun handleRemovedDevice(device: UsbDevice) {
+        if (BuildConfig.DEBUG) {
+            Log.d(LOG_TAG, "disconnected $device")
+        }
+
+        disconnectReporters.remove(device.deviceName)?.reportDisconnect()
+        permissionRequestManager.reportResult(device, false)
+    }
+}

app/src/main/java/io/timelimit/android/u2f/usb/descriptors/ConfigurationDescriptor.kt

@@ -0,0 +1,68 @@
+/*
+ * 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.u2f.usb.descriptors
+
+import io.timelimit.android.u2f.usb.UsbException
+
+data class ConfigurationDescriptor(val interfaces: List<InterfaceDescriptor>) {
+    companion object {
+        const val DESCRIPTOR_TYPE = 2.toByte()
+
+        fun parse(input: ByteArray): Pair<ConfigurationDescriptor, ByteArray> {
+            val descriptorLength = input[0].toUByte().toInt()
+
+            if (descriptorLength < 9 || input.size < descriptorLength)
+                throw UsbException.InvalidDescriptorLengthException()
+
+            if (input[1] != DESCRIPTOR_TYPE)
+                throw UsbException.InvalidDescriptorTypeException()
+
+            val totalLength = input[2].toUByte().toInt() or input[3].toUByte().toInt().shl(8)
+
+            if (input.size < totalLength)
+                throw UsbException.InvalidDescriptorLengthException()
+
+            val numInterfaces = input[4].toInt()
+            val interfaces = mutableListOf<InterfaceDescriptor>()
+
+            var remaining = input.sliceArray(descriptorLength until totalLength)
+
+            while (remaining.isNotEmpty()) {
+                if (remaining.size < 2)
+                    throw UsbException.InvalidDescriptorLengthException()
+
+                val type = remaining[1]
+
+                if (type == InterfaceDescriptor.DESCRIPTOR_TYPE) {
+                    val (newDescriptor, newRemaining) = InterfaceDescriptor.parse(remaining)
+
+                    if (newDescriptor.index != interfaces.size)
+                        throw UsbException.InvalidIndexException()
+
+                    remaining = newRemaining
+                    interfaces.add(newDescriptor)
+                } else remaining = UnknownDescriptor.parse(remaining)
+            }
+
+            if (numInterfaces != interfaces.size)
+                throw UsbException.WrongCounterException("interfaces", numInterfaces, interfaces.size)
+
+            return ConfigurationDescriptor(
+                interfaces = interfaces
+            ) to input.sliceArray(totalLength until input.size)
+        }
+    }
+}

app/src/main/java/io/timelimit/android/u2f/usb/descriptors/DeviceDescriptor.kt

@@ -0,0 +1,56 @@
+/*
+ * 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.u2f.usb.descriptors
+
+import io.timelimit.android.u2f.usb.UsbException
+
+data class DeviceDescriptor(val configurations: List<ConfigurationDescriptor>) {
+    companion object {
+        private const val DESCRIPTOR_TYPE = 1.toByte()
+
+        fun parse(input: ByteArray): DeviceDescriptor {
+            val descriptorLength = input[0].toUByte().toInt()
+
+            if (descriptorLength < 17 || input.size < descriptorLength)
+                throw UsbException.InvalidDescriptorLengthException()
+
+            if (input[1] != DESCRIPTOR_TYPE)
+                throw UsbException.InvalidDescriptorTypeException()
+
+            val numConfigurations = input[17].toUByte().toInt()
+            val configurations = mutableListOf<ConfigurationDescriptor>()
+
+            var remaining = input.sliceArray(descriptorLength until input.size)
+
+            while (remaining.isNotEmpty()) {
+                if (remaining.size < 2)
+                    throw UsbException.InvalidDescriptorLengthException()
+
+                if (remaining[1] == ConfigurationDescriptor.DESCRIPTOR_TYPE) {
+                    val (newDescriptor, newRemaining) = ConfigurationDescriptor.parse(remaining)
+
+                    remaining = newRemaining
+                    configurations.add(newDescriptor)
+                } else remaining = UnknownDescriptor.parse(remaining)
+            }
+
+            if (numConfigurations != configurations.size)
+                throw UsbException.WrongCounterException("configuration", numConfigurations, configurations.size)
+
+            return DeviceDescriptor(configurations = configurations)
+        }
+    }
+}

app/src/main/java/io/timelimit/android/u2f/usb/descriptors/EndpointDescriptor.kt

@@ -0,0 +1,44 @@
+/*
+ * 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.u2f.usb.descriptors
+
+import io.timelimit.android.u2f.usb.UsbException
+
+data class EndpointDescriptor(val address: Int, val attributes: Int, val maxPacketSize: Int) {
+    companion object {
+        const val DESCRIPTOR_TYPE = 5.toByte()
+
+        fun parse(input: ByteArray): Pair<EndpointDescriptor, ByteArray> {
+            val descriptorLength = input[0].toUByte().toInt()
+
+            if (descriptorLength < 7 || input.size < descriptorLength)
+                throw UsbException.InvalidDescriptorLengthException()
+
+            if (input[1] != DESCRIPTOR_TYPE)
+                throw UsbException.InvalidDescriptorTypeException()
+
+            val address = input[2].toUByte().toInt()
+            val attributes = input[3].toUByte().toInt()
+            val maxPacketSize = input[4].toUByte().toInt() or input[5].toUByte().toInt().shl(8)
+
+            return EndpointDescriptor(
+                address = address,
+                attributes = attributes,
+                maxPacketSize = maxPacketSize
+            ) to input.sliceArray(descriptorLength until input.size)
+        }
+    }
+}

app/src/main/java/io/timelimit/android/u2f/usb/descriptors/HidDescriptor.kt

@@ -0,0 +1,40 @@
+/*
+ * 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.u2f.usb.descriptors
+
+import io.timelimit.android.u2f.usb.UsbException
+
+data class HidDescriptor(val reportDescriptorSize: Int) {
+    companion object {
+        const val DESCRIPTOR_TYPE = 33.toByte()
+
+        fun parse(input: ByteArray): Pair<HidDescriptor, ByteArray> {
+            val descriptorLength = input[0].toUByte().toInt()
+
+            if (descriptorLength < 9 || input.size < descriptorLength)
+                throw UsbException.InvalidDescriptorLengthException()
+
+            if (input[1] != DESCRIPTOR_TYPE)
+                throw UsbException.InvalidDescriptorTypeException()
+
+            val reportDescriptorSize = input[7].toUByte().toInt() or input[8].toUByte().toInt().shl(8)
+
+            return HidDescriptor(
+                reportDescriptorSize = reportDescriptorSize
+            ) to input.sliceArray(descriptorLength until input.size)
+        }
+    }
+}

app/src/main/java/io/timelimit/android/u2f/usb/descriptors/InterfaceDescriptor.kt

@@ -0,0 +1,84 @@
+/*
+ * 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.u2f.usb.descriptors
+
+import io.timelimit.android.u2f.usb.UsbException
+
+data class InterfaceDescriptor(
+    val index: Int,
+    val interfaceClass: Int,
+    val interfaceSubclass: Int,
+    val interfaceProtocol: Int,
+    val hid: HidDescriptor?,
+    val endpoints: List<EndpointDescriptor>
+) {
+    companion object {
+        const val DESCRIPTOR_TYPE = 4.toByte()
+
+        fun parse(input: ByteArray): Pair<InterfaceDescriptor, ByteArray> {
+            val descriptorLength = input[0].toUByte().toInt()
+
+            if (descriptorLength < 9 || input.size < descriptorLength)
+                throw UsbException.InvalidDescriptorLengthException()
+
+            if (input[1] != DESCRIPTOR_TYPE)
+                throw UsbException.InvalidDescriptorTypeException()
+
+            val index = input[2].toUByte().toInt()
+            val numEndpoints = input[4].toUByte().toInt()
+            val interfaceClass = input[5].toUByte().toInt()
+            val interfaceSubclass = input[6].toUByte().toInt()
+            val interfaceProtocol = input[7].toUByte().toInt()
+
+            var hid: HidDescriptor? = null
+            val endpoints = mutableListOf<EndpointDescriptor>()
+
+            var remaining = input.sliceArray(descriptorLength until input.size)
+
+            while (remaining.isNotEmpty()) {
+                if (remaining.size < 2)
+                    throw UsbException.InvalidDescriptorLengthException()
+
+                val type = remaining[1]
+
+                if (type == DESCRIPTOR_TYPE) break
+                else if (type == EndpointDescriptor.DESCRIPTOR_TYPE) {
+                    val (newDescriptor, newRemaining) = EndpointDescriptor.parse(remaining)
+
+                    remaining = newRemaining
+                    endpoints.add(newDescriptor)
+                } else if (type == HidDescriptor.DESCRIPTOR_TYPE) {
+                    val (newDescriptor, newRemaining) = HidDescriptor.parse(remaining)
+
+                    remaining = newRemaining
+                    hid = newDescriptor
+                } else remaining = UnknownDescriptor.parse(remaining)
+            }
+
+            if (numEndpoints != endpoints.size)
+                throw UsbException.WrongCounterException("endpoints", numEndpoints, endpoints.size)
+
+            return InterfaceDescriptor(
+                index = index,
+                interfaceClass = interfaceClass,
+                interfaceSubclass = interfaceSubclass,
+                interfaceProtocol = interfaceProtocol,
+                hid = hid,
+                endpoints = endpoints
+            ) to remaining
+        }
+    }
+}

app/src/main/java/io/timelimit/android/u2f/usb/descriptors/ReportDescriptor.kt

@@ -0,0 +1,127 @@
+/*
+ * 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.u2f.usb.descriptors
+
+import io.timelimit.android.u2f.usb.UsbException
+
+data class ReportDescriptor (val items: List<Item>) {
+    companion object {
+        fun parse(input: ByteArray) = ReportDescriptor(Item.parseList(input))
+
+        data class Item(
+            val tag: Int,
+            val type: Int,
+            val data: ByteArray
+        ) {
+            companion object {
+                object Type {
+                    const val MAIN = 0
+                    const val GLOBAL = 1
+                    const val LOCAL = 2
+                }
+
+                val usagePageFido = Item(tag = 0, type = Type.GLOBAL, data = byteArrayOf(0xd0.toByte(), 0xf1.toByte()))
+                val usageU2F = Item(tag = 0, type = Type.LOCAL, data = byteArrayOf(1))
+
+                fun parse(input: ByteArray): Pair<Item, ByteArray> {
+                    if (input.isEmpty())
+                        throw UsbException.InvalidDescriptorLengthException()
+
+                    val baseTag = input[0].toUByte().toInt().ushr(4)
+                    val tag: Int
+                    val type = input[0].toUByte().toInt().ushr(2) and 3
+                    val dataLength: Int
+                    val dataOffset: Int
+
+                    if (baseTag == 15) {
+                        // long item
+
+                        if (input.size < 3)
+                            throw UsbException.InvalidDescriptorLengthException()
+
+                        tag = input[2].toUByte().toInt()
+                        dataLength = input[1].toUByte().toInt()
+                        dataOffset = 3
+                    } else {
+                        // regular item
+                        tag = baseTag
+                        dataLength = when (input[0].toUByte().toInt() and 3) {
+                            0 -> 0
+                            1 -> 1
+                            2 -> 2
+                            3 -> 4
+                            else -> throw IllegalStateException()
+                        }
+                        dataOffset = 1
+                    }
+
+                    if (input.size < dataOffset + dataLength)
+                        throw UsbException.InvalidDescriptorLengthException()
+
+                    val data = input.sliceArray(dataOffset until dataOffset + dataLength)
+
+                    return Item(
+                        tag = tag,
+                        type = type,
+                        data = data
+                    ) to input.sliceArray(dataOffset + dataLength until input.size)
+                }
+
+                fun parseList(input: ByteArray): List<Item> {
+                    val result = mutableListOf<Item>()
+
+                    var remaining = input
+
+                    while (!remaining.isEmpty()) {
+                        val (newItem, newRemaining) = parse(remaining)
+
+                        remaining = newRemaining
+                        result.add(newItem)
+                    }
+
+                    return result
+                }
+            }
+
+            override fun equals(other: Any?): Boolean {
+                if (this === other) return true
+                if (javaClass != other?.javaClass) return false
+
+                other as Item
+
+                if (tag != other.tag) return false
+                if (type != other.type) return false
+                if (!data.contentEquals(other.data)) return false
+
+                return true
+            }
+
+            override fun hashCode(): Int {
+                var result = tag
+                result = 31 * result + type
+                result = 31 * result + data.contentHashCode()
+                return result
+            }
+        }
+    }
+
+    val isU2F = kotlin.run {
+        val index1 = items.indexOf(Item.usagePageFido)
+        val index2 = items.indexOf(Item.usageU2F)
+
+        -1 < index1 && index1 < index2
+    }
+}

app/src/main/java/io/timelimit/android/u2f/usb/descriptors/UnknownDescriptor.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.u2f.usb.descriptors
+
+import io.timelimit.android.u2f.usb.UsbException
+
+object UnknownDescriptor {
+    fun parse(raw: ByteArray): ByteArray {
+        val descriptorLength = raw[0].toUByte().toInt()
+
+        if (raw.size < descriptorLength)
+            throw UsbException.InvalidDescriptorLengthException()
+
+        return raw.sliceArray(descriptorLength until raw.size)
+    }
+}

app/src/main/java/io/timelimit/android/u2f/util/U2FException.kt

@@ -15,11 +15,12 @@
  */
 package io.timelimit.android.u2f.util
 
-sealed class U2FException: RuntimeException() {
-    class CommunicationException: U2FException()
-    class DisconnectedException: U2FException()
-    class InvalidDataException: U2FException()
-    class DeviceException: U2FException()
-    class BadKeyHandleException: U2FException()
-    class UserInteractionRequired: U2FException()
+sealed class U2FException(message: String): RuntimeException(message) {
+    class CommunicationException: U2FException("communication error")
+    class DisconnectedException: U2FException("disconnected error")
+    class InvalidDataException: U2FException("invalid data")
+    class DeviceException(status: UShort): U2FException("device reported error $status")
+    class BadKeyHandleException: U2FException("bad key handle")
+    class UserInteractionRequired: U2FException("user interaction required")
+    class BadRequestLength: U2FException("wrong request length")
 }

app/src/main/java/io/timelimit/android/u2f/util/U2FId.kt

@@ -0,0 +1,25 @@
+/*
+ * 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.u2f.util
+
+import io.timelimit.android.crypto.HexString
+import java.security.SecureRandom
+
+object U2FId {
+    private val random = SecureRandom()
+
+    fun generate() = ByteArray(32).also { random.nextBytes(it) }.let { HexString.toHex(it) }
+}

app/src/main/java/io/timelimit/android/u2f/util/U2FThread.kt

@@ -19,5 +19,6 @@ import java.util.concurrent.Executors
 
 object U2FThread {
     val nfc by lazy { Executors.newFixedThreadPool(2) }
+    val usb by lazy { Executors.newFixedThreadPool(2) }
     val crypto by lazy { Executors.newSingleThreadExecutor() }
 }

app/src/main/java/io/timelimit/android/ui/login/AuthTokenLoginProcessor.kt

@@ -45,98 +45,99 @@ object AuthTokenLoginProcessor {
 
         runAsync {
             try {
-                val session = device.connect()
-                val keys = Threads.database.executeAndWait { model.logic.database.u2f().getAllSync() }
-                val random = SecureRandom()
-                val applicationId = U2FApplicationId.fromUrl(U2FApplicationId.URL)
-
-                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(
-                                mode = U2FRequest.Login.Mode.DoNotEnforcePresence,
-                                challenge = challenge,
-                                applicationId = applicationId,
-                                keyHandle = key.keyHandle
-                            )
-                        )
+                device.connect().use { session ->
+                    val keys = Threads.database.executeAndWait { model.logic.database.u2f().getAllSync() }
+                    val random = SecureRandom()
+                    val applicationId = U2FApplicationId.fromUrl(U2FApplicationId.URL)
 
+                    for (key in keys) {
                         if (BuildConfig.DEBUG) {
-                            Log.d(LOG_TAG, "got response $response")
+                            Log.d(LOG_TAG, "try key $key")
                         }
 
-                        val signatureValid = U2FThread.crypto.executeAndWait {
-                            U2FSignatureValidation.validate(
-                                applicationId = applicationId,
-                                challenge = challenge,
-                                response = response,
-                                publicKey = key.publicKey
+                        val challenge = ByteArray(32).also { random.nextBytes(it) }
+
+                        try {
+                            val response = session.login(
+                                U2FRequest.Login(
+                                    mode = U2FRequest.Login.Mode.DoNotEnforcePresence,
+                                    challenge = challenge,
+                                    applicationId = applicationId,
+                                    keyHandle = key.keyHandle
+                                )
                             )
-                        }
 
-                        if (!signatureValid) {
-                            toast(R.string.u2f_login_error_invalid)
+                            if (BuildConfig.DEBUG) {
+                                Log.d(LOG_TAG, "got response $response")
+                            }
 
-                            break
-                        }
+                            val signatureValid = U2FThread.crypto.executeAndWait {
+                                U2FSignatureValidation.validate(
+                                    applicationId = applicationId,
+                                    challenge = challenge,
+                                    response = response,
+                                    publicKey = key.publicKey
+                                )
+                            }
 
-                        val userEntry = Threads.database.executeAndWait {
-                            if (
-                                model.logic.database.u2f().updateCounter(
-                                    parentUserId = key.userId,
-                                    keyHandle = key.keyHandle,
-                                    publicKey = key.publicKey,
-                                    counter = response.counter.toLong()
-                                ) > 0
-                            ) {
-                                model.logic.database.user().getUserByIdSync(key.userId)!!
-                            } else null
-                        }
+                            if (!signatureValid) {
+                                toast(R.string.u2f_login_error_invalid)
 
-                        if (userEntry == null) {
-                            toast(R.string.u2f_login_error_invalid)
+                                break
+                            }
 
-                            break
-                        }
+                            val userEntry = Threads.database.executeAndWait {
+                                if (
+                                    model.logic.database.u2f().updateCounter(
+                                        parentUserId = key.userId,
+                                        keyHandle = key.keyHandle,
+                                        publicKey = key.publicKey,
+                                        counter = response.counter.toLong()
+                                    ) > 0
+                                ) {
+                                    model.logic.database.user().getUserByIdSync(key.userId)!!
+                                } else null
+                            }
 
-                        val allowLoginStatus = Threads.database.executeAndWait {
-                            AllowUserLoginStatusUtil.calculateSync(
-                                logic = model.logic,
-                                userId = userEntry.id,
-                                didSync = false
+                            if (userEntry == null) {
+                                toast(R.string.u2f_login_error_invalid)
+
+                                break
+                            }
+
+                            val allowLoginStatus = Threads.database.executeAndWait {
+                                AllowUserLoginStatusUtil.calculateSync(
+                                    logic = model.logic,
+                                    userId = userEntry.id,
+                                    didSync = false
+                                )
+                            }
+
+                            val shouldSignIn = allowLoginStatus is AllowUserLoginStatus.Allow
+
+                            if (!shouldSignIn) {
+                                toast(LoginDialogFragmentModel.formatAllowLoginStatusError(allowLoginStatus, model.getApplication()))
+
+                                return@runAsync
+                            }
+
+                            model.setAuthenticatedUser(
+                                AuthenticatedUser(
+                                    userId = key.userId,
+                                    authenticatedBy = AuthenticationMethod.KeyCode,
+                                    firstPasswordHash = userEntry.password,
+                                    secondPasswordHash = "u2f"
+                                )
                             )
+
+                            return@runAsync // no need to try more
+                        } catch (ex: U2FException.BadKeyHandleException) {
+                            // ignore and try the next one
                         }
-
-                        val shouldSignIn = allowLoginStatus is AllowUserLoginStatus.Allow
-
-                        if (!shouldSignIn) {
-                            toast(LoginDialogFragmentModel.formatAllowLoginStatusError(allowLoginStatus, model.getApplication()))
-
-                            return@runAsync
-                        }
-
-                        model.setAuthenticatedUser(
-                            AuthenticatedUser(
-                                userId = key.userId,
-                                authenticatedBy = AuthenticationMethod.KeyCode,
-                                firstPasswordHash = userEntry.password,
-                                secondPasswordHash = "u2f"
-                            )
-                        )
-
-                        return@runAsync // no need to try more
-                    } catch (ex: U2FException.BadKeyHandleException) {
-                        // ignore and try the next one
                     }
-                }
 
-                toast(R.string.u2f_login_error_unknown)
+                    toast(R.string.u2f_login_error_unknown)
+                }
             } catch (ex: U2FException.DisconnectedException) {
                 if (BuildConfig.DEBUG) {
                     Log.d(LOG_TAG, "disconnected", ex)

app/src/main/java/io/timelimit/android/ui/manage/parent/u2fkey/Adapter.kt

@@ -35,6 +35,8 @@ class Adapter() : RecyclerView.Adapter<Adapter.Holder>() {
     var items: List<U2FKeyListItem> by Delegates.observable(emptyList()) { _, _, _ -> notifyDataSetChanged() }
     var listener: Handlers? = null
 
+    init { setHasStableIds(true) }
+
     override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): Holder = when (viewType) {
         TYPE_ADD -> Holder.Add(AddItemViewBinding.inflate(LayoutInflater.from(parent.context), parent, false)).also {
             it.binding.label = parent.context.getString(R.string.manage_parent_u2f_add_key)

app/src/main/java/io/timelimit/android/ui/manage/parent/u2fkey/add/AddU2FDialogFragment.kt

@@ -71,6 +71,7 @@ class AddU2FDialogFragment: BottomSheetDialogFragment() {
                     AddU2FModel.Status.ConnectionInterrupted -> getString(R.string.manage_parent_u2f_status_interrupted)
                     AddU2FModel.Status.RequestFailed -> getString(R.string.manage_parent_u2f_status_failed)
                     AddU2FModel.Status.AlreadyLinked -> getString(R.string.manage_parent_u2f_status_already_linked)
+                    AddU2FModel.Status.NeedsUserInteraction -> getString(R.string.manage_parent_u2f_status_needs_user_interaction)
                     is AddU2FModel.Status.Done -> {
                         if (!status.commited) {
                             activityModel.tryDispatchParentAction(status.action)

app/src/main/java/io/timelimit/android/ui/manage/parent/u2fkey/add/AddU2FModel.kt

@@ -33,6 +33,7 @@ import io.timelimit.android.u2f.protocol.U2FRequest
 import io.timelimit.android.u2f.protocol.login
 import io.timelimit.android.u2f.protocol.register
 import io.timelimit.android.u2f.util.U2FException
+import kotlinx.coroutines.delay
 import java.security.SecureRandom
 
 class AddU2FModel(application: Application): AndroidViewModel(application), U2fManager.DeviceFoundListener {
@@ -59,36 +60,56 @@ class AddU2FModel(application: Application): AndroidViewModel(application), U2fM
             try {
                 val applicationId = U2FApplicationId.fromUrl(U2FApplicationId.URL)
 
-                val session = device.connect()
+                device.connect().use { session ->
+                    val currentKeys = Threads.database.executeAndWait {logic.database.u2f().getAllSync() }
 
-                val currentKeys = Threads.database.executeAndWait { logic.database.u2f().getAllSync() }
-
-                for (key in currentKeys) {
-                    try {
-                        session.login(
-                            U2FRequest.Login(
-                                mode = U2FRequest.Login.Mode.CheckOnly,
-                                challenge = ByteArray(32).also { SecureRandom().nextBytes(it) },
-                                applicationId = applicationId,
-                                keyHandle = key.keyHandle
+                    for (key in currentKeys) {
+                        try {
+                            session.login(
+                                U2FRequest.Login(
+                                    mode = U2FRequest.Login.Mode.CheckOnly,
+                                    challenge = ByteArray(32).also { SecureRandom().nextBytes(it) },
+                                    applicationId = applicationId,
+                                    keyHandle = key.keyHandle
+                                )
                             )
-                        )
-                    } catch (ex: U2FException.BadKeyHandleException) {
-                        continue
-                    } catch (ex: U2FException.UserInteractionRequired) {
-                        statusInternal.value = Status.AlreadyLinked
+                        } catch (ex: U2FException.BadKeyHandleException) {
+                            continue
+                        } catch (ex: U2FException.UserInteractionRequired) {
+                            statusInternal.value = Status.AlreadyLinked
 
-                        return@runAsync
+                            return@runAsync
+                        }
+                    }
+
+                    val challenge = ByteArray(32).also { SecureRandom().nextBytes(it) }
+
+                    while (true) {
+                        try {
+                            val registerResponse = session.register(
+                                U2FRequest.Register(
+                                    challenge = challenge,
+                                    applicationId = applicationId
+                                )
+                            )
+
+                            statusInternal.value = Status.Done(
+                                AddParentU2FKey(
+                                    keyHandle = registerResponse.keyHandle,
+                                    publicKey = registerResponse.publicKey
+                                )
+                            )
+
+                            break
+                        } catch (ex: U2FException.UserInteractionRequired) {
+                            if (statusInternal.value != Status.NeedsUserInteraction) {
+                                statusInternal.value = Status.NeedsUserInteraction
+                            }
+
+                            delay(50)
+                        }
                     }
                 }
-
-                val challenge = ByteArray(32).also { SecureRandom().nextBytes(it) }
-
-                val registerResponse = session.register(U2FRequest.Register(challenge = challenge, applicationId = applicationId))
-
-                statusInternal.value = Status.Done(
-                    AddParentU2FKey(keyHandle = registerResponse.keyHandle, publicKey = registerResponse.publicKey)
-                )
             } catch (ex: U2FException.DisconnectedException) {
                 if (BuildConfig.DEBUG) {
                     Log.d(LOG_TAG, "connection interrupted", ex)
@@ -111,6 +132,7 @@ class AddU2FModel(application: Application): AndroidViewModel(application), U2fM
         object ConnectionInterrupted: Status()
         object RequestFailed: Status()
         object AlreadyLinked: Status()
+        object NeedsUserInteraction: Status()
         data class Done(val action: AddParentU2FKey, var commited: Boolean = false): Status()
     }
 }

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

@@ -1027,7 +1027,7 @@
     <string name="manage_parent_change_password_toast_wrong_password">Das alte Passwort ist falsch</string>
 
     <string name="manage_parent_u2f_title">U2F-Schlüssel</string>
-    <string name="manage_parent_u2f_description">NFC U2F-Tokens zum Authentifizieren einrichten</string>
+    <string name="manage_parent_u2f_description">U2F-Tokens (über USB oder NFC) zum Authentifizieren einrichten</string>
 
     <string name="manage_parent_restore_password_text_require_mail">
         Dies ermöglicht es, ein neues Passwort festzulegen, ohne das alte Passwort zu kennen.
@@ -1657,7 +1657,7 @@
     <string name="notify_permission_rejected_toast">abgelehnt; möglicherweise können Sie dies nur noch über die Systemeinstellungen erlauben</string>
 
     <string name="manage_parent_u2f_add_key">Token hinzufügen</string>
-    <string name="manage_parent_u2f_status_wait_key">Warte auf einen Schlüssel; NFC %s</string>
+    <string name="manage_parent_u2f_status_wait_key">Warte auf einen Schlüssel; Verbinden Sie jetzt den Schlüssel; NFC %s</string>
     <string name="manage_parent_u2f_status_wait_key_nfc_enabled">ist aktiviert</string>
     <string name="manage_parent_u2f_status_wait_key_nfc_disabled">ist deaktiviert</string>
     <string name="manage_parent_u2f_status_wait_key_nfc_unsupported">wird von Ihrem Gerät nicht unterstützt</string>
@@ -1665,6 +1665,7 @@
     <string name="manage_parent_u2f_status_interrupted">Verbindung unterbrochen</string>
     <string name="manage_parent_u2f_status_failed">Anfrage fehlgeschlagen</string>
     <string name="manage_parent_u2f_status_already_linked">Dieses Gerät ist bereits verknüpft</string>
+    <string name="manage_parent_u2f_status_needs_user_interaction">Warte auf Druck der Bestätigen-Taste am Schlüssel</string>
     <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>

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

@@ -1075,7 +1075,7 @@
     <string name="manage_parent_change_password_toast_wrong_password">The old password is invalid</string>
 
     <string name="manage_parent_u2f_title">U2F Keys</string>
-    <string name="manage_parent_u2f_description">Setup NFC U2F Tokens to authenticate</string>
+    <string name="manage_parent_u2f_description">Setup U2F Tokens (using USB or NFC) to authenticate</string>
 
     <string name="manage_parent_restore_password_title" translatable="false">@string/restore_parent_password_title</string>
     <string name="manage_parent_restore_password_text_require_mail">
@@ -1709,7 +1709,7 @@
     <string name="notify_permission_rejected_toast">rejected; it could be that you can only change this using the system settings</string>
 
     <string name="manage_parent_u2f_add_key">Add Token</string>
-    <string name="manage_parent_u2f_status_wait_key">Waiting for your key; NFC is %s</string>
+    <string name="manage_parent_u2f_status_wait_key">Waiting for your key; Connect the key now; NFC is %s</string>
     <string name="manage_parent_u2f_status_wait_key_nfc_enabled">enabled</string>
     <string name="manage_parent_u2f_status_wait_key_nfc_disabled">disabled</string>
     <string name="manage_parent_u2f_status_wait_key_nfc_unsupported">unsupported</string>
@@ -1717,6 +1717,7 @@
     <string name="manage_parent_u2f_status_interrupted">Connection was interrupted</string>
     <string name="manage_parent_u2f_status_failed">The Request Failed</string>
     <string name="manage_parent_u2f_status_already_linked">This device is already linked</string>
+    <string name="manage_parent_u2f_status_needs_user_interaction">Waiting for button press at the key</string>
     <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>