Fido: Add support for proper attestation

play-services-fido-core/build.gradle

@@ -13,6 +13,8 @@ dependencies {
     api project(':play-services-fido-api')
 
     implementation project(':play-services-base-core')
+    implementation project(':play-services-safetynet')
+    implementation project(':play-services-tasks-ktx')
 
     implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlinVersion"
     implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:$coroutineVersion"

play-services-fido-core/src/main/kotlin/org/microg/gms/fido/core/RequestHandling.kt

@@ -64,6 +64,9 @@ val RequestOptions.rpId: String
         SIGN -> signOptions.rpId
     }
 
+val PublicKeyCredentialCreationOptions.skipAttestation: Boolean
+    get() = attestationConveyancePreference in setOf(AttestationConveyancePreference.NONE, null)
+
 fun RequestOptions.checkIsValid(context: Context) {
     if (type == REGISTER) {
         if (registerOptions.authenticatorSelection.requireResidentKey == true) {

play-services-fido-core/src/main/kotlin/org/microg/gms/fido/core/privileged/Fido2PrivilegedService.kt

@@ -17,8 +17,10 @@ import android.os.Parcel
 import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.LifecycleOwner
 import androidx.lifecycle.lifecycleScope
+import com.google.android.gms.common.Feature
 import com.google.android.gms.common.api.CommonStatusCodes
 import com.google.android.gms.common.api.Status
+import com.google.android.gms.common.internal.ConnectionInfo
 import com.google.android.gms.common.internal.GetServiceRequest
 import com.google.android.gms.common.internal.IGmsCallbacks
 import com.google.android.gms.fido.fido2.api.IBooleanCallback
@@ -43,10 +45,15 @@ const val TAG = "Fido2Privileged"
 
 class Fido2PrivilegedService : BaseService(TAG, FIDO2_PRIVILEGED) {
     override fun handleServiceRequest(callback: IGmsCallbacks, request: GetServiceRequest, service: GmsService) {
-        callback.onPostInitComplete(
+        callback.onPostInitCompleteWithConnectionInfo(
             CommonStatusCodes.SUCCESS,
             Fido2PrivilegedServiceImpl(this, lifecycle).asBinder(),
-            null
+            ConnectionInfo().apply {
+                features = arrayOf(
+                    Feature("is_user_verifying_platform_authenticator_available", 1),
+                    Feature("is_user_verifying_platform_authenticator_available_for_credential", 1)
+                )
+            }
         );
     }
 }

play-services-fido-core/src/main/kotlin/org/microg/gms/fido/core/protocol/AndroidKeyAttestationObject.kt

@@ -0,0 +1,30 @@
+/*
+ * SPDX-FileCopyrightText: 2022 microG Project Team
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package org.microg.gms.fido.core.protocol
+
+import com.google.android.gms.fido.fido2.api.common.Algorithm
+import com.upokecenter.cbor.CBORObject
+
+class AndroidKeyAttestationObject(
+    authData: AuthenticatorData,
+    val alg: Algorithm,
+    val sig: ByteArray,
+    val x5c: List<ByteArray>
+) :
+    AttestationObject(authData.encode()) {
+    override val fmt: String
+        get() = "android-key"
+    override val attStmt: CBORObject
+        get() = CBORObject.NewMap().apply {
+            set("alg", alg.algoValue.encodeAsCbor())
+            set("sig", sig.encodeAsCbor())
+            set("x5c", CBORObject.NewArray().apply {
+                for (certificate in x5c) {
+                    Add(certificate.encodeAsCbor())
+                }
+            })
+        }
+}

play-services-fido-core/src/main/kotlin/org/microg/gms/fido/core/protocol/AttestedCredentialData.kt

@@ -5,10 +5,7 @@
 
 package org.microg.gms.fido.core.protocol
 
-import android.util.Base64
-import android.util.Log
 import com.upokecenter.cbor.CBORObject
-import org.microg.gms.utils.toBase64
 import java.io.ByteArrayInputStream
 import java.nio.ByteBuffer
 import java.nio.ByteOrder

play-services-fido-core/src/main/kotlin/org/microg/gms/fido/core/protocol/AuthenticatorData.kt

@@ -5,7 +5,6 @@
 
 package org.microg.gms.fido.core.protocol
 
-import com.upokecenter.cbor.CBORObject
 import java.nio.ByteBuffer
 import java.nio.ByteOrder
 import kotlin.experimental.and

play-services-fido-core/src/main/kotlin/org/microg/gms/fido/core/transport/TransportHandler.kt

@@ -117,8 +117,11 @@ abstract class TransportHandler(val transport: Transport, val callback: Transpor
                     0,
                     credentialData
                 )
-                val attestationObject =
+                val attestationObject = if (options.registerOptions.skipAttestation) {
+                    NoneAttestationObject(authData)
+                } else {
                     FidoU2fAttestationObject(authData, response.signature, response.attestationCertificate)
+                }
                 val ctap2Response = AuthenticatorMakeCredentialResponse(
                     authData.encode(),
                     attestationObject.fmt,

play-services-fido-core/src/main/kotlin/org/microg/gms/fido/core/transport/screenlock/ScreenLockCredentialStore.kt

@@ -8,13 +8,15 @@ package org.microg.gms.fido.core.transport.screenlock
 import android.content.Context
 import android.database.sqlite.SQLiteDatabase
 import android.database.sqlite.SQLiteOpenHelper
+import android.os.Build
 import android.security.keystore.KeyGenParameterSpec
 import android.security.keystore.KeyProperties
 import android.util.Base64
 import android.util.Log
 import androidx.annotation.RequiresApi
 import org.microg.gms.utils.toBase64
 import java.security.*
+import java.security.cert.Certificate
 import java.security.spec.ECGenParameterSpec
 import kotlin.random.Random
 
@@ -27,25 +29,27 @@ class ScreenLockCredentialStore(val context: Context) {
     private fun getPrivateKey(rpId: String, keyId: ByteArray) = keyStore.getKey(getAlias(rpId, keyId), null) as? PrivateKey
 
     @RequiresApi(23)
-    fun createKey(rpId: String): ByteArray {
+    fun createKey(rpId: String, challenge: ByteArray): ByteArray {
         val keyId = Random.nextBytes(32)
         val identifier = getAlias(rpId, keyId)
         Log.d(TAG, "Creating key for $identifier")
         val generator = KeyPairGenerator.getInstance("EC", "AndroidKeyStore")
-        generator.initialize(
-            KeyGenParameterSpec.Builder(identifier, KeyProperties.PURPOSE_SIGN)
-                .setDigests(KeyProperties.DIGEST_SHA256)
-                .setAlgorithmParameterSpec(ECGenParameterSpec("secp256r1"))
-                .setUserAuthenticationRequired(true)
-                .build()
-        )
+        val builder = KeyGenParameterSpec.Builder(identifier, KeyProperties.PURPOSE_SIGN)
+            .setDigests(KeyProperties.DIGEST_SHA256)
+            .setAlgorithmParameterSpec(ECGenParameterSpec("secp256r1"))
+            .setUserAuthenticationRequired(true)
+        if (Build.VERSION.SDK_INT >= 24) builder.setAttestationChallenge(challenge)
+        generator.initialize(builder.build())
         generator.generateKeyPair()
         return keyId
     }
 
     fun getPublicKey(rpId: String, keyId: ByteArray): PublicKey? =
         keyStore.getCertificate(getAlias(rpId, keyId))?.publicKey
 
+    fun getCertificateChain(rpId: String, keyId: ByteArray): Array<Certificate> =
+        keyStore.getCertificateChain(getAlias(rpId, keyId))
+
     fun getSignature(rpId: String, keyId: ByteArray): Signature? {
         val privateKey = getPrivateKey(rpId, keyId) ?: return null
         val signature = Signature.getInstance("SHA256withECDSA")

play-services-fido-core/src/main/kotlin/org/microg/gms/fido/core/transport/screenlock/ScreenLockTransportHandler.kt

@@ -7,12 +7,17 @@ package org.microg.gms.fido.core.transport.screenlock
 
 import android.app.KeyguardManager
 import android.os.Build
+import android.util.Log
 import androidx.annotation.RequiresApi
 import androidx.biometric.BiometricPrompt
 import androidx.core.content.getSystemService
 import androidx.fragment.app.FragmentActivity
 import com.google.android.gms.fido.fido2.api.common.*
+import com.google.android.gms.fido.fido2.api.common.AttestationConveyancePreference.NONE
+import com.google.android.gms.safetynet.SafetyNet
+import com.google.android.gms.tasks.await
 import kotlinx.coroutines.suspendCancellableCoroutine
+import org.microg.gms.basement.BuildConfig
 import org.microg.gms.fido.core.*
 import org.microg.gms.fido.core.protocol.*
 import org.microg.gms.fido.core.transport.Transport
@@ -23,12 +28,13 @@ import java.security.interfaces.ECPublicKey
 import kotlin.coroutines.resume
 import kotlin.coroutines.resumeWithException
 
+@RequiresApi(23)
 class ScreenLockTransportHandler(private val activity: FragmentActivity, callback: TransportHandlerCallback? = null) :
     TransportHandler(Transport.SCREEN_LOCK, callback) {
     private val store by lazy { ScreenLockCredentialStore(activity) }
 
     override val isSupported: Boolean
-        get() = Build.VERSION.SDK_INT >= 23 && activity.getSystemService<KeyguardManager>()?.isDeviceSecure == true
+        get() = activity.getSystemService<KeyguardManager>()?.isDeviceSecure == true
 
     suspend fun showBiometricPrompt(applicationName: String, signature: Signature?) {
         suspendCancellableCoroutine<BiometricPrompt.AuthenticationResult> { continuation ->
@@ -76,15 +82,15 @@ class ScreenLockTransportHandler(private val activity: FragmentActivity, callbac
         return signature
     }
 
-    fun getCredentialData(credentialId: CredentialId, coseKey: CoseKey) = AttestedCredentialData(
-        ByteArray(16), // 0xb93fd961f2e6462fb12282002247de78 for SafetyNet
+    fun getCredentialData(aaguid: ByteArray, credentialId: CredentialId, coseKey: CoseKey) = AttestedCredentialData(
+        aaguid,
         credentialId.encode(),
         coseKey.encode()
     )
 
     fun getAuthenticatorData(
         rpId: String,
-        credentialData: AttestedCredentialData,
+        credentialData: AttestedCredentialData?,
         userPresent: Boolean = true,
         userVerified: Boolean = true,
         signCount: Int = 0
@@ -96,7 +102,6 @@ class ScreenLockTransportHandler(private val activity: FragmentActivity, callbac
         attestedCredentialData = credentialData
     )
 
-    @RequiresApi(23)
     suspend fun register(
         options: RequestOptions,
         callerPackage: String
@@ -111,34 +116,72 @@ class ScreenLockTransportHandler(private val activity: FragmentActivity, callbac
             }
         }
         val (clientData, clientDataHash) = getClientDataAndHash(activity, options, callerPackage)
-        if (options.registerOptions.attestationConveyancePreference in setOf(
-                AttestationConveyancePreference.NONE,
-                null
-            )
-        ) {
-            // No attestation needed
-        } else {
-            // TODO: SafetyNet
-            throw RequestHandlingException(ErrorCode.NOT_SUPPORTED_ERR, "SafetyNet Attestation not yet supported")
-        }
-        val keyId = store.createKey(options.rpId)
+        val aaguid = if (options.registerOptions.skipAttestation) ByteArray(16) else AAGUID
+        val keyId = store.createKey(options.rpId, clientDataHash)
         val publicKey =
             store.getPublicKey(options.rpId, keyId) ?: throw RequestHandlingException(ErrorCode.INVALID_STATE_ERR)
 
         // We're ignoring the signature object as we don't need it for registration
-        getActiveSignature(options, callerPackage, keyId)
+        val signature = getActiveSignature(options, callerPackage, keyId)
 
         val (x, y) = (publicKey as ECPublicKey).w.let { it.affineX to it.affineY }
         val coseKey = CoseKey(EC2Algorithm.ES256, x, y, 1, 32)
         val credentialId = CredentialId(1, keyId, options.rpId, publicKey)
 
-        val credentialData = getCredentialData(credentialId, coseKey)
+        val credentialData = getCredentialData(aaguid, credentialId, coseKey)
         val authenticatorData = getAuthenticatorData(options.rpId, credentialData)
 
+        val attestationObject = if (options.registerOptions.skipAttestation) {
+            NoneAttestationObject(authenticatorData)
+        } else {
+            try {
+                if (Build.VERSION.SDK_INT >= 24) {
+                    createAndroidKeyAttestation(signature, authenticatorData, clientDataHash, options.rpId, keyId)
+                } else {
+                    createSafetyNetAttestation(authenticatorData, clientDataHash)
+                }
+            } catch (e: Exception) {
+                Log.w("FidoScreenLockTransport", e)
+                NoneAttestationObject(authenticatorData)
+            }
+        }
+
         return AuthenticatorAttestationResponse(
             credentialId.encode(),
             clientData,
-            NoneAttestationObject(authenticatorData).encode()
+            attestationObject.encode()
+        )
+    }
+
+    @RequiresApi(24)
+    private fun createAndroidKeyAttestation(
+        signature: Signature,
+        authenticatorData: AuthenticatorData,
+        clientDataHash: ByteArray,
+        rpId: String,
+        keyId: ByteArray
+    ): AndroidKeyAttestationObject {
+        signature.update(authenticatorData.encode() + clientDataHash)
+        val sig = signature.sign()
+        return AndroidKeyAttestationObject(
+            authenticatorData,
+            EC2Algorithm.ES256,
+            sig,
+            store.getCertificateChain(rpId, keyId).map { it.encoded })
+    }
+
+    private suspend fun createSafetyNetAttestation(
+        authenticatorData: AuthenticatorData,
+        clientDataHash: ByteArray
+    ): AndroidSafetyNetAttestationObject {
+        val response = SafetyNet.getClient(activity).attest(
+            (authenticatorData.encode() + clientDataHash).digest("SHA-256"),
+            "AIzaSyDqVnJBjE5ymo--oBJt3On7HQx9xNm1RHA"
+        ).await()
+        return AndroidSafetyNetAttestationObject(
+            authenticatorData,
+            BuildConfig.VERSION_CODE.toString(),
+            response.jwsResult.toByteArray()
         )
     }
 
@@ -173,10 +216,7 @@ class ScreenLockTransportHandler(private val activity: FragmentActivity, callbac
         val keyId = credentialId.data
 
         val (x, y) = (credentialId.publicKey as ECPublicKey).w.let { it.affineX to it.affineY }
-        val coseKey = CoseKey(EC2Algorithm.ES256, x, y, 1, 32)
-
-        val credentialData = getCredentialData(credentialId, coseKey)
-        val authenticatorData = getAuthenticatorData(options.rpId, credentialData)
+        val authenticatorData = getAuthenticatorData(options.rpId, null)
 
         val signature = getActiveSignature(options, callerPackage, keyId)
         signature.update(authenticatorData.encode() + clientDataHash)
@@ -191,7 +231,7 @@ class ScreenLockTransportHandler(private val activity: FragmentActivity, callbac
         )
     }
 
-    @RequiresApi(23)
+    @RequiresApi(24)
     override suspend fun start(options: RequestOptions, callerPackage: String): AuthenticatorResponse =
         when (options.type) {
             RequestOptionsType.REGISTER -> register(options, callerPackage)
@@ -212,4 +252,11 @@ class ScreenLockTransportHandler(private val activity: FragmentActivity, callbac
         }
         return false
     }
+
+    companion object {
+        private val AAGUID = byteArrayOf(
+            0xb9.toByte(), 0x3f, 0xd9.toByte(), 0x61, 0xf2.toByte(), 0xe6.toByte(), 0x46, 0x2f,
+            0xb1.toByte(), 0x22, 0x82.toByte(), 0x00, 0x22, 0x47, 0xde.toByte(), 0x78
+        )
+    }
 }

play-services-fido-core/src/main/kotlin/org/microg/gms/fido/core/ui/AuthenticatorActivity.kt

@@ -59,7 +59,7 @@ class AuthenticatorActivity : AppCompatActivity(), TransportHandlerCallback {
             BluetoothTransportHandler(this, this),
             NfcTransportHandler(this, this),
             if (Build.VERSION.SDK_INT >= 21) UsbTransportHandler(this, this) else null,
-            ScreenLockTransportHandler(this, this)
+            if (Build.VERSION.SDK_INT >= 23) ScreenLockTransportHandler(this, this) else null
         )
     }
 

play-services-fido/src/main/java/com/google/android/gms/fido/fido2/Fido2ApiClient.java

@@ -8,7 +8,6 @@
 
 package com.google.android.gms.fido.fido2;
 
-import android.app.Activity;
 import android.app.PendingIntent;
 import android.content.Context;
 

play-services-fido/src/main/java/org/microg/gms/fido/fido2/Fido2PrivilegedGmsClient.java

@@ -22,7 +22,7 @@
 
 public class Fido2PrivilegedGmsClient extends GmsClient<IFido2PrivilegedService> {
     public Fido2PrivilegedGmsClient(Context context, ConnectionCallbacks callbacks, OnConnectionFailedListener connectionFailedListener) {
-        super(context, callbacks, connectionFailedListener, GmsService.OSS_LICENSES.ACTION);
+        super(context, callbacks, connectionFailedListener, GmsService.FIDO2_PRIVILEGED.ACTION);
         serviceId = GmsService.FIDO2_PRIVILEGED.SERVICE_ID;
     }