Testing EncryptedSharedPreferences from Android Jetpack Security with Robolectric

EncryptedSharedPreferencesTest.kt

/*
 * Copyright 2020 Appmattus Limited
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.appmattus

import android.content.Context
import androidx.security.crypto.EncryptedSharedPreferences
import androidx.security.crypto.MasterKey
import androidx.test.core.app.ApplicationProvider
import com.appmattus.FakeAndroidKeyStore
import org.junit.Assert.assertEquals
import org.junit.BeforeClass
import org.junit.Test
import org.junit.runner.RunWith
import org.robolectric.RobolectricTestRunner
import org.robolectric.annotation.Config

@RunWith(RobolectricTestRunner::class)
@Config(manifest = Config.NONE, sdk = [22, 28])
class EncryptedSharedPreferencesTest {

    private val context = ApplicationProvider.getApplicationContext<Context>()

    private val masterKey = MasterKey.Builder(context)
        .setKeyScheme(MasterKey.KeyScheme.AES256_GCM)
        .build()

    private val sharedPreferences =
        EncryptedSharedPreferences.create(
            context,
            "testPrefs",
            masterKey,
            EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
            EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM
        )

    @Test
    fun `verify string storage`() {
        sharedPreferences.edit().apply {
            putString("key", "value")
        }.apply()

        assertEquals("value", sharedPreferences.getString("key", "default"))
    }

    companion object {
        @JvmStatic
        @BeforeClass
        fun beforeClass() {
            FakeAndroidKeyStore.setup
        }
    }
}

FakeAndroidKeyStore.kt

/*
 * Copyright 2020 Appmattus Limited
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.appmattus

import java.io.InputStream
import java.io.OutputStream
import java.security.Key
import java.security.KeyStore
import java.security.KeyStoreSpi
import java.security.Provider
import java.security.SecureRandom
import java.security.Security
import java.security.cert.Certificate
import java.security.spec.AlgorithmParameterSpec
import java.util.Date
import java.util.Enumeration
import javax.crypto.KeyGenerator
import javax.crypto.KeyGeneratorSpi
import javax.crypto.SecretKey

object FakeAndroidKeyStore {

    val setup by lazy {
        Security.addProvider(object : Provider("AndroidKeyStore", 1.0, "") {
            init {
                put("KeyStore.AndroidKeyStore", FakeKeyStore::class.java.name)
                put("KeyGenerator.AES", FakeAesKeyGenerator::class.java.name)
            }
        })
    }

    @Suppress("unused")
    class FakeKeyStore : KeyStoreSpi() {
        private val wrapped = KeyStore.getInstance(KeyStore.getDefaultType())

        override fun engineIsKeyEntry(alias: String?): Boolean = wrapped.isKeyEntry(alias)
        override fun engineIsCertificateEntry(alias: String?): Boolean = wrapped.isCertificateEntry(alias)
        override fun engineGetCertificate(alias: String?): Certificate = wrapped.getCertificate(alias)
        override fun engineGetCreationDate(alias: String?): Date = wrapped.getCreationDate(alias)
        override fun engineDeleteEntry(alias: String?) = wrapped.deleteEntry(alias)
        override fun engineSetKeyEntry(alias: String?, key: Key?, password: CharArray?, chain: Array<out Certificate>?) =
            wrapped.setKeyEntry(alias, key, password, chain)

        override fun engineSetKeyEntry(alias: String?, key: ByteArray?, chain: Array<out Certificate>?) = wrapped.setKeyEntry(alias, key, chain)
        override fun engineStore(stream: OutputStream?, password: CharArray?) = wrapped.store(stream, password)
        override fun engineSize(): Int = wrapped.size()
        override fun engineAliases(): Enumeration<String> = wrapped.aliases()
        override fun engineContainsAlias(alias: String?): Boolean = wrapped.containsAlias(alias)
        override fun engineLoad(stream: InputStream?, password: CharArray?) = wrapped.load(stream, password)
        override fun engineGetCertificateChain(alias: String?): Array<Certificate> = wrapped.getCertificateChain(alias)
        override fun engineSetCertificateEntry(alias: String?, cert: Certificate?) = wrapped.setCertificateEntry(alias, cert)
        override fun engineGetCertificateAlias(cert: Certificate?): String = wrapped.getCertificateAlias(cert)
        override fun engineGetKey(alias: String?, password: CharArray?): Key = wrapped.getKey(alias, password)
    }

    @Suppress("unused")
    class FakeAesKeyGenerator : KeyGeneratorSpi() {
        private val wrapped = KeyGenerator.getInstance("AES")

        override fun engineInit(random: SecureRandom?) = Unit
        override fun engineInit(params: AlgorithmParameterSpec?, random: SecureRandom?) = Unit
        override fun engineInit(keysize: Int, random: SecureRandom?) = Unit
        override fun engineGenerateKey(): SecretKey = wrapped.generateKey()
    }
}

I am also facing same issue in with android 34, any suggestions?