Pin code: add some tests

libraries/cryptography/impl/src/main/kotlin/io/element/android/libraries/cryptography/impl/AESEncryptionDecryptionService.kt

@@ -16,56 +16,31 @@
 
 package io.element.android.libraries.cryptography.impl
 
-import android.security.keystore.KeyGenParameterSpec
-import android.security.keystore.KeyProperties
 import com.squareup.anvil.annotations.ContributesBinding
-import io.element.android.libraries.cryptography.api.CryptoService
+import io.element.android.libraries.cryptography.api.AESEncryptionSpecs
+import io.element.android.libraries.cryptography.api.EncryptionDecryptionService
 import io.element.android.libraries.cryptography.api.EncryptionResult
 import io.element.android.libraries.di.AppScope
-import java.security.KeyStore
 import javax.crypto.Cipher
-import javax.crypto.KeyGenerator
 import javax.crypto.SecretKey
 import javax.crypto.spec.GCMParameterSpec
 import javax.inject.Inject
 
-private const val ANDROID_KEYSTORE = "AndroidKeyStore"
-private const val ENCRYPTION_BLOCK_MODE = KeyProperties.BLOCK_MODE_GCM
-private const val ENCRYPTION_PADDING = KeyProperties.ENCRYPTION_PADDING_NONE
-private const val ENCRYPTION_ALGORITHM = KeyProperties.KEY_ALGORITHM_AES
-private const val ENCRYPTION_AES_TRANSFORMATION = "$ENCRYPTION_ALGORITHM/$ENCRYPTION_BLOCK_MODE/$ENCRYPTION_PADDING"
-
+/**
+ * Default implementation of [EncryptionDecryptionService] using AES encryption.
+ */
 @ContributesBinding(AppScope::class)
-class DefaultCryptoService @Inject constructor() : CryptoService {
-
-    override fun getOrCreateSecretKey(alias: String): SecretKey {
-        val keyStore = KeyStore.getInstance(ANDROID_KEYSTORE)
-        val secretKeyEntry = (keyStore.getEntry(alias, null) as? KeyStore.SecretKeyEntry)
-            ?.secretKey
-        return if (secretKeyEntry == null) {
-            val generator = KeyGenerator.getInstance(ENCRYPTION_ALGORITHM, ANDROID_KEYSTORE)
-            val keyGenSpec = KeyGenParameterSpec.Builder(
-                alias,
-                KeyProperties.PURPOSE_ENCRYPT or KeyProperties.PURPOSE_DECRYPT
-            )
-                .setBlockModes(ENCRYPTION_BLOCK_MODE)
-                .setEncryptionPaddings(ENCRYPTION_PADDING)
-                .setKeySize(128)
-                .build()
-            generator.init(keyGenSpec)
-            generator.generateKey()
-        } else secretKeyEntry
-    }
+class AESEncryptionDecryptionService @Inject constructor() : EncryptionDecryptionService {
 
     override fun createEncryptionCipher(key: SecretKey): Cipher {
-        return Cipher.getInstance(ENCRYPTION_AES_TRANSFORMATION).apply {
+        return Cipher.getInstance(AESEncryptionSpecs.CIPHER_TRANSFORMATION).apply {
             init(Cipher.ENCRYPT_MODE, key)
         }
     }
 
     override fun createDecryptionCipher(key: SecretKey, initializationVector: ByteArray): Cipher {
         val spec = GCMParameterSpec(128, initializationVector)
-        return Cipher.getInstance(ENCRYPTION_AES_TRANSFORMATION).apply {
+        return Cipher.getInstance(AESEncryptionSpecs.CIPHER_TRANSFORMATION).apply {
             init(Cipher.DECRYPT_MODE, key, spec)
         }
     }

libraries/cryptography/impl/src/main/kotlin/io/element/android/libraries/cryptography/impl/KeyStoreSecretKeyProvider.kt

@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2023 New Vector Ltd
+ *
+ * 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 io.element.android.libraries.cryptography.impl
+
+import android.security.keystore.KeyGenParameterSpec
+import android.security.keystore.KeyProperties
+import io.element.android.libraries.cryptography.api.AESEncryptionSpecs
+import io.element.android.libraries.cryptography.api.SecretKeyProvider
+import java.security.KeyStore
+import javax.crypto.KeyGenerator
+import javax.crypto.SecretKey
+
+private const val ANDROID_KEYSTORE = "AndroidKeyStore"
+
+/**
+ * Default implementation of [SecretKeyProvider] that uses the Android Keystore to store the keys.
+ * The generated key uses AES algorithm, with a key size of 128 bits, and the GCM block mode.
+ */
+class KeyStoreSecretKeyProvider : SecretKeyProvider {
+
+    override fun getOrCreateKey(alias: String): SecretKey {
+        val keyStore = KeyStore.getInstance(ANDROID_KEYSTORE)
+        val secretKeyEntry = (keyStore.getEntry(alias, null) as? KeyStore.SecretKeyEntry)
+            ?.secretKey
+        return if (secretKeyEntry == null) {
+            val generator = KeyGenerator.getInstance(AESEncryptionSpecs.ALGORITHM, ANDROID_KEYSTORE)
+            val keyGenSpec = KeyGenParameterSpec.Builder(
+                alias,
+                KeyProperties.PURPOSE_ENCRYPT or KeyProperties.PURPOSE_DECRYPT
+            )
+                .setBlockModes(AESEncryptionSpecs.BLOCK_MODE)
+                .setEncryptionPaddings(AESEncryptionSpecs.PADDINGS)
+                .setKeySize(AESEncryptionSpecs.KEY_SIZE)
+                .build()
+            generator.init(keyGenSpec)
+            generator.generateKey()
+        } else {
+            secretKeyEntry
+        }
+    }
+}

libraries/cryptography/impl/src/test/kotlin/io/element/android/libraries/cryptography/impl/AESEncryptionDecryptionServiceTest.kt

@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2023 New Vector Ltd
+ *
+ * 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 io.element.android.libraries.cryptography.impl
+
+import android.security.keystore.KeyProperties
+import com.google.common.truth.Truth.assertThat
+import org.junit.Assert.assertThrows
+import org.junit.Test
+import java.security.GeneralSecurityException
+import javax.crypto.KeyGenerator
+
+class AESEncryptionDecryptionServiceTest {
+
+    private val encryptionDecryptionService = AESEncryptionDecryptionService()
+
+    @Test
+    fun given_a_valid_key_then_encrypt_decrypt_work() {
+        val keyGenerator = KeyGenerator.getInstance(KeyProperties.KEY_ALGORITHM_AES)
+        keyGenerator.init(128)
+        val key = keyGenerator.generateKey()
+        val input = "Hello World".toByteArray()
+        val encryptionResult = encryptionDecryptionService.encrypt(key, input)
+        val decrypted = encryptionDecryptionService.decrypt(key, encryptionResult)
+        assertThat(decrypted).isEqualTo(input)
+    }
+
+    @Test
+    fun given_a_wrong_key_then_decrypt_fail() {
+        val keyGenerator = KeyGenerator.getInstance(KeyProperties.KEY_ALGORITHM_AES)
+        keyGenerator.init(128)
+        val encryptionKey = keyGenerator.generateKey()
+        val input = "Hello World".toByteArray()
+        val encryptionResult = encryptionDecryptionService.encrypt(encryptionKey, input)
+        val decryptionKey = keyGenerator.generateKey()
+        assertThrows(GeneralSecurityException::class.java) {
+            encryptionDecryptionService.decrypt(decryptionKey, encryptionResult)
+        }
+    }
+
+}