Added module for securely storing seeds and keys.

The underlying library is not perfect but it will do for now. Closes #11. Closes #12.

app/build.gradle

@@ -75,6 +75,8 @@ dependencies {
     implementation fileTree(dir: 'libs', include: ['*.jar'])
     implementation project(':qrecycler')
     implementation project(':feedback')
+    implementation project(':mnemonic')
+    implementation project(':lockbox')
 
     //  Kotlin
     implementation Deps.Kotlin.STDLIB

lockbox/.gitignore

@@ -0,0 +1 @@
+/build

lockbox/build.gradle

@@ -0,0 +1,48 @@
+import cash.z.ecc.android.Deps
+
+apply plugin: 'com.android.library'
+apply plugin: 'kotlin-android'
+apply plugin: 'kotlin-android-extensions'
+
+repositories {
+    google()
+    jcenter()
+}
+
+android {
+    compileSdkVersion Deps.compileSdkVersion
+    buildToolsVersion Deps.buildToolsVersion
+
+    useLibrary 'android.test.runner'
+
+    defaultConfig {
+        minSdkVersion Deps.minSdkVersion
+        targetSdkVersion Deps.targetSdkVersion
+        versionCode 1
+        versionName "1.0"
+
+        testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
+        testInstrumentationRunnerArguments clearPackageData: 'true'
+
+        consumerProguardFiles 'consumer-rules.pro'
+    }
+
+    buildTypes {
+        release {
+            minifyEnabled false
+            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
+        }
+    }
+
+}
+
+dependencies {
+    implementation Deps.Kotlin.STDLIB
+    implementation Deps.AndroidX.APPCOMPAT
+    implementation Deps.AndroidX.CORE_KTX
+
+    implementation "de.adorsys.android:securestoragelibrary:1.2.2"
+
+    androidTestImplementation Deps.Test.Android.JUNIT
+    androidTestImplementation Deps.Test.Android.ESPRESSO
+}

lockbox/proguard-rules.pro

@@ -0,0 +1,21 @@
+# Add project specific ProGuard rules here.
+# You can control the set of applied configuration files using the
+# proguardFiles setting in build.gradle.
+#
+# For more details, see
+#   http://developer.android.com/guide/developing/tools/proguard.html
+
+# If your project uses WebView with JS, uncomment the following
+# and specify the fully qualified class name to the JavaScript interface
+# class:
+#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
+#   public *;
+#}
+
+# Uncomment this to preserve the line number information for
+# debugging stack traces.
+#-keepattributes SourceFile,LineNumberTable
+
+# If you keep the line number information, uncomment this to
+# hide the original source file name.
+#-renamesourcefileattribute SourceFile

lockbox/src/androidTest/java/cash/z/ecc/android/lockbox/LockBoxText.kt

@@ -0,0 +1,52 @@
+package cash.z.ecc.android.lockbox
+
+import android.content.Context
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import androidx.test.platform.app.InstrumentationRegistry
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Before
+import org.junit.Test
+import org.junit.runner.RunWith
+
+@RunWith(AndroidJUnit4::class)
+class LockBoxText {
+
+    private lateinit var appContext: Context
+    private lateinit var lockBox: LockBoxProvider
+
+    @Before
+    fun start() {
+        appContext = InstrumentationRegistry.getInstrumentation().targetContext
+        lockBox = LockBox(appContext)
+    }
+
+    @Test
+    fun testSeed_store() {
+        val testMessage = "Some Bytes To Test"
+        val testBytes = testMessage.toByteArray()
+        lockBox.setBytes("seed", testBytes)
+        assertEquals(testMessage, String(lockBox.getBytes("seed")))
+    }
+
+    @Test
+    fun testSeed_storeNegatives() {
+        val testBytes = byteArrayOf(0x00, 0x00, -0x0F, -0x0B)
+        lockBox.setBytes("seed", testBytes)
+        assertTrue(testBytes.contentEquals(lockBox.getBytes("seed")))
+    }
+
+    @Test
+    fun testSeed_storeLeadingZeros() {
+        val testBytes = byteArrayOf(0x00, 0x00, 0x0F, 0x0B)
+        lockBox.setBytes("seed", testBytes)
+        assertTrue(testBytes.contentEquals(lockBox.getBytes("seed")))
+    }
+
+    @Test
+    fun testPrivateKey_retrieve() {
+        val testMessage = "Some Bytes To Test"
+        lockBox.setCharsUtf8("spendingKey", testMessage.toCharArray())
+        assertEquals(testMessage, String(lockBox.getCharsUtf8("spendingKey")))
+    }
+}

lockbox/src/main/AndroidManifest.xml

@@ -0,0 +1,3 @@
+<manifest
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    package="cash.z.ecc.android.lockbox" />

lockbox/src/main/java/cash/z/ecc/android/lockbox/LockBox.kt

@@ -0,0 +1,64 @@
+package cash.z.ecc.android.lockbox
+
+import android.content.Context
+import de.adorsys.android.securestoragelibrary.SecurePreferences
+import java.nio.ByteBuffer
+import java.nio.CharBuffer
+import java.nio.charset.StandardCharsets
+import java.util.*
+
+
+class LockBox(private val appContext: Context) : LockBoxProvider {
+
+    override fun setBytes(key: String, value: ByteArray) {
+        SecurePreferences.setValue(appContext, key, value.toHex())
+    }
+
+    override fun getBytes(key: String): ByteArray {
+        return SecurePreferences.getStringValue(appContext, key, null)!!.fromHex()
+    }
+
+    override fun setCharsUtf8(key: String, value: CharArray) {
+        setBytes(key, value.toBytes())
+    }
+
+    override fun getCharsUtf8(key: String): CharArray {
+        return getBytes(key).fromBytes()
+    }
+
+
+    //
+    // Extensions (TODO: find library that works better with arrays of bytes and chars)
+    //
+
+    private fun ByteArray.toHex(): String {
+        val sb = StringBuilder(size * 2)
+        for (b in this)
+            sb.append(String.format("%02x", b))
+        return sb.toString()
+    }
+
+    private fun String.fromHex(): ByteArray {
+        val len = length
+        val data = ByteArray(len / 2)
+        var i = 0
+        while (i < len) {
+            data[i / 2] =
+                ((Character.digit(this[i], 16) shl 4) + Character.digit(this[i + 1], 16)).toByte()
+            i += 2
+        }
+        return data
+    }
+
+    private fun CharArray.toBytes(): ByteArray {
+        val byteBuffer = StandardCharsets.UTF_8.encode(CharBuffer.wrap(this))
+        return Arrays.copyOf(byteBuffer.array(), byteBuffer.limit());
+    }
+
+    private fun ByteArray.fromBytes(): CharArray {
+        val charBuffer = StandardCharsets.UTF_8.decode(ByteBuffer.wrap(this))
+        return Arrays.copyOf(charBuffer.array(), charBuffer.limit())
+    }
+}
+
+

lockbox/src/main/java/cash/z/ecc/android/lockbox/LockBoxProvider.kt

@@ -0,0 +1,13 @@
+package cash.z.ecc.android.lockbox
+
+/**
+ * Generic interface to separate the underlying implementation used by this module and the code that
+ * interacts with it.
+ */
+interface LockBoxProvider {
+    fun setBytes(key: String, value: ByteArray)
+    fun getBytes(key: String): ByteArray
+
+    fun setCharsUtf8(key: String, value: CharArray)
+    fun getCharsUtf8(key: String): CharArray
+}

lockbox/src/test/java/cash/z/ecc/android/lockbox/ExampleUnitTest.kt

@@ -0,0 +1,17 @@
+package cash.z.ecc.android.lockbox
+
+import org.junit.Test
+
+import org.junit.Assert.*
+
+/**
+ * Example local unit test, which will execute on the development machine (host).
+ *
+ * See [testing documentation](http://d.android.com/tools/testing).
+ */
+class ExampleUnitTest {
+    @Test
+    fun addition_isCorrect() {
+        assertEquals(4, 2 + 2)
+    }
+}

settings.gradle

@@ -1,2 +1,2 @@
 rootProject.name='Zcash Wallet'
-include ':app', ':qrecycler', ':feedback', ':mnemonic'
+include ':app', ':qrecycler', ':feedback', ':mnemonic', ':lockbox'