[APT-9577] Add DRM for downloads for offline usage : update SecureSto…

…rage to it can store the DRM key id

Update SecureStorage to add new methods to save and fetch DRM key id.
This ID will later be used to fetch the DRM key needed to decrypt a DRM-protected content.
The ID is saved per content (per audio URL) and per DRM technology (we currently only support Widevine).

Also make SecureStorage injectable with Dagger.

Armadillo/build.gradle

@@ -14,6 +14,7 @@ plugins {
     // Extension of maven plugin that properly handles android dependencies
     id 'digital.wup.android-maven-publish' version "${MAVEN_PUBLISH_VERSION}"
     id 'org.jetbrains.dokka' version "${DOKKA_VERSION}" // Official Kotlin documentation engine - does both Kotlin and Java docs
+    id 'org.jetbrains.kotlin.plugin.serialization' version '1.6.0'
 }
 
 android {
@@ -59,6 +60,8 @@ dependencies {
     implementation "com.google.dagger:dagger:${DAGGER_VERSION}"
     kapt "com.google.dagger:dagger-compiler:${DAGGER_VERSION}"
     implementation 'androidx.media:media:1.6.0'
+    implementation "org.jetbrains.kotlinx:kotlinx-serialization-json:${SERIALIZATON_VERSION}"
+
     testImplementation "org.robolectric:robolectric:4.5.1"
     testImplementation 'junit:junit:4.13.2'
     testImplementation("org.assertj:assertj-core:3.10.0")
@@ -85,7 +88,7 @@ publishing {
 
     publications {
         android.libraryVariants.all { variant ->
-            "${variant.name.capitalize()}Aar" (MavenPublication) {
+            "${variant.name.capitalize()}Aar"(MavenPublication) {
                 from(components[variant.name])
                 groupId project.PACKAGE_NAME
                 version project.LIBRARY_VERSION
@@ -98,7 +101,7 @@ publishing {
         }
 
         android.libraryVariants.all { variant ->
-            "${variant.name.capitalize()}SnapshotAar" (MavenPublication) {
+            "${variant.name.capitalize()}SnapshotAar"(MavenPublication) {
                 from(components[variant.name])
                 groupId project.PACKAGE_NAME
                 version "${project.LIBRARY_VERSION}-SNAPSHOT"

Armadillo/src/main/java/com/scribd/armadillo/di/DownloadModule.kt

@@ -14,16 +14,18 @@ import com.scribd.armadillo.download.ArmadilloDatabaseProviderImpl
 import com.scribd.armadillo.download.ArmadilloDownloadManagerFactory
 import com.scribd.armadillo.download.CacheManager
 import com.scribd.armadillo.download.CacheManagerImpl
-import com.scribd.armadillo.download.MaxAgeCacheEvictor
 import com.scribd.armadillo.download.DefaultExoplayerDownloadService
 import com.scribd.armadillo.download.DownloadEngine
 import com.scribd.armadillo.download.DownloadManagerFactory
 import com.scribd.armadillo.download.DownloadTracker
 import com.scribd.armadillo.download.ExoplayerDownloadEngine
 import com.scribd.armadillo.download.ExoplayerDownloadTracker
 import com.scribd.armadillo.download.HeaderAwareDownloaderFactory
+import com.scribd.armadillo.download.MaxAgeCacheEvictor
+import com.scribd.armadillo.encryption.ArmadilloSecureStorage
 import com.scribd.armadillo.encryption.ExoplayerEncryption
 import com.scribd.armadillo.encryption.ExoplayerEncryptionImpl
+import com.scribd.armadillo.encryption.SecureStorage
 import com.scribd.armadillo.exoplayerExternalDirectory
 import dagger.Module
 import dagger.Provides
@@ -92,6 +94,10 @@ internal class DownloadModule {
     @Provides
     fun exoplayerEncryption(exoplayerEncryption: ExoplayerEncryptionImpl): ExoplayerEncryption = exoplayerEncryption
 
+    @Singleton
+    @Provides
+    fun secureStorage(secureStorage: ArmadilloSecureStorage): SecureStorage = secureStorage
+
     @Singleton
     @Provides
     fun downloadManagerFactory(downloadManagerFactory: ArmadilloDownloadManagerFactory): DownloadManagerFactory = downloadManagerFactory

Armadillo/src/main/java/com/scribd/armadillo/encryption/ExoplayerEncryption.kt

@@ -19,9 +19,9 @@ interface ExoplayerEncryption {
  * This class provides the plumbing for encrypting downloaded content & then reading this encrypted content.
  */
 @Singleton
-internal class ExoplayerEncryptionImpl @Inject constructor(applicationContext: Context) : ExoplayerEncryption {
+internal class ExoplayerEncryptionImpl @Inject constructor(applicationContext: Context,
+                                                           secureStorage: SecureStorage) : ExoplayerEncryption {
 
-    private val secureStorage: SecureStorage = ArmadilloSecureStorage()
     private val secret = secureStorage.downloadSecretKey(applicationContext)
 
     override fun dataSinkFactory(downloadCache: Cache) = DataSink.Factory {
@@ -30,6 +30,6 @@ internal class ExoplayerEncryptionImpl @Inject constructor(applicationContext: C
     }
 
     override fun dataSourceFactory(upstream: DataSource.Factory) =
-            DataSource.Factory { AesCipherDataSource(secret, upstream.createDataSource()) }
+        DataSource.Factory { AesCipherDataSource(secret, upstream.createDataSource()) }
 
 }

Armadillo/src/main/java/com/scribd/armadillo/encryption/SecureStorage.kt

@@ -1,42 +1,95 @@
 package com.scribd.armadillo.encryption
 
 import android.content.Context
+import android.util.Base64
 import android.util.Log
+import com.scribd.armadillo.models.DrmDownload
+import com.scribd.armadillo.models.DrmType
+import kotlinx.serialization.encodeToString
+import kotlinx.serialization.json.Json
+import java.nio.charset.StandardCharsets
 import java.security.MessageDigest
+import javax.inject.Inject
+import javax.inject.Singleton
 
 internal interface SecureStorage {
     fun downloadSecretKey(context: Context): ByteArray
+    fun saveDrmDownload(context: Context, audioUrl: String, drmDownload: DrmDownload)
+    fun getDrmDownload(context: Context, audioUrl: String, drmType: DrmType): DrmDownload?
+    fun getAllDrmDownloads(context: Context): Map<String, DrmDownload>
+    fun removeDrmDownload(context: Context, audioUrl: String, drmType: DrmType)
+    fun removeDrmDownload(context: Context, key: String)
 }
 
-internal class ArmadilloSecureStorage : SecureStorage {
+@Singleton
+internal class ArmadilloSecureStorage @Inject constructor() : SecureStorage {
     private companion object {
         const val DOWNLOAD_KEY = "download_key"
         const val STRING_LENGTH = 20
         const val ALLOWED_CHARS = "ABCDEFGHIJKLMNOPQRSTUVWXTZabcdefghiklmnopqrstuvwxyz0123456789"
         const val DEFAULT = "82YEDKqPBEqA2qAb4bUU"
-        const val LOCATION = "armadillo.storage"
+        const val STANDARD_STORAGE_FILENAME = "armadillo.storage"
+        const val DOWNLOAD_FILENAME = "armadillo.download"
         const val TAG = "SecureStorage"
     }
 
     override fun downloadSecretKey(context: Context): ByteArray {
-            val sharedPreferences = context.getSharedPreferences(LOCATION, Context.MODE_PRIVATE)
-            return if (sharedPreferences.contains(DOWNLOAD_KEY)) {
-                val storedKey = sharedPreferences.getString(DOWNLOAD_KEY, DEFAULT)!!
-                if(storedKey == DEFAULT){
-                    Log.e(TAG, "Storage Is Out of Alignment")
-                }
-                storedKey.toSecretByteArray
-            } else {
-                createRandomString().also {
-                    sharedPreferences.edit().putString(DOWNLOAD_KEY, it).apply()
-                }.toSecretByteArray
+        val sharedPreferences = context.getSharedPreferences(STANDARD_STORAGE_FILENAME, Context.MODE_PRIVATE)
+        return if (sharedPreferences.contains(DOWNLOAD_KEY)) {
+            val storedKey = sharedPreferences.getString(DOWNLOAD_KEY, DEFAULT)!!
+            if (storedKey == DEFAULT) {
+                Log.e(TAG, "Storage Is Out of Alignment")
             }
+            storedKey.toSecretByteArray
+        } else {
+            createRandomString().also {
+                sharedPreferences.edit().putString(DOWNLOAD_KEY, it).apply()
+            }.toSecretByteArray
         }
+    }
 
     private fun createRandomString(): String {
-            return (1..STRING_LENGTH)
-                    .map { ALLOWED_CHARS.random() }
-                    .joinToString("")
+        return (1..STRING_LENGTH)
+            .map { ALLOWED_CHARS.random() }
+            .joinToString("")
+    }
+
+    override fun saveDrmDownload(context: Context, audioUrl: String, drmDownload: DrmDownload) {
+        context.getSharedPreferences(DOWNLOAD_FILENAME, Context.MODE_PRIVATE).also { sharedPrefs ->
+            val key = Base64.encodeToString(audioUrl.toSecretByteArray + drmDownload.drmType.name.toSecretByteArray, Base64.NO_WRAP)
+            val value = Base64.encodeToString(Json.encodeToString(drmDownload).toByteArray(StandardCharsets.UTF_8), Base64.NO_WRAP)
+            sharedPrefs.edit().putString(key, value).apply()
+        }
+    }
+
+    override fun getDrmDownload(context: Context, audioUrl: String, drmType: DrmType): DrmDownload? =
+        context.getSharedPreferences(DOWNLOAD_FILENAME, Context.MODE_PRIVATE).let { sharedPrefs ->
+            val key = Base64.encodeToString(audioUrl.toSecretByteArray + drmType.name.toSecretByteArray, Base64.NO_WRAP)
+            sharedPrefs.getString(key, null)?.let { drmResult ->
+                Json.decodeFromString<DrmDownload>(drmResult)
+            }
+        }
+
+    override fun removeDrmDownload(context: Context, audioUrl: String, drmType: DrmType) {
+        context.getSharedPreferences(DOWNLOAD_FILENAME, Context.MODE_PRIVATE).also { sharedPrefs ->
+            val key = Base64.encodeToString(audioUrl.toSecretByteArray + drmType.name.toSecretByteArray, Base64.NO_WRAP)
+            sharedPrefs.edit().remove(key).apply()
+        }
+    }
+
+    override fun removeDrmDownload(context: Context, key: String) {
+        context.getSharedPreferences(DOWNLOAD_FILENAME, Context.MODE_PRIVATE).also { sharedPrefs ->
+            sharedPrefs.edit().remove(key).apply()
+        }
+    }
+
+    override fun getAllDrmDownloads(context: Context): Map<String, DrmDownload> =
+        context.getSharedPreferences(DOWNLOAD_FILENAME, Context.MODE_PRIVATE).let { sharedPrefs ->
+            sharedPrefs.all.mapNotNull {
+                sharedPrefs.getString(it.key, null)?.let { drmResult ->
+                    it.key to Json.decodeFromString<DrmDownload>(drmResult)
+                }
+            }.toMap()
         }
 
     private val String.toSecretByteArray: ByteArray

Armadillo/src/main/java/com/scribd/armadillo/models/Models.kt

@@ -3,6 +3,7 @@ package com.scribd.armadillo.models
 import android.os.Parcel
 import android.os.Parcelable
 import com.google.android.exoplayer2.C
+import com.google.android.exoplayer2.C.ContentType
 import com.scribd.armadillo.Milliseconds
 import com.scribd.armadillo.extensions.toPrint
 import com.scribd.armadillo.time.milliseconds
@@ -143,6 +144,36 @@ data class Chapter(
 
 data class DrmInfo(val drmType: DrmType, val licenseServer: String, val drmHeaders: Map<String, String> = emptyMap()) : Serializable
 
+@kotlinx.serialization.Serializable
+data class DrmDownload(
+    val drmKeyId: ByteArray,
+    val drmType: DrmType,
+    val licenseServer: String,
+    @ContentType val audioType: Int,
+) {
+    override fun equals(other: Any?): Boolean {
+        if (this === other) return true
+        if (javaClass != other?.javaClass) return false
+
+        other as DrmDownload
+
+        if (!drmKeyId.contentEquals(other.drmKeyId)) return false
+        if (drmType != other.drmType) return false
+        if (licenseServer != other.licenseServer) return false
+        if (audioType != other.audioType) return false
+
+        return true
+    }
+
+    override fun hashCode(): Int {
+        var result = drmKeyId.contentHashCode()
+        result = 31 * result + drmType.hashCode()
+        result = 31 * result + licenseServer.hashCode()
+        result = 31 * result + audioType
+        return result
+    }
+}
+
 enum class DrmType {
     WIDEVINE;