Backup: introduce Aes256 algorithm

Author: ganfra

matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/crypto/keysbackup/algorithm/KeysBackupAes256Algorithm.kt

@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2022 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 org.matrix.android.sdk.internal.crypto.keysbackup.algorithm
+
+import org.matrix.android.sdk.api.crypto.MXCRYPTO_ALGORITHM_AES_256_BACKUP
+import org.matrix.android.sdk.api.session.crypto.keysbackup.KeysVersionResult
+import org.matrix.android.sdk.api.session.crypto.keysbackup.MegolmBackupAes256AuthData
+import org.matrix.android.sdk.api.session.crypto.keysbackup.MegolmBackupAuthData
+import org.matrix.android.sdk.api.util.JsonDict
+import org.matrix.android.sdk.internal.crypto.MegolmSessionData
+import org.matrix.android.sdk.internal.crypto.keysbackup.model.rest.KeysBackupData
+
+internal class KeysBackupAes256Algorithm(keysVersions: KeysVersionResult) : KeysBackupAlgorithm {
+
+    override val untrusted: Boolean = true
+
+    private val aesAuthData: MegolmBackupAes256AuthData
+
+    init {
+        if (keysVersions.algorithm != MXCRYPTO_ALGORITHM_AES_256_BACKUP) {
+            throw IllegalStateException("Algorithm doesn't match")
+        }
+        aesAuthData = keysVersions.getAuthDataAsMegolmBackupAuthData() as MegolmBackupAes256AuthData
+    }
+
+    override fun encryptSession(sessionData: MegolmSessionData): JsonDict? {
+        TODO("Not yet implemented")
+    }
+
+    override fun decryptSessions(recoveryKey: String, data: KeysBackupData): List<MegolmSessionData> {
+        TODO("Not yet implemented")
+    }
+
+    override fun release() {
+        TODO("Not yet implemented")
+    }
+
+    override val authData: MegolmBackupAuthData = aesAuthData
+
+    override fun keyMatches(key: String): Boolean {
+        TODO("Not yet implemented")
+    }
+}

matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/crypto/keysbackup/algorithm/KeysBackupAlgorithmFactory.kt

@@ -29,7 +29,7 @@ internal class KeysBackupAlgorithmFactory @Inject constructor() {
                 KeysBackupCurve25519Algorithm(keysVersion)
             }
             MXCRYPTO_ALGORITHM_AES_256_BACKUP -> {
-                throw IllegalStateException("AES_256 is not yet handled")
+                KeysBackupAes256Algorithm(keysVersion)
             }
             else -> {
                 throw IllegalStateException("Unknown algorithm")