Create CirclesKeystoreProvider

matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/crypto/CirclesKeystoreProvider.kt

+package org.matrix.android.sdk.internal.crypto
+
+import android.content.Context
+import android.security.keystore.KeyGenParameterSpec
+import android.security.keystore.KeyProperties
+import android.util.Base64
+import androidx.core.content.edit
+import org.matrix.android.sdk.api.extensions.tryOrNull
+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
+
+//Created for Circles
+class CirclesKeystoreProvider @Inject constructor(
+        context: Context
+) {
+    private val sharedPreferences = context.getSharedPreferences(PREF_NAME, Context.MODE_PRIVATE)
+
+    private val keyStore
+        get() = KeyStore.getInstance(ANDROID_KEYS_TORE).apply { load(null) }
+
+    fun storeBsSpekePrivateKey(keyBytes: ByteArray, keyId: String) {
+        tryOrNull {
+            val alias = "$ORG_FUTO_SSSS_KEY_PREFIX.$keyId"
+            val masterKey = getOrGenerateMasterKeyIfNotExist(alias)
+                    ?: throw IllegalArgumentException("Failed to get master key")
+            val encrypted = encryptData(keyBytes, masterKey)
+            storeBSspekeEncryptedPrivateKeyBase64(alias, encrypted)
+        }
+    }
+
+    fun getBsSpekePrivateKey(keyId: String): ByteArray? = tryOrNull {
+        val alias = "$ORG_FUTO_SSSS_KEY_PREFIX.$keyId"
+        val masterKey = getOrGenerateMasterKeyIfNotExist(alias)
+                ?: throw IllegalArgumentException("Failed to get master key")
+        val encrypted = getBSspekeEncryptedPrivateKeyBase64(alias)
+                ?: throw IllegalArgumentException("Not saved in preferences $alias")
+        decryptData(encrypted, masterKey)
+    }
+
+    private fun getOrGenerateMasterKeyIfNotExist(alias: String): SecretKey? {
+        if (!keyStore.containsAlias(alias)) {
+            KeyGenerator.getInstance(KeyProperties.KEY_ALGORITHM_AES, ANDROID_KEYS_TORE).apply {
+                init(
+                        KeyGenParameterSpec.Builder(
+                                alias, KeyProperties.PURPOSE_ENCRYPT or KeyProperties.PURPOSE_DECRYPT
+                        )
+                                .setKeySize(KEY_SIZE)
+                                .setBlockModes(KeyProperties.BLOCK_MODE_GCM)
+                                .setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_NONE)
+                                .build()
+                )
+                generateKey()
+            }
+        }
+        return keyStore.getKey(alias, null) as? SecretKey
+    }
+
+    private fun encryptData(data: ByteArray, masterKey: SecretKey): String {
+        val cipher = Cipher.getInstance(AES_NO_PADDING)
+        cipher.init(Cipher.ENCRYPT_MODE, masterKey)
+        val ivString = Base64.encodeToString(cipher.iv, Base64.DEFAULT)
+        val encryptedBytes: ByteArray = cipher.doFinal(data)
+        return ivString + IV_SEPARATOR + Base64.encodeToString(encryptedBytes, Base64.DEFAULT)
+    }
+
+    private fun decryptData(encryptedData: String, masterKey: SecretKey): ByteArray {
+        val (iv64, encrypted64) = encryptedData.split(IV_SEPARATOR)
+        val cipher = Cipher.getInstance(AES_NO_PADDING)
+        val spec = GCMParameterSpec(KEY_SIZE, Base64.decode(iv64, Base64.DEFAULT))
+        cipher.init(Cipher.DECRYPT_MODE, masterKey, spec)
+        return cipher.doFinal(Base64.decode(encrypted64, Base64.DEFAULT))
+    }
+
+    private fun getBSspekeEncryptedPrivateKeyBase64(alias: String): String? {
+        return sharedPreferences.getString(alias, null)
+    }
+
+    private fun storeBSspekeEncryptedPrivateKeyBase64(alias: String, key: String) {
+        sharedPreferences.edit { putString(alias, key) }
+    }
+
+    companion object {
+        private const val PREF_NAME = "org.futo.circles.keystore"
+        private const val AES_NO_PADDING = "AES/GCM/NoPadding"
+        private const val IV_SEPARATOR = "]"
+        private const val KEY_SIZE = 128
+        private const val ANDROID_KEYS_TORE = "AndroidKeyStore"
+        private const val ORG_FUTO_SSSS_KEY_PREFIX = "org.futo.ssss.key"
+    }
+}