wLv1rjzX

1class Decryptor(private val storage: SharedPreferences) {
2    private val ANDROID_KEY_STORE = "AndroidKeyStore"
3    private val TRANSFORMATION = "AES/GCM/NoPadding"
4
5    private var keyStore: KeyStore? = null
6
7    init {
8        initKeyStore()
9    }
10
11    @Throws(Exception::class)
12    private fun initKeyStore() {
13        keyStore = KeyStore.getInstance(ANDROID_KEY_STORE)
14        keyStore!!.load(null)
15    }
16
17    @Throws(Exception::class)
18    fun decryptDataWithAES(alias: String): String {
19        var alias = alias
20        alias = alias + "_AES"
21
22        val base64InitVector = storage.getString(alias + "_initVector", null)
23        val base64Encryption = storage.getString(alias + "_encryption", null)
24
25        if (TextUtils.isEmpty(base64InitVector) || TextUtils.isEmpty(base64Encryption))
26            throw NullPointerException("Not found initialization vector or encryption data for specified alias")
27
28        val encryptionIv = Base64.decode(base64InitVector, Base64.NO_WRAP)
29        val encryptedData = Base64.decode(base64Encryption, Base64.NO_WRAP)
30
31        Log.d("AndroidKeyStore", "encrypted data: " + Arrays.toString(encryptedData) + " encrypted iv: "
32                + Arrays.toString(encryptionIv))
33        val cipher = Cipher.getInstance(TRANSFORMATION)
34        val spec = GCMParameterSpec(128, encryptionIv)
35        cipher.init(Cipher.DECRYPT_MODE, getSecretKey(alias), spec)
36
37        return String(cipher.doFinal(encryptedData), StandardCharsets.UTF_8)
38    }
39
40    fun decryptDataWithRSA(alias: String): String {
41        var alias = alias
42        alias = alias + "_RSA"
43        val base64PublicKey = storage.getString(alias + "_publicKey", null)
44        val base64Encryption = storage.getString(alias + "_encryption", null)
45
46        val keyBytes = Base64.decode(base64PublicKey, Base64.NO_WRAP)
47        val encryption = Base64.decode(base64Encryption, Base64.NO_WRAP)
48        val spec = X509EncodedKeySpec(keyBytes)
49
50        var decodedBytes = ByteArray(0)
51        try {
52            val keyFactory = KeyFactory.getInstance(KeyProperties.KEY_ALGORITHM_RSA)
53            val key = keyFactory.generatePublic(spec)
54            val cipher = Cipher.getInstance(KeyProperties.KEY_ALGORITHM_RSA)
55            cipher.init(Cipher.DECRYPT_MODE, key)
56            decodedBytes = cipher.doFinal(encryption)
57        } catch (e: Exception) {
58            e.printStackTrace()
59        }
60
61        return String(decodedBytes, StandardCharsets.UTF_8)
62    }
63
64    @Throws(Exception::class)
65    private fun getSecretKey(alias: String): SecretKey {
66        return (keyStore!!.getEntry(alias, null) as KeyStore.SecretKeyEntry).getSecretKey()
67    }
68}