55 lines
2.1 KiB
Kotlin
55 lines
2.1 KiB
Kotlin
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package com.longnh15.heimdall.common
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import android.security.keystore.KeyGenParameterSpec
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import android.security.keystore.KeyProperties
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import java.security.KeyStore
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import javax.crypto.Cipher
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import javax.crypto.KeyGenerator
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import javax.crypto.SecretKey
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import javax.crypto.spec.GCMParameterSpec
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import kotlin.io.encoding.Base64
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object TokenCrypto {
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private const val PROVIDER = "AndroidKeyStore"
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private const val ALIAS = "auth_token_key"
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private const val TRANSFORMATION = "AES/GCM/NoPadding"
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private const val IV_SIZE = 12
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private const val TAG_BITS = 128
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private val keystore = KeyStore.getInstance(PROVIDER).apply { load(null) }
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private fun getOrCreateKey(): SecretKey {
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(keystore.getEntry(ALIAS, null) as? KeyStore.SecretKeyEntry)?.let {
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return it.secretKey
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}
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val keyGen = KeyGenerator.getInstance(KeyProperties.KEY_ALGORITHM_AES, PROVIDER)
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keyGen.init(
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KeyGenParameterSpec.Builder(
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ALIAS,
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KeyProperties.PURPOSE_ENCRYPT or KeyProperties.PURPOSE_DECRYPT
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)
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.setBlockModes(KeyProperties.BLOCK_MODE_GCM)
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.setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_NONE)
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.setKeySize(256)
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.build()
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)
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return keyGen.generateKey()
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}
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fun encrypt(plainText: String): String {
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val cipher = Cipher.getInstance(TRANSFORMATION)
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cipher.init(Cipher.ENCRYPT_MODE, getOrCreateKey())
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val iv = cipher.iv // 12-byte IV, generated by Keystore
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val cipherText = cipher.doFinal(plainText.toByteArray(Charsets.UTF_8))
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return Base64.encode(iv + cipherText) // prepend IV
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}
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fun decrypt(encoded: String): String {
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val combined = Base64.decode(encoded)
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val iv = combined.copyOfRange(0, IV_SIZE)
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val cipherText = combined.copyOfRange(IV_SIZE, combined.size)
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val cipher = Cipher.getInstance(TRANSFORMATION)
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cipher.init(Cipher.DECRYPT_MODE, getOrCreateKey(), GCMParameterSpec(TAG_BITS, iv))
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return cipher.doFinal(cipherText).toString(Charsets.UTF_8)
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}
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}
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