com.pubnub.api.crypto.cryptor.AesCbcCryptor.kt Maven / Gradle / Ivy

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package com.pubnub.api.crypto.cryptor

import com.pubnub.api.PubNubError
import com.pubnub.api.PubNubException
import com.pubnub.api.crypto.checkMinSize
import com.pubnub.api.crypto.data.EncryptedData
import com.pubnub.api.crypto.data.EncryptedStreamData
import java.io.BufferedInputStream
import java.io.InputStream
import java.security.MessageDigest
import java.security.SecureRandom
import javax.crypto.Cipher
import javax.crypto.CipherInputStream
import javax.crypto.spec.IvParameterSpec
import javax.crypto.spec.SecretKeySpec

private const val CIPHER_TRANSFORMATION = "AES/CBC/PKCS5Padding"
private const val RANDOM_IV_SIZE = 16

class AesCbcCryptor(val cipherKey: String) : Cryptor {
    private val newKey: SecretKeySpec = createNewKey()

    override fun id(): ByteArray {
        return byteArrayOf('A'.code.toByte(), 'C'.code.toByte(), 'R'.code.toByte(), 'H'.code.toByte())
    }

    override fun encrypt(data: ByteArray): EncryptedData {
        validateData(data)
        return try {
            val ivBytes: ByteArray = createRandomIv()
            val cipher = createInitializedCipher(ivBytes, Cipher.ENCRYPT_MODE)
            val encryptedData: ByteArray = cipher.doFinal(data)
            EncryptedData(metadata = ivBytes, data = encryptedData)
        } catch (e: Exception) {
            throw PubNubException(errorMessage = e.message, pubnubError = PubNubError.CRYPTO_ERROR)
        }
    }

    override fun decrypt(encryptedData: EncryptedData): ByteArray {
        validateData(encryptedData.data)
        return try {
            val ivBytes: ByteArray = encryptedData.metadata?.takeIf { it.size == RANDOM_IV_SIZE }
                ?: throw PubNubException(errorMessage = "Invalid random IV", pubnubError = PubNubError.CRYPTO_ERROR)
            val cipher = createInitializedCipher(ivBytes, Cipher.DECRYPT_MODE)
            val decryptedData = cipher.doFinal(encryptedData.data)
            decryptedData
        } catch (e: Exception) {
            throw PubNubException(errorMessage = e.message, pubnubError = PubNubError.CRYPTO_ERROR)
        }
    }

    override fun encryptStream(stream: InputStream): EncryptedStreamData {
        val bufferedInputStream = validateInputStreamAndReturnBuffered(stream)
        try {
            val ivBytes: ByteArray = createRandomIv()
            val cipher = createInitializedCipher(ivBytes, Cipher.ENCRYPT_MODE)
            val cipheredStream = CipherInputStream(bufferedInputStream, cipher)

            return EncryptedStreamData(
                metadata = ivBytes,
                stream = cipheredStream
            )
        } catch (e: Exception) {
            throw PubNubException(e.message, PubNubError.CRYPTO_ERROR)
        }
    }

    override fun decryptStream(encryptedData: EncryptedStreamData): InputStream {
        val bufferedInputStream = validateInputStreamAndReturnBuffered(encryptedData.stream)
        try {
            val ivBytes: ByteArray = encryptedData.metadata?.takeIf { it.size == RANDOM_IV_SIZE }
                ?: throw PubNubException(errorMessage = "Invalid random IV", pubnubError = PubNubError.CRYPTO_ERROR)
            val cipher = createInitializedCipher(ivBytes, Cipher.DECRYPT_MODE)
            return CipherInputStream(bufferedInputStream, cipher)
        } catch (e: Exception) {
            throw PubNubException(errorMessage = e.message, pubnubError = PubNubError.CRYPTO_ERROR)
        }
    }

    private fun validateData(data: ByteArray) {
        if (data.isEmpty()) {
            throw PubNubException(
                errorMessage = "Encryption/Decryption of empty data not allowed.",
                pubnubError = PubNubError.ENCRYPTION_AND_DECRYPTION_OF_EMPTY_DATA_NOT_ALLOWED
            )
        }
    }

    private fun createInitializedCipher(iv: ByteArray, mode: Int): Cipher {
        return Cipher.getInstance(CIPHER_TRANSFORMATION).also {
            it.init(mode, newKey, IvParameterSpec(iv))
        }
    }

    private fun createNewKey(): SecretKeySpec {
        val keyBytes = sha256(cipherKey.toByteArray(Charsets.UTF_8))
        return SecretKeySpec(keyBytes, "AES")
    }

    private fun createRandomIv(): ByteArray {
        val ivBytes = ByteArray(RANDOM_IV_SIZE)
        SecureRandom().nextBytes(ivBytes)
        return ivBytes
    }

    private fun sha256(input: ByteArray): ByteArray {
        val digest: MessageDigest
        return try {
            digest = MessageDigest.getInstance("SHA-256")
            digest.digest(input)
        } catch (e: java.lang.Exception) {
            throw PubNubException(errorMessage = e.message, pubnubError = PubNubError.CRYPTO_ERROR)
        }
    }

    private fun validateInputStreamAndReturnBuffered(stream: InputStream): BufferedInputStream {
        val bufferedInputStream = stream.buffered()
        bufferedInputStream.checkMinSize(1) {
            throw PubNubException(
                errorMessage = "Encryption/Decryption of empty data not allowed.",
                pubnubError = PubNubError.ENCRYPTION_AND_DECRYPTION_OF_EMPTY_DATA_NOT_ALLOWED
            )
        }
        return bufferedInputStream
    }
}