# KeyModelDTO.kt

    /*
     * The MIT License
     *
     * Original work sponsored and donated by The Danish Health Data Authority (http://www.sundhedsdatastyrelsen.dk)
     *
     * Copyright (C) 2021 The Danish Health Data Authority (http://www.sundhedsdatastyrelsen.dk)
     *
     *
     * Permission is hereby granted, free of charge, to any person obtaining a copy of
     * this software and associated documentation files (the "Software"), to deal in
     * the Software without restriction, including without limitation the rights to
     * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
     * of the Software, and to permit persons to whom the Software is furnished to do
     * so, subject to the following conditions:
     *
     *
     * The above copyright notice and this permission notice shall be included in all
     * copies or substantial portions of the Software.
     *
     *
     * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
     * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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     * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
     * SOFTWARE.
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    package dk.nsp.api.auth.keyserver.models

    import android.os.Parcelable
    import android.util.Base64
    import dk.nsp.shared.tryAndLog
    import kotlinx.parcelize.Parcelize

    import java.security.Key
    import javax.crypto.Cipher
    import javax.crypto.spec.IvParameterSpec
    import javax.crypto.spec.SecretKeySpec

    /**
     * @property key String the AES key
     * @property keyId String the key's id
     * @property longSecret String the longsecret working like a second password
     * @constructor
     */
    @Parcelize
    data class KeyModelDTO(
        val key: String,
        val keyId: String,
        val longSecret: String
    ) : Parcelable

    //region Crypto helpers
    private const val aesCipher: String = "AES"
    private const val aesCipherCbc5Padding = "$aesCipher/CBC/PKCS5Padding"

    //An iv of null's / 0's /128 bit => 16 characters
    private val iv: IvParameterSpec = IvParameterSpec(ByteArray(16) { 0 })

    /**
     * Encrypts the given data with [KeyModelDTO.key]
     * @receiver KeyModel
     * @param data ByteArray
     * @return ByteArray?
     */
    fun KeyModelDTO.encrypt(data: ByteArray): ByteArray? {
        val encryptionKey: Key = aesKey() ?: return null
        return tryAndLog {
            Cipher.getInstance(aesCipherCbc5Padding)?.let { cipher ->
                cipher.init(Cipher.ENCRYPT_MODE, encryptionKey, iv)
                cipher.doFinal(data)
            }
        }
    }

    /**
     * Decrypts the given content using [KeyModelDTO.key]
     * @receiver KeyModel
     * @param data ByteArray
     * @return ByteArray?
     */
    fun KeyModelDTO.decrypt(data: ByteArray): ByteArray? {
        val decryptionKey: Key = aesKey() ?: return null
        return tryAndLog {
            Cipher.getInstance(aesCipherCbc5Padding)?.let { cipher ->
                cipher.init(Cipher.DECRYPT_MODE, decryptionKey, iv)
                cipher.doFinal(data)
            }
        }
    }

    /**
     * Unpacks the AES key for this [KeyModelDTO]
     * @receiver KeyModel
     * @return Key?
     */
    private fun KeyModelDTO.aesKey(): Key? {
        //Decode the base 64 encoding
        val decodedKey = Base64.decode(key, Base64.DEFAULT) ?: return null
        return SecretKeySpec(decodedKey, aesCipher)
    }
    //endregion