Sesame-iOS/Sesame/KeyManagement.swift

import Foundation
import CryptoKit
import SwiftUI

final class KeyManagement {

    static let tag = "com.ch.sesame.key".data(using: .utf8)!

    private static let label = "sesame"

    private static let keyType = kSecAttrKeyTypeEC

    private static let keyClass = kSecAttrKeyClassSymmetric

    private static let query: [String: Any] = [
        kSecClass as String: kSecClassInternetPassword,
        kSecAttrAccount as String: "account",
        kSecAttrServer as String: "christophhagen.de",
        kSecAttrLabel as String: "sesame"]

    private static func loadKeys() -> Data? {
        var query = query
        query[kSecReturnData as String] = kCFBooleanTrue

        var item: CFTypeRef?
        let status = SecItemCopyMatching(query as CFDictionary, &item)
        guard status == errSecSuccess else {
            print("Failed to get key: \(status)")
            return nil
        }
        let key = item as! CFData
        print("Key loaded from keychain")
        return key as Data
    }

    private static func deleteKeys() {
        let status = SecItemDelete(query as CFDictionary)
        guard status == errSecSuccess || status == errSecItemNotFound else {
            print("Failed to remove key: \(status)")
            return
        }
        print("Key removed from keychain")
    }

    private static func saveKeys(_ data: Data) {
        var query = query
        query[kSecValueData as String] = data
        let status = SecItemAdd(query as CFDictionary, nil)
        guard status == errSecSuccess else {
            print("Failed to store key: \(status)")
            return
        }
        print("Key saved to keychain")
    }

    private static var keyData: Data? = loadKeys() {
        didSet {
            guard let data = keyData else {
                deleteKeys()
                return
            }
            saveKeys(data)
        }
    }

    static var hasKey: Bool {
        key != nil
    }

    private(set) static var key: (device: SymmetricKey, remote: SymmetricKey)? {
        get {
            guard let data = keyData else {
                return nil
            }
            let device = SymmetricKey(data: data.prefix(32))
            let remote = SymmetricKey(data: data.advanced(by: 32))
            return (device, remote)
        }
        set {
            guard let key = newValue else {
                keyData = nil
                return
            }
            keyData = key.device.data + key.remote.data
        }
    }

    static func generateNewKeys() {
        let device = SymmetricKey(size: .bits256)
        let remote = SymmetricKey(size: .bits256)
        key = (device, remote)
        print("New keys:")
        print("Device: \(device.data.hexEncoded)")
        print("Remote: \(remote.data.hexEncoded)")
    }
}