first commit

CamperMonitor/Store/KeychainStore.swift

@@ -0,0 +1,59 @@
+import Foundation
+import Security
+
+/// Ablage für die Victron-Verschlüsselungsschlüssel. Die gehören nicht in die
+/// UserDefaults, deshalb Keychain.
+enum KeychainStore {
+
+    private static let service = "de.fritob.CamperMonitor.victronKeys"
+
+    static func setKey(_ hex: String?, for deviceID: UUID) {
+        let account = deviceID.uuidString
+        var query: [String: Any] = [
+            kSecClass as String: kSecClassGenericPassword,
+            kSecAttrService as String: service,
+            kSecAttrAccount as String: account,
+        ]
+        SecItemDelete(query as CFDictionary)
+
+        guard let hex, let data = hex.data(using: .utf8) else { return }
+        query[kSecValueData as String] = data
+        query[kSecAttrAccessible as String] = kSecAttrAccessibleAfterFirstUnlock
+        SecItemAdd(query as CFDictionary, nil)
+    }
+
+    static func key(for deviceID: UUID) -> String? {
+        let query: [String: Any] = [
+            kSecClass as String: kSecClassGenericPassword,
+            kSecAttrService as String: service,
+            kSecAttrAccount as String: deviceID.uuidString,
+            kSecReturnData as String: true,
+            kSecMatchLimit as String: kSecMatchLimitOne,
+        ]
+        var result: AnyObject?
+        guard SecItemCopyMatching(query as CFDictionary, &result) == errSecSuccess,
+              let data = result as? Data else { return nil }
+        return String(data: data, encoding: .utf8)
+    }
+}
+
+extension String {
+    /// Wandelt einen Hex-String in Bytes. Leerzeichen, Doppelpunkte und ein
+    /// führendes "0x" werden ignoriert, damit sich der Schlüssel aus
+    /// VictronConnect einfach einfügen lässt.
+    var hexBytes: [UInt8]? {
+        var cleaned = self.lowercased()
+            .replacingOccurrences(of: "0x", with: "")
+            .filter { $0.isHexDigit }
+        guard !cleaned.isEmpty, cleaned.count % 2 == 0 else { return nil }
+        var bytes: [UInt8] = []
+        bytes.reserveCapacity(cleaned.count / 2)
+        while !cleaned.isEmpty {
+            let pair = String(cleaned.prefix(2))
+            cleaned.removeFirst(2)
+            guard let byte = UInt8(pair, radix: 16) else { return nil }
+            bytes.append(byte)
+        }
+        return bytes
+    }
+}