Get password from keychain using persistent reference

OpenVPN Tunnel Provider/KeychainAccess+Reference.swift

@@ -0,0 +1,45 @@
+//
+//  KeychainAccess+Reference.swift
+//  OpenVPN iOS Client
+//
+//  Created by Sergey Abramchuk on 07.03.17.
+//
+//
+
+import Foundation
+import KeychainAccess
+
+extension Keychain {
+    
+    public func get(ref: Data) throws -> String? {
+        guard let data = try getData(ref: ref) else {
+            return nil
+        }
+        
+        return String(data: data, encoding: .utf8)
+    }
+    
+    public func getData(ref: Data) throws -> Data? {
+        let query: [String: Any] = [
+            String(kSecClass): itemClass.rawValue,
+            String(kSecReturnData): kCFBooleanTrue,
+            String(kSecValuePersistentRef): ref as CFData
+        ]
+        
+        var result: AnyObject?
+        let status = SecItemCopyMatching(query as CFDictionary, &result)
+        
+        switch status {
+        case errSecSuccess:
+            guard let data = result as? Data else {
+                throw Status.unexpectedError
+            }
+            return data
+        case errSecItemNotFound:
+            return nil
+        default:
+            throw Status(status: status)
+        }
+    }
+    
+}