Simple password storage, update, retrieval and deletion in Keychain macOS

KeychainService.swift

import Cocoa
import Security

// Adaptation of https://stackoverflow.com/a/37539998/1694526
// Arguments for the keychain queries
let kSecClassValue = NSString(format: kSecClass)
let kSecAttrAccountValue = NSString(format: kSecAttrAccount)
let kSecValueDataValue = NSString(format: kSecValueData)
let kSecClassGenericPasswordValue = NSString(format: kSecClassGenericPassword)
let kSecAttrServiceValue = NSString(format: kSecAttrService)
let kSecMatchLimitValue = NSString(format: kSecMatchLimit)
let kSecReturnDataValue = NSString(format: kSecReturnData)
let kSecMatchLimitOneValue = NSString(format: kSecMatchLimitOne)

public class KeychainService: NSObject {
    
    class func updatePassword(service: NSString, account:NSString, data: NSString) {
        let dataFromString: NSData = data.data(using: String.Encoding.utf8.rawValue, allowLossyConversion: false)! as NSData
        
        // Instantiate a new default keychain query
        let keychainQuery: NSMutableDictionary = NSMutableDictionary(objects: [kSecClassGenericPasswordValue, service, account, kCFBooleanTrue, kSecMatchLimitOneValue], forKeys: [kSecClassValue, kSecAttrServiceValue, kSecAttrAccountValue, kSecReturnDataValue, kSecMatchLimitValue])
        
        let status = SecItemUpdate(keychainQuery as CFDictionary, [kSecValueDataValue:dataFromString] as CFDictionary)
        
        if (status != errSecSuccess) {
            print("Read failed: \(SecCopyErrorMessageString(status, nil))")
        }

    }
    
    
    class func removePassword(service: NSString, account:NSString) {
        
        // Instantiate a new default keychain query
       let keychainQuery: NSMutableDictionary = NSMutableDictionary(objects: [kSecClassGenericPasswordValue, service, account, kCFBooleanTrue, kSecMatchLimitOneValue], forKeys: [kSecClassValue, kSecAttrServiceValue, kSecAttrAccountValue, kSecReturnDataValue, kSecMatchLimitValue])
        
        // Delete any existing items
       let status = SecItemDelete(keychainQuery as CFDictionary)
        if (status != errSecSuccess) {
            print("Delete failed: \(SecCopyErrorMessageString(status, nil))")
        }

    }
    
 
    class func savePassword(service: NSString, account:NSString, data: NSString) {
        let dataFromString: NSData = data.data(using: String.Encoding.utf8.rawValue, allowLossyConversion: false)! as NSData
        
        // Instantiate a new default keychain query
        let keychainQuery: NSMutableDictionary = NSMutableDictionary(objects: [kSecClassGenericPasswordValue, service, account, dataFromString], forKeys: [kSecClassValue, kSecAttrServiceValue, kSecAttrAccountValue, kSecValueDataValue])
        
        // Add the new keychain item
        let status = SecItemAdd(keychainQuery as CFDictionary, nil)
        
        if (status != errSecSuccess) {    // Always check the status
            print("Write failed: \(SecCopyErrorMessageString(status, nil)).")
        }

    }
    
       class func loadPassword(service: NSString, account:NSString) -> NSString? {
        // Instantiate a new default keychain query
        // Tell the query to return a result
        // Limit our results to one item
        let keychainQuery: NSMutableDictionary = NSMutableDictionary(objects: [kSecClassGenericPasswordValue, service, account, kCFBooleanTrue, kSecMatchLimitOneValue], forKeys: [kSecClassValue, kSecAttrServiceValue, kSecAttrAccountValue, kSecReturnDataValue, kSecMatchLimitValue])
        
        var dataTypeRef :AnyObject?
        
        // Search for the keychain items
        let status: OSStatus = SecItemCopyMatching(keychainQuery, &dataTypeRef)
        var contentsOfKeychain: NSString? = nil
        
        if status == errSecSuccess {
            if let retrievedData = dataTypeRef as? NSData {
                contentsOfKeychain = NSString(data: retrievedData as Data, encoding: String.Encoding.utf8.rawValue)
            }
        } else {
            print("Nothing was retrieved from the keychain. Status code \(status)")
        }
    
        return contentsOfKeychain
    }

}