Console App Credentials and the Windows Credential Manager

In working on a little utility to query JIRA tickets in a sprint, I needed a JIRA username and password to pass along to the Atlassian.Net SDK. I didn’t want to prompt for those credentials each time but I also didn’t want to store the credentials myself either, even if encrypted. Using the Windows Credential Manager sounded ideal, but I didn’t recall working with it programmatically before. A quick search lead me to a CredentialManagement NuGet package that handles all the low level Win32 code.

A ConsoleInput class checks the credential store and prompts for the needed credentials if not found. It also deals with I/O helpers like masking the password.

using System;
using System.Collections.Generic;
using System.Linq;
namespace JIRASprintQuery
{
    public class ConsoleInput
    {
        public bool IsValid { get; private set; }
        public string Username { get; private set; }
        public string Password { get; private set; }
        public string SprintName { get; private set; }
        public ConsoleInput Get()
        {
            // If we have saved Windows credentials in Credential Manager, use those, else prompt.
            var cred = Credentials.Get();
            if (cred.User == null || cred.Pass == null)
            {
                Username = ReadLine("JIRA Username");
                if (string.IsNullOrEmpty(Username)) return this;
                Password = ReadPassword("JIRA Password");
                if (string.IsNullOrEmpty(Password)) return this;
                Credentials.Save(Username, Password);
            }
            else
            {
                Username = cred.User;
                Password = cred.Pass;
            }
            SprintName = GetSprintName(ReadLine("Sprint name or number"));
            if (string.IsNullOrWhiteSpace(SprintName)) return this;
            IsValid = true;
            return this;
        }
        private string ReadLine(string label, bool trim = true)
        {
            Console.WriteLine($"{label}:");
            var input = Console.ReadLine();
            Console.WriteLine();
            if (trim) input = input?.Trim();
            
            if (string.IsNullOrEmpty(input))
            {
                IsValid = false;
                Console.WriteLine($"{label} is required, exiting.");
            }            
            return input;
        }
        private static string GetSprintName(string sprint)
        {
            if (int.TryParse(sprint, out int sprintNumber))
            {
                // i.e. <add key="SprintNamePattern" value="Project - Sprint {SprintNumber}" />
                var template = AppSettings.SprintNamePattern;
                sprint = template.Replace("{SprintNumber}", sprintNumber.ToString());
            }
            return sprint?.Trim();
        }
        public static string ReadPassword(string label, char mask = '*')
        {
            const int enter = 13, backsp = 8, ctrlbacksp = 127;
            int[] filtered = { 0, 27, 9, 10 /*, 32 space, if you care */ }; // const
            var pass = new Stack<char>();
            char chr;
            Console.WriteLine($"{label}:");
            while ((chr = Console.ReadKey(true).KeyChar) != enter)
            {
                if (chr == backsp)
                {
                    if (pass.Count > 0)
                    {
                        Console.Write("\b \b");
                        pass.Pop();
                    }
                }
                else if (chr == ctrlbacksp)
                {
                    while (pass.Count > 0)
                    {
                        Console.Write("\b \b");
                        pass.Pop();
                    }
                }
                else if (filtered.Count(x => chr == x) > 0) { }
                else
                {
                    pass.Push(chr);
                    Console.Write(mask);
                }
            }
            Console.WriteLine();
            Console.WriteLine();
            return new string(pass.Reverse().ToArray());
        }
    }
}

Credential loading and saving was very easy with the Credential class of the CredentialManagment NuGet package. Note the use of named value tuples in the Get method (requiring System.ValueTuple package at the moment).

using CredentialManagement;
using System.Reflection;
namespace JIRASprintQuery
{
    public static class Credentials
    {
        private static string Target()
        {
            // Just use assembly short name as identifier in credential store.
            return Assembly.GetEntryAssembly().GetName().Name;
        }
        public static void Save(string username, string password)
        {
            using (var cred = new Credential())
            {
                cred.Username = username;
                cred.Password = password;
                cred.Target = Target();
                cred.Type = CredentialType.Generic;
                cred.PersistanceType = PersistanceType.LocalComputer;
                cred.Save();
            }
        }
        public static (string User, string Pass) Get()
        {
            using (var cred = new Credential())
            {
                cred.Target = Target();
                cred.Load();
                return (cred.Username, cred.Password);
            }
        }
    }
}

I used the ConsoleInput class as follows, making use of async Main. That required switching to Visual Studio 2017 Preview 2, and Enabling C# 7 compilation. It seemed odd C# 7.1 (required for async Main) or the “latest minor version” was not the default for me, but “latest major version” (7.0) was.

using System.Threading.Tasks;
namespace JIRASprintQuery
{
    public class Program
    {
        // async main requires C# 7.1 in project properties and Rosyln support (VS 2017 Preview 2 currently)
        public static async Task<int> Main(string[] args)
        {
            var consoleInput = new ConsoleInput().Get();
            if (!consoleInput.IsValid) return -1;
            // Main logic here...
            return 0;
        }
    }
}

Running the app for the first time prompts for credentials which appear in Credential Manager immediately after entered. Subsequent runs will use the persisted credentials and won’t prompt. For a real world app I’d probably want a mechanism to prompt again in the event of changed credentials, such as after detecting an authentication exception.