.NET Core: How to access Windows Credential Manager if running on Windows (otherwise ignore)?

Question

So far, to store and retrieve secrets (like credentials) in .NET applications, I successfully used the CredentialManagement package on Windows. Now I'd like to go cross-platform.

So I need to access the Windows Credential Manager from a .NET Core cross-platform application. If it's running on Windows - use the Credential Manager. If it's running on Linux - don't crash (use key chain or whatever, that is the next step).

How would this be done?

(Note: I'm open to alternatives to the Windows Credential Manager but they should provide an equal level of protection.)

Answer 1

I ended up using the Data Protection API for Windows (DPAPI) to store secrets in a file that is encrypted within the scope of the logged in user.

Encrypted storage of a password:

try
{
    var passwordBytes = Encoding.UTF8.GetBytes(password);
    var protectedPasswordBytes = ProtectedData.Protect(passwordBytes, null, DataProtectionScope.CurrentUser);
    var protectedPasswordBytesBase64 = Convert.ToBase64String(protectedPasswordBytes);
    File.WriteAllText(passwordFilePath, protectedPasswordBytesBase64);
} catch (PlatformNotSupportedException)
{
    Debug.WriteLine("Could not store credentials");
}

Decryption:

if (File.Exists(passwordFilePath))
{
    var protectedPasswordBytesBase64 = File.ReadAllText(passwordFilePath);
    var protectedPasswordBytes = Convert.FromBase64String(protectedPasswordBytesBase64);
    var passwordBytes = ProtectedData.Unprotect(protectedPasswordBytes, null, DataProtectionScope.CurrentUser);
    password = Encoding.UTF8.GetString(passwordBytes);
}

(Only works on Windows, for other OSes I'll use other solutions.)

Answer 2

To determine the operating system on which your application is running. This can help, for reference

1. RuntimeInformation.IsOSPlatform(OSPlatform) Method
2. OSPlatform.Windows Property

A complete example for windows(CredentialManagement + Detect Operating System),

using CredentialManagement;
using System;
using System.Diagnostics;
using System.Runtime.InteropServices;

namespace DetectOSCredentialManagement
{
    class Program
    {
        static void Main(string[] args)
        {
            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
            {
                Console.WriteLine("Hello Beauty!");
                Program.SetCredentials("FOO", "friday", "fr!d@y0", PersistanceType.LocalComputer);
                var userpass = Program.GetCredential("FOO");
                Console.WriteLine($"User: {userpass.Username} Password: {userpass.Password}");
                Program.RemoveCredentials("FOO");
                Debug.Assert(Program.GetCredential("FOO") == null);
            }
            else if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux))
            {
                Console.WriteLine("Hello Cutie!");
            }
            else if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
            {
                Console.WriteLine("Too Costly!");
            }
        }

        public static UserPass GetCredential(string target)
        {
            var cm = new Credential { Target = target };
            if (!cm.Load())
            {
                return null;
            }

            // UserPass is just a class with two string properties for user and pass
            return new UserPass(cm.Username, cm.Password);
        }

        public static bool SetCredentials(
             string target, string username, string password, PersistanceType persistenceType)
        {
            return new Credential
            {
                Target = target,
                Username = username,
                Password = password,
                PersistanceType = persistenceType
            }.Save();
        }

        public static bool RemoveCredentials(string target)
        {
            return new Credential { Target = target }.Delete();
        }
    }
    public class UserPass
    {
        public string Username { get; set; }
        public string Password { get; set; }

        public UserPass(string username, string password)
        {
            Username = username;
            Password = password;
        }
    }
}

System.Security.Permissions -- This dll is also need to run above application.