junian / Standard.licensing

About

Easy-to-use licensing library for .NET Framework, Mono, .NET Core, and Xamarin products.

This is project is derived from Portable.Licensing library. The purpose of this fork is to add support for more .NET platforms, especially .NET Standard and .NET Core.

There is also a plan to decouple from Bouncy Castle library and use System.Security.Cryptography.Cng for modern .NET platforms.

Installation

Get Standard.Licensing from NuGet.

PM> Install-Package Standard.Licensing

Usage

Create a private and public key for your product

Standard.Licensing uses the Elliptic Curve Digital Signature Algorithm (ECDSA) to ensure the license cannot be altered after creation.

First you need to create a new public/private key pair for your product:

var keyGenerator = Standard.Licensing.Security.Cryptography.KeyGenerator.Create(); 
var keyPair = keyGenerator.GenerateKeyPair(); 
var privateKey = keyPair.ToEncryptedPrivateKeyString(passPhrase);  
var publicKey = keyPair.ToPublicKeyString();

Store the private key securely and distribute the public key with your product. Normally you create one key pair for each product, otherwise it is possible to use a license with all products using the same key pair. If you want your customer to buy a new license on each major release you can create a key pair for each release and product.

Create the license generator

Now we need something to generate licenses. This could be easily done with the LicenseFactory:

var license = License.New()  
    .WithUniqueIdentifier(Guid.NewGuid())  
    .As(LicenseType.Trial)  
    .ExpiresAt(DateTime.Now.AddDays(30))  
    .WithMaximumUtilization(5)  
    .WithProductFeatures(new Dictionary<string, string>  
        {  
            {"Sales Module", "yes"},  
            {"Purchase Module", "yes"},  
            {"Maximum Transactions", "10000"}  
        })  
    .LicensedTo("John Doe", "[email protected]")  
    .CreateAndSignWithPrivateKey(privateKey, passPhrase);

Now you can take the license and save it to a file:

File.WriteAllText("License.lic", license.ToString(), Encoding.UTF8);

or

license.Save(xmlWriter);

Validate the license in your application

The easiest way to assert the license is in the entry point of your application.

First load the license from a file or resource:

var license = License.Load(...);

Then you can assert the license:

using Standard.Licensing.Validation;

var validationFailures = license.Validate()  
                                .ExpirationDate()  
                                .When(lic => lic.Type == LicenseType.Trial)  
                                .And()  
                                .Signature(publicKey)  
                                .AssertValidLicense();

Standard.Licensing will not throw any Exception and just return an enumeration of validation failures.

Now you can iterate over possible validation failures:

foreach (var failure in validationFailures)
     Console.WriteLine(failure.GetType().Name + ": " + failure.Message + " - " + failure.HowToResolve);

Or simply check if there is any failure:

if (validationFailures.Any())
   // ...

Make sure to call validationFailures.ToList() or validationFailures.ToArray() before using the result multiple times.

Credits

• dnauck/Portable.Licensing for the original work.

License

This project is licensed under MIT License.