SignedUrl

A NuGet package that generates signed query strings.

Usage

Currently, only ASP.NET projects are supported. If you can't use it, you need to implement ISignatureProtector yourself.
The implementation MUST NOT return the bytes as is, as this would make your signature prone to brute force attacks.

Install two NuGet packages:

SignedUrl and
SignedUrl.AspNet

// use dependency injection
builder.Services.AddSingleton<ISignatureProtector, DataProtectionSignatureProtector>();
builder.Services.AddSingleton<IQuerySigner, DigestQuerySigner>();

Then consume the IQuerySigner:

public class MyUrlService(IQuerySigner signer) {
    public string GenerateSomeUrl() {
        var query = new Dictionary<string, string?>
        {
            { "time", CurrentUnixTimestamp().ToString() },
        };

        return "https://example.com/?" + signer.GenerateSignature(query);
    }
}

The above class will generate a URL like this:

https://example.com/?time=1702855023&s=vJ89aMd%2bkkZaLamPOKuCgGAiuDDRqn7XtIdM%2bXpCYZw%3d

Observations:

The dictionary containing a key time and a value of the current Unix timestamp is appended to the query string
The s parameter is the signature of the query string

And to verify the signature:

public class MyUrlService(IQuerySigner signer) {
    // [...omitted for brevity...]

    public bool VerifySomeUrl(string url) {
        var query = HttpUtility.ParseQueryString(new Uri(url).Query);

        return signer.VerifySignature(query);
    }
}

Development

Pre-requisites

.NET 8

Extensions

If you want to write extensions, you can use the SignedUrl.Abstractions package, which contains the interfaces used by the SignedUrl implementations.

Testing

The project uses xUnit for testing. To run the tests, run dotnet test in the root directory.

Publishing

There are 3 NuGet packages that need to be published:

SignedUrl
SignedUrl.Abstractions
SignedUrl.AspNet

Make sure all the versions are the same. Then, run dotnet pack in each project directory.

License

Licensed under MIT.

ricardoboss/SignedUrl