Unsupported Grant Type with CustomGrantValidator with IdentityServer 3 - identityserver3

Question

I'm trying to set up our IdentityServer solution to accept a custom Grant Validator. Our API project is accessed by to UIs, one that uses Password authentication (which is working) and now one that will use a 3rd party authentication.
In our API I've set up IdentityServer like so:
Startup.cs
public void Configuration(IAppBuilder app)
{
var factory = new IdentityServerServiceFactory()
.UseInMemoryClients(Clients.Get())
.UseInMemoryScopes(Scopes.Get());
var userService = new IdentityUserService();
factory.UserService = new Registration<IUserService>(resolver => userService);
factory.CustomGrantValidators.Add(
new Registration<ICustomGrantValidator, MyGrantValidator>());
var options = new IdentityServerOptions
{
SiteName = "My App Name",
SigningCertificate = Certificate.Get(),
Factory = factory
};
app.Map("/identity", identityServerApp =>
{
identityServerApp.UseIdentityServer(options);
});
}
MyGrantValidator.cs:
public class MyGrantValidator : ICustomGrantValidator
{
public async Task<CustomGrantValidationResult> ValidateAsync(ValidatedTokenRequest request)
{
// For now I just want a basic response. More logic will come later.
var authResult = new AuthenticateResult(
subject: "1234", // user.AccountId.ToString(),
name: "bob" //context.UserName
);
var grantResult = new CustomGrantValidationResult
{
IsError = authResult.IsError,
Error = authResult.ErrorMessage,
ErrorDescription = authResult.ErrorMessage,
Principal = authResult.User
};
return await Task.FromResult(grantResult);
}
public string GrantType => "myGrantType";
}
In my UI, I setup a client like this:
var owinContext = HttpContext.GetOwinContext();
var token = owinContext.Authentication.User.FindFirst(c => c.Type == "myToken")?.Value;
var tokenId = owinContext.Authentication.User.FindFirst(c => c.Type == ClaimTypes.Sid)?.Value;
var client = new TokenClient(
ConfigurationManager.AppSettings["IdentityServerBaseUrl"] + "/connect/token",
"MyUser",
ConfigurationManager.AppSettings["MyClientSecret"],
AuthenticationStyle.Custom
);
var tokenResponse = client.RequestCustomGrantAsync(
"myGrantType",
"read write",
new Dictionary<string, string>
{
{ "token", token },
{ "tokenId", tokenId }
}
).Result;
return Redirect(returnUrl);
When the Request is triggered, I get: unsupported_grant_type
What am I missing?

Answer 1

You're using a client called "MyUser" (weird name for a client, but ok). Is that client registered as one of the in-memory clients with grant type set to "custom"?