How to add a custom grant type in OpenIddict

ITokenExtensionGrant

Create a class that inherits ITokenExtensionGrant, and then register it with the framework.

In the MyTokenExtensionGrant class below we try to get the token details, The ForbidResult handles the failure case and SignInResult returns a new token response, You can pass more parameters to implement business checks.

public class MyTokenExtensionGrant : ITokenExtensionGrant
{
    public const string ExtensionGrantName = "MyTokenExtensionGrant";

    public string Name => ExtensionGrantName;
    public async Task<IActionResult>  HandleAsync(ExtensionGrantContext context)
    {
        var userToken = context.Request.GetParameter("token").ToString();

        if (string.IsNullOrEmpty(userToken))
        {
            return new ForbidResult(
                new[] {OpenIddictServerAspNetCoreDefaults.AuthenticationScheme},
                properties: new AuthenticationProperties(new Dictionary<string, string>
                {
                    [OpenIddictServerAspNetCoreConstants.Properties.Error] = OpenIddictConstants.Errors.InvalidRequest
                }!));
        }

        var transaction = await context.HttpContext.RequestServices.GetRequiredService<IOpenIddictServerFactory>().CreateTransactionAsync();
        transaction.EndpointType = OpenIddictServerEndpointType.Introspection;
        transaction.Request = new OpenIddictRequest
        {
            ClientId = context.Request.ClientId,
            ClientSecret = context.Request.ClientSecret,
            Token = userToken
        };

        var notification = new OpenIddictServerEvents.ProcessAuthenticationContext(transaction);
        var dispatcher = context.HttpContext.RequestServices.GetRequiredService<IOpenIddictServerDispatcher>();
        await dispatcher.DispatchAsync(notification);

        if (notification.IsRejected)
        {
            return new ForbidResult(
                new []{ OpenIddictServerAspNetCoreDefaults.AuthenticationScheme },
                properties: new AuthenticationProperties(new Dictionary<string, string>
                {
                    [OpenIddictServerAspNetCoreConstants.Properties.Error] = notification.Error ?? OpenIddictConstants.Errors.InvalidRequest,
                    [OpenIddictServerAspNetCoreConstants.Properties.ErrorDescription] = notification.ErrorDescription,
                    [OpenIddictServerAspNetCoreConstants.Properties.ErrorUri] = notification.ErrorUri
                }));
        }

        var principal = notification.GenericTokenPrincipal;
        if (principal == null)
        {
            return new ForbidResult(
                new []{ OpenIddictServerAspNetCoreDefaults.AuthenticationScheme },
                properties: new AuthenticationProperties(new Dictionary<string, string>
                {
                    [OpenIddictServerAspNetCoreConstants.Properties.Error] = notification.Error ?? OpenIddictConstants.Errors.InvalidRequest,
                    [OpenIddictServerAspNetCoreConstants.Properties.ErrorDescription] = notification.ErrorDescription,
                    [OpenIddictServerAspNetCoreConstants.Properties.ErrorUri] = notification.ErrorUri
                }));
        }

        var userId = principal.FindUserId();
        var userManager = context.HttpContext.RequestServices.GetRequiredService<IdentityUserManager>();
        var user = await userManager.GetByIdAsync(userId.Value);
        var userClaimsPrincipalFactory = context.HttpContext.RequestServices.GetRequiredService<IUserClaimsPrincipalFactory<IdentityUser>>();
        var claimsPrincipal = await userClaimsPrincipalFactory.CreateAsync(user);
        claimsPrincipal.SetScopes(principal.GetScopes());
        claimsPrincipal.SetResources(await GetResourcesAsync(context, principal.GetScopes()));

        //abp version < 7.3
        await context.HttpContext.RequestServices.GetRequiredService<AbpOpenIddictClaimDestinationsManager>().SetAsync(claimsPrincipal);

        //For abp version >= 7.3
        await context.HttpContext.RequestServices.GetRequiredService<AbpOpenIddictClaimsPrincipalManager>().HandleAsync(context.Request, claimsPrincipal);

        return new SignInResult(OpenIddictServerAspNetCoreDefaults.AuthenticationScheme, claimsPrincipal);
    }

    private async Task<IEnumerable<string>> GetResourcesAsync(ExtensionGrantContext context, ImmutableArray<string> scopes)
    {
        var resources = new List<string>();
        if (!scopes.Any())
        {
            return resources;
        }

        await foreach (var resource in context.HttpContext.RequestServices.GetRequiredService<IOpenIddictScopeManager>().ListResourcesAsync(scopes))
        {
            resources.Add(resource);
        }
        return resources;
    }
}

public override void PreConfigureServices(ServiceConfigurationContext context)
{
    //...
    PreConfigure<OpenIddictServerBuilder>(builder =>
    {
        builder.Configure(openIddictServerOptions =>
        {
            openIddictServerOptions.GrantTypes.Add(MyTokenExtensionGrant.ExtensionGrantName);
        });
    });
    //...
}

public override void ConfigureServices(ServiceConfigurationContext context)
{
    //...
    Configure<AbpOpenIddictExtensionGrantsOptions>(options =>
    {
        options.Grants.Add(MyTokenExtensionGrant.ExtensionGrantName, new MyTokenExtensionGrant());
    });
    //...
}

Source code

https://github.com/abpframework/abp/commit/3210f138454697647689b4868c8d4b7b3da02d44