ASP.NET Web API (OWIN): Authorization
This tutorial demonstrates how to add authorization to an ASP.NET OWIN API using the standard JWT middleware. We recommend you to Log in to follow this quickstart with examples configured for your account.
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Get a sample configured with your account settings or check it out on Github.
Please note that the Auth0.OpenIdConnectSigningKeyResolver NuGet package used in this tutorial is only compatible with the OWIN 4.x packages. Attempting to use Auth0.OpenIdConnectSigningKeyResolver with OWIN 3.x will result in errors.
Configure Auth0 APIs
Create an API
In the APIs section of the Auth0 dashboard, click Create API. Provide a name and an identifier for your API, for example
https://quickstarts/api. You will use the identifier as an
audience later, when you are configuring the Access Token verification. For Signing Algorithm, select RS256.
By default, your API uses RS256 as the algorithm for signing tokens. Since RS256 uses a private/public keypair, it verifies the tokens against the public key for your Auth0 account. The public key is in the JSON Web Key Set (JWKS) format, and can be accessed here.
Scopes let you define which resources can be accessed by the user with a given Access Token. For example, you might choose to grant read access to the
messages resource if users have the manager access level, and a write access to that resource if they have the administrator access level.
You can add the required scopes in the Scopes tab of the Auth0 Dashboard's APIs section.
This example demonstrates:
Configure the Sample Project
The sample code has an
appsettings section in
Web.config which configures it to use the correct Auth0 Domain and API Identifier for your API. If you download the code from this page it will be automatically filled. If you use the example from Github, you will need to fill it yourself.
Validate Access Tokens
To use Auth0 Access Tokens with ASP.NET Core you will use the OWIN JWT Middleware which is available in the
Microsoft.Owin.Security.Jwt NuGet package. Also install the
Auth0.OpenIdConnectSigningKeyResolver NuGet package which will assist you in verifying the token signature.
Auth0.OpenIdConnectSigningKeyResolver package which you installed will automatically download the JSON Web Key Set which was used to sign the RS256 tokens by interrogating the OpenID Connect Configuration endpoint (at
/.well-known/openid-configuration). You can then use it subsequently to resolve the Issuer Signing Key, as will be demonstrated in the JWT registration code below.
Go to the
Configuration method of your
Startup class and add a call to
UseJwtBearerAuthentication passing in the configured
JwtBearerAuthenticationOptions needs to specify your Auth0 API Identifier in the
ValidAudience property, and the full path to your Auth0 domain as the
ValidIssuer. You will need to configure the
IssuerSigningKeyResolver to use the instance of
OpenIdConnectSigningKeyResolver to resolve the signing key:
Do not forget the trailing backslash
Please ensure that the URL specified for
ValidIssuer contains a trailing backslash as this needs to match exactly with the issuer claim of the JWT. This is a common misconfiguration error which will cause your API calls to not be authenticated correctly.
The JWT middleware above verifies that the Access Token included in the request is valid; however, it doesn't yet include any mechanism for checking that the token has the sufficient scope to access the requested resources.
Create a class called
ScopeAuthorizeAttribute which inherits from
System.Web.Http.AuthorizeAttribute. This Authorization Attribute will check that the
scope claim issued by your Auth0 tenant is present, and if so it will ensure that the
scope claim contains the requested scope.
Protect API Endpoints
The routes shown below are available for the following requests:
GET /api/public: available for non-authenticated requests
GET /api/private: available for authenticated requests containing an Access Token with no additional scopes
GET /api/private-scoped: available for authenticated requests containing an Access Token with the
The JWT middleware integrates with the standard ASP.NET Authentication and Authorization mechanisms, so you only need to decorate your controller action with the
[Authorize] attribute to secure an endpoint.
To ensure that a scope is present in order to call a particular API endpoint, you simply need to decorate the action with the
ScopeAuthorize attribute, and pass the name of the required
scope in the