csharp

authdog authn on csharp

Smallest .NET token validator using Authdog.Sdk. The package is not on NuGet. Point this sample at a pinned checkout of authdog/sdk. It takes a bearer token you already have and resolves it against GET /v1/userinfo. This SDK does not use a public key.

What this sample shows

Authentication (authn): who the caller is, proven by validating an access token. Authentication is not authorization. This sample does not host sign-in; pair it with a framework SDK or your own callback that obtains the token.

What you need first

An access token to validate. Never ask for or embed the secret key (sk_...). This core SDK is constructed with https://api.authdog.com and does not take a pk_... public key.

.NET 8.0+ is required.

Run

git clone https://github.com/authdog/sdk.git /tmp/authdog-sdk
git -C /tmp/authdog-sdk checkout 9b9ad52f4b23e5e0bdcffa6dc591ecdb08c7e180
export AUTHDOG_SDK=/tmp/authdog-sdk
dotnet run -- <access-token>

Do not run dotnet add package Authdog.Sdk from nuget.org — that package is not published.

What to try

1. dotnet run -- <valid-token> → prints the userinfo user.
2. dotnet run -- <bad-token> → prints 401 Unauthorized and exits non-zero.

Gotchas

• Not on NuGet: set AUTHDOG_SDK to a pinned authdog/sdk checkout. Do not write a production dotnet add package Authdog.Sdk.
• This validates tokens, it doesn't issue them: obtain the token from a framework SDK's callback or your own redirect handler before calling GetUserInfoAsync.
• Dispose clients you own: this sample uses await using so the HttpClient is released.
• AuthenticationException is the 401 path: a bad, expired, or revoked token is not a fabricated user.
• Do not log access tokens.
• Bearer tokens go only to a trusted HTTPS identity host.

Next concept

Authorization for this stack is Present: authz/csharp. Apply authorization after GetUserInfoAsync. Do not treat a successful userinfo call as a permission grant.