sdk/dotnet

Status

Implemented and verified locally. Real IdP round-trip verification (JWKS fetch, token sign/verify against a live XID instance) has not been performed yet and must be completed before production use.

XID publishes no packages to any registry. This SDK is distributed as source in the XID repository; use it from a checkout of the repository.

Request authentication is Bearer-only by default. An application-owned JWT cookie is read only when its exact name is configured. The opaque __Host-xid.rt.* Core cookie is never scanned or verified locally; exchange it by forwarding the complete Cookie header to exact same-origin POST /v1/sessions/token with redirects disabled, and accept only a response containing the token field.

Install

.NET 8 target required.

<ItemGroup>
  <ProjectReference Include="../xid/sdk/dotnet/Xid.csproj" />
</ItemGroup>

ASP.NET Core setup (recommended)

// Program.cs
using Xid;

builder.Services.AddXid(options =>
{
    options.Issuer   = "https://xid.dev";
    options.Audience = "your-client-id"; // optional
});

Authenticate a request

// Controller / Minimal API
public class MyController(XidClient xid) : ControllerBase
{
    [HttpGet("/me")]
    public async Task<IActionResult> GetMe()
    {
        var auth = await xid.AuthenticateRequestAsync(
            authorizationHeader: Request.Headers.Authorization);

        if (!auth.Authenticated)
            return Unauthorized(auth.Reason);

        return Ok(new { sub = auth.Claims!.Sub, email = auth.Claims.Email });
    }

    private Task<string> ExchangeSessionAsync() => xid.ExchangeSessionTokenAsync(
        $"{Request.Scheme}://{Request.Host}{Request.Path}",
        Request.Headers.Cookie.ToString());
}

Verify token directly

using Xid;

var client = new XidClient(new XidOptions { Issuer = "https://xid.dev" });

try
{
    var claims = await client.VerifyTokenAsync("eyJ...");
    Console.WriteLine($"sub={claims.Sub} email={claims.Email}");
}
catch (TokenVerificationException ex)
{
    Console.WriteLine($"Invalid token: {ex.Message}");
}

Verify webhook

app.MapPost("/webhooks/xid", async (HttpRequest req, XidClient xid) =>
{
    using var ms = new MemoryStream();
    await req.Body.CopyToAsync(ms);
    var body = ms.ToArray();

    var headers = new Dictionary<string, string>
    {
        ["svix-id"]        = req.Headers["svix-id"].ToString(),
        ["svix-timestamp"] = req.Headers["svix-timestamp"].ToString(),
        ["svix-signature"] = req.Headers["svix-signature"].ToString(),
    };

    var webhookSecret = Environment.GetEnvironmentVariable("XID_WEBHOOK_SECRET")
        ?? throw new InvalidOperationException("XID_WEBHOOK_SECRET is required");

    try
    {
        var webhook = xid.VerifyWebhook(body, headers, secret: webhookSecret);
        return Results.Ok();
    }
    catch (WebhookVerificationException ex)
    {
        return Results.BadRequest(ex.Message);
    }
});

XidOptions

Property	Default	Description
`Issuer`	required	XID issuer URL
`Audience`	`null`	Expected aud claim; null skips validation
`JwksTtl`	1 hour	JWKS in-memory cache TTL
`SessionCookieName`	`disabled`	Application-owned JWT cookie name; disabled unless explicitly configured
`ClockSkew`	5 minutes	JWT exp/nbf clock skew tolerance
`WebhookToleranceWindow`	5 minutes	Webhook replay prevention window

XidClient API

Method	Description
`VerifyTokenAsync(token, ct)`	Verify JWT string; throws `TokenVerificationException` on failure.
`AuthenticateRequestAsync(authHeader, cookies, ct)`	Extract and verify token; returns `AuthStatus`; does not throw.
`VerifyWebhook(payload, headers, secret)`	Validate webhook signature; throws `WebhookVerificationException` on failure. Synchronous.

Platform notes

Uses Microsoft.IdentityModel.Tokens and System.IdentityModel.Tokens.Jwt 8.x. ES256 is primary; RS256 and PS256 are supported.
AddXid() registers XidClient as a singleton and wires IHttpClientFactory for JWKS fetching.
Exception hierarchy: XidException -> JwksException, TokenVerificationException, WebhookVerificationException.