Posted on Aug 7, 2023 • Originally published at rmauro.dev on Aug 7, 2023

C# Get JWT Token from Request

This blog post will explore extracting a JWT token from incoming requests using C#.

We will explore two methods using Minimal APIs, but it's the same process for MVC Controllers.

JSON Web Tokens (JWT) have become famous for securing web applications and APIs. JWTs provide a way to transmit claims between parties securely and are widely used for authentication and authorization purposes.

Method 1: Getting JWT from Authentication Context

This is the best way because it doesn't rely on the HTTP Headers. It uses the Authentication process instead.

PS.: The Authentication pipeline should be processed at this time.

using Microsoft.AspNetCore.Authentication; app.MapGet("/jwt-token/context", async (HttpContext ctx) => { //get the access token from the HttpContext string token = await ctx.GetTokenAsync("access_token"); return TypedResults.Ok(new { token = token }); });

Get Access Token from Authentication Context

Method 2: Parsing JWT Token from HTTP Headers

To retrieve the JWT token from a request, we need to access the request headers and extract the value of the "Authorization" header.

Here's a second example of how to parse the JWT token from a request:

app.MapGet("/jwt-token/headers", (HttpContext ctx) => { if (ctx.Request.Headers.TryGetValue("Authorization", out var headerAuth)) { var jwtToken = headerAuth.First().Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries)[1]; return Task.FromResult( TypedResults.Ok(new { token = jwtToken }) ); } return Task.FromResult( TypedResults.NotFound(new { message = "jwt not found" }) ); });