Basic Authentication For Azure Functions (Open API) .Net 6

Line 10 - extract the header from the HTTP request

Line 11 - pass the header parameter to validatetoken method for further validation and based on a response add a valid response as okobjectresult or make it the unauthorized response.

[FunctionName("Function1")]
[OpenApiOperation(operationId: "Run", tags: new [] {
    "http"
}, Summary = "Basic authentication token flow via header", Description = "This shows the basic authentication token flow via header", Visibility = OpenApiVisibilityType.Important)]
[OpenApiSecurity("basic_auth", SecuritySchemeType.Http, Scheme = OpenApiSecuritySchemeType.Basic)]
[OpenApiParameter(name: "name", In = ParameterLocation.Query, Required = true, Type = typeof(string), Description = "The **Name** parameter")]
[OpenApiResponseWithBody(statusCode: HttpStatusCode.OK, contentType: "text/plain", bodyType: typeof(string), Description = "The OK response")]
public async Task < IActionResult > Run(
    [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = null)] HttpRequest req) {
    //Getting the Header - extracting from the request
    var headers = req.Headers["Authorization"];
    if (ValidateToken(headers)) {
        _logger.LogInformation("C# HTTP trigger function processed a request.");
        string name = req.Query["name"];
        string requestBody = await new StreamReader(req.Body).ReadToEndAsync();
        dynamic data = JsonConvert.DeserializeObject(requestBody);
        name = name ?? data?.name;
        string responseMessage = string.IsNullOrEmpty(name) ? "This HTTP triggered function executed successfully. Pass a name in the query string or in the request body for a personalized response." : $ "Hello, {name}. This HTTP triggered function executed successfully.";
        return new OkObjectResult(responseMessage);
    } else {
        return new UnauthorizedResult();
    }
}

Final Code

using System;
using System.IO;
using System.Linq;
using System.Net;
using System.Text;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.Http;
using Microsoft.Azure.WebJobs.Extensions.OpenApi.Core.Attributes;
using Microsoft.Azure.WebJobs.Extensions.OpenApi.Core.Enums;
using Microsoft.Extensions.Logging;
using Microsoft.OpenApi.Models;
using Newtonsoft.Json;
namespace BasicAuth_AzureFunction_API {
    public class Function1 {
        private readonly ILogger < Function1 > _logger;
        public Function1(ILogger < Function1 > log) {
                _logger = log;
            }
            [FunctionName("Function1")]
            [OpenApiOperation(operationId: "Run", tags: new [] {
                "http"
            }, Summary = "Basic authentication token flow via header", Description = "This shows the basic authentication token flow via header", Visibility = OpenApiVisibilityType.Important)]
            [OpenApiSecurity("basic_auth", SecuritySchemeType.Http, Scheme = OpenApiSecuritySchemeType.Basic)]
            [OpenApiParameter(name: "name", In = ParameterLocation.Query, Required = true, Type = typeof(string), Description = "The **Name** parameter")]
            [OpenApiResponseWithBody(statusCode: HttpStatusCode.OK, contentType: "text/plain", bodyType: typeof(string), Description = "The OK response")]
        public async Task < IActionResult > Run(
            [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = null)] HttpRequest req) {
            //Getting the Header - extracting from the request
            var headers = req.Headers["Authorization"];
            if (ValidateToken(headers)) {
                _logger.LogInformation("C# HTTP trigger function processed a request.");
                string name = req.Query["name"];
                string requestBody = await new StreamReader(req.Body).ReadToEndAsync();
                dynamic data = JsonConvert.DeserializeObject(requestBody);
                name = name ?? data?.name;
                string responseMessage = string.IsNullOrEmpty(name) ? "This HTTP triggered function executed successfully. Pass a name in the query string or in the request body for a personalized response." : $ "Hello, {name}. This HTTP triggered function executed successfully.";
                return new OkObjectResult(responseMessage);
            } else {
                return new UnauthorizedResult();
            }
        }
        private bool ValidateToken(string header) {
            //Checking the header
            if (!string.IsNullOrEmpty(header) && header.StartsWith("Basic")) {
                //Extracting credentials
                // Removing "Basic " Substring
                string encodedUsernamePassword = header.Substring("Basic ".Length).Trim();
                //Decoding Base64
                Encoding encoding = Encoding.GetEncoding("iso-8859-1");
                string usernamePassword = encoding.GetString(Convert.FromBase64String(encodedUsernamePassword));
                //Splitting Username:Password
                int seperatorIndex = usernamePassword.IndexOf(':');
                // Extracting the individual username and password
                var username = usernamePassword.Substring(0, seperatorIndex);
                var password = usernamePassword.Substring(seperatorIndex + 1);
                //Validating the credentials 
                if (username is "Jay" && password is "12345") return true;
                else return false;
            } else {
                return false;
            }
        }
    }
}

Step 8

Run the app to see the terminal open like below.

Step 9

Copy the above URL and open it in the browser to see the Swagger UI like below.

To authenticate your endpoint, you should enter the Username and Password, added to the Authorization header.

The result screen shows the request header of Authorization with the base64 encoded value.

In this article, we learned how can set up basic authentication for Azure function HTTP trigger API via Swagger and Run and test it with Postman. If you want to clone the project, click here.

I hope this article helps you. Keep learning!