How to access username from controller

Question

I'm writing my first Web API 2. I'm performing authorization using a custom HttpMessageHandler. However, my controller needs to know the username specified in the credentials.

Researching this, it appears that ApiController does not have a Controller.HttpContext property. And I see there are potential issues accessing HttpContext.Current. So while I am actually able to store the username in HttpContext.Current.Items in my HttpMessageHandler and then access that information from my controller, I'm not sure that will always be reliable.

I also saw recommendations to use the RequestContext.Principal property; however, I could not find the current request's username anywhere in this data.

How can my controller reliably get the username for the current request?

NOTE: I refer to the username but in this case the actual user is another piece of software calling the API. The "username" reflects the software that is making the call.

Answer 1

@Win: Well, that part is what I am developing. But currently basic authentication seems appropriate, where the username identifies the software contacting us and the password is a special key

Here is the sample code for BasicAuthenticationMessageHandler which uses message handler to support HTTP Basic Authentication.

You can read more at Page 121 of ASP.NET Web API 2: Building a REST Service from Start to Finish.

IBasicSecurityService

public interface IBasicSecurityService
{
    bool SetPrincipal(string username, string password);
}

BasicSecurityService

public class BasicSecurityService : IBasicSecurityService
{
    public bool SetPrincipal(string username, string password)
    {
        // Get user from database
        var user = GetUser(username);
        IPrincipal principal = null;
        if (user == null || (principal = GetPrincipal(user)) == null)
        {
            // System could not validate user
            return false;
        }

        Thread.CurrentPrincipal = principal;
        if (HttpContext.Current != null)
        {
            HttpContext.Current.User = principal;
        }

        return true;
    }

    public virtual IPrincipal GetPrincipal(User user)
    {
        var identity = new GenericIdentity(user.Username, Constants.SchemeTypes.Basic);

        identity.AddClaim(new Claim(ClaimTypes.GivenName, user.Firstname));
        identity.AddClaim(new Claim(ClaimTypes.Surname, user.Lastname));
        // Get authroized roles and add them as Role Claim.
        identity.AddClaim(new Claim(ClaimTypes.Role, "Manager"));

        return new ClaimsPrincipal(identity);
    }
}

BasicAuthenticationMessageHandler

public class BasicAuthenticationMessageHandler : DelegatingHandler
{
    public const char AuthorizationHeaderSeparator = ':';
    private const int UsernameIndex = 0;
    private const int PasswordIndex = 1;
    private const int ExpectedCredentialCount = 2;

    private readonly IBasicSecurityService _basicSecurityService;

    public BasicAuthenticationMessageHandler(IBasicSecurityService basicSecurityService)
    {
        _basicSecurityService = basicSecurityService;
    }

    protected override async Task<HttpResponseMessage> SendAsync(
        HttpRequestMessage request,
        CancellationToken cancellationToken)
    {
        if (HttpContext.Current.User.Identity.IsAuthenticated)
        {
            // Already authenticated; passing on to next handler...
            return await base.SendAsync(request, cancellationToken);
        }

        if (!CanHandleAuthentication(request))
        {
            // Not a basic auth request; passing on to next handler...
            return await base.SendAsync(request, cancellationToken);
        }

        bool isAuthenticated;
        try
        {
            isAuthenticated = Authenticate(request);
        }
        catch (Exception e)
        {
            // Failure in auth processing
            return CreateUnauthorizedResponse();
        }

        if (isAuthenticated)
        {
            var response = await base.SendAsync(request, cancellationToken);
            return response;
        }

        return CreateUnauthorizedResponse();
    }

    public bool CanHandleAuthentication(HttpRequestMessage request)
    {
        return (request.Headers != null
                && request.Headers.Authorization != null
                && request.Headers.Authorization.Scheme.ToLowerInvariant() == Constants.SchemeTypes.Basic);
    }

    public bool Authenticate(HttpRequestMessage request)
    {
        // Attempting to authenticate...
        var authHeader = request.Headers.Authorization;
        if (authHeader == null)
        {
            return false;
        }

        var credentialParts = GetCredentialParts(authHeader);
        if (credentialParts.Length != ExpectedCredentialCount)
        {
            return false;
        }

        return _basicSecurityService.SetPrincipal(credentialParts[UsernameIndex], credentialParts[PasswordIndex]);
    }

    public string[] GetCredentialParts(AuthenticationHeaderValue authHeader)
    {
        var encodedCredentials = authHeader.Parameter;
        var credentialBytes = Convert.FromBase64String(encodedCredentials);
        var credentials = Encoding.ASCII.GetString(credentialBytes);
        var credentialParts = credentials.Split(AuthorizationHeaderSeparator);
        return credentialParts;
    }

    public HttpResponseMessage CreateUnauthorizedResponse()
    {
        var response = new HttpResponseMessage(HttpStatusCode.Unauthorized);
        response.Headers.WwwAuthenticate.Add(new AuthenticationHeaderValue(Constants.SchemeTypes.Basic));
        return response;
    }
}