Authentication, Authorization, User and Role Management and general Security in .NET

Question

I need to know how to go about implementing general security for a C# application. What options do I have in this regard? I would prefer to use an existing framework if it meets my needs - I don't want to re-invent the wheel.

My requirements are as follows:

• the usual username/password authentication
• managing of users - assign permissions to users
• managing of roles - assign users to roles, assign permissions to roles
• authorization of users based on their username and role

I am looking for a free / open-source framework/library that has been time-tesed and used by the .Net community.

My application takes a client/server approach, with the server running as a windows service, connecting to a SQL Server database. Communication between client and server will be through WCF.

One other thing that is important is that I need to be able to assign specific users or roles permissions to View/Update/Delete a specific entity, whether it be a Customer, or Product etc. For e.g. Jack can view a certain 3 of 10 customers, but only update the details of customers Microsoft, Yahoo and Google, and can only delete Yahoo.

Answer 1

For coarse-grained security, you might find the inbuilt principal code useful; the user object (and their roles) are controlled in .NET by the "principal", but usefully the runtime itself can enforce this.

The implementation of a principal can be implementation-defined, and you can usually inject your own; for example in WCF.

To see the runtime enforcing coarse access (i.e. which functionality can be accessed, but not limited to which specific data):

static class Roles {
    public const string Administrator = "ADMIN";
}
static class Program {
    static void Main() {
        Thread.CurrentPrincipal = new GenericPrincipal(
            new GenericIdentity("Fred"), new string[] { Roles.Administrator });
        DeleteDatabase(); // fine
        Thread.CurrentPrincipal = new GenericPrincipal(
            new GenericIdentity("Barney"), new string[] { });
        DeleteDatabase(); // boom
    }

    [PrincipalPermission(SecurityAction.Demand, Role = Roles.Administrator)]
    public static void DeleteDatabase()
    {
        Console.WriteLine(
            Thread.CurrentPrincipal.Identity.Name + " has deleted the database...");
    }
}

However, this doesn't help with the fine-grained access (i.e. "Fred can access customer A but not customer B").

---

Additional; Of course, for fine-grained, you can simply check the required roles at runtime, by checking IsInRole on the principal:

static void EnforceRole(string role)
{
    if (string.IsNullOrEmpty(role)) { return; } // assume anon OK
    IPrincipal principal = Thread.CurrentPrincipal;
    if (principal == null || !principal.IsInRole(role))
    {
        throw new SecurityException("Access denied to role: " + role);
    }
}
public static User GetUser(string id)
{
    User user = Repository.GetUser(id);
    EnforceRole(user.AccessRole);
    return user;
}

You can also write your own principal / identity objects that do lazy tests / caching of the roles, rather than having to know them all up-front:

class CustomPrincipal : IPrincipal, IIdentity
{
    private string cn;
    public CustomPrincipal(string cn)
    {
        if (string.IsNullOrEmpty(cn)) throw new ArgumentNullException("cn");
        this.cn = cn;
    }
    // perhaps not ideal, but serves as an example
    readonly Dictionary<string, bool> roleCache =
        new Dictionary<string, bool>();
    public override string ToString() { return cn; }
    bool IIdentity.IsAuthenticated { get { return true; } }
    string IIdentity.AuthenticationType { get { return "iris scan"; } }
    string IIdentity.Name { get { return cn; } }
    IIdentity IPrincipal.Identity { get { return this; } }

    bool IPrincipal.IsInRole(string role)
    {
        if (string.IsNullOrEmpty(role)) return true; // assume anon OK
        lock (roleCache)
        {
            bool value;
            if (!roleCache.TryGetValue(role, out value)) {
                value = RoleHasAccess(cn, role);
                roleCache.Add(role, value);
            }
            return value;
        }
    }
    private static bool RoleHasAccess(string cn, string role)
    {
        //TODO: talk to your own security store
    }
}