08 authentication

Authentication in ASP.NET MVC Best practices for user and group management

Topics � The membership and role provider model � Authorizing action methods � Best practices

The provider model �  ASP.NET has a robust and simple way to

handling authentication; The membership and role provider model

�  Configured in web.config (ASP.NET Configuration Tool)

�  It is highly extensible! Can customize it via some programming

�  Much more secure than home-grown ways �  Uses good design patterns �  Abstracts away most user functions

Coding with the Provider Model �  All features are simple ... MembershipCreateStatus status; Membership.CreateUser(

"dschrute", //username "recyclops", //password "dwight@dundermifflin.com", //email "Which color is most dominant?", //passwd reminder question "black", //response true, //is approved? out status

); if (status != MembershipCreateStatus.Success)

throw new Exception("Fail!"); �  Other features are similarly easy �  Best feature, though is ... �  No programming necessary!

To Authenticate a user FormsAuthenticate.SetAuthCookie("ferb", false);!

Who am I? User.Identity.Name;!

But I have another authentication method in place. I need to use it! � No problem. Just create your own class

that inherits from MembershipProvider and override the parts you need.

Overriding authentication methods

class MyMembershipProvider : MembershipProvider!{! public override MembershipUser GetUser(string username, ! bool userIsOnline)! {! var a = ExistingMethod.GetUserByUserName(username);! return new MyMembershipUser(a.Id, a.Email);! }!! public override bool ValidateUser(string username, ! string password)! {! return Existing.Valid(username, password); ! }!}!

To use your own groups/roles methods, override RoleProvider public class AccountRoleProvider : RoleProvider!{! public override void AddUsersToRoles(string[] usernames,! string[] roleNames)! {! //Use your existing system to add users to groups;! }! public override string[] GetRolesForUser(string id)! {! return ExistingWay(id);! }! public override bool RoleExists(string roleName)! {! return ExistingDoesRoleExist(roleName);! }!}!

One last step; we need to register our providers in web.config <system.web>! <membership defaultProvider="AccountMembershipProvider">! <providers>! <clear/>! <add name="AccountMembershipProvider"! type="MyProj.AccountMembershipProvider" />! </providers>! </membership>! ! <roleManager enabled="true"! defaultProvider="AccountRoleProvider">! <providers>! <clear/>! <add name="AccountRoleProvider"! type="MyProj.AccountRoleProvider" />! </providers>! </roleManager>!...!</system.web>!

Best practices � Avoid canned questions � When resetting the password, never email it � Don't allow the website to "Remember me" � Turn autocomplete off so the username

and/or password can't be pulled from the browser cache

� Use strong passwords

Allow the user to set his own password reset question.

� Never force from a small list � Too easy to research

�  High school mascot �  Mother's maiden name �  Pet's name �  Birth city

� Too easy to guess �  Favorite color

Remember me is convenient but it opens security holes

� Worst option is to save username and password in a cookie

�  If you must remember me, do it like Microsoft's provider does and store it in a persistent authentication cookie

Turn browser caching off

� Guessing a username is half the battle � If the form helps the user to fill a username

he has a major leg up � And if we do that for a password, that

would be horrible � Turn remembering off like this: <form id="f1" autocomplete="off">

Sometimes Often Usually our efforts to increase security actually decrease it

Password rules are enforced on backend

� Set in web.config in membership - providers:

<add name="AspNetSqlMembershipProvider" type="..."

minRequiredPasswordLength="1"

minRequiredNonalphanumericCharacters="0" passwordFormat="Hashed"

maxInvalidPasswordAttempts="5" passwordStrengthRegularExpression="" />

Summary � Good authentication practices go a long

way toward establishing security � Use a role provider based on Microsoft's � Use Microsoft's built-in controls � Enforce strong passwords, but don't go

crazy