asp.net - Automatically Sign In Sharepoint 2013 -

i want sign in sharepoint portal through calling web page. forms based authentication enabled on sharepoint. scenario follows:

1. calling /_forms/default.aspx?username=userx. default page forms authentication in sharepoint.
2. the page create , set authentication ticket userx without asking password.
3. the page redirected default page.

i have tried manipulated /_forms/default.aspx create ticket using federatedauthentication.sessionauthenticationmodule.authenticatesessionsecuritytoken, no result. i'd appreciated if 1 helps me.