Can Ajax make a Cross-Origin Login? - ajax

Question

I'm trying to login from one of my servers to another in order to send cross-origin requests that requires being logged. is it possible?
I have two web servers, A and B. Lets say www.a.com and www.b.com.
B has an API that can be used only if the client is logged in. I need to use that API from A clients.
So, I send from A client an ajax (post) login request to B. B responses with CORS headers, the session cookie and a successful redirection to B's home/index.
But when I make a second ajax request (jsonp request) from A client to B server, this request doesn't send the previous session cookie received, therefore the login request failed.
If I login to www.b.com manually (in a second browser tab), all requests from A to B are successful detected as a logged user, so, the B API works from A.
I think that the session cookie received from my login requests is not being saved to the browser.
This is my login request:
$.post("www.b.com/login", { 'j_username': 'username', 'j_password': 'password' } );
Using:
jqXHR.withCredentials = true;
settings.crossDomain = true;
Response headers:
Access-Control-Allow-Headers:x-requested-with
Access-Control-Allow-Methods:POST, GET, OPTIONS
Access-Control-Allow-Origin:*
...
Location:http://www.b.com/home
...
Set-Cookie:JSESSIONID=tY++VWlMSxTTUkjvyaRelZ0o; Path=/
The cookie received is being saved to www.a.com or to www.b.com? How can I set this cookie to www.b.com from an A client ajax request? I think that is the problem.

Answer 1

As apsillers said, we can't use the wildcard Access-Control-Allow-Origin:*.
But this doesn't solved the problem.
I was setting jqXHR.withCredentials = true; inside a beforeSend handler function.
$.post({
...
beforeSend: function(xhr) {
xhr.withCredentials = true;
},
...
});
And for some reason, this doesn't work. I had to set the use of credentials directly:
$.post({
...
xhrFields: {
withCredentials: true
},
...
});
This code works perfectly !
Thanks you.