Logging into salesforce from visualforce controller

Question

I'm attempting to do a redirect from a visualforce page to a salesforce page but when it loads, I end up with the login.salesforce.com page.

The visual force controller builds the http request, and retrieves the response to send back to javascript to render the that response as HTML.

@RemoteAction
public static string HTTPRequest(string requestURL)
{
    HttpRequest request = new HttpRequest();
    request.setHeader('Authorization', 'Bearer ' + UserInfo.getSessionId());
    request.setEndpoint(requestURL);
    request.setCompressed(true);
    request.setMethod('GET');

    Http http = new Http();
    HttpResponse response = http.send(request);

    return response.getBody();
}

I figured that if I add the authorization header with the current user session ID (as the user is currently logged into a visual force page), that it would authenticate but I appear to be wrong.

After the login page displays, and if I manually log in, i get the expected page that I want to display.

Is this possible to do and have I just missed something?

EDIT

I forgot to mention that the RemoteAction is directly affecting an IFrame... thus bypassing cross-origin issues and rendering the content within an IFrame without reloading the page. Reloading the page is not an option due to content that remains "open" within the page.

Answer 1

Visualforce like this:

<apex:commandButton value="To New Page" action="{! toNewPage }"/>

and a controller method like this:

public PageReference toNewPage() {
    String url = ...;
    PageReference pr = new PageReference(url);
    pr.getParameters().put('p1', ...);
    pr.getParameters().put('p2', ...);
    return pr;
}

will do the job of "redirect from a visualforce page to a salesforce page" correctly preserving the session.