Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 7956)
+++ wp-includes/functions.php	(working copy)
@@ -1765,4 +1765,7 @@
 	return 0;
 }
 
+function is_ssl() {
+	return ( 'on' == $_SERVER['HTTPS'] ) ? true : false; 
+}
 ?>
Index: wp-includes/link-template.php
===================================================================
--- wp-includes/link-template.php	(revision 7956)
+++ wp-includes/link-template.php	(working copy)
@@ -774,4 +774,45 @@
 
 	return apply_filters('shortcut_link', $link);
 }
+
+function admin_url($path = '') {
+	global $_wp_admin_url;
+
+	if ( !isset($_wp_admin_url) ) {
+		$_wp_admin_url = get_option( 'siteurl' ) . '/wp-admin/';
+		if ( is_ssl() )
+			$_wp_admin_url =  str_replace('http://', 'https://', $_wp_admin_url);
+	}
+
+	$url = $_wp_admin_url;
+
+	if ( !empty($path) )
+		$url .= ltrim($path, '/');
+
+	if ( is_ssl() )
+		$url =  str_replace('http://', 'https://', $url);
+
+	return $url;
+}
+
+function includes_url($path = '') {
+	global $_wp_includes_url;
+
+	if ( !isset($_wp_includes_url) ) {
+		$_wp_includes_url = get_option( 'siteurl' ) . '/' . WPINC . '/';
+		if ( is_ssl() )
+			$_wp_includes_url =  str_replace('http://', 'https://', $_wp_includes_url);
+	}
+
+	$url = $_wp_includes_url;
+
+	if ( !empty($path) )
+		$url .= ltrim($path, '/');
+
+	if ( is_ssl() )
+		$url =  str_replace('http://', 'https://', $url);
+
+	return $url;
+}
+
 ?>
Index: wp-includes/general-template.php
===================================================================
--- wp-includes/general-template.php	(revision 7956)
+++ wp-includes/general-template.php	(working copy)
@@ -1136,7 +1136,7 @@
 			$_file = $color->url;
 			$_file = ('css/colors-rtl' == $file) ? str_replace('.css','-rtl.css',$_file) : $_file;
 		} else {
-			$_file = get_option( 'siteurl' ) . "/wp-admin/$file.css";
+			$_file = admin_url("$file.css");
 		}
 	}
 	$_file = add_query_arg( 'version', get_bloginfo( 'version' ),  $_file );
Index: wp-includes/pluggable.php
===================================================================
--- wp-includes/pluggable.php	(revision 7956)
+++ wp-includes/pluggable.php	(working copy)
@@ -469,9 +469,14 @@
  */
 function wp_validate_auth_cookie($cookie = '') {
 	if ( empty($cookie) ) {
-		if ( empty($_COOKIE[AUTH_COOKIE]) )
+		if ( is_ssl() )
+			$cookie_name = SECURE_AUTH_COOKIE;
+		else
+			$cookie_name = AUTH_COOKIE;
+
+		if ( empty($_COOKIE[$cookie_name]) )
 			return false;
-		$cookie = $_COOKIE[AUTH_COOKIE];
+		$cookie = $_COOKIE[$cookie_name];
 	}
 
 	$cookie_elements = explode('|', $cookie);
@@ -514,9 +519,10 @@
  *
  * @param int $user_id User ID
  * @param int $expiration Cookie expiration in seconds
+ * @param bool $secure Whether the cookie is for https delivery only or not.  Not used by default.  For plugin use.
  * @return string Authentication cookie contents
  */
-function wp_generate_auth_cookie($user_id, $expiration) {
+function wp_generate_auth_cookie($user_id, $expiration, $secure = false) {
 	$user = get_userdata($user_id);
 
 	$key = wp_hash($user->user_login . '|' . $expiration);
@@ -524,7 +530,7 @@
 
 	$cookie = $user->user_login . '|' . $expiration . '|' . $hash;
 
-	return apply_filters('auth_cookie', $cookie, $user_id, $expiration);
+	return apply_filters('auth_cookie', $cookie, $user_id, $expiration, $secure);
 }
 endif;
 
@@ -550,13 +556,21 @@
 		$expire = 0;
 	}
 
-	$cookie = wp_generate_auth_cookie($user_id, $expiration);
+	if ( is_ssl() ) {
+		$secure = true;
+		$cookie_name = SECURE_AUTH_COOKIE;
+	} else {
+		$secure = false;
+		$cookie_name = AUTH_COOKIE;
+	}
 
-	do_action('set_auth_cookie', $cookie, $expire);
+	$cookie = wp_generate_auth_cookie($user_id, $expiration, $secure);
 
-	setcookie(AUTH_COOKIE, $cookie, $expire, COOKIEPATH, COOKIE_DOMAIN);
+	do_action('set_auth_cookie', $cookie, $expire, $secure);
+
+	setcookie($cookie_name, $cookie, $expire, COOKIEPATH, COOKIE_DOMAIN, $secure);
 	if ( COOKIEPATH != SITECOOKIEPATH )
-		setcookie(AUTH_COOKIE, $cookie, $expire, SITECOOKIEPATH, COOKIE_DOMAIN);
+		setcookie($cookie_name, $cookie, $expire, SITECOOKIEPATH, COOKIE_DOMAIN, $secure);
 }
 endif;
 
@@ -569,6 +583,8 @@
 function wp_clear_auth_cookie() {
 	setcookie(AUTH_COOKIE, ' ', time() - 31536000, COOKIEPATH, COOKIE_DOMAIN);
 	setcookie(AUTH_COOKIE, ' ', time() - 31536000, SITECOOKIEPATH, COOKIE_DOMAIN);
+	setcookie(SECURE_AUTH_COOKIE, ' ', time() - 31536000, COOKIEPATH, COOKIE_DOMAIN);
+	setcookie(SECURE_AUTH_COOKIE, ' ', time() - 31536000, SITECOOKIEPATH, COOKIE_DOMAIN);
 
 	// Old cookies
 	setcookie(USER_COOKIE, ' ', time() - 31536000, COOKIEPATH, COOKIE_DOMAIN);
@@ -604,14 +620,36 @@
  */
 function auth_redirect() {
 	// Checks if a user is logged in, if not redirects them to the login page
-	if ( (!empty($_COOKIE[AUTH_COOKIE]) &&
-				!wp_validate_auth_cookie($_COOKIE[AUTH_COOKIE])) ||
-			(empty($_COOKIE[AUTH_COOKIE])) ) {
-		nocache_headers();
 
-		wp_redirect(get_option('siteurl') . '/wp-login.php?redirect_to=' . urlencode($_SERVER['REQUEST_URI']));
-		exit();
+	if ( is_ssl() || (defined('FORCE_HTTPS_LOGIN') && FORCE_HTTPS_LOGIN) )
+		$secure = true;
+	else
+		$secure = false;
+
+	// If https is required and request is http, redirect
+	if ( $secure && !is_ssl() ) {
+		if ( false !== strpos($_SERVER['REQUEST_URI'], 'http') ) {
+			wp_redirect(str_replace('http://', 'https://', $_SERVER['REQUEST_URI']));
+			exit();
+		} else {
+			wp_redirect('https://' . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI']);
+			exit();			
+		}
 	}
+
+	if ( wp_validate_auth_cookie() )
+		return;  // The cookie is good so we're done
+
+	// The cookie is no good so force login
+	nocache_headers();
+
+	$login_url = get_option('siteurl') . '/wp-login.php?redirect_to=' . urlencode($_SERVER['REQUEST_URI']);
+
+	//  Redirect to https if connection is secure
+	if ( $secure )
+		$login_url = str_replace('http://', 'https://', $login_url);
+	wp_redirect($login_url);
+	exit();
 }
 endif;
 
Index: wp-includes/script-loader.php
===================================================================
--- wp-includes/script-loader.php	(revision 7956)
+++ wp-includes/script-loader.php	(working copy)
@@ -137,11 +137,11 @@
 			$this->add( 'upload', '/wp-admin/js/upload.js', array('jquery'), '20070518' );
 			$this->add( 'postbox', '/wp-admin/js/postbox.js', array('jquery'), '20080128' );
 			$this->localize( 'postbox', 'postboxL10n', array(
-				'requestFile' => get_option( 'siteurl' ) . '/wp-admin/admin-ajax.php',
+				'requestFile' => admin_url('admin-ajax.php'),
 			) );
 			$this->add( 'slug', '/wp-admin/js/slug.js', array('jquery'), '20080208' );
 			$this->localize( 'slug', 'slugL10n', array(
-				'requestFile' => get_option( 'siteurl' ) . '/wp-admin/admin-ajax.php',
+				'requestFile' => admin_url('admin-ajax.php'),
 				'save' => __('Save'),
 				'cancel' => __('Cancel'),
 			) );
Index: wp-settings.php
===================================================================
--- wp-settings.php	(revision 7956)
+++ wp-settings.php	(working copy)
@@ -307,6 +307,13 @@
 
 /**
  * It is possible to define this in wp-config.php
+ * @since 2.6
+ */
+if ( !defined('SECURE_AUTH_COOKIE') )
+	define('SECURE_AUTH_COOKIE', 'wordpress_sec_' . COOKIEHASH);
+
+/**
+ * It is possible to define this in wp-config.php
  * @since 2.3.0
  */
 if ( !defined('TEST_COOKIE') )
Index: wp-admin/admin.php
===================================================================
--- wp-admin/admin.php	(revision 7956)
+++ wp-admin/admin.php	(working copy)
@@ -26,8 +26,8 @@
 
 wp_reset_vars(array('profile', 'redirect', 'redirect_url', 'a', 'popuptitle', 'popupurl', 'text', 'trackback', 'pingback'));
 
-wp_admin_css_color('classic', __('Classic'), get_option( 'siteurl' ) . "/wp-admin/css/colors-classic.css", array('#07273E', '#14568A', '#D54E21', '#2683AE'));
-wp_admin_css_color('fresh', __('Fresh'), get_option( 'siteurl' ) . "/wp-admin/css/colors-fresh.css", array('#464646', '#CEE1EF', '#D54E21', '#2683AE'));
+wp_admin_css_color('classic', __('Classic'), admin_url("css/colors-classic.css"), array('#07273E', '#14568A', '#D54E21', '#2683AE'));
+wp_admin_css_color('fresh', __('Fresh'), admin_url("css/colors-fresh.css"), array('#464646', '#CEE1EF', '#D54E21', '#2683AE'));
 
 wp_enqueue_script( 'common' );
 wp_enqueue_script( 'jquery-color' );