Domain http instead of https

Hello,

I have a problem with creating new Sites on WordPress 3.2.1 MultiSite (Sub-directory Sites).

the webserver (apache) on our hosting server is listening on port 80.
Clients are redirected from our proxies with https to the webserver.

after fresh installing wordpress, the new created admin account was not able to login.
Solution was to correct the siteurl option value from http to https in the mysql DB.

mysql> select option_name, option_value from wp_options where option_name = ‘siteurl’;
+————-+—————————————+
| option_name | option_value |
+————-+—————————————+
| siteurl | https://<webserver>.at/<user>/wordpress |
+————-+—————————————+
1 row in set (0.00 sec)

Now I have another problem.
I can’t create new sites in Network Admin –> Sites –> Add New.
After clicking on “Add Site”, a Securiy Warning:
….
Although this page is encrypted, the information you have entered is to be sent over an unencrypted connection and could easily be read by a third party.
Are you sure you want to continue sending this information?
…..
pops up.

After clicking on Continue, a blank site with “Are you sure you want to do this?” comes up.

I think, the problem is the “Domain” Statement, which point to http instead of https.
(Network Admin –> All Sites –> /<user>/wordpress –> Edit:
Domain https://<webserver&gt;.at
Path /<user>/wordpress/

How can I change the Domain from http to https?

I’ve already tried some changes (one by one) in .htaccess and wp-config.php:
* .htaccess:
….
RewriteEngine On
#RewriteCond %{HTTP_HOST} !^<webserver>\.at$ [NC]
#RewriteRule ^/~(.*) https://<webserver&gt;.at/$1 [L,R=301]
#RedirectMatch permanent ^/(.*) https://<webserver&gt;.at/$1
#RewriteCond %{REQUEST_FILENAME} -d
#RewriteCond %{REQUEST_URI} !(/$)
#RewriteCond %{SERVER_PORT} 80
#RewriteRule (.*) https://<webserver&gt;.at%{REQUEST_URI}/$1/ [R=301,L]
#RewriteCond %{SERVER_PORT} 80
#RewriteRule ^(.*)$ https://<webserver&gt;.at%{REQUEST_URI}/$1 [R,L]
#RewriteCond %{HTTPS} off
#RewriteRule .* https://<webserver&gt;.at%{REQUEST_URI} [last]
#RewriteCond %{SERVER_PORT} !^443$
#RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI} [R,L]
RewriteBase /<user>/wordpress/
RewriteRule ^index\.php$ – [L]
….
* wp-config.php:
….
define(‘WP_DEBUG’, false);
define(‘WP_ALLOW_MULTISITE’, true);
define( ‘MULTISITE’, true );
define( ‘SUBDOMAIN_INSTALL’, false );
$base = ‘/<user>/wordpress/’;
define( ‘DOMAIN_CURRENT_SITE’, ‘<webserver>.at’ );
define( ‘PATH_CURRENT_SITE’, ‘/<user>/wordpress/’ );
define( ‘SITE_ID_CURRENT_SITE’, 1 );
define( ‘BLOG_ID_CURRENT_SITE’, 1 );
#if ( $_SERVER[“HTTP_HOST”] == “<webserver>.at” ) {
# define(‘FORCE_SSL_ADMIN’, true);
#}
#define( ‘WP_CONTENT_URL’, ‘https://<webserver&gt;.at/<user>/wordpress/wp-content’);
#define(‘FORCE_SSL_LOGIN’, true);
#define(‘FORCE_SSL_ADMIN’, true);
….

I have also tried the plugin “wp-multi-network”
Site Admin –> Tools –> Networks:
No change: Domain = http

my question is: how can I change the Domain from http to https?

many thanks
Richard