### SSL/TLS Encryption The traffic between Parallels RAS users and a RAS Secure Client Gateway can be encrypted. The SSL/TLS tab allows you to configure data encryption options. Using Site defaults To use Site default settings, click the Inherit default settings option. To specify your own settings, clear the option. For more info, see Site Defaults (Gateways). Enforcing HSTS The Configure button in the HSTS section allows you to enforce HTTP Strict Transport Security (HSTS), which is a mechanism that makes a web browser to communicate with the web server using only secure HTTPS connections. When HSTS is enforced for a RAS Secure Client Gateway, all web requests to it will be forced to use HTTPS. This specifically affects the RAS HTML5 Gateway, which can normally accept both HTTP and HTTPS requests. When you click the Configure button, the HSTS Settings dialog opens where you can specify the following: Enforce HTTP strict transport security (HSTS): Enables or disables HSTS for the gateway. Max-age: Specifies the max-age for HSTS, which is the time (in our case in months) that the web browser should remember that it can only communicate with the gateway using HTTPS. The default (and recommended) value is 12 months. Acceptable values are 4 to 120 months. Include subdomains: Specifies whether to include subdomains (if you have them). Preload: Enables or disables HSTS preloading. This is a mechanism whereby a list of hosts that wish to enforce the use of SSL/TLS on their Site is hardcoded into a web browser. The list is compiled by Google and is used by Chrome, Firefox, Safari, Internet Explorer 11, and Edge browsers. When HSTS preload is used, a web browser will not even try to send a request using HTTP, but will use HTTPS every time. Please also read the important note below. Note: To use HSTS preload, you have to submit your domain name for inclusion in Chrome's HSTS preload list. Your domain will be hardcoded into all web browser that use the list. Important: Inclusion in the preload list cannot easily be undone. You should only request inclusion if you are sure that you can support HTTPS for your entire Site and all its subdomains in the long term (usually 1-2 years). Please also note the following requirements: Your website must have a valid SSL certificate. See Assessing SSL Server Configuration. All subdomains (if any) must be covered in your SSL Certificate. Consider ordering a Wildcard Certificate. Configuring SSL By default, a self-signed certificate is assigned to a RAS Secure Client Gateway when the gateway is installed. Each RAS Secure Client Gateway must have a certificate assigned and the certificate should be added to Trusted Root Authorities on the client side to avoid security warnings. SSL certificates are created on the Site level using the Farm / Site / Certificates subcategory in the RAS Console. Once a certificate is created, it can be assigned to a RAS Secure Client Gateway. For the information about creating and managing certificates, refer to the SSL Certificate Management chapter. To configure SSL for a gateway: Select the Enable SSL on Port option and specify a port number (default is 443). In the Accepted SSL Versions drop-down list, select the SSL version accepted by the RAS Secure Client Gateway. In the Cipher Strength field, select a desired cipher strength. In the Cipher field, specify the cipher. A stronger cipher allows for stronger encryption, which increases the effort needed to break it. In the Certificates drop-down list, select a desired certificate. For the information on how to create a new certificate and make it appear in this list, see the SSL Certificate Management chapter. The <All matching usage> option will use any certificate configured to be used by gateways. When you create a certificate, you specify the "Usage" property where you can select "Gateway", "HALB", or both. If this property has the "Gateway" option selected, it can be used with a gateway. Please note that if you select this option, but not a single certificate matching it exists, you will see a warning and will have to create a certificate first. Encrypting Parallels Client connection By default, the only type of connection that is encrypted is a connection between a gateway and backend servers. To encrypt a connection between Parallels Client and the gateway, you also need to configure connection properties on the client side. To do so, in Parallels Client, open connection properties and set the connection mode to Gateway SSL. To simplify the Parallels Client configuration, it is recommended to use a certificate issued either by a third party Trusted Certificate Authority or Enterprise Certificate Authority (CA). If an Enterprise CA certificate is used, Windows clients receive a Root or Intermediate Enterprise CA certificate from Active Directory. Client devices on other platforms require manual configuration. If a third-party certificate issued by a well-known Trusted Certificate Authority is used, the client device trusts using Trusted Certificate Authority updates for the platform. Parallels Clients Configuration In case the certificate is self-signed, or the certificate issued by Enterprise CA, Parallels Clients should be configured as follows: Export the certificate in Base-64 encoded X.509 (.CER) format. Open the exported certificate with a text editor, such as notepad or WordPad, and copy the contents to the clipboard. To add the certificate with the list of trusted authorities on the client side and enable Parallels Client to connect over SSL with a certificate issued from an organization’s Certificate Authority: On the client side in the directory "C:\Program Files\Parallels\Remote Application Server Client\" there should be a file called `trusted.pem`. This file contains certificates of common trusted authorities. Paste the content of the exported certificate (attached to the list of the other certificates). Securing RDP-UDP Connections A Parallels Client normally communicates with a RAS Secure Client Gateway over a TCP connection. Recent Windows clients may also utilize a UDP connection to improve WAN performance. To provide the SSL protection for UDP connections, DTLS must be used. To use DTLS on a RAS Secure Client Gateway: On the SSL/TLS tab, make sure that the Enable SSL on Port option is selected. On the Network tab, make sure that the Enable RDP UDP Data Tunneling option is selected. The Parallels Clients must be configured to use the Gateway SSL Mode. This option can be set in the Connections Settings > Connection Mode drop-down list on the client side. Once the above options are correctly set, both TCP and UDP connections will be tunneled over SSL.