Explicit web proxy

Explicit web proxy can be configured on FortiGate for proxying HTTP and HTTPS traffic.

To deploy explicit proxy, individual client browsers can be manually configured to send requests directly to the proxy, or they can be configured to download proxy configuration instructions from a Proxy Auto-Configuration (PAC) file.

When explicit proxy is configured on an interface, the interface IP address can be used by client browsers to forward requests directly to the FortiGate. FortiGate also supports PAC file configuration.

For FortiOS 7.4.0, SSL VPN web mode, explicit web proxy, and interface mode IPsec VPN features will not work with the following configuration: An IP pool with ARP reply enabled is configured. This IP pool is configured as the source IP address in a firewall policy for SSL VPN web mode, in a proxy policy for explicit web proxy, or as the local gateway in the Phase 1 settings for an interface mode IPsec VPN. A matching blackhole route is configured for IP pool reply traffic. Configuring an IP pool as the source NAT IP address in a regular firewall policy works as before. For details, see Technical Tip: IP pool and virtual IP behaviour changes in FortiOS 6.4, 7.0, 7.2, and 7.4.

To configure explicit web proxy in the GUI:

1. Enable and configure explicit web proxy:

   1. Go to Network > Explicit Proxy.

   2. Enable Explicit Web Proxy.

   3. Select port2 as the Listen on Interfaces and set the HTTP Port to 8080.

   4. Configure the remaining settings as needed.

      

   5. Click Apply.

2. Create an explicit web proxy policy:

   1. Go to Policy & Objects > Proxy Policy.

   2. Click Create New.

   3. Set Proxy Type to Explicit Web and Outgoing Interface to port1.

   4. Also set Source and Destination to all, Schedule to always, Service to webproxy, and Action to ACCEPT.

      

   5. Click OK to create the policy.

This example creates a basic policy. If required, security profiles can be enabled, and deep SSL inspection can be selected to inspect HTTPS traffic.

3. Configure a client to use the FortiGate explicit proxy:

   Set the FortiGate IP address as the proxy IP address in the browser, or use an automatic configuration script for the PAC file.

To configure explicit web proxy in the CLI:

1. Enable and configure explicit web proxy:

   config web-proxy explicit
       set status enable
       set ftp-over-http enable
       set socks enable
       set http-incoming-port 8080
       set ipv6-status enable
       set unknown-http-version best-effort
   end
   config system interface
       edit "port2"
           set vdom "vdom1"
           set ip 10.1.100.1 255.255.255.0
           set allowaccess ping https ssh snmp http telnet
           set type physical
           set explicit-web-proxy enable
           set snmp-index 12
           end
       next
   end

2. Create an explicit web proxy policy:

   config firewall proxy-policy
       edit 1
           set name "proxy-policy-explicit"
           set proxy explicit-web
           set dstintf "port1"
           set srcaddr "all"
           set dstaddr "all"
           set service "webproxy"
           set action accept
           set schedule "always"
           set logtraffic all
       next
   end

This example creates a basic policy. If required, security profiles can be enabled, and deep SSL inspection can be selected to inspect HTTPS traffic.

3. Configure a client to use the FortiGate explicit web proxy:

   Set the FortiGate IP address as the proxy IP address in the browser, or use an automatic configuration script for the PAC file.

Downloading a PAC file using HTTPS

PAC files can be downloaded for an explicit proxy through the FortiGate's captive portal using HTTPS to ensure a secure download.

In this example, a Windows PC has an HTTPS URL configured in its proxy settings to download a PAC file from a FortiGate by using a download link, https://cp.myqalab.local:7831/proxy.pac, through a captive portal. Once the PAC file is securely downloaded using HTTPS, browsers installed on the PC can use the proxy in the PAC file to visit a website.

The global web proxy settings must be configured to use a customized SSL certificate because the default Fortinet_Factory certificate will not be accepted by Windows due to security restrictions. The customized SSL certificate is used as the HTTPS server's certificate on the FortiGate. All CA certificates in the server certificate must be installed and trusted on the Windows PC.

To download a PAC file using HTTPS:

1. Configure the explicit web proxy to get a PAC file through HTTPS:

   config web-proxy explicit
       set pac-file-server-status enable
       unset pac-file-server-port
       set pac-file-name "proxy.pac"
       set pac-file-data "function FindProxyForURL(url, host) {
      // testtest
      return \"PROXY 10.1.100.1:8080\";
   }
   "
       set pac-file-through-https enable
   end

2. Configure the captive portal to be used as an HTTPS server to provide the service to download the PAC file:

   config authentication setting
       set captive-portal-type ip
       set captive-portal-ip 10.1.100.1
       set captive-portal-ssl-port 7831
   end

3. Configure the global web proxy settings to use a customized SSL certificate:

   config web-proxy global
       set ssl-cert "server_cert"
   end

4. On the Windows PC, go to Settings > Network & Internet > Proxy.

   

5. In the Automatic proxy setup section, click Save to trigger the PAC file download from the HTTPS URL.