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Unable to block https sites in transparent bridge mode in InterScan Web Security Virtual Appliance (IWSVA)

    • Updated:
    • 8 Jun 2017
    • Product/Version:
    • InterScan Web Security Virtual Appliance 6.0
    • InterScan Web Security Virtual Appliance 6.5
    • Platform:
    • N/A N/A
Summary

When using URL filtering, you are unable to block some https websites such as facebook. After refreshing the page, only then will the website be blocked.

In the debug logs, entries like the following can be seen:

  • The client accesses HTTPs website using the IP address instead of URL hostname.
  • IWSVA cannot get the Hostname from the client hello.

    16:30:12.527 <DBG><7:15305:15335> Cannot get host name from client hello
    16:30:12.528 <DBG<7:15305:15335> NAT mode=false
    16:30:12.528 <DBG><7:15305:15335> Original destination ip is X.X.X.X, destination port is 443
    16:30:12.528 <DBG><7:15305:15335> 59 bytes read from [285].

    16:30:12.528 <DBG><7:15305:15335> HTTP request -- method "CONNECT" version "1.1" URI "X.X.X.X:443"

  • The traffic was tunneled by IWSVA, and client will never try to access the URL second time.

    16:30:12.545 <DBG><7:15305:15335> [286] Connected to the server on port 1214.
    16:30:12.545 <DBG><7:15305:15335> Entering into tunnel mode ( SSL-relay )

  • The following setting under [https-scanning] in the file /etc/iscan/intscan.ini has been set to "no":

    client_hello_no_host_tunnel=no

Details
Public

The issue occurs when IWSVA attempts to access a website with 2 connections.

To resolve this, enable IWSVA to tunnel the HTTPS connection when it cannot retrieve the server name from the client hello packet using the following procedure:

  1. Open the /etc/iscan/intscan.ini file using a text editor.
  2. Locate the following key under the https-scanning section and set its value to "yes".

    client_hello_no_host_tunnel=yes

     
    The default value is "yes". To disable the feature, set client_hello_no_host_tunnel=no".
  3. Save the changes and close the file.
  4. Restart the IWSVA services using the following command:

    /etc/iscan/rcIwss restart

Premium
Internal
Rating:
Category:
Troubleshoot
Solution Id:
1117526
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