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The HTTPS decryption limitation for multiple domains with the same IP address in InterScan Web Security Virtual Appliance (IWSVA) 6.5

    • Updated:
    • 17 May 2018
    • Product/Version:
    • InterScan Web Security Virtual Appliance 6.5
    • Platform:
    • N/A N/A
Summary

It is possible that multiple domains are resolved to the same IP address. For example, multiple domains might contain “Domain A” and “Domain B”.

If the internet traffic goes through IWSVA 6.5 in transparent mode (transparent bridge or WCCP mode) and your policies require “Domain A” to be tunneled while “Domain B” to be decrypted by a policy, “Domain B” will be tunneled if any user visits “Domain A” first.

Details
Public

This behavior is caused by the FQDN cache, which results in the IP address to be cached with only one domain.

If “Domain A” is in the FQDN cache, all the domains’ HTTPS traffic with the same IP address will be tunneled by IWSVA since IWSVA consders all the subsequent traffic as “Domain A”’s traffic.

There are two ways to resolve this issue:

  1. Change the DNS server’s records for these domains and make sure they are resolved to different IP addresses.
  2. Disable the FQDN cache:

     
    Disabling the FQDN cache may lead to client browser latency for HTTPS websites.
    1. Log in to the IWSVA Linux shell as root, for example via PuTTy.
    2. Edit the /etc/iscan/intscan.ini file by executing the following command:

      vi /etc/iscan/intscan.ini

    3. Change the following parameter from "yes" to "no".

      # FQDN cache for HTTPS
      https_fqdn_cache_enable=no

    4. Save the file and exit.
    5. Restart the HTTP daemon.

      $ /etc/iscan/S99ISproxy stop
      $ /etc/iscan/S99ISproxy start

Premium
Internal
Rating:
Category:
Configure; Troubleshoot
Solution Id:
1119906
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