Why adding a Base64 image to the reference proxy exception page prevents the Cloud SWG policy from being deployed?

Products

• Cloud Secure Web Gateway - Cloud SWG

Issue/Introduction

The customer made a change to their exception page to have the company logo shown even if the device does not have Internet access.

To do this they have encoded the logo image as a Base64 string so that the image can be embedded directly in the html code (and does not need to be downloaded from a private or public site).

However after the modification was completed pushing the Cloud SWG policy failed with the error shown below:

 

Environment

CloudSWG with Management Center to manage the customer Cloud SWG policy.

Cause

The max size for a CPL string is 8000 char, and the image that was embedded din the html code was fairly large (30KiB) which exceed this 8000 character per line limit.

Resolution

Because the image is Base64 encoded we can introduce new line in the html code to break it in multiple smaller increments (without affecting how the image is handled and displayed).

Once the image file was split into many smaller line and the exception policy was saved on the reference proxy, pushing the policy to Cloud SWG completed without any issues.