Verification of the X-Forwarded-For (XFF) header

Products

• ProxySG Software - SGOS

Issue/Introduction

We need to check that only IP addresses separated by commas appear in the X-Forwarded-For (XFF) header, that the IP addresses that appear are well constructed and that no strange characters appear in the text string

Resolution

The following CPL  code will fulfill the request:

 

<proxy>
url.domain="www.domainname.ltd" condition=conditionXFF ALLOW

define condition condicionXFF
   request.header.x-forwarded-for.exists=no
   request.header.x-forwarded-for="^(\d{1,3}\.){3}\d{1,3}(,*(\d{1,3}\.){3}\d{1,3})*$"
end condition conditionXFF