EdgeSWG throwing HTTP 400 response for POST requests after upgrading to SG OS 7.4 (7.4.2.1 and above)

Products

• ProxySG Software - SGOS

Issue/Introduction

EdgeSWG throwing HTTP 400 response for POST requests after upgrading to SG OS 7.4

Upgrade was done to SG OS 7.4.2.1 and above

In the EdgeSWG policy trace, following is seen

location-id=0 access_type=unknown
time: 2025-05-28 00:09:25 UTC
POST https://example.com/post
  DNS lookup was unrestricted
User-Agent: example
user: unauthenticated
authentication status='not_attempted' authorization status='not_attempted'
user: authenticated=false authorized=true relative username=''
verdict: EXCEPTION(invalid_request): Request could not be handled
  url.category: none@Policy;example;Technology/Internet@Blue Coat
    category groups: Business Related@Blue Coat;Technology@Blue Coat
    total categorization time: 2
    static categorization time: 2
server.response.code: 0
client.response.code: 400

Cause

Starting SG OS 7.4.2.1, to improve security, the appliance now blocks unencrypted HTTP POST requests from the client that contain a HTTPS URL. Now, when the appliance receives an HTTPS POST request over plain HTTP, the appliance returns a “400 Bad Request” response by default.

To configure the behavior of the appliance for these types of requests, use the following CPL property (the default is no):
http.allow_https_post_over_http(yes|no)

Resolution

Enable unencrypted HTTP POST requests from the client that contain a HTTPS URL using the following CPL in web access layer

http.allow_https_post_over_http(yes)