We have begun to roll out another SWA update - version 22.214.171.124. This update should be available to all customers within the next week.
This update was made necessary by an upcoming change to Google Chrome. In version 58 of Chrome, HTTPS certificate validation rules are changing. Chrome will no longer consider the Common Name field of the certificate when checking to see if the certificate is valid for the web site. It will now only consider the Subject Alternative Name field.
This change is consistent with the relevant RFC for HTTPS. Use of the Common Name when Subject Alternative Name is not present, but the specification also deprecates use of the Common Name as best practice for certificate issuers. Chrome is not the first mainstream browser to have taken the step of enforcing this deprecation: Firefox also made this change recently. But Firefox only enforces it for certificates signed by a CA in their Trusted CA list, so it has not impacted on SWA users in the same way.
We had hoped to roll out this update before Google released version 58. Unfortunately the release came sooner than expected. Any users who update to Chrome v58 in the coming days may experience SSL validation messages until your SWA is updated to v126.96.36.199.
Chrome also recently made it harder to visually inspect a certificate from the main UI. Unlike other browsers, you need to open Chrome's Developer Tools in order to visually check the certificate. But of course, we don't expect users to have to do that.
For SWA customers there are two main areas impacted:
- connecting to the SWA's Admin user interface and login pages (UI & Portal Certificate)
- connecting to websites using HTTPS decryption, or HTTPS websites that are blocked (HTTPS Decryption)
UI & Portal Certificate
Customers who are using the default, automatically-generated certificate for the Appliance's UI will notice that Chrome v58 will show certificate warnings when connecting. The same certificate is also used for AD SSO authentication in Transparent mode.
Once your SWA has updated to version 188.8.131.52, you can eliminate this problem by going to Configuration > System > Certificates, selecting the 'UI & Portal Certificate' tab and clicking 'Regenerate Certificate'. The new certificate will use the Subject Alternative Name field.
If you are using a Custom Certificate, you may need to ask your certificate issuer to provide you with an updated one. However, if you have purchased a certificate from a commercial CA, it may well already use the Subject Alternative Name field.
|Viewing a certificate's contents via Chrome's Developer Tools. The Common Name is part of the basic properties of the certificate.
|Subject Alternative Name is an extension that allows a single certificate to be used for many websites.
When decrypting HTTPS traffic for inspection, the Sophos Web Appliance automatically creates 'shadow' certificates for each website visited by end-users. Because the certificates are created on a site-by-site basis, and do not have to support multiple sites like some original certificates do, the product has just used the Common Name field to identify the site. From version 58, Chrome will report to end-users that the certificate is not valid.
This problem will automatically be resolved by updating to version 184.108.40.206. It requires no further action.
This is the only change in v220.127.116.11, but for the record, the release notes for are available here.