Tracking Your CloudFlare DNS Configuration

Posted by Alistair Pialek

Email is a mission critical application that is relied on to power business communication and collaboration capabilities on a day-to-day basis. It is a vital component of modern business and being able to send and receive email is of paramount importance. If you were to make a list of applications to track and control configuration changes of, email would be at the top of that list.

Underpinning web and email communication, a businesses DNS zone file ranks as one of the most important configuration files you have probably never heard of and should certainly be continuously monitored. Even stored in the cloud through a service such as CloudFlare, changes to your DNS zone file can still occur causing disruptions to mission critical applications such as email, which is what today's scenario will explore.

Scenario

It’s that time of year again and the security auditors are back in town to provide their report on your organisation's recent vulnerability assessment. With pages of recommendations mostly pertaining to lots of small fixes you hand-off the report to your BAU team and consider this year's audit done and dusted. 

Later that evening you receive a call from a frustrated remote worker claiming that no one is receiving their emails. You patiently walk through some troubleshooting steps over the phone but to no avail. Email is being sent successfully but apparently no emails are reaching their intended destinations.

You decide to call into the office to check if this is a widespread issue and reach support. Apparently all emails being sent internally are reaching their audience but many remote workers and vendors that send email on behalf of the organisation are reporting that emails are either not being received or are heading to spam folders.

With the recent security fixes that were applied you realise that something must have have affected email. Luckily, UpGuard is on hand to diagnose the problem. 

Step 1: Scan Your CloudFlare Instance

Scanning your CloudFlare instance is just a matter of adding a web app, selecting CloudFlare and entering in your CloudFlare details

scan_a2

Step 2: Compare To Another Scan

We can then proceed to compare the current CloudFlare instance state to a time before the security fixes were applied by clicking the Compare To Another Scan drop down list and selecting the desired scan time. The diff wheel will now update to show our configuration differences graphically and we can clearly see an orange section representing some modified CloudFlare configuration.

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Step 3: Drill Down

From here we will want to check out what this changed configuration is regarding and click the Diff Only button to see only the configuration differences and then Table View to get a content based view.

scan_ab_table

The changes made to the SPF record above have changed the way we determine if an email message is authorised to send from a domain. Prior to the change we had a soft fail flag configured by ~all which means that our email messages, even if they were sent from a domain outside our IP address range, would not be considered as spam. This is quite commonly allowed for vendors or external parties to legitimately send emails on the companies behalf. Now, we can see that we are using the hard fail flag configured by -all which means that these email messages will now be considered as spam because the message was sent from an IP address outside our domain.

An organisation will usually configure the hard fail flag to control who can send messages on behalf of the organisation or has concerns over email security. Additionally, when email messages are forwarded, it also requires a soft fail to be configured because SPF checks do not survive email forwarding.

The pros and cons of hard vs soft fail SPF flags is beyond the scope of this post but needless to say, we know exactly what has changed and how to fix the problem.

Summary

We’ve detected a small yet critical change in our CloudFlare DNS zone configuration file in a matter of minutes. Nodes are scanned daily by default on UpGuard and the results, reporting any configuration changes, are sent straight through to your inbox. Web and email applications are mission critical to your business and spending time manually wading through all the configuration flags and settings that your DNS zone file contains trying to resolve issues like the above is costly, time consuming and error prone.

 

Next article: Get Started Monitoring CloudFlareFun fact: UpGuard exposes CloudFlare configurations that aren't even visible in the CloudFlare UI.

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