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April 10, 2014By Stefan Zier

Mitigating the Heartbleed Vulnerability

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By now, you have likely read about the security vulnerability known as the Heartbleed bug. It is a vulnerability in the widespread OpenSSL library. It allows stealing the information protected, under normal conditions, by the SSL/TLS encryption used to encrypt traffic on the Internet (including Sumo Logic).

How did we eliminate the threat?

When we were notified about the issue, we quickly discovered that our own customer-facing SSL implementation was vulnerable to the attack — thankfully, the advisory was accompanied by some scripts and tools to test for the vulnerability. Mitigation happened in four steps:

  1. Fix vulnerable servers. As a first step, we needed to make sure to close the information leak. In some cases, that meant working with third party vendors (most notably, Amazon Web Services, who runs our Elastic Load Balancers) to get all servers patched. This step was concluded once we confirmed that all of load balancers on the DNS rotation were no longer vulnerable.

  2. Replace SSL key pairs. Even though we had no reason to believe there was any actual attack against our SSL private keys, it was clear all of them had to be replaced as a precaution. Once we had them deployed out to all the servers and load balancers, we revoked all previous certificates with our CA, GeoTrust. All major browsers perform revocation checks against OCSP responders or CRLs.

  3. Notify customers. Shortly after we resolved the issues, we sent an advisory to all of our customers, recommending a password change. Again, this was a purely precautionary measure, as there is no evidence of any passwords leaking.

  4. Update Collectors. We have added a new feature to our Collectors that will automatically replace the Collector’s credentials. Once we complete testing, we will recommend all customers to upgrade to the new version. We also enabled support for certificate revocation checking, which wasn’t enabled previously.

How has this affected our customers?

Thus far, we have not seen any signs of unusual activity, nor have we seen any customers lose data due to this bug. Unfortunately, we’ve had to inconvenience our customers with requests to change passwords and update Collectors, but given the gravity of the vulnerability, we felt the inconvenience was justified.

Internal impact

Our intranet is hosted on AWS and our users use OpenVPN to connect to it. The version of OpenVPN we had been running needed to be updated to a version that was released today. Other servers behind OpenVPN also needed updating.

Sumo Logic uses on the order of 60-70 SaaS services internally. Shortly after we resolved our customer facing issues, we performed an assessment of all those SaaS services. We used the scripts to test for the vulnerability combined with DNS lookups. If a service looked like it was hosted with a provider/service that was known to have been vulnerable (such as AWS ELB), we added it to our list. We are now working our way through the list and changing passwords on all affected applications, starting with the most critical ones. Unfortunately, manually changing passwords in all of the affected applications takes time and presents a burden on our internal IT users. We plan to have completed this process by the end of the week.

Interesting Days

Overall, the past few days were pretty interesting on the internet. Many servers (as many as 66% of SSL servers on the net) are running OpenSSL, and most were affected. Big sites, including Yahoo Mail and many others were affected. The pace of exploitation and spread of the issue were both concerning. Thankfully, Codenomicon, the company that discovered this vulnerability, did an amazing job handling and disclosing it in a pragmatic and responsible fashion. This allowed everybody to fix the issue rapidly and minimize impact on their users.

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Stefan Zier

Stefan was Sumo’s first engineer and Chief Architect. He enjoys working on cloud plumbing and is plotting to automate his job fully, so he can spend all his time skiing in Tahoe.

More posts by Stefan Zier.

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