Situational Awareness Alert for OpenSSL Vulnerability (Update C)

This alert update provides additional information, updating NCCIC/ICS-CERT Alert titled ICS-ALERT-14-009-01B Situational Awareness Alert for OpenSSL Vulnerability (UPDATE B) that was published April 12, 2014, on the ICS-CERT web site.

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SUMMARY

This alert update is a follow-up to the updated NCCIC/ICS-CERT Alert titled ICS-ALERT-14-009-01B Situational Awareness Alert for OpenSSL Vulnerability that was published April 12, 2014, on the ICS-CERT web site.

ICS-CERT is aware of a public report of a vulnerability with proof-of-concept (PoC) exploit code that could expose private secure sockets layer (SSL) keys used in the OpenSSL implementation of secure communication. According to this report, the vulnerability in OpenSSL Versions 1.0.1 through 1.0.1f contains a flaw in its implementation of the transport layer security/datagram transport layer security (TLS/DTLS) heartbeat functionality that could disclose private/encrypted information to an attacker. This vulnerability is commonly referred to as “heartbleed.” This vulnerability was discovered by a team of security engineers (Riku, Antti, and Matti) at Codenomicon and Neel Mehta of Google Security, who reported this vulnerability to the National Cyber Security Centre Finland (NCSC-FI) for vulnerability coordination and reporting to the OpenSSL team. This report was released without coordination with either the vendor or ICS-CERT. ICS-CERT is issuing this alert to provide early notice of the report and identify baseline mitigations for reducing risks to this and other cybersecurity attacks.

The report included vulnerability details and PoC exploit code for the following vulnerability:

To date, the following noninclusive list of references are available for analysis:

http://heartbleed.com/

http://www.kb.cert.org/vuls/id/720951

http://digital-forensics.sans.org/blog/2014/04/10/heartbleed-links-simulcast-etc/

The vulnerability exists in the Heartbeat extension (RFC6520) to OpenSSL’s Transport Layer Security (TLS) and the Datagram Transport Layer Security (DTLS) protocols. The Heartbeat extension is functionally a “keep-alive” between end-users and the secure server. It works by sending periodic “data pulses” of 64 KB in size to the secure server and once the server receives that data; it reciprocates by resending the same data at the same size.CVE, https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-0160, web site last accessed April 12, 2014.

The out-of-bounds “read” vulnerability exists because the Heartbeat extension does not properly validate the data being sent from the end-user. As a result, a malicious actor could send a specially crafted heartbeat request to the vulnerable server and obtain sensitive information stored in memory on the server. Furthermore, even though each heartbeat only allows requests to have a data size limited to 64 KB segments, it is possible to send repeated requests to retrieve more 64 KB segments, which could include encryption keys used for certificates, passwords, usernames, and even sensitive content that were stored at the time. An attacker could harvest enough data from the 64 KB segments to piece together larger groupings of information, which could help an attacker develop a broader understanding of the information being acquired.SANS OpenSSL Vulnerability, http://digital-forensics.sans.org/blog/2014/04/10/heartbleed-links-simulcast-etc, web site last accessed April 12, 2014.

Upgrade affected TLS/TDLS clients and servers to OpenSSL version 1.0.1g. Alternatively, affected versions of OpenSSL may be recompiled with the option “-DOPENSSL_NO_HEARTBEATS” to mitigate the vulnerability until an upgrade can be performed.

Contact equipment vendors for specific mitigation information as the implementations may vary. In addition, IDS signatures are available that may provide awareness of an attack of this nature occurring. An example of these rule sets can be found hereIDS signature examples, http://blog.fox-it.com/2014/04/08/openssl-heartbleed-bug-live-blog/, web site last accessed April 12, 2014.:

alert tcp any [!80,!445] -> any [!80,!445] (msg:"FOX-SRT - Suspicious - SSLv3 Large Heartbeat Response"; flow:established,to_client; content:"|18 03 00|"; depth: 3; byte_test:2, >, 200, 3, big; byte_test:2, <, 16385, 3, big; threshold:type limit, track by_src, count 1, seconds 600; reference:cve,2014-0160; classtype:bad-unknown; sid: 1000000; rev:4;)

Additional Snort signatures have been provided by the FBI, “Mitigation against Open Secure Socket Layer Heartbeat Extension Vulnerability” at http://ics-cert.us-cert.gov/UPDATE-FBI-Snort-Signatures-Heartbleed-April-2014.

Snort community rules can be found at http://www.snort.org/snort-rules/#community.

Additional indicators of compromise are available on the Control Systems compartment of the US-CERT secure portal for owners and operators of critical infrastructure.

ICS-CERT encourages U.S. asset owners and operators to join the Control Systems compartment of the US-CERT secure portal. Send your name, e-mail address, and company affiliation to ics-cert@hq.dhs.gov.

NOTE:  ICS-CERT has not tested the validity or efficacy of these rule sets and cautions users to thoroughly test these solutions before implementing them into production environments!

ICS-CERT recommends that users take defensive measures to minimize the risk of exploitation of these vulnerabilities. Specifically, users should: