KL-001-2017-022 : Splunk Local Privilege Escalation

KL-001-2017-022 : Splunk Local Privilege Escalation Title: Splunk Local Privilege Escalation Advisory ID: KL-001-2017-022 Publication Date: 2017.11.03 Publication URL: https://www.korelogic.com/Resources/Advisories/KL-001-2017-022.txt 1. Vulnerability Details Affected Vendor: Splunk Affected Product: Splunk Enterprise Affected Version: 6.6.x Platform: Embedded Linux CWE Classification: CWE-280: Improper Handling of Insufficient Permissions or Privileges Impact: Privilege Escalation Attack vector: Local 2. Vulnerability Description Splunk can be configured to run as a non-root user. However, that user owns the configuration file that specifies the user to run as, so it can trivially gain root privileges. 3. Technical Description Splunk runs multiple daemons and network listeners as root by default. It can be configured to drop privileges to a specified non-root user at startup such as user splunk, via the SPLUNK_OS_USER variable in the splunk-launch.conf file in $SPLUNK_HOME/etc/ (such as /opt/splunk/etc/splunk-launch.conf). However, the instructions for enabling such a setup call for chown'ing the entire $SPLUNK_HOME directory to that same non-root user. For instance: http://docs.splunk.com/Documentation/Splunk/6.6.2/Installation/RunSplunkasadifferentornon-rootuser "4. Run the chown command to change the ownership of the splunk directory and everything under it to the user that you want to run the software. chown -R splunk:splunk $SPLUNK_HOME" Therefore, if an attacker gains control of the splunk account, they can modify $SPLUNK_HOME/etc/splunk-launch.conf to remove/unset SPLUNK_OS_USER so that the software will retain root privileges, and place backdoors under $SPLUNK_HOME/bin/, etc. that will take malicious actions as user root the next time Splunk is restarted. 4. Mitigation and Remediation Recommendation The vendor has published a mitigation for this vulnerability at: https://www.splunk.com/view/SP-CAAAP3M 5. Credit This vulnerability was discovered by Hank Leininger of KoreLogic, Inc. 6. Disclosure Timeline 2017.08.17 - KoreLogic submits vulnerability details to Splunk. 2017.08.17 - Splunk confirms receipt. 2017.08.22 - Splunk notifies KoreLogic that the issue has been assigned an internal ticket and will be addressed. 2017.09.29 - 30 business days have elapsed since the vulnerability was reported to Splunk. 2017.10.17 - KoreLogic requests an update from Splunk. 2017.10.18 - Splunk informs KoreLogic that they will issue an advisory on October 28th. 2017.10.23 - 45 business days have elapsed since the vulnerability was reported to Splunk. 2017.10.30 - Splunk notifies KoreLogic that the advisory is published. 2017.11.03 - KoreLogic public disclosure. 7. Proof of Concept See 3. Technical Description. The contents of this advisory are copyright(c) 2017 KoreLogic, Inc. and are licensed under a Creative Commons Attribution Share-Alike 4.0 (United States) License: http://creativecommons.org/licenses/by-sa/4.0/ KoreLogic, Inc. is a founder-owned and operated company with a proven track record of providing security services to entities ranging from Fortune 500 to small and mid-sized companies. We are a highly skilled team of senior security consultants doing by-hand security assessments for the most important networks in the U.S. and around the world. We are also developers of various tools and resources aimed at helping the security community. https://www.korelogic.com/about-korelogic.html Our public vulnerability disclosure policy is available at: https://www.korelogic.com/KoreLogic-Public-Vulnerability-Disclosure-Policy.v2.2.txt