Tag: mud

Yet another IoT bug

Miele could have benefited from MUD, as well as the experience of the Internet security community.

The Register is reporting a new IoT bug involving Miele PG 8528 professional dishwashers, used in hospitals and elsewhere.  In this case, it is a directory traversal bug involving an HTTP server that resides on port 80.  In all likelihood, the most harm this vulnerability will directly cause is that the dishwasher would run when it shouldn’t.  However, the indirect risk is that the device could be used to exfiltrate private information about patients and staff.  The vulnerability is reported here.

Manufacturers expect that it will be very simple to provide Internet services on their devices.  To them, initially, they think that it’s fine to slap a transceiver and a simple stack on a device and they’re finished.  They’re not.  They need to correct vulnerabilities such as this one.  They apparently have no mechanism to do so.  Manufacturers such as Miele are experts within their domains, such as building dishwashers.  They are not experts in Internet security.  It is a new world when these two domains intersect.

We need MUD

And yes, Manufacturer Usage Descriptions would have helped here, by restricting communication either to all local devices or to specifically authorized devices.

MUD sliding along

Your chance to try and chime in on Manufacturer Usage Descriptions, a way to protect IoT devices.

You may recall that I am working on a mechanism known as Manufacturer Usage Descriptions (MUD).  This is the system by which manufacturers can inform the network about how best to protect their products.  The draft for this work is now about to enter “working group last call” at the IETF.  This means that now would be a very good time for people to chime in with their views on the subject.

In the meantime, MUD Maker has also been coming along. This is a tool that generates manufacturer usage descriptions.  You can find the tool here.

MUD isn’t meant to be the whole enchilada of IoT security.  Other tools are needed to authenticate devices onto the network, and to securely update them.  And manufacturers have to take seriously not only their customers’ needs, but what risk they may impose on others, as Mirai reminded us.  Had MUD been around at the time, it’s possible that Mirai would not have happened.

How hard is it to secure a baby monitor?

Philips In.Sight B120/37Parents often seek the security of a baby monitor to know that their child is resting comfortably.  Unfortunately that security is often misplaced.  Last year Rapid7 produced a damning report, exposing numerous vulnerabilities in these devices.  As an example, the Philips In.Sight B120/37 made use of a fixed password over an insecure telnet or web service that resides on TCP port 8080.

Don AdamsThe thing is- the In.Sight came very close to getting right, or as the great Maxwell Smart would say, “Missed it by that much!”  That’s because Philips also offers a cloud-based service that would not otherwise require the device to listen to any TCP port.  That’s a good way to go because it is harder to probe the device for vulnerabilities.

One good reason to offer a local service is that some some people do not trust cloud services, and they particularly do not trust cloud services involving images of their children.  Indeed this makes for a very difficult choice, because that same Rapid7 report notes problems with some cloud based services, and so parents wouldn’t be wrong to worry.

Either way, I’ve built a MUD file using MudFileMaker.

A brief view of the application alongside tcpdump together with a quick view of the server binary seems to indicate that cloud communications are to api.ivideon.com.  We can thus come up with an appropriate MUD file as follows:

{
  "ietf-mud:meta-info": {
    "lastUpdate": "2016-10-03T12:56:08+02:00",
    "systeminfo": "Philips In.Sight B120/37 Baby Monitor",
    "cacheValidity": 1440
  },
  "ietf-acl:access-lists": {
    "ietf-acl:access-list": [
      {
        "acl-name": "mud-94344-v4in",
        "acl-type": "ipv4-acl",
        "ietf-mud:packet-direction": "to-device",
        "access-list-entries": {
          "ace": [
            {
              "rule-name": "clout0-in",
              "matches": {
                "ietf-acldns:src-dnsname": "api.ivideon.com",
                "protocol": 6,
                "source-port-range": {
                  "lower-port": 443,
                  "upper-port": 443
                }
              },
              "actions": {
                "permit": [
                  null
                ]
              }
            },
            {
              "rule-name": "entin0-in",
              "matches": {
                "ietf-mud:controller": "http://ivideon.com/babymonitors",
                "protocol": 6,
                "source-port-range": {
                  "lower-port": 8080,
                  "upper-port": 8080
                }
              },
              "actions": {
                "permit": [
                  null
                ]
              }
            }
          ]
        }
      },
      {
        "acl-name": "mud-94344-v4out",
        "acl-type": "ipv4-acl",
        "ietf-mud:packet-direction": "from-device",
        "access-list-entries": {
          "ace": [
            {
              "rule-name": "clout0-in",
              "matches": {
                "ietf-acldns:src-dnsname": "api.ivideon.com",
                "protocol": 6,
                "source-port-range": {
                  "lower-port": 443,
                  "upper-port": 443
                }
              },
              "actions": {
                "permit": [
                  null
                ]
              }
            },
            {
              "rule-name": "entin0-in",
              "matches": {
                "ietf-mud:controller": "http://ivideon.com/babymonitors",
                "protocol": 6,
                "source-port-range": {
                  "lower-port": 8080,
                  "upper-port": 8080
                }
              },
              "actions": {
                "permit": [
                  null
                ]
              }
            }
          ]
        }
      }
    ]
  }
}

Remember, the router needs to fill out which devices are authorized to be in class http://ivideon.com/babymonitors.  Note the use of incoming tcp port 8080.  It is possible at least for the server software run on another port if the configuration is changed.  At that moment, the above MUD file would be too restrictive, and the device would not function.  To fix that, one would simply remove the TCP port filter.

Again, note that only authorized communications are listed in the file, and so just because the developer left a telnet server in place doesn’t mean that just anyone would be able to access it.  This serves as a means to confirm the intentions of the developers.  Of course developers should never leave back doors, but if they do, perhaps MUD can reduce their impact, and let parents rest just a little easier.

How MUD could help against the Krebs Attack

CybercrimeIn the attack against krebsonsecurity.com, one of the systems that is said to have been used was the “H.264 Network DVR“.  This device accepts HTTP connections, and communicates outbound using FTP and EMail.  There may also be an undocumented protocol for a proprietary interface.

As I’ve previously discussed, use of Manufacturer Usage Descriptions (MUD) can limit the attack surface of a device, and it can also prevent devices from being used to source an attack.    MUD allows for manufacturers to define classes, and now one simply needs to fill them in on deployment.  From the manufacturer’s side, one needs to provide the file.  For the DVR in question, I used MudMaker to create a description that a network device could use to create appropriate network protections:

{
  "ietf-mud:meta-info": {
    "lastUpdate": "2016-10-02T08:28:19+02:00",
    "systeminfo": "DVR H.264",
    "cacheValidity": 1440
  },
  "ietf-acl:access-lists": {
    "ietf-acl:access-list": [
      {
        "acl-name": "mud-65333-v4in",
        "acl-type": "ipv4-acl",
        "ietf-mud:packet-direction": "to-device",
        "access-list-entries": {
          "ace": [
            {
              "rule-name": "entout0-in",
              "matches": {
                "ietf-mud:controller": "http://dvr264.example.com/controller"
              },
              "actions": {
                "permit": [
                  null
                ]
              }
            },
            {
              "rule-name": "entin0-in",
              "matches": {
                "ietf-mud:controller": "http://dvr264.example.com/controller",
                "protocol": 6,
                "source-port-range": {
                  "lower-port": 80,
                  "upper-port": 80
                }
              },
              "actions": {
                "permit": [
                  null
                ]
              }
            }
          ]
        }
      },
      {
        "acl-name": "mud-65333-v4out",
        "acl-type": "ipv4-acl",
        "ietf-mud:packet-direction": "from-device",
        "access-list-entries": {
          "ace": [
            {
              "rule-name": "entout0-in",
              "matches": {
                "ietf-mud:controller": "http://dvr264.example.com/controller"
              },
              "actions": {
                "permit": [
                  null
                ]
              }
            },
            {
              "rule-name": "entin0-in",
              "matches": {
                "ietf-mud:controller": "http://dvr264.example.com/controller",
                "protocol": 6,
                "source-port-range": {
                  "lower-port": 80,
                  "upper-port": 80
                }
              },
              "actions": {
                "permit": [
                  null
                ]
              }
            }
          ]
        }
      }
    ]
  }
}

What is left for the controller to do that is specific to this device is define which devices are in the class http://dvr64.example.com.  That might include the FTP-based logging system that this model uses, for instance, as well as those systems that are authorized to connect to the HTTP port.

The important part of that description is what you don’t see.  You don’t see any of the attack vectors used, because through this whitelist approach, you only specify what is permitted, and everything else aside from name service and time queries is explicitly denied.  This device uses a good few services, and so I haven’t specified each one in the example for brevity’s sake.

This may well have stopped the hacker from gaining access to the device in the first place, and would have stopped the device from being able to attack the blogger, and many other attacks as well.

Krebs attacked: IoT devices blamed, and MUD could help

CybercrimeIt’s rare that hackers give you a gift, but last week that’s exactly what happened.  Brian Krebs is one of the foremost security experts in the industry, and his well known web site krebsonsecurity.com was brought down due to a distributed denial of service (DDoS) attack.  Attackers made use of what is said to be the largest botnet ever to attack Akamai, Kreb’s content service provider.

Why would one consider this a gift?  First of all, nobody was hurt.  This attack took down a web site that is not critical to anyone’s survival, not even Krebs’, and the web site was rehomed and back online in a very short period of time.

Second, the attackers revealed at least some of their capabilities by lighting up the network of hacked devices for researchers to examine and eventually take town.  One aspect of this attack is the use of “IoT” devices, or non-general purpose computers that are used to control some other function.  According to Krebs, the attacks made use of thermostats, web cameras, digital video recorders (DVRs) and, yes, Internet routers.  The attacks themselves created an HTTP connection to the web site, retrieved a page, and closed.  That’s a resource intensive attack from the defense standpoint.

Let’s ask this question: why would any of Mudpitthose systems normally talk to anything other than a small number of cloud services that are intended to support them?  This is what Manufacturer Usage Descriptions (MUD) is meant to defend against.  MUD works by providing a formal language and mechanism for manufacturers to specify which systems a device is designed to connect with.  The converse, therefore, is that the network can prevent the device from both being attacked and attacking others.  The key to all of this are manufacturer and their willingness to describe these devices.  The evolving technical details of MUD can be found in an Internet Draft, and you can create a test MUD file against that draft by using MUD File Maker.  I’ll go into more detail about MUD File Maker in a later post.

Would MUD eliminate all attacks?  No, but MUD adds an additional helpful layer of protection to those manufacturers and networks should use.

This time it was a blog that was taken down.  We are in a position to reduce attacks the next time, when they may be more serious.  That’s the gift hackers gave us this time.  Now we just need to act.