Home wireless security challenges for Things

It’s hard – but not impossible – for Things to connect to a home network in some sort of automated fashion.

Wifi What’s the right way to connect a Thing to your home network? Way back in the good old days, say last year, in order to connect a device to your home network, you could do it easily enough because the system had a display and a touch screen or a keyboard. With many Things, there is no display and there is no keyboard, and some of the devices we are connecting may themselves not be that accessible to the home owner. Think attic fans or even some light bulbs. A means is needed first to tell these devices which network is the correct network to join, and then what the credentials for that network are. In order to do any of this, there needs to be a way for the home router to communicate with the device in a secure and confidential way. That means that each end requires some secret. Public key cryptography is perfect for this, and it is how things would work in the enterprise.

WPA2 Enterprise makes use of individual keys and a flexible means to authenticate individuals and devices. It looks a little like this:

EAP over Radius

EAP stands for Extensible Access Protocol, and it is just that. There are many different authentication mechanisms available with EAP. One method called EAP-TLS calls for both sides of the communication to transmit a certificate in an authentication transaction that contains their identities as certified by someone. Initially, a device may be certified by its manufacturer, but then later it would use a certificate that is certified by the local network system.

A QR code

One challenge is getting the device certificate to be known by the network. One simple method to do this is to have an application tied to a camera that scans a QR code that points to a URL containing a signed copy of the device’s identity or certificate. For instance, the QR code to the right encodes this URL:

https://www.ofcourseimright.com/qr/2834298343404739274639374630463934

which in turn gets you a certificate. The next challenge is whether the device should trust the network. In the enterprise, there is a new approach being developed known as Bootstrapping Remote Secure Key Infrastructures (BRSKI) (sometimes pronounced “brewski”). In this case the manufacturer tells the device that the network is the correct one to join by essentially providing the device the network’s operational trust anchor. This allows the device to validate the network’s certificate.

That’s something of a tall order even in the enterprise, but one that is worth aiming for. If the home can leverage a service offered either by a service provider or by a new fangled home router company, if THEY can authenticate the home, and the manufacturer can authenticate them, then we have ourselves a ball game. More work needed to get all the elements in place.

Let’s not blame Yahoo! for a difficult policy problem

Yahoo! Many in the tech community are upset over reports from The New York Times and others that Yahoo! responded to an order issued by the Foreign Intelligence Surveillance Act Court (FISC) to search across their entire account base a specific “signatures” of people believed to be terrorists.

It is not clear what capabilities Yahoo! already has, but it would not be unreasonable to expect them to have the ability to scan incoming messages for spam and malware, for instance. What’s more, we are all the better for this sort of capability. Consider that around 85% of all email is spam, a small amount of which contains malware, and Yahoo! users don’t see most of that. Much of that can be rejected without Yahoo! having to look at the content by just examining the source IP address of the device attempting to send Yahoo! mail, but in all likelihood they do look at some, as many systems do. In fact one of the most popular open source systems in the early days known as SpamAssassin did just this. The challenge from a technical perspective is to implement such a mechanism without the mechanism itself having a large target surface.

If the government asking for certain messages sounds creepy, we have to ask what a signature is. A signature normally refers to characteristics of a communication that would either identify its source or that it has some quality. For instance, viruses all have signatures. In this case, what is claimed is that terrorists communicated in a certain way such that they could be identified. According to The Times, the government demonstrated probably cause that this was true, and that the signature was “highly unique”*. That is, the signature likely matches very few actual messages that the government would see, although we don’t know how small that number really is. Yahoo! has denied having a capability to scan across all messages in their system, but beyond that not enough is public to know what they would have done. It may well not have been reasonable to search specific accounts because one can easily create an account, and the terrorists may have many. The government publicly revealing either the probable cause or the signature would tantamount to alerting terrorists that they are in fact investigation, and that they can be tracked.

The risk to civil liberties is that there are no terrorists at all, and this is just a fishing expedition, or worse, persecution of some form. The FISC and its appellate courts are intended to provide some level of protection against abuse, but in all other cases, the public as a view to whether that abuse is actually occurring. Many have complained about a lack of transparent oversight of the FISC, but the question is how to have that oversight without alerting The Bad Guys.

The situation gets more complex if one considers that other countries would want the same right to demand information from their mail service providers that the U.S. enjoys, as Yahoo’s own transparency report demonstrates.

In short we are left with a set of difficult compromises that pit gathering of intelligence on terrorists and other criminals against the risk of government abuse. That’s not Yahoo!’s fault. This is a hard problem that requires thoughtful consideration of these trade offs, and the timing is right to think about this. Once again, the Foreign Intelligence Surveillance Act (FISA) will be up for reauthorization in Congress next year. And in this case, let’s at least consider the possibility that the government is trying to fulfill its responsibility of protecting its citizens and residents, and Yahoo! is trying to be a good citizen in looking at each individual request on its merits and in accordance with relevant laws.

* No I don’t know the difference between “unique” and “highly unique” either.

How hard is it to secure a baby monitor?

Philips In.Sight B120/37 Parents 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 Adams The 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

Cybercrime In 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.

Turning the Home Router from a Threat to a Helping Hand

lybid_1002 The Federal Communications Commission is set to vote on a proposed rule that would require cable companies to offer consumers more choices about whether they use a rented cable box or home router or their own. More choice is good, and one could make a strong argument that lack of consumer choice has retarded development of home routers. However, this decision may come with a few pitfalls from a security perspective.

Home routers were recently a component of the attack against krebsonsecurity.com. There are many reasons that this would be the case. Some routers have as a blank password with user name “admin” that allows anyone to access them. Others have well-known vulnerabilities in their software that has gone unpatched for years. If the service provider is providing the router, then we can say that it is responsible for the device’s maintenance. On the other hand, the consumer has a particularly bad track record of doing a good job protecting the device.

Second, because most consumers do not employ security professionals to protect devices in their homes, the service provider is in a good position to offer that protection. It does require that the service provider have access to the home router to identify threats within the home itself. By having some control over that device and having access to logging information, the home router is in a position to identify potential attacks within the home itself. But the router itself needs some guidance to perform that task, and the router itself typically cannot retain all of the necessary knowledge. Cloud services are useful for this purpose, whether managed by the SP or by some other entity.

Regardless of what the FCC orders, SPs are in the position of setting the standards necessary to connect a router to the Internet. CableLabs has set several standards, one known as DOCSIS. While the current specification has a limited security section, one could easily envision additional capabilities that would protect device within the home. As new entrants such as Google and Ubiquiti develop additional capabilities, they may have more to say about security in the home. If home users are to have a choice, one choice they should have is to allow service providers to protect them.

Picture courtesy Sergiy dk on Wikimedia CC BY-SA 3.0