Network protocols and their use: Security and privacy

By on 17 Jun 2019

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In June, I participated in a workshop organized by the Internet Architecture Board on the topic of protocol design and effect, looking at the differences between initial design expectations and deployment realities. These are my impressions from the discussions that took place at this workshop.

In this, the third of four posts, I’ll discuss the experience with security and privacy.

History is against us

These days any form of consideration about the Internet and its technology base needs to either address the topic of security and privacy in all its forms or explicitly explain this glaring omission. Obviously, this workshop headed directly into this space, asking whether the IETF was looking at topical and current threat models, and also asking about likely evolution in this space.

Exhortations about security practices for service operators made through standards bodies are often ineffectual in isolation. RFC 2827 is almost 20 years old, and is ignored by network operators to about the same extent that it was ignored at the time of its publication. It may be better known as BCP 38, or packet filtering to prevent source address spoofing in IP packets. It’s important because there is a class of DDoS attack using UDP amplification where the UDP response is far larger than the query. It’s a fine practice and we should all be doing this form of filtering.

Twenty years later, the attacks persist because the filtering is just not happening. What may make such forms of advice more effective is the association of some form of liability for service operators, or explicit obligations as part of liability insurance. In isolation, advice relating to security measures is often seen as an imposing cost without immediate direct benefit. And in circumstances such as this case, where the defensive approach is only effective when most operators undertake the practice, benefits for early adopters are simply not present.

Another example is the standardization of Client Subnet extensions in the DNS. Despite the standard specification RFC 7871 containing the advice that this feature should be turned off by default and users be permitted to opt out, this has not happened. This is in spite of the potential for serious privacy leaks through attribution of DNS queries to end users.

The environment of attacks escalates, as the growing population of devices allows the formation of larger pools of co-opted devices that in concert can mount massive DDoS attacks. Given our inability to prevent such attacks from recurring, the reaction has been the formation of a market in robust content hosting. As the attacks increase in intensity, the content hosting operators require larger defensive measures and economies of scale in content hosting come into play.

The content hosting and associated distribution network sector is increasingly concentrated into a handful of providers. In many ways, this is a classic case of markets identifying and filling a need. The distortion of that market into a very small handful of providers is a case of economies of scale coming into play. As with the CA market, the market has now seen the entrance of zero cost actors, which has significantly lifted the barrier to further new entrants in this market. What remains now appears to be simply a process of further consolidation in the market for content hosting.

As is the evolving nature of technology and threats

The threat model is also evolving. RFC 3552, published in 2003, explicitly assumed that the end systems that are communicating have not themselves been compromised in any way. Is this a reasonable assumption these days? Can an application assume the platform is entirely passive and trustable, or should the application assume the underlying platform may divulge or alter the application’s information in unanticipated ways? To what extent can or should applications lift common network functionality into the user space and deliberately withhold almost all aspects of a communication transaction from other concurrently running applications, from the common platform and from the network? Do approaches like DoH and QUIC represent reasonable templates for responding to this evolved threat model? Can we build protocols that explicitly limit information disclosure when one of the ends of the communication may have been compromised?

Is protocol extensibility a vector for abuse and leakage, such as the Client Subnet DNS extension in the DNS, or the session ticket in TLS? And where are our points of trust to allow us to validate what we receive? As already pointed out, DNSSEC is not faring well and the major trust point is the Web PKI. Unfortunately, this system suffers from a multiplicity of indistinguishable trust and our efforts to detect compromises have shrunk to logging, in the form of Certificate Transparency. Such a measure is not responsive in real time and rapid attacks are still way too effective.

A single trust anchor breeds a natural monopoly at the apex. And across the diversity of the global Internet there is a lot of distrust in that single point, particularly when geopolitics enters the conversation. This single trust broker is a natural choke point and is one that tends to drift towards rent-seeking if operated by the private sector, and distrust if operated by the public sector. Designs for trust need to take such factors into account.

The issue of security popups in the browser world can be compared to the silent discard of the response in the DNSSEC world, as they offer two different views of security management. Placing the user into the security model leads to a lack of relevant information and an observed tendency for the user to accept obviously fraudulent certificates because of no better information. From that perspective, removing the user from the picture improves the efficacy of the security measure. On the other hand, there is some disquiet about the concept of removing the user from security controls. Giving the user no information and no ability to recognize potentially misrepresenting situations may be a disservice to the user.

Do our standards promote and encode the ‘state of the art’ as a means of shedding liability for negligence while still acknowledging that the state of the art is not infallible? Or do they purport to represent a basic tenet of security that, if correctly executed, is infallible?

The Internet of (insecure) Things is an interesting failure case, and the predatory view of the consumer often distracts from the ethos of customer care and the safeguarding of customer’s enduring interests. Grappling with conformance to demanding operational standards in a low-cost, highly diverse, and high-volume industry is challenging. Perhaps more so is the tendency of the IETF to develop many responses simultaneously and confront the industry with not one but many measures. Already we’ve seen proposals that use some level of manufacture cooperation, such as nesting public/private key pair, QR code, MUD profile or boot server handshake.

Read: The Internet of Stupid Things

A safe mode of operation would require that the device cannot cold start, nor even continue to operate without some level of handshake. Is this realistic? Will manufacturers cooperate? Will this improve the overall security of the IoT space? Are these expectations of manufacturers realistic? Will a kickstart IoT toothbrush comply with all these requirements? Will these requirements impose factory costs that make the device prone to manufacturer errors and increase the costs to the consumer without any change in the perceived function and benefit of the device?

An IoT toothbrush will still brush teeth irrespective of the level of conformance to some generic standard security profile. The failure in the October 2016 botnet DNS attack that used readily compromisable webcams was not a failure of information or protocol. It was a failure of markets, as there was no disincentive to bring to market an invisibly flawed, but cheap, and otherwise perfectly functional product.

We tend to see the IoT marketplace as a device market. In contrast, effective device security is an ongoing relationship between the consumer and the device manufacturer and requires a service model rather than a single sale transaction.

The prospect of a regulatory impost to provide channels to the retail market that include conformance to national profiles is nigh on certain. Will the inevitable diversity of such regional, national or even state profiles add or detract from the resultant picture of IoT security? Will we end up with a new marketplace for compliance that offers an insubstantial veneer of effective security for such devices? It’s very hard to maintain a sunny optimistic outlook in this space.

Human behaviour also works against such efforts as well. Our experience points to an observation that users of a technology care a whole lot less about authentication and validation than we had assumed was the case. Most folks don’t turn on validation of mail, validation of DNS responses and similar, even when they had access to the tools to do so. When we observed the low authentication rates post-deployment, our subsequent efforts to convince users to adopt more secure practices were ineffectual. Posters in the Paris Metro informing Metro users as to what makes a password harder to guess really have not made an impact. In the consumer market, users don’t understand security and don’t value such an intangible attribute as part of a product or service.

It would be good to think that we have finally stopped using the old security threat model of the malicious actor in the middle. We have more complex models that describe secure and/or trusted enclaves, with an unknown model of the surrounding environment. Is this device security or really a case of ‘data security’? We need to associate semantics with that data and describe its access policies to safeguard elements of personal privacy.

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The views expressed by the authors of this blog are their own and do not necessarily reflect the views of APNIC. Please note a Code of Conduct applies to this blog.

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