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ICANN CTO: no reason to delay KSK rollover

Kevin Murphy, August 15, 2018, 11:34:20 (UTC), Domain Tech

ICANN’s board of directors will be advised to go ahead with a key security change at the DNS root — “the so-called KSK rollover” — this October, according to the organization’s CTO.

“We don’t see any reason to postpone again,” David Conrad told DI on Monday.

If it does go ahead as planned, the rollover will see ICANN change the key-signing key that acts as the trust anchor for the whole DNSSEC-using internet, for the first time since DNSSEC came online in 2010.

It’s been delayed since last October after it emerged that misconfigurations elsewhere in the DNS cloud could see potentially millions of internet users see glitches when the key is rolled.

Ever since then, ICANN and others have been trying to figure out how many people could be adversely affected by the change, and to reduce that number to the greatest extent possible.

The impact has been tricky to estimate due to patchy data.

While it’s been possible to determine a number of resolvers — about 8,000 — that definitely are poorly configured, that only represents a subset of the total number. It’s also been hard to map that to endpoints due to “resolvers behind resolvers behind resolvers”, Conrad said.

“The problem here is that it’s sort of a subjective evaluation,” he said. “We can’t rely on the data were seeing. We’re seeing the resolvers but we’re not seeing the users behind the resolvers.”

Some say that the roll is still too risky to carry out without better visibility into the potential impact, but others say that more delays would lead to more networks and devices becoming DNSSEC-compatible, potentially leading to even greater problems after the eventual rollover.

ICANN knows of about 8,000 resolver IP addresses that are likely to stop working properly after the rollover, because they only support the current KSK, but that’s only counting resolvers that automatically report their status to the root using a relatively new internet standard. There’s a blind spot concerning resolvers that do not have that feature turned on.

ICANN has also had difficulty reaching out to the network operators behind these resolvers, with good contact information apparently only available for about a quarter of the affected IP addresses, Conrad said.

Right now, the best data available suggests that 0.05% of the internet’s population could see access issues after the October 11 rollover, according to Conrad.

That’s about two million people, but it’s 10 times fewer people than the 0.5% acceptable collateral damage threshold outlined in ICANN’s rollover plan.

The 0.05% number comes from research by APNIC, which used Google’s advertising system to place “zero-pixel ads” to check whether individual user endpoints were using compatible resolvers or not.

If problems do emerge October 11 the temporary solution is apparently quite quick to implement — network operators can simply turn off DNSSEC, assuming they know that’s what they’re supposed to do.

But still, if a million or two internet users could have their day ruined by the rollover, why do it at all?

It’s not as if the KSK is in any danger of being cracked any time soon. Conrad explained that a successful brute-force attack on the 2048-bit RSA key would take longer than the lifetime of the universe using current technology.

Rather, the practice of rolling the key every five years is to get network operators and developers accustomed to the idea that the KSK is not a permanent fixture that can be hard-coded into their systems, Conrad said.

It’s a problem comparable to new gTLD name collisions or the Y2K problem, instances where developers respectively hard-coded assumptions about valid TLDs or the century into their software.

ICANN has already been reaching out to the managers of open-source projects on repositories such as Github that have been seen to hard-code the current KSK into their software, Conrad said.

Separately, Wes Hardaker at the University of Southern California Information Sciences Institute discovered that a popular VPN client was misconfigured. Outreach to the developer saw the problem fixed, reducing the number of users who will be affected by the roll.

“What we’re trying to avoid is having these keys hardwired into firmware, so that that it would never be changeable,” he said. “The idea is if you exercise the infrastructure frequently enough, people will know the that the key is not permanent configuration, it’s not something embedded in concrete.”

One change that ICANN may want to make in future is to change the algorithm used to generate the KSK.

Right now it’s using RSA, but Conrad said it has downsides such as rather large signature size, which leads to heavier DNSSEC traffic. By switching to elliptical curve cryptography, signatures could be reduced by “orders of magnitude”, leading to a more efficient and slimline DNS infrastructure, Conrad said.

Last week, ICANN’s Root Server Stability Advisory Committee issued an advisory (pdf) that essentially gave ICANN the all-clear to go ahead with the roll.

The influential Security and Stability Advisory Committee has yet to issue its own advisory, however, despite being asked to do so by August 10.

Could SSAC be more cautious in its advice? We’ll have to wait and see, but perhaps not too long; the current plan is for the ICANN board to consider whether to go ahead with the roll during its three-day Brussels retreat, which starts September 14.

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