The Security Impact of HTTPS Interception [pdf]

From the conclusion:

> We deployed these heuristics on three diverse networks:

> (1) Mozilla Firefox update servers,

> (2) a set of popular e-commerce sites, and

> (3) the Cloudflare content distribution network.

> In each case, we find more than an order of magnitude more interception than previously estimated, ranging from 4–11%.

> As a class, interception products drastically reduce connection security. Most concerningly, 62% of traffic that traverses a network middlebox has reduced security and 58% of middlebox connections have severe vulnerabilities. We investigated popular antivirus and corporate proxies, finding that nearly all reduce connection security and that many introduce vulnerabilities (e.g., fail to validate certificates).

It stands for autonomous system, part of BGP

I was surprised by this note (on page 2):

> Contrary to widespread belief, public key pinning [19] — an HTTPS feature that allows websites to restrict connections to a specific key — does not prevent this interception. Chrome, Firefox, and Safari only enforce pinned keys when a certificate chain terminates in an authority shipped with the browser or operating system. The extra validation is skipped when the chain terminates in a locally installed root (i.e., a CA certificate installed by an administrator).

Seems like a strange default to me. I feel like the user should be notified of this, for instance if they're using a work computer to access their bank account or something like that.

Trying to fight a local attacker with root (which is necessary to add a certificate to the trust stores on most platforms) isn't worth the effort. It's easy for the admin to bypass and would cause even more warning fatigue.

That's not to say I disagree with the sentiment that this is something employers (and other organizations providing access to devices) should be obliged to disclose, but that is perhaps more of a legal and educational issue.