On Wed, 11 Mar 2020 15:39:34 -0700 Kathleen Wilson via dev-security-policy <[email protected]> wrote:
> What do you all think about also limiting the re-use of domain > validation? I'm strongly in favor of this change, and think domain validation reuse should eventually be limited to a period much shorter than one year (days or even hours), even if certificates lifetimes remain capped at one year. Others have already touched on the issue of domain ownership transfer (BygoneSSL), but I'd like to highlight a related issue: if a domain's DNS, email, or web infrastructure is ever compromised, even briefly, then the attacker can obtain two-year-long domain validation authorizations from any number of CAs. Then at any point in the next two years, the attacker can obtain a one-year certificate, and ask the CA not to log it to CT. Even if Firefox did enforce CT, the attacker could wait to log the certificate until right before using it in an attack. The consequence of the above is that even if a website suffers a fleeting compromise, they and their users are at risk of attack from an illegitimate certificate for three entire years. Anecdotally, I've found that website operators are surprised when they learn this. It's intuitive that the attack window would be lower-bounded by certificate lifetime, but the additional attack time from domain validation reuse comes as an unpleasant surprise. Therefore, Firefox should aim to make the attack window as close to the maximum certificate lifetime as possible, which requires reducing validation reuse time to the order of hours/days. Limiting to one year is a good first step. Regards, Andrew _______________________________________________ dev-security-policy mailing list [email protected] https://lists.mozilla.org/listinfo/dev-security-policy
