I exploited TLS-SNI-01 issuing Let's Encrypt SSL-certs for any domain (2018)
For a while I found it funny that the web&#x27;s security is based on the strength of (1) new standards from Let&#x27;s Encrypt, and (2) the quality of their codebase. It&#x27;s been shown multiple times that they have failed in both of these, yet nobody has taken them to task as failing to uphold the responsibility that CAs have to keep the web secure. (<a href="https:&#x2F;&#x2F;community.letsencrypt.org&#x2F;c&#x2F;incidents" rel="nofollow">https:&#x2F;&#x2F;community.letsencrypt.org&#x2F;c&#x2F;incidents</a>)<p>At first I thought that their biggest issue was properly verifying that a domain owner is requesting a certificate (they don&#x27;t do that, but anyway..). They actually have multiple categories of security holes relating to web pki, because it&#x27;s a pretty big sandbox.<p>The holes affecting LE include everything from OCSP support, to actually not issuing any certificates during Google outages (yes, if Google is down, LE is down, as well as other CAs, and it&#x27;s happened multiple times), to exposing the personal information of LE users, to bugs in their protocol allowing any cert to be issued, to mis-handling blocklists, leaking API keys, and so on. Basically, a litany of different security holes could at any time compromise the security of the whole damn web.<p>The thing is, this isn&#x27;t specific just to LE. All these things and more probably affect every CA. LE is just more experimental and new, using less robust infrastructure and technology, and their &quot;growing pains&quot; provide a much more visible and much <i>wider</i> attack surface for abusing PKI.<p>I don&#x27;t think the industry organizations connected to CAs care enough to put in stringent security practices in place. But I do think it&#x27;s about time to start producing these standards. It&#x27;s probably going to be up to hobbyists and privacy aficionados to do this work, because they&#x27;re the ones who care enough. I&#x27;m also surprised that governments aren&#x27;t more active in enforcing more stringent security practices, seeing as they&#x27;re affected just as much.<p>Interestingly, following the CT Policy mailing list is a good way to be told about holes in the current CA system: <a href="https:&#x2F;&#x2F;groups.google.com&#x2F;a&#x2F;chromium.org&#x2F;d&#x2F;msg&#x2F;ct-policy&#x2F;_csiMYrwsxc&#x2F;2S6bMnSCDwAJ" rel="nofollow">https:&#x2F;&#x2F;groups.google.com&#x2F;a&#x2F;chromium.org&#x2F;d&#x2F;msg&#x2F;ct-policy&#x2F;_cs...</a>