3 ms·

But doesn’t antose comment still apply? If all the certificates issued by letsencrypts old CA have expired (since they’ve stopped issuing certs for a year, and

But doesn’t antose comment still apply? If all the certificates issued by letsencrypts old CA have expired (since they’ve stopped issuing certs for a year, and their certificates only last 3 months) wouldn’t it stand to reason that if a certificate on and old CA have been replaced with a new CA certificate? And it would then stand to reason any devices that aren’t updated would have slowly watched the web degrade already? In other words with letsencrypt there’s no cliff everyone walks off when the root ca expires, it’s more a 90-day descending hill.

tialaramex 5y ago
You're failing to think about it as a graph. Here's a graph to look at: https://letsencrypt.org/certificates/ https://letsencrypt.org/certificates/ Let's try a concrete example, https://letest.tlrmx.org/ https://letest.tlrmx.org/ is a simple test site, it has a normal Let's Encrypt certificate. This certificate was issued by R3, the same intermediate issuing most (but not all) Let's Encrypt end-entity certificates today and this certificate doesn't expire until November. On the graph that certificate is a labelled edge from what we'll call the R3 keypair to my keypair for letest.tlrmx.org, saying that R3 certifies this is really letest.tlrmx.org (and www.letest.tlrmx.org) But, because it's a graph there are two certificates (actually three but we'll ignore that) for that R3 keypair. One of them is signed by DST Root CA X3, this one says R3 is certified as a CA by DST Root CA X3, and since DST Root CA X3 expires later this month, that certificate too expires later this month. However, there is also a certificate for R3 saying it's a CA, signed by ISRG Root X1 and that doesn't expire until 2025. If we trust DST Root CA X3 this is all fine... for about a week. But if we trust ISRG Root X1 it's still fine until 2025, which is ages. Immediately one bug rears its head. Software such as older OpenSSL versions may trust DST Root CA X3, notice it's expiring and then falsely conclude this is untrustworthy, even though it also trusts ISRG Root X1. That's a pretty bad idea, but you can bet some people are still running this. We can continue following the graph to ISRG Root X1 but is this enough that you now see why atonse's simple view of the world is wrong?

tialaramex 5y ago

You're failing to think about it as a graph. Here's a graph to look at: https://letsencrypt.org/certificates/ https://letsencrypt.org/certificates/ Let's try a concrete example, https://letest.tlrmx.org/ https://letest.tlrmx.org/ is a simple test site, it has a normal Let's Encrypt certificate. This certificate was issued by R3, the same intermediate issuing most (but not all) Let's Encrypt end-entity certificates today and this certificate doesn't expire until November. On the graph that certificate is a labelled edge from what we'll call the R3 keypair to my keypair for letest.tlrmx.org, saying that R3 certifies this is really letest.tlrmx.org (and www.letest.tlrmx.org) But, because it's a graph there are two certificates (actually three but we'll ignore that) for that R3 keypair. One of them is signed by DST Root CA X3, this one says R3 is certified as a CA by DST Root CA X3, and since DST Root CA X3 expires later this month, that certificate too expires later this month. However, there is also a certificate for R3 saying it's a CA, signed by ISRG Root X1 and that doesn't expire until 2025. If we trust DST Root CA X3 this is all fine... for about a week. But if we trust ISRG Root X1 it's still fine until 2025, which is ages. Immediately one bug rears its head. Software such as older OpenSSL versions may trust DST Root CA X3, notice it's expiring and then falsely conclude this is untrustworthy, even though it also trusts ISRG Root X1. That's a pretty bad idea, but you can bet some people are still running this. We can continue following the graph to ISRG Root X1 but is this enough that you now see why atonse's simple view of the world is wrong?