old chain: R3 / ISRG Root X1
new chain: E1 / ISRG Root X2
No user interaction or migration is required for existing installations
as we install 'E1' and 'ISRG Root X2' for some time already.
This is used by Cloudflare DNS (1.1.1.1) and Quard9 (9.9.9.9).
$CertificateAvailable "DigiCert TLS Hybrid ECC SHA384 2020 CA1"
/ip dns set use-doh-server=https://1.1.1.1/dns-query verify-doh-cert=yes
$CertificateAvailable "DigiCert TLS Hybrid ECC SHA384 2020 CA1"
/ip dns set use-doh-server=https://9.9.9.9/dns-query verify-doh-cert=yes
Let's Encrypt planned the transition to ISRG's root certificate ("ISRG Root
X1") on July 8, 2019, but postponed several times.
Finally they found another solution: A certificate 'ISRG Root X1', but
cross-signed with 'DST Root CA X3' and with a livetime that exceeds that
of the root CA. This is said to work for most operating system where root
certificate authorities are just 'trust anchors'.
I doubt this is true for RouterOS, where certificates are just imported
into the certificate store. So let's migrate to 'ISRG Root X1' now.
Also order certificates, so we have:
* intermediate
* root
* alternative root, if any
Let's add 'ISRG Root X1' for 'E1' as there will be a valid cross-signed
chain 'E1' -> 'ISRG Root X2' -> 'ISRG Root X1'.
