Using debian-installer on a server with a Let's Encrypt cert dies

[Mathew Binkley]

While using debian-installer to install Ubuntu Focal, I get the following error:

    May 16 22:02:41 base-installer: Certificate verification failed: The certificate is NOT trusted. The certificate chain uses expired certificate. Could not handshake: Error in the certificate verification. [IP: 129.59.59.10 443]

There was an issue in 2021, where the "DST_Root_CA_X3.crt" certificate used by Let's Encrypt expired.

    https://letsencrypt.org/docs/dst-root-ca-x3-expiration-september-2021/

The problem is that the certificate is still included in the "ca-certificates_20190110ubuntu1_all.deb" that debian-installer fetches during install.

    May 16 22:02:17 debootstrap: Preparing to unpack .../ca-certificates_20190110ubuntu1_all.deb ...
    May 16 22:02:17 debootstrap: Unpacking ca-certificates (20190110ubuntu1) ...
    May 16 22:02:31 debootstrap: Setting up ca-certificates (20190110ubuntu1) ...
    May 16 22:02:40 debootstrap: Processing triggers for ca-certificates (20190110ubuntu1) ...
    May 16 22:02:40 debootstrap: Running hooks in /etc/ca-certificates/update.d...

Because the certificate is expired, debian-installer dies with:

    May 16 22:02:41 base-installer: Certificate verification failed: The certificate is NOT trusted. The certificate chain uses expired certificate. Could not handshake: Error in the certificate verification. [IP: 129.59.59.10 443]
te is NOT trusted. The certificate chain uses expired certificate. Could not handshake: Error in the certificate verification. [IP: 129.59.59.10 443]

Can Ubuntu update the ca-certificate .deb pulled during install to one that does not have DST_Root_CA_X3.crt? Thanks.

[Alex Murray (alexmurray)]

I believe this is caused by debootstrap - it only uses packages from the release pocket (and this is frozen from the time Ubuntu 20.04 LTS was originally released). This is a known issue https://askubuntu.com/questions/744684/latest-security-updates-with-debootstrap but I am not sure if there is much you can do to get debian-installer to say use multistrap instead of debootstrap.