If you have sign up to tangled.sh you will have published your SSH public key on the Bluesky ATproto network. Have a browse to your Bluesky ID, or mine. Look under sh.tangled.publicKey.

BlueSky ATproto SSH Public Key Extractor extracts this public key information and outputs one public key at a time. The format is suitable to use with the AuthorizedKeysCommand parameter in your /etc/sshd/ssh_config file.

Build the project:

opam install . --deps-only
dune build

Install the binary by copying it to the local system. Setting the ownership and permissions is essential.

cp _build/install/default/bin/bluesky-ssh-key-extractor /usr/local/bin
chmod 755 /usr/local/bin/bluesky-ssh-key-extractor
chown root:root /usr/local/bin/bluesky-ssh-key-extractor

Test the command is working:

$ bluesky-ssh-key-extractor mtelvers.tunbury.org rosemary.caelum.ci.dev mte24
ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIA7UrJmBFWR3c7jVzpoyg4dJjON9c7t9bT9acfrj6G7i mark.elvers@tunbury.org

If that works, then edit your /etc/sshd/ssh_config:-

AuthorizedKeysCommand /usr/local/bin/bluesky-ssh-key-extractor mtelvers.tunbury.org rosemary.caelum.ci.dev %u
AuthorizedKeysCommandUser nobody

Now you should be able to SSH to the machine using your published key

ssh user@your_host