OpenSSH client configuration

This repository contains my personal OpenSSH client configuration.

Secret settings, such as those for employers' environments, reside in separate repositories that are kept private and included as submodules.

installation

POSIX

On POSIX-compliant systems, check out this repository by executing the following command with a POSIX shell:

git clone -- https://codeberg.org/djsp/ssh_config.git ~/.ssh

Windows

On Windows, check out this repository by executing the following command with cmd.exe:

git clone -- https://codeberg.org/djsp/ssh_config.git "%USERPROFILE%\.ssh"

updating

POSIX

Update configuration by executing the following command:

git -C ~/.ssh pull --rebase

Windows

Update configuration by executing the following command:

git -C "%USERPROFILE%\.ssh" pull --rebase

host public keys

For some SSH hosts, the public keys are published:

• GitHub
• GitLab SaaS

fingerprints

For some SSH hosts, the public keys are not published, but their fingerprints are:

• GitLab instances: https://${instance_domain}/help/instance_configuration#ssh-host-keys-fingerprints
• SourceForge

To get the public keys of such SSH hosts:

1. Gather their public keys with the command ssh-keyscan(1).

   Invoke it as follows:

   ssh-keyscan -- gitlab.archlinux.org

   The output looks as follows:

   # gitlab.archlinux.org:22 SSH-2.0-OpenSSH_8.9p1 Ubuntu-3ubuntu0.6
   gitlab.archlinux.org ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCxid4CSjzD5QiM1y12qxNAUdR4kgy+YTym1lY4Arwdf+GC+UGvFP/IzGdlmL681nQeLZN7j2+3Bbm30JZNraA9gesW6BNoOr8QJbuayZJIoQklOUEmvaP7z5PlNChJiwNiXiyXRZzw7BwR4gYGWGSiJtzGYRtIgJDBB+Tc7rVwSy0u16YG2TpFOnxCJ8S25FhRIoyp0A5A+eJgCUe4HDI4Zud+94QdZUVuvpsjzHxXiPr8U8jbsJrG/beWxOnFFx7rhtz/OoQn8sg3anJue+mgtZm/PBs4fccVl30c0Xqfizvdx09sapqyrNf326s9L8NToyi2aHxMEzXfGspOoYtl
   # gitlab.archlinux.org:22 SSH-2.0-OpenSSH_8.9p1 Ubuntu-3ubuntu0.6
   gitlab.archlinux.org ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBL+Hs65GpF45799k+r9AW5+xxIRLOdOrOUFsce1BVD8f/tFGBpu6ay06f3tvXXUHVA9iRI6wogDVTpy4x5ch4jY=
   # gitlab.archlinux.org:22 SSH-2.0-OpenSSH_8.9p1 Ubuntu-3ubuntu0.6
   gitlab.archlinux.org ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAICjT2SuA0k/xc5Cbyp+eBY5uN3bRL2K7GdpNtltOK6vy
   # gitlab.archlinux.org:22 SSH-2.0-OpenSSH_8.9p1 Ubuntu-3ubuntu0.6
   # gitlab.archlinux.org:22 SSH-2.0-OpenSSH_8.9p1 Ubuntu-3ubuntu0.6
   

2. Generate the fingerprint for each key.

   base64_key='AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBL+Hs65GpF45799k+r9AW5+xxIRLOdOrOUFsce1BVD8f/tFGBpu6ay06f3tvXXUHVA9iRI6wogDVTpy4x5ch4jY='

   base64 --decode <<< "${base64_key}" | openssl dgst -sha256 -binary | base64

3. Compare the generated fingerprints with the known fingerprints.

4. If the generated fingerprints match the known fingerprints, trust the public keys gathered with ssh-keyscan(1).