Add keys to known hosts file for a list of domains.

add-ssh-hosts

#!/usr/bin/env bash

SSH_SCAN_HOSTNAMES=${1:-"${SSH_SCAN_HOSTNAMES}"}
SSH_SCAN_HOSTNAMES=${SSH_SCAN_HOSTNAMES:-"github.com gitlab.com"}
SSH_DIR="$HOME/.ssh"

command -v ssh-keyscan >/dev/null 2>&1 || { echo >&2 "I require ssh-keygen but it's not installed.  Aborting."; exit 1; }
command -v tee >/dev/null 2>&1 || { echo >&2 "I require tee but it's not installed.  Aborting."; exit 1; }

for SSH_SCAN_HOSTNAME in $SSH_SCAN_HOSTNAMES; do
  if [ ! -d "$SSH_DIR" ]; then
    mkdir -p "${SSH_DIR}"
  fi
  if [ ! -f "$SSH_DIR/known_hosts" ]; then
    touch "${SSH_DIR}/known_hosts"
    chmod 600 "${SSH_DIR}/known_hosts"
  fi
  ESCAPED_HOSTNAME=`echo "$SSH_SCAN_HOSTNAME" | sed 's/\./\\./g'`
  if ! grep -qE "^$ESCAPED_HOSTNAME" "${SSH_DIR}/known_hosts"; then
    echo "Getting ssh-keys for $SSH_SCAN_HOSTNAME"
    ssh-keyscan "${SSH_SCAN_HOSTNAME}" >> "${SSH_DIR}/known_hosts" || { echo >&2 "Failed to get key for $SSH_SCAN_HOSTNAME"; exit 1; }
  else
    echo "We already have the keys for $SSH_SCAN_HOSTNAME"
  fi
done
echo "All Done!"

exit 0