gistfile1.txt

#!/bin/bash

set -e
set -o nounset
set -o pipefail

client=
server=

make_ssh_key() {
  local keyfile="$(mktemp -u $TMPDIR/sshkey.XXXXXXXXXX)"
  local keyfile_b="$(basename $keyfile)"
  local keyfile_rand=$(echo "$keyfile_b" | cut -f2 -d'.')
  ssh-keygen -t ed25519 -N '' -f "${keyfile}" -C "$(hostname) temp:${keyfile_rand}" > /dev/null
  echo "$keyfile"
}

serverauthkeys_entry() {
  echo -n "no-pty,no-port-forwarding,no-agent-forwarding,no-x11-forwarding,no-user-rc,command=\"/nail/sys/bin/rrsync $1\" "
  cat "$2"
}

add_authkey() {
  local client="$1"
  local server="$2"
  local dir="$3"
  local keyfile="$4"
  local keyfile_b="$(basename $keyfile)"
  local keyfile_rand=$(echo "$keyfile_b" | cut -f2 -d'.')
  local public_keyfile="${keyfile}.pub"
  serverauthkeys_entry "$dir" "$public_keyfile" | ssh "$server" -- "/nail/sys/bin/add_temp_authorized_key '${keyfile_rand}'"
  cat "$public_keyfile" | ssh "$client" -- "/nail/sys/bin/add_temp_authorized_key '${keyfile_rand}'"
}

if [[ "${E:-}" == "5" ]]; then
  ssh-add "$1" 2> /dev/null
  shift
  ssh "$client" -- rsync "$@" "${server}:"
else
  keyfile="$(make_ssh_key)"
  add_authkey "$client" "$server" "/tmp" "${keyfile}"
  E=5 ssh-agent "$0" "${keyfile}" "$@"
fi