prezto/modules/ssh/init.zsh

#
# Provides for an easier use of SSH by setting up ssh-agent.
#
# Authors:
#   Sorin Ionescu <sorin.ionescu@gmail.com>
#

# Return if requirements are not found.
if (( ! $+commands[ssh-agent] )); then
  return 1
fi

# Set the path to the SSH directory.
_ssh_dir="$HOME/.ssh"

# Set the path to the environment file if not set by another module.
_ssh_agent_env="${_ssh_agent_env:-${TMPDIR:-/tmp}/ssh-agent.env.$UID}"

# Set the path to the persistent authentication socket.
_ssh_agent_sock="${TMPDIR:-/tmp}/ssh-agent.sock.$UID"

# default options
_ssh_add_options=""

# Start ssh-agent if not started.
if [[ ! -S "$SSH_AUTH_SOCK" ]]; then
  # Export environment variables.
  source "$_ssh_agent_env" 2> /dev/null

  # Start ssh-agent if not started.
  if ! ps -U "$LOGNAME" -o pid,ucomm | grep -q -- "${SSH_AGENT_PID:--1} ssh-agent"; then
    eval "$(ssh-agent | sed '/^echo /d' | tee "$_ssh_agent_env")"
  fi
fi

# Create a persistent SSH authentication socket.
if [[ -S "$SSH_AUTH_SOCK" && "$SSH_AUTH_SOCK" != "$_ssh_agent_sock" ]]; then
  ln -sf "$SSH_AUTH_SOCK" "$_ssh_agent_sock"
  export SSH_AUTH_SOCK="$_ssh_agent_sock"
fi

# store passphrases in your keychain. only macOS
if [[ "$(uname 2> /dev/null)" == "Darwin" ]]; then
  _ssh_add_options="-K"
fi

# Load identities.
if ssh-add -l 2>&1 | grep -q 'The agent has no identities'; then
  zstyle -a ':prezto:module:ssh:load' identities '_ssh_identities'
  # ssh-add has strange requirements for running SSH_ASKPASS, so we duplicate
  # them here. Essentially, if the other requirements are met, we redirect stdin
  # from /dev/null in order to meet the final requirement.
  #
  # From ssh-add(1):
  # If ssh-add needs a passphrase, it will read the passphrase from the current
  # terminal if it was run from a terminal. If ssh-add does not have a terminal
  # associated with it but DISPLAY and SSH_ASKPASS are set, it will execute the
  # program specified by SSH_ASKPASS and open an X11 window to read the
  # passphrase.
  if [[ -n "$DISPLAY" && -x "$SSH_ASKPASS" ]]; then
    ssh-add $_ssh_add_options ${_ssh_identities:+$_ssh_dir/${^_ssh_identities[@]}} < /dev/null 2> /dev/null
  else
    ssh-add $_ssh_add_options ${_ssh_identities:+$_ssh_dir/${^_ssh_identities[@]}} 2> /dev/null
  fi
fi

# Clean up.
unset _ssh_{dir,identities} _ssh_agent_{env,sock}