wsl-ssh-agent-relay

#!/bin/bash

#### Add following lines to your shell rc file (.zshrc .bashrc)
# ${HOME}/.local/libexec/wsl-ssh-agent-relay start
# export SSH_AUTH_SOCK=${HOME}/.ssh/wsl-ssh-agent.sock

# For debugging startup problems uncomment next line
# exec 2> >(tee -a -i "$HOME/error.log")

#### Assuming ~/winhome links to %USERPROFILE on Windows side
RELAY_BIN="/mnt/c/Users/USER/Tools/npiperelay.exe"

PIDFILE="${HOME}/.ssh/wsl-ssh-agent-relay.pid"
WSL_AGENT_SSH_SOCK="${HOME}/.ssh/wsl-ssh-agent.sock"
WIN_PIPE="//./pipe/ssh-pageant"

log() {
    echo >&2 "$@"
}

is_pid_running() {
    if [[ -z "$1" ]]; then
        return 1
    fi
    ps -p "$1" >/dev/null
    return $?
}

_cleanup() {
    log "Cleaning up relay to ${WSL_AGENT_SSH_SOCK}..."
    if is_pid_running "${SOCAT_WSL_AGENT_SSH_PID}"; then
        kill -SIGTERM "${SOCAT_WSL_AGENT_SSH_PID}" || log "Failed."
    fi
}

die() {
    if [[ -n "$1" ]]; then
        log "$1"
    fi
    log "Exiting."
    exit 1
}

usage() {
    log "Usage: wsl-ssh-agent-relay [OPTIONS] COMMAND"
    log ""
    log "  SUMMARY: Relay Windows openssh named pipe to local SSH socket in order to integrate WSL2 and host."
    log "           To debug use foreground command"
    log ""
    log "  OPTIONS:"
    log "    -h|--help     this page"
    log ""
    log "    -v|--verbose  verbose mode"
    log ""
    log "  COMMAND: start, stop, foreground"
}

fg_opts() {
    FG_OPTS=()
    # Generate opts for passing it to foreground version
    if [[ -n "$VERBOSE" ]]; then
        FG_OPTS+=("-v")
    fi
}

main() {

    POSITIONAL=()
    VERBOSE=""
    while (($# > 0)); do
        case "$1" in
        -v | --verbose)
            VERBOSE="ENABLED"
            shift # shift once since flags have no values
            ;;

        -h | --help)
            usage
            exit 0
            ;;

        *) # unknown flag/switch
            POSITIONAL+=("$1")
            shift
            if [[ "${#POSITIONAL[@]}" -gt 1 ]]; then
                usage
                die
            fi
            ;;
        esac
    done

    set -- "${POSITIONAL[@]}" # restore positional params

    if [[ -z "$VERBOSE" ]]; then
        QUIET="QUIET"
    fi

    case "${POSITIONAL[0]}" in
    start)
        fg_opts
        start-stop-daemon --start --oknodo --pidfile "${PIDFILE}" --name wsl-ssh-agent-r --make-pidfile --background --startas "$0" ${VERBOSE:+--verbose} ${QUIET:+--quiet} -- foreground "${FG_OPTS[@]}"
        ;;

    stop)
        start-stop-daemon --pidfile "${PIDFILE}" --stop --remove-pidfile ${VERBOSE:+--verbose} ${QUIET:+--quiet}
        ;;

    status)
        start-stop-daemon --pidfile "${PIDFILE}" --status ${VERBOSE:+--verbose} ${QUIET:+--quiet}
        local result=$?
        case $result in
        0) log "$0 is running" ;;
        1 | 3) log "$0 is not running" ;;
        4) log "$0 unable to determine status" ;;
        esac
        return $result
        ;;

    foreground)
        relay
        ;;

    *)
        usage
        die
        ;;
    esac
}

relay() {

    trap _cleanup EXIT

    [[ -f "${RELAY_BIN}" ]] || die "Unable to access ${RELAY_BIN}"

    if pgrep -fx "^ssh-agent\s.+" >/dev/null; then
        log "Killing previously started local ssh-agent..."
        SSH_AGENT_PID="$(pidof ssh-agent)" ssh-agent -k >/dev/null 2>&1
    fi

    if [ -e "${WSL_AGENT_SSH_SOCK}" ]; then
        log "WSL has been shutdown ungracefully, leaving garbage behind"
        rm "${WSL_AGENT_SSH_SOCK}"
    fi

    socat UNIX-LISTEN:"\"${WSL_AGENT_SSH_SOCK}\"",fork EXEC:"\"\'${RELAY_BIN}\' -ei -s \'${WIN_PIPE}\'\"",nofork 1>/dev/null 2>&1 &
    SOCAT_WSL_AGENT_SSH_PID="$!"
    if ! is_pid_running "${SOCAT_WSL_AGENT_SSH_PID}"; then
        log "Relay for ${SOCAT_WSL_AGENT_SSH_PID} failed"
        return 1
    fi
    log "Relay is running with PID: ${SOCAT_WSL_AGENT_SSH_PID}"

    log -n "Polling remote ssh-agent..."
    SSH_AUTH_SOCK="${WSL_AGENT_SSH_SOCK}" ssh-add -L >/dev/null 2>&1 || die "[$?] Failure communicating with ssh-agent"
    log "OK"

    # Everything checks, we are ready for actions
    log "Entering wait..."
    wait ${SOCAT_WSL_AGENT_SSH_PID}
}

main "$@"