diodemail/smtp/commands.go

/* diodemail - send-only smtp server
 * Copyright (c) 2024 Gnarwhal
 *
 * This file is part of diodemail.
 *
 * diodemail is free software: you can redistribute it and/or modify it under the terms of
 * the GNU General Public License as published by the Free Software Foundation,
 * either version 3 of the License, or (at your option) any later version.
 *
 * diodemail is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * diodemail. If not, see <https://www.gnu.org/licenses/>.
 */

package smtp

import (
	"fmt"
	"strings"
)

type Command struct {
	name string
	Exec func(*SMTPSession, string)(bool, error)
}

func (self Command) GetName() string {
	return self.name
}

func (self Command) Check(message string) bool {
	return strings.HasPrefix(message, self.name)
}

func Greet(smtp_session *SMTPSession) error {
	err := smtp_session.Write(
		fmt.Sprintf(
			"220 %v ESMTP diodemail -- Service ready" + "\n",
			smtp_session.GetHost(),
		),
	)
	if err != nil {
		return err
	}

	return nil
}

func Helo(smtp_session *SMTPSession, message string) (bool, error) {
	err := smtp_session.Write(
		fmt.Sprintf(
			"250 %v is shy" + "\r\n",
			smtp_session.GetHost(),
		),
	)
	if err != nil {
		return true, err
	}

	smtp_session.HasHelloed = true
	return false, nil
}

func Ehlo(smtp_session *SMTPSession, message string) (bool, error) {
	enable_auth := ""
	if smtp_session.RequiresAuthentication() {
		enable_auth = "250-AUTH PLAIN\r\n"
	}
	err := smtp_session.Write(
		fmt.Sprintf(
			"250-%v is shy"  + "\r\n" +
			"%v"                      +
			"250-8BITMIME"   + "\r\n" +
			"250 SMTPUTF8"   + "\r\n",
			smtp_session.GetHost(),
			enable_auth,
		),
	)
	if err != nil {
		return true, err
	}

	smtp_session.HasHelloed = true
	return false, nil
}

func Auth(smtp_session *SMTPSession, message string) (bool, error) {
	if !smtp_session.HasHelloed {
		err := smtp_session.Write(
			"503 Must HELO/EHLO first\n",
		)
		if err != nil {
			return true, err
		}
		return false, nil
	}
	parts := strings.Split(message, " ")[1:]
	if parts[0] == "PLAIN" {
		var password string
		if len(parts) > 1 {
			password = parts[1][:len(parts[1]) - 1]
		} else {
			err := smtp_session.Write("334 \n")
			if err != nil {
				return true, nil
			}
			password, err = smtp_session.ReadUntil("\r\n")
			if err != nil {
				return true, nil
			}
		}
		if smtp_session.ValidatePassword(password) {
			smtp_session.Write("235 Authentication successful\n")
		} else {
			smtp_session.Write("535 Authentication credentials invalid\n")
		}
	}
	return false, nil
}

func MailFrom(smtp_session *SMTPSession, message string) (bool, error) {
	if !smtp_session.HasHelloed {
		err := smtp_session.Write(
			"503 Must HELO/EHLO first\n",
		)
		if err != nil {
			return true, err
		}
		return false, nil
	}
	if !smtp_session.AuthenticationSatisfied() {
		err := smtp_session.Write(
			"530 Authentication required\n",
		)
		if err != nil {
			return true, err
		}
		return false, nil
	}
	match := ReversePath.FindStringSubmatch(message)
	if match == nil {
		err := smtp_session.Write(
			"501 Could not parse reverse-path\n",
		)
		if err != nil {
			return true, err
		}
	} else if len(match) > 1 {
		smtp_session.MailFrom(match[1])
		err := smtp_session.Write(
			"250 OK\n",
		)
		if err != nil {
			return true, err
		}
	}

	return false, nil
}

func RcptTo(smtp_session *SMTPSession, message string) (bool, error) {
	if !smtp_session.HasHelloed {
		err := smtp_session.Write(
			"503 Must HELO/EHLO first\n",
		)
		if err != nil {
			return true, err
		}
		return false, nil
	}
	if !smtp_session.AuthenticationSatisfied() {
		err := smtp_session.Write(
			"530 Authentication required\n",
		)
		if err != nil {
			return true, err
		}
		return false, nil
	}
	match := ForwardPath.FindStringSubmatch(message)
	if match == nil {
		err := smtp_session.Write(
			"501 Could not parse forward-path\n",
		)
		if err != nil {
			return true, err
		}
	} else {
		smtp_session.AddRecipient(match[1])
		err := smtp_session.Write(
			"250 OK\n",
		)
		if err != nil {
			return true, err
		}
	}

	return false, nil
}

func Data(smtp_session *SMTPSession, message string) (bool, error) {
	if !smtp_session.HasHelloed {
		err := smtp_session.Write(
			"503 Must HELO/EHLO first\n",
		)
		if err != nil {
			return true, err
		}
		return false, nil
	}
	if !smtp_session.AuthenticationSatisfied() {
		err := smtp_session.Write(
			"530 Authentication required\n",
		)
		if err != nil {
			return true, err
		}
		return false, nil
	}
	err := smtp_session.Write(
		"354 Start Input\n",
	)
	if err != nil {
		return true, err
	}
	data, err := smtp_session.ReadUntil("\r\n.\r\n")
	if err != nil {
		smtp_session.Write(
			"550 Action not taken\n",
		)
		return false, err
	}
	err = smtp_session.SendMail(data)
	if err != nil {
		smtp_session.Write(
			"550 Action not taken\n",
		)
		return false, err
	}
	smtp_session.Reset()
	err = smtp_session.Write(
		"250 OK\n",
	)
	if err != nil {
		return true, err
	}

	return false, nil
}

func Quit(smtp_session *SMTPSession, message string) (bool, error) {
	err := smtp_session.Write(
		"221 Goodbye :)\n",
	)
	if err != nil {
		return true, err
	}

	return true, nil
}

func Noop(smtp_session *SMTPSession, message string) (bool, error) {
	err := smtp_session.Write(
		"250 OK\n",
	)
	if err != nil {
		return true, err
	}

	return false, nil
}

func Rset(smtp_session *SMTPSession, message string) (bool, error) {
	smtp_session.Reset()
	err := smtp_session.Write(
		"250 Reset\n",
	)
	if err != nil {
		return true, err
	}

	return false, nil
}