smtpd

README

smtpd

Go library for implementing simple SMTP servers. It's responsible for handling the SMTP server side protocol, nothing more, nothing less.

Usage

Create a type that implements the smtpd.Handler interface.

Create a smtp.Server instance with specific options and a listener.

Pass each connection together with a handler instance to ServeSMTP().

Testing

For testing authentication a TLS connection is used. Create a self-signed certificate before running the tests:

mkdir testdata
openssl genrsa 2048 > testdata/key.pem
openssl req -x509 -new -key key.pem > testdata/cert.pem

Documentation

Overview

Package smtpd implements the SMTP server protocol.

Index

• Variables
• type Handler
• type Server
  • func (s *Server) ServeSMTP(conn net.Conn, handler Handler) error

Variables

var Debug = false

Debug can be set to true to print SMTP traces to the default Logger in package log.

var DefaultHostname, _ = os.Hostname()

DefaultHostname is used in the banner greeting when Server#hostname is empty.

Types

type Handler

type Handler interface {
	// Connect is called after connecting
	Connect(source string) error

	// Hello is called after EHLO/HELO
	Hello(hostname string) error

	// Authenticate is called after AUTH
	//Authenticate(identity, username, password_or_response string) error
	AuthUser(identity, username string) (password string, err error)

	// Sender is called after MAIL FROM
	Sender(address string) error

	// Recipient is called after RCPT TO
	Recipient(address string) error

	// Message is called after DATA. The reader returns the message data
	// after dot unstuffing. The final ".\r\n" is not included in the data.
	// When the complete message is consumed io.EOF is returned. It's not
	// required to consume all data. Any remaining data will be discarded
	// after Message() returns and the reader will become invalid.
	Message(reader io.Reader) error
}

Handler should be implemented by the application for handling SMTP command parameters and message data on a connection.

Each member can return an error to reject the command or to indicate processing failure. If the error text starts with a three digit status code, then the error text is returned as-is in the SMTP reply. If the error does not start with three digits, then "451 Requested action aborted: " is returned in the SMTP reply with the error text appended.

type Server

type Server struct {
	// Hostname to use in responses
	Hostname string

	// Set to enable STARTTLS
	// must include at least one certificate or else set GetCertificate
	TLSConfig *tls.Config

	// Set to enable PIPELINING
	Pipelining bool
}

Server represents an SMTP server configuration.

func (*Server) ServeSMTP

func (s *Server) ServeSMTP(conn net.Conn, handler Handler) error

ServeSMTP should be called by the application for each incoming connection.

The application provides a new instance of the Handler interface that can be used to process command parameters and read the message data.

The application should close the connection after ServeSMTP returns.