kit/pkg/emailclient/emailclient.go

package emailclient

import (
	"crypto/tls"
	"errors"
	"fmt"
	"net"
	"net/mail"
	"net/smtp"

	log "github.com/sirupsen/logrus"
)

// SMTPCredentials is a struc holding the information needed to connect to a SMTP server
type SMTPCredentials struct {
	Host     string
	Email    string
	Password string
}

// emailClient is a struct holding the information requiered to send with SMTP
type emailClient struct {
	client *smtp.Client
}

// EmailClient is the generic interface for all client sending emails
type EmailClient interface {
	SendMsg(headers map[string]string, body string)
}

// NewSMTPClient (host, user, password) returns a SMTPClient
//
//	host is the SMTP server used to connect
//	port is the SMTP port used to connect
//	user is usually the email address use to connect to SMTP
//	password is the associated password
func NewSMTPClient(host string, port string, user string, password string) (EmailClient, error) {
	var ec emailClient

	log.Infof("user: (%s) pass: (%s)", user, password)

	auth := smtp.PlainAuth("", user, password, host)

	// TLS config
	tlsconfig := &tls.Config{
		InsecureSkipVerify: false,
		ServerName:         host,
	}

	// Here is the key, you need to call tls.Dial instead of smtp.Dial
	// for smtp servers running on 465 that require an ssl connection
	// from the very beginning (no starttls)
	var conn *tls.Conn
	var c *smtp.Client
	var err error
	if port == "465" {
		conn, err = tls.Dial("tcp", host+":"+port, tlsconfig)
		if err != nil {
			log.Error("[sendMail] ERROR while dialing: " + err.Error())
			return ec, err
		}

		c, err = smtp.NewClient(conn, host)
		if err != nil {
			log.Error("[sendMail] ERROR while NewClient: " + err.Error())
			return ec, err
		}
	} else {
		c, err = smtp.Dial(host + ":" + port)
		if err != nil {
			log.Error("[sendMail] ERROR while Dialing: " + err.Error())
			return ec, err
		}
		err = c.StartTLS(tlsconfig)
		if err != nil {
			log.Error("[sendMail] ERROR while StartTLS: " + err.Error())
			return ec, err
		}
	}
	// defer c.Quit()
	// defer c.Close()

	ec.client = c

	// Auth
	if err = ec.client.Auth(auth); err != nil {
		log.Error("[sendMail] ERROR while Auth: " + err.Error())
		return ec, err
	}

	return ec, nil
}

// NewGmailClient returns a GmailClient
func NewGmailClient(email, pass string) (EmailClient, error) {
	var ec emailClient

	// cred.Host = "smtp.gmail.com:587"
	echost := "smtp.gmail.com:465"
	if pass == "" {
		log.Error("Email password missing")
		return ec, errors.New("Email password missing")
	}

	host, _, _ := net.SplitHostPort(echost)
	auth := smtp.PlainAuth("", email, pass, host)

	// TLS config
	tlsconfig := &tls.Config{
		InsecureSkipVerify: true,
		ServerName:         host,
	}

	// Cavehat, you need to call tls.Dial instead of smtp.Dial
	// for smtp servers running on 465 that require an ssl connection
	// from the very beginning (no starttls)
	conn, err := tls.Dial("tcp", echost, tlsconfig)
	if err != nil {
		log.Error(fmt.Sprintf("Dial error: " + err.Error()))
		return ec, err
	}

	client, err := smtp.NewClient(conn, host)
	if err != nil {
		log.Error(fmt.Sprintf("NewClient error: " + err.Error()))
		return ec, err
	}
	ec.client = client

	// Auth
	if err = ec.client.Auth(auth); err != nil {
		log.Error(fmt.Sprintf("Auth error: %s (%s)", err, host))
		return ec, err
	}

	return ec, nil
}

// SendMsg send a message (email) to rcpt which is in the 'headers' parameter ('To' key) and whose content is the 'body' parameter.
// Ohter keys of interest in headers are 'Subject' and 'MIME-version'
func (ec emailClient) SendMsg(headers map[string]string, body string) {
	from := mail.Address{Name: "", Address: headers["From"]}
	to := mail.Address{Name: "", Address: headers["To"]}

	// headers["To"] = to.String()
	if _, ok := headers["Subject"]; ok {
		headers["Subject"] = "Subject unknown"
	}

	log.Printf("from = %s", headers["From"])
	log.Printf("to = %s", headers["To"])
	log.Printf("subj = %s", headers["Subject"])

	// Setup message
	message := ""
	for k, v := range headers {
		message += fmt.Sprintf("%s: %s\r\n", k, v)
	}
	message += "\r\n" + body

	c := ec.client

	// To && From
	if err := c.Mail(from.Address); err != nil {
		log.Error("Can't set From: " + err.Error())
		return
	}

	if err := c.Rcpt(to.Address); err != nil {
		log.Error("Can't set To: " + err.Error())
		return
	}

	// Data
	w, err := c.Data()
	if err != nil {
		log.Error("Can't set Data: " + err.Error())
		return
	}

	_, err = w.Write([]byte(message))
	if err != nil {
		log.Error("Can't write Data: " + err.Error())
		return
	}

	err = w.Close()
	if err != nil {
		log.Error("Can't Close: " + err.Error())
		return
	}

	err = c.Quit()
	if err != nil {
		log.Error("Can't Quit: " + err.Error())
		return
	}
	c.Close()
}