func()

in notify/email/email.go [126:336]


func (n *Email) Notify(ctx context.Context, as ...*types.Alert) (bool, error) {
	var (
		c       *smtp.Client
		conn    net.Conn
		err     error
		success = false
	)
	if n.conf.Smarthost.Port == "465" {
		tlsConfig, err := commoncfg.NewTLSConfig(&n.conf.TLSConfig)
		if err != nil {
			return false, fmt.Errorf("parse TLS configuration: %w", err)
		}
		if tlsConfig.ServerName == "" {
			tlsConfig.ServerName = n.conf.Smarthost.Host
		}

		conn, err = tls.Dial("tcp", n.conf.Smarthost.String(), tlsConfig)
		if err != nil {
			return true, fmt.Errorf("establish TLS connection to server: %w", err)
		}
	} else {
		var (
			d   = net.Dialer{}
			err error
		)
		conn, err = d.DialContext(ctx, "tcp", n.conf.Smarthost.String())
		if err != nil {
			return true, fmt.Errorf("establish connection to server: %w", err)
		}
	}
	c, err = smtp.NewClient(conn, n.conf.Smarthost.Host)
	if err != nil {
		conn.Close()
		return true, fmt.Errorf("create SMTP client: %w", err)
	}
	defer func() {
		// Try to clean up after ourselves but don't log anything if something has failed.
		if err := c.Quit(); success && err != nil {
			level.Warn(n.logger).Log("msg", "failed to close SMTP connection", "err", err)
		}
	}()

	if n.conf.Hello != "" {
		err = c.Hello(n.conf.Hello)
		if err != nil {
			return true, fmt.Errorf("send EHLO command: %w", err)
		}
	}

	// Global Config guarantees RequireTLS is not nil.
	if *n.conf.RequireTLS {
		if ok, _ := c.Extension("STARTTLS"); !ok {
			return true, fmt.Errorf("'require_tls' is true (default) but %q does not advertise the STARTTLS extension", n.conf.Smarthost)
		}

		tlsConf, err := commoncfg.NewTLSConfig(&n.conf.TLSConfig)
		if err != nil {
			return false, fmt.Errorf("parse TLS configuration: %w", err)
		}
		if tlsConf.ServerName == "" {
			tlsConf.ServerName = n.conf.Smarthost.Host
		}

		if err := c.StartTLS(tlsConf); err != nil {
			return true, fmt.Errorf("send STARTTLS command: %w", err)
		}
	}

	if ok, mech := c.Extension("AUTH"); ok {
		auth, err := n.auth(mech)
		if err != nil {
			return true, fmt.Errorf("find auth mechanism: %w", err)
		}
		if auth != nil {
			if err := c.Auth(auth); err != nil {
				return true, fmt.Errorf("%T auth: %w", auth, err)
			}
		}
	}

	var (
		tmplErr error
		data    = notify.GetTemplateData(ctx, n.tmpl, as, n.logger)
		tmpl    = notify.TmplText(n.tmpl, data, &tmplErr)
	)
	from := tmpl(n.conf.From)
	if tmplErr != nil {
		return false, fmt.Errorf("execute 'from' template: %w", tmplErr)
	}
	to := tmpl(n.conf.To)
	if tmplErr != nil {
		return false, fmt.Errorf("execute 'to' template: %w", tmplErr)
	}

	addrs, err := mail.ParseAddressList(from)
	if err != nil {
		return false, fmt.Errorf("parse 'from' addresses: %w", err)
	}
	if len(addrs) != 1 {
		return false, fmt.Errorf("must be exactly one 'from' address (got: %d)", len(addrs))
	}
	if err = c.Mail(addrs[0].Address); err != nil {
		return true, fmt.Errorf("send MAIL command: %w", err)
	}
	addrs, err = mail.ParseAddressList(to)
	if err != nil {
		return false, fmt.Errorf("parse 'to' addresses: %w", err)
	}
	for _, addr := range addrs {
		if err = c.Rcpt(addr.Address); err != nil {
			return true, fmt.Errorf("send RCPT command: %w", err)
		}
	}

	// Send the email headers and body.
	message, err := c.Data()
	if err != nil {
		return true, fmt.Errorf("send DATA command: %w", err)
	}
	defer message.Close()

	buffer := &bytes.Buffer{}
	for header, t := range n.conf.Headers {
		value, err := n.tmpl.ExecuteTextString(t, data)
		if err != nil {
			return false, fmt.Errorf("execute %q header template: %w", header, err)
		}
		fmt.Fprintf(buffer, "%s: %s\r\n", header, mime.QEncoding.Encode("utf-8", value))
	}

	if _, ok := n.conf.Headers["Message-Id"]; !ok {
		fmt.Fprintf(buffer, "Message-Id: %s\r\n", fmt.Sprintf("<%d.%d@%s>", time.Now().UnixNano(), rand.Uint64(), n.hostname))
	}

	multipartBuffer := &bytes.Buffer{}
	multipartWriter := multipart.NewWriter(multipartBuffer)

	fmt.Fprintf(buffer, "Date: %s\r\n", time.Now().Format(time.RFC1123Z))
	fmt.Fprintf(buffer, "Content-Type: multipart/alternative;  boundary=%s\r\n", multipartWriter.Boundary())
	fmt.Fprintf(buffer, "MIME-Version: 1.0\r\n\r\n")

	// TODO: Add some useful headers here, such as URL of the alertmanager
	// and active/resolved.
	_, err = message.Write(buffer.Bytes())
	if err != nil {
		return false, fmt.Errorf("write headers: %w", err)
	}

	if len(n.conf.Text) > 0 {
		// Text template
		w, err := multipartWriter.CreatePart(textproto.MIMEHeader{
			"Content-Transfer-Encoding": {"quoted-printable"},
			"Content-Type":              {"text/plain; charset=UTF-8"},
		})
		if err != nil {
			return false, fmt.Errorf("create part for text template: %w", err)
		}
		body, err := n.tmpl.ExecuteTextString(n.conf.Text, data)
		if err != nil {
			return false, fmt.Errorf("execute text template: %w", err)
		}
		qw := quotedprintable.NewWriter(w)
		_, err = qw.Write([]byte(body))
		if err != nil {
			return true, fmt.Errorf("write text part: %w", err)
		}
		err = qw.Close()
		if err != nil {
			return true, fmt.Errorf("close text part: %w", err)
		}
	}

	if len(n.conf.HTML) > 0 {
		// Html template
		// Preferred alternative placed last per section 5.1.4 of RFC 2046
		// https://www.ietf.org/rfc/rfc2046.txt
		w, err := multipartWriter.CreatePart(textproto.MIMEHeader{
			"Content-Transfer-Encoding": {"quoted-printable"},
			"Content-Type":              {"text/html; charset=UTF-8"},
		})
		if err != nil {
			return false, fmt.Errorf("create part for html template: %w", err)
		}
		body, err := n.tmpl.ExecuteHTMLString(n.conf.HTML, data)
		if err != nil {
			return false, fmt.Errorf("execute html template: %w", err)
		}
		qw := quotedprintable.NewWriter(w)
		_, err = qw.Write([]byte(body))
		if err != nil {
			return true, fmt.Errorf("write HTML part: %w", err)
		}
		err = qw.Close()
		if err != nil {
			return true, fmt.Errorf("close HTML part: %w", err)
		}
	}

	err = multipartWriter.Close()
	if err != nil {
		return false, fmt.Errorf("close multipartWriter: %w", err)
	}

	_, err = message.Write(multipartBuffer.Bytes())
	if err != nil {
		return false, fmt.Errorf("write body buffer: %w", err)
	}

	success = true
	return false, nil
}