133 lines
3.0 KiB
Go
133 lines
3.0 KiB
Go
package smtp
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import (
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"context"
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"crypto/tls"
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"fmt"
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"io"
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"net"
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"net/smtp"
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"strings"
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"gitlab.com/etke.cc/go/logger"
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"maunium.net/go/mautrix/id"
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"gitlab.com/etke.cc/postmoogle/utils"
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)
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// Bot interface to send emails into matrix
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type Bot interface {
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GetMapping(string) (id.RoomID, bool)
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Send2Matrix(ctx context.Context, email *utils.Email) error
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SetMTA(mta utils.MTA)
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}
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// mta is Mail Transfer Agent
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type mta struct {
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log *logger.Logger
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}
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// SMTPAddrs priority list
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var SMTPAddrs = []string{":25", ":587", ":465"}
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func NewMTA(loglevel string) utils.MTA {
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return &mta{
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log: logger.New("smtp/mta.", loglevel),
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}
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}
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func (m *mta) Send(from, to, data string) error {
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m.log.Debug("Sending email from %s to %s", from, to)
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conn, err := m.connect(from, to)
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if err != nil {
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m.log.Error("cannot connect to SMTP server of %s: %v", to, err)
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return err
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}
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defer conn.Close()
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err = conn.Mail(from)
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if err != nil {
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m.log.Error("cannot call MAIL command: %v", err)
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return err
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}
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err = conn.Rcpt(to)
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if err != nil {
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m.log.Error("cannot send RCPT command: %v", err)
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return err
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}
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var w io.WriteCloser
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w, err = conn.Data()
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if err != nil {
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m.log.Error("cannot send DATA command: %v", err)
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return err
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}
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defer w.Close()
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m.log.Debug("sending DATA:\n%s", data)
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_, err = strings.NewReader(data).WriteTo(w)
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if err != nil {
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m.log.Debug("cannot write DATA: %v", err)
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return err
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}
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m.log.Debug("email has been sent")
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return nil
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}
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func (m *mta) tryServer(localname, mxhost, addr string) *smtp.Client {
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m.log.Debug("trying SMTP connection to %s%s", mxhost, addr)
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conn, err := smtp.Dial(mxhost + addr)
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if err != nil {
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m.log.Warn("cannot connect to the %s%s: %v", mxhost, addr, err)
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return nil
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}
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err = conn.Hello(localname)
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if err != nil {
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m.log.Warn("cannot call HELLO command of the %s%s: %v", mxhost, addr, err)
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return nil
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}
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if ok, _ := conn.Extension("STARTTLS"); ok {
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m.log.Debug("%s supports STARTTLS", mxhost)
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config := &tls.Config{ServerName: mxhost}
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err = conn.StartTLS(config)
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if err != nil {
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m.log.Warn("STARTTLS connection to the %s failed: %v", mxhost, err)
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}
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}
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return conn
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}
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func (m *mta) connect(from, to string) (*smtp.Client, error) {
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localname := strings.SplitN(from, "@", 2)[1]
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hostname := strings.SplitN(to, "@", 2)[1]
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m.log.Debug("performing MX lookup of %s", hostname)
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mxs, err := net.LookupMX(hostname)
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if err != nil {
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m.log.Error("cannot perform MX lookup: %v", err)
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return nil, err
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}
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for _, mx := range mxs {
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for _, addr := range SMTPAddrs {
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client := m.tryServer(localname, strings.TrimSuffix(mx.Host, "."), addr)
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if client != nil {
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return client, nil
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}
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}
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}
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// If there are no MX records, according to https://datatracker.ietf.org/doc/html/rfc5321#section-5.1,
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// we're supposed to try talking directly to the host.
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if len(mxs) == 0 {
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for _, addr := range SMTPAddrs {
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client := m.tryServer(localname, hostname, addr)
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if client != nil {
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return client, nil
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}
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}
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}
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return nil, fmt.Errorf("target SMTP server not found")
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}
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