ntfy/server/smtp_server.go
2022-05-21 20:20:44 -04:00

206 lines
4.6 KiB
Go

package server
import (
"bytes"
"errors"
"github.com/emersion/go-smtp"
"io"
"mime"
"mime/multipart"
"net/mail"
"strings"
"sync"
)
var (
errInvalidDomain = errors.New("invalid domain")
errInvalidAddress = errors.New("invalid address")
errInvalidTopic = errors.New("invalid topic")
errTooManyRecipients = errors.New("too many recipients")
errUnsupportedContentType = errors.New("unsupported content type")
)
// smtpBackend implements SMTP server methods.
type smtpBackend struct {
config *Config
sub subscriber
success int64
failure int64
mu sync.Mutex
}
func newMailBackend(conf *Config, sub subscriber) *smtpBackend {
return &smtpBackend{
config: conf,
sub: sub,
}
}
func (b *smtpBackend) Login(state *smtp.ConnectionState, username, password string) (smtp.Session, error) {
return &smtpSession{backend: b}, nil
}
func (b *smtpBackend) AnonymousLogin(state *smtp.ConnectionState) (smtp.Session, error) {
return &smtpSession{backend: b}, nil
}
func (b *smtpBackend) Counts() (success int64, failure int64) {
b.mu.Lock()
defer b.mu.Unlock()
return b.success, b.failure
}
// smtpSession is returned after EHLO.
type smtpSession struct {
backend *smtpBackend
topic string
mu sync.Mutex
}
func (s *smtpSession) AuthPlain(username, password string) error {
return nil
}
func (s *smtpSession) Mail(from string, opts smtp.MailOptions) error {
return nil
}
func (s *smtpSession) Rcpt(to string) error {
return s.withFailCount(func() error {
conf := s.backend.config
addressList, err := mail.ParseAddressList(to)
if err != nil {
return err
} else if len(addressList) != 1 {
return errTooManyRecipients
}
to = addressList[0].Address
if !strings.HasSuffix(to, "@"+conf.SMTPServerDomain) {
return errInvalidDomain
}
to = strings.TrimSuffix(to, "@"+conf.SMTPServerDomain)
if conf.SMTPServerAddrPrefix != "" {
if !strings.HasPrefix(to, conf.SMTPServerAddrPrefix) {
return errInvalidAddress
}
to = strings.TrimPrefix(to, conf.SMTPServerAddrPrefix)
}
if !topicRegex.MatchString(to) {
return errInvalidTopic
}
s.mu.Lock()
s.topic = to
s.mu.Unlock()
return nil
})
}
func (s *smtpSession) Data(r io.Reader) error {
return s.withFailCount(func() error {
conf := s.backend.config
b, err := io.ReadAll(r) // Protected by MaxMessageBytes
if err != nil {
return err
}
msg, err := mail.ReadMessage(bytes.NewReader(b))
if err != nil {
return err
}
body, err := readMailBody(msg)
if err != nil {
return err
}
body = strings.TrimSpace(body)
if len(body) > conf.MessageLimit {
body = body[:conf.MessageLimit]
}
m := newDefaultMessage(s.topic, body)
subject := strings.TrimSpace(msg.Header.Get("Subject"))
if subject != "" {
dec := mime.WordDecoder{}
subject, err := dec.DecodeHeader(subject)
if err != nil {
return err
}
m.Title = subject
}
if m.Title != "" && m.Message == "" {
m.Message = m.Title // Flip them, this makes more sense
m.Title = ""
}
if err := s.backend.sub(m); err != nil {
return err
}
s.backend.mu.Lock()
s.backend.success++
s.backend.mu.Unlock()
return nil
})
}
func (s *smtpSession) Reset() {
s.mu.Lock()
s.topic = ""
s.mu.Unlock()
}
func (s *smtpSession) Logout() error {
return nil
}
func (s *smtpSession) withFailCount(fn func() error) error {
err := fn()
s.backend.mu.Lock()
defer s.backend.mu.Unlock()
if err != nil {
s.backend.failure++
}
return err
}
func readMailBody(msg *mail.Message) (string, error) {
if msg.Header.Get("Content-Type") == "" {
return readPlainTextMailBody(msg)
}
contentType, params, err := mime.ParseMediaType(msg.Header.Get("Content-Type"))
if err != nil {
return "", err
}
if contentType == "text/plain" {
return readPlainTextMailBody(msg)
} else if strings.HasPrefix(contentType, "multipart/") {
return readMultipartMailBody(msg, params)
}
return "", errUnsupportedContentType
}
func readPlainTextMailBody(msg *mail.Message) (string, error) {
body, err := io.ReadAll(msg.Body)
if err != nil {
return "", err
}
return string(body), nil
}
func readMultipartMailBody(msg *mail.Message, params map[string]string) (string, error) {
mr := multipart.NewReader(msg.Body, params["boundary"])
for {
part, err := mr.NextPart()
if err != nil { // may be io.EOF
return "", err
}
partContentType, _, err := mime.ParseMediaType(part.Header.Get("Content-Type"))
if err != nil {
return "", err
}
if partContentType != "text/plain" {
continue
}
body, err := io.ReadAll(part)
if err != nil {
return "", err
}
return string(body), nil
}
}