ntfy/server/smtp_server.go

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package server
import (
"bytes"
"errors"
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"fmt"
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"github.com/emersion/go-smtp"
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"heckel.io/ntfy/log"
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"io"
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"mime"
"mime/multipart"
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"net"
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"net/http"
"net/http/httptest"
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"net/mail"
"strings"
"sync"
)
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var (
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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")
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)
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// smtpBackend implements SMTP server methods.
type smtpBackend struct {
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config *Config
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handler func(http.ResponseWriter, *http.Request)
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success int64
failure int64
mu sync.Mutex
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}
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func newMailBackend(conf *Config, handler func(http.ResponseWriter, *http.Request)) *smtpBackend {
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return &smtpBackend{
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config: conf,
handler: handler,
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}
}
func (b *smtpBackend) Login(state *smtp.ConnectionState, username, password string) (smtp.Session, error) {
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log.Debug("%s Incoming mail, login with user %s", logSMTPPrefix(state), username)
return &smtpSession{backend: b, state: state}, nil
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}
func (b *smtpBackend) AnonymousLogin(state *smtp.ConnectionState) (smtp.Session, error) {
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log.Debug("%s Incoming mail, anonymous login", logSMTPPrefix(state))
return &smtpSession{backend: b, state: state}, nil
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}
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func (b *smtpBackend) Counts() (total int64, success int64, failure int64) {
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b.mu.Lock()
defer b.mu.Unlock()
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return b.success + b.failure, b.success, b.failure
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}
// smtpSession is returned after EHLO.
type smtpSession struct {
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backend *smtpBackend
state *smtp.ConnectionState
topic string
mu sync.Mutex
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}
func (s *smtpSession) AuthPlain(username, password string) error {
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log.Debug("%s AUTH PLAIN (with username %s)", logSMTPPrefix(s.state), username)
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return nil
}
func (s *smtpSession) Mail(from string, opts smtp.MailOptions) error {
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log.Debug("%s MAIL FROM: %s (with options: %#v)", logSMTPPrefix(s.state), from, opts)
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return nil
}
func (s *smtpSession) Rcpt(to string) error {
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log.Debug("%s RCPT TO: %s", logSMTPPrefix(s.state), to)
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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
})
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}
func (s *smtpSession) Data(r io.Reader) error {
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return s.withFailCount(func() error {
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conf := s.backend.config
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b, err := io.ReadAll(r) // Protected by MaxMessageBytes
if err != nil {
return err
}
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if log.IsTrace() {
log.Trace("%s DATA: %s", logSMTPPrefix(s.state), string(b))
} else if log.IsDebug() {
log.Debug("%s DATA: %d byte(s)", logSMTPPrefix(s.state), len(b))
}
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msg, err := mail.ReadMessage(bytes.NewReader(b))
if err != nil {
return err
}
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body, err := readMailBody(msg)
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if err != nil {
return err
}
body = strings.TrimSpace(body)
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if len(body) > conf.MessageLimit {
body = body[:conf.MessageLimit]
}
m := newDefaultMessage(s.topic, body)
subject := strings.TrimSpace(msg.Header.Get("Subject"))
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if subject != "" {
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dec := mime.WordDecoder{}
subject, err := dec.DecodeHeader(subject)
if err != nil {
return err
}
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m.Title = subject
}
if m.Title != "" && m.Message == "" {
m.Message = m.Title // Flip them, this makes more sense
m.Title = ""
}
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if err := s.publishMessage(m); err != nil {
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return err
}
s.backend.mu.Lock()
s.backend.success++
s.backend.mu.Unlock()
return nil
})
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}
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func (s *smtpSession) publishMessage(m *message) error {
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// Extract remote address (for rate limiting)
remoteAddr, _, err := net.SplitHostPort(s.state.RemoteAddr.String())
if err != nil {
remoteAddr = s.state.RemoteAddr.String()
}
// Call HTTP handler with fake HTTP request
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url := fmt.Sprintf("%s/%s", s.backend.config.BaseURL, m.Topic)
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req, err := http.NewRequest("POST", url, strings.NewReader(m.Message))
req.RequestURI = "/" + m.Topic // just for the logs
req.RemoteAddr = remoteAddr // rate limiting!!
req.Header.Set("X-Forwarded-For", remoteAddr)
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if err != nil {
return err
}
if m.Title != "" {
req.Header.Set("Title", m.Title)
}
rr := httptest.NewRecorder()
s.backend.handler(rr, req)
if rr.Code != http.StatusOK {
return errors.New("error: " + rr.Body.String())
}
return nil
}
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func (s *smtpSession) Reset() {
s.mu.Lock()
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s.topic = ""
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s.mu.Unlock()
}
func (s *smtpSession) Logout() error {
return nil
}
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func (s *smtpSession) withFailCount(fn func() error) error {
err := fn()
s.backend.mu.Lock()
defer s.backend.mu.Unlock()
if err != nil {
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// Almost all of these errors are parse errors, and user input errors.
// We do not want to spam the log with WARN messages.
log.Debug("%s Incoming mail error: %s", logSMTPPrefix(s.state), err.Error())
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s.backend.failure++
}
return err
}
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func readMailBody(msg *mail.Message) (string, error) {
if msg.Header.Get("Content-Type") == "" {
return readPlainTextMailBody(msg)
}
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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"))
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if err != nil {
return "", err
}
if partContentType != "text/plain" {
continue
}
body, err := io.ReadAll(part)
if err != nil {
return "", err
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}
return string(body), nil
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}
}