fix(smtp): proper SMTP dialogue, encoded mails, optional skip-verify
- Explicit SMTP flow (dial -> EHLO -> STARTTLS -> AUTH -> MAIL/RCPT/DATA) with errors naming the refusing step (also logged as smtp_step) - EHLO with the sender's domain instead of "localhost" - Envelope gets the bare address; "Name <addr>" stays in the From header (was rejected as invalid MAIL FROM) - Date and Message-ID headers, RFC 2047 subject, quoted-printable body - SMTP_SKIP_VERIFY / admin switch for self-signed certificates; SMTP checkboxes are switches now - Tests against a fake SMTP server (STARTTLS, 451, display names) Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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sandrodachandClaude Opus 5.5 committed
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@@ -0,0 +1,215 @@
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package api
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import (
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"bufio"
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"crypto/ecdsa"
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"crypto/elliptic"
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"crypto/rand"
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"crypto/tls"
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"crypto/x509"
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"crypto/x509/pkix"
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"errors"
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"math/big"
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"net"
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"strings"
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"sync"
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"testing"
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"time"
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)
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// fakeSMTP is a minimal ESMTP server with STARTTLS (self-signed) and AUTH PLAIN.
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type fakeSMTP struct {
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addr string
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rcptCode string // e.g. "451 4.3.2 Internal server error" to refuse RCPT TO
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mu sync.Mutex
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ehlo string
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mailFrom string
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rcptTo string
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data string
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}
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func selfSignedCert(t *testing.T) tls.Certificate {
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t.Helper()
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key, _ := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
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tmpl := &x509.Certificate{
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SerialNumber: big.NewInt(1),
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Subject: pkix.Name{CommonName: "mail.intern"},
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DNSNames: []string{"mail.intern"},
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NotBefore: time.Now().Add(-time.Hour),
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NotAfter: time.Now().Add(time.Hour),
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}
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der, err := x509.CreateCertificate(rand.Reader, tmpl, tmpl, &key.PublicKey, key)
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if err != nil {
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t.Fatalf("cert: %v", err)
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}
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return tls.Certificate{Certificate: [][]byte{der}, PrivateKey: key}
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}
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func startFakeSMTP(t *testing.T, rcptCode string) *fakeSMTP {
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t.Helper()
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ln, err := net.Listen("tcp", "127.0.0.1:0")
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if err != nil {
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t.Fatalf("listen: %v", err)
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}
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t.Cleanup(func() { _ = ln.Close() })
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f := &fakeSMTP{addr: ln.Addr().String(), rcptCode: rcptCode}
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tlsCfg := &tls.Config{Certificates: []tls.Certificate{selfSignedCert(t)}}
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go func() {
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for {
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conn, err := ln.Accept()
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if err != nil {
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return
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}
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go f.serve(conn, tlsCfg)
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}
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}()
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return f
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}
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func (f *fakeSMTP) serve(conn net.Conn, tlsCfg *tls.Config) {
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defer conn.Close()
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r, w := bufio.NewReader(conn), bufio.NewWriter(conn)
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reply := func(s string) { _, _ = w.WriteString(s + "\r\n"); _ = w.Flush() }
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reply("220 fake ESMTP")
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secure := false
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for {
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line, err := r.ReadString('\n')
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if err != nil {
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return
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}
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cmd := strings.TrimRight(line, "\r\n")
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upper := strings.ToUpper(cmd)
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switch {
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case strings.HasPrefix(upper, "EHLO "):
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f.mu.Lock()
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f.ehlo = cmd[5:]
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f.mu.Unlock()
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if secure {
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reply("250-fake\r\n250 AUTH PLAIN")
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} else {
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reply("250-fake\r\n250-STARTTLS\r\n250 AUTH PLAIN")
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}
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case upper == "STARTTLS":
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reply("220 go ahead")
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tlsConn := tls.Server(conn, tlsCfg)
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if err := tlsConn.Handshake(); err != nil {
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return
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}
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conn, secure = tlsConn, true
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r, w = bufio.NewReader(conn), bufio.NewWriter(conn)
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case strings.HasPrefix(upper, "AUTH "):
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reply("235 ok")
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case strings.HasPrefix(upper, "MAIL FROM"):
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f.mu.Lock()
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f.mailFrom = strings.TrimSpace(cmd[len("MAIL FROM:"):])
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f.mu.Unlock()
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reply("250 ok")
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case strings.HasPrefix(upper, "RCPT TO"):
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f.mu.Lock()
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f.rcptTo = strings.TrimSpace(cmd[len("RCPT TO:"):])
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f.mu.Unlock()
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if f.rcptCode != "" {
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reply(f.rcptCode)
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} else {
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reply("250 ok")
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}
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case upper == "DATA":
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reply("354 go")
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var sb strings.Builder
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for {
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l, err := r.ReadString('\n')
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if err != nil {
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return
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}
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if l == ".\r\n" {
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break
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}
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sb.WriteString(l)
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}
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f.mu.Lock()
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f.data = sb.String()
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f.mu.Unlock()
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reply("250 queued")
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case upper == "QUIT":
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reply("221 bye")
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return
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default:
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reply("250 ok")
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}
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}
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}
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func (f *fakeSMTP) settings(skipVerify bool) smtpSettings {
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host, port, _ := net.SplitHostPort(f.addr)
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return smtpSettings{Host: host, Port: port, User: "alarm@firma.de", Pass: "geheim", From: "alarm@firma.de", TLS: true, SkipVerify: skipVerify}
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}
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func TestSendMailStartTLSWithSelfSignedCertificate(t *testing.T) {
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f := startFakeSMTP(t, "")
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// The certificate is self-signed: refused unless verification is switched off
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err := sendMail(f.settings(false), "anna@example.com", "Test", "Hallo")
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var stepErr *smtpStepError
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if !errors.As(err, &stepErr) || stepErr.Step != "STARTTLS" {
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t.Fatalf("expected a STARTTLS error with verification on, got %v", err)
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}
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if err := sendMail(f.settings(true), "anna@example.com", "⏰ Aufgabe fällig: Müll", "Zeile 1\nZeile 2 mit Ümlaut"); err != nil {
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t.Fatalf("send with SkipVerify failed: %v", err)
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}
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f.mu.Lock()
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ehlo, data := f.ehlo, f.data
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f.mu.Unlock()
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if ehlo != "firma.de" {
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t.Errorf("EHLO should name the sender domain, got %q", ehlo)
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}
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for _, header := range []string{"Date: ", "Message-ID: <", "Content-Transfer-Encoding: quoted-printable"} {
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if !strings.Contains(data, header) {
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t.Errorf("message lacks %q:\n%s", header, data)
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}
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}
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if !strings.Contains(data, "Subject: =?utf-8?q?") {
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t.Errorf("subject with emoji/umlauts must be RFC 2047 encoded:\n%s", data)
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}
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if strings.Contains(data, "fällig") {
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t.Errorf("raw non-ASCII must not appear in the message:\n%s", data)
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}
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}
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func TestSendMailReportsTheRefusingStep(t *testing.T) {
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f := startFakeSMTP(t, "451 4.3.2 Internal server error")
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err := sendMail(f.settings(true), "anna@example.com", "Test", "Hallo")
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var stepErr *smtpStepError
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if !errors.As(err, &stepErr) || stepErr.Step != "RCPT TO" || !strings.Contains(err.Error(), "451") {
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t.Fatalf("expected the 451 to be reported at RCPT TO, got %v", err)
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}
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}
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// The admin UI suggests "MindSift <alerts@domain>" as sender; the envelope must carry the bare address
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func TestSendMailWithDisplayNameSender(t *testing.T) {
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f := startFakeSMTP(t, "")
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cfg := f.settings(true)
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cfg.From = "MindSift Alarme <alarm@firma.de>"
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if err := sendMail(cfg, "Anna <anna@example.com>", "Test", "Hallo"); err != nil {
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t.Fatalf("send failed: %v", err)
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}
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f.mu.Lock()
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defer f.mu.Unlock()
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if f.mailFrom != "<alarm@firma.de>" || f.rcptTo != "<anna@example.com>" {
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t.Errorf("envelope must hold bare addresses, got MAIL FROM %q, RCPT TO %q", f.mailFrom, f.rcptTo)
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}
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if !strings.Contains(f.data, `From: "MindSift Alarme" <alarm@firma.de>`) {
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t.Errorf("header From should keep the display name:\n%s", f.data)
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}
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}
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func TestEHLONameNeverLocalhost(t *testing.T) {
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if got := ehloName("Alarm <alarm@mail.example.org>"); got != "mail.example.org" {
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t.Errorf("got %q", got)
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}
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if got := ehloName("noreply"); got == "localhost" || got == "" {
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t.Errorf("fallback must not be localhost, got %q", got)
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}
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}
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