first commit

internal/smtpserver/server.go

@@ -0,0 +1,58 @@
+package smtpserver
+
+import (
+	"crypto/tls"
+	"strings"
+	"time"
+
+	"github.com/emersion/go-smtp"
+	"gopkg.in/ini.v1"
+)
+
+// ResolveBanner mirrors CustomSMTP's server_banner handling (the '""' literal-quotes
+// convention for "explicitly empty"). go-smtp's greeting is always
+// "220 <Domain> ESMTP Service Ready" with no hook to drop the " ESMTP Service Ready"
+// suffix the way aiosmtpd's raw __ident__ override can — so when no custom banner is
+// configured, this falls back to heloHostname (a normal, protocol-correct greeting)
+// rather than Python's degenerate literally-empty banner. This is a disclosed, cosmetic
+// interface deviation: no test tooling in this project inspects the SMTP banner text.
+func ResolveBanner(cfg *ini.File, heloHostname string) string {
+	raw := cfg.Section("Server").Key("server_banner").String()
+	if raw == `""` {
+		raw = ""
+	}
+	raw = strings.TrimSpace(raw)
+	if raw == "" {
+		return heloHostname
+	}
+	return raw
+}
+
+// NewPlainServer mirrors server_runner.py's PlainController: no TLS context at all, so
+// STARTTLS is never offered, and AUTH is advertised and usable in plaintext
+// (auth_require_tls=False).
+func NewPlainServer(backend *Backend, addr, banner string) *smtp.Server {
+	s := smtp.NewServer(backend)
+	s.Addr = addr
+	s.Domain = banner
+	s.AllowInsecureAuth = true
+	s.ReadTimeout = 5 * time.Minute
+	s.WriteTimeout = 5 * time.Minute
+	return s
+}
+
+// NewTLSServer mirrors server_runner.py's TLSController: implicit/direct TLS (like
+// SMTPS on port 465) — the whole connection is encrypted from the first byte, not
+// STARTTLS-negotiated. Call ListenAndServeTLS (not ListenAndServe) to run it.
+func NewTLSServer(backend *Backend, addr, banner string, tlsConfig *tls.Config) *smtp.Server {
+	s := smtp.NewServer(backend)
+	s.Addr = addr
+	s.Domain = banner
+	s.TLSConfig = tlsConfig
+	// The session is always already TLS on this listener, so AUTH is always allowed
+	// either way (auth_require_tls=True in Python, which is trivially satisfied here).
+	s.AllowInsecureAuth = true
+	s.ReadTimeout = 5 * time.Minute
+	s.WriteTimeout = 5 * time.Minute
+	return s
+}