move dnsbl command to per-mailbox spamcheck:rbl; refactor smtp a bit

README.md

@@ -26,6 +26,7 @@ so you can use it to send emails from your apps and scripts as well.
 - [x] SMTP verification
 - [x] DKIM verification
 - [x] SPF verification
+- [x] RBL verification
 - [x] MX verification
 - [x] Spamlist of emails (wildcards supported)
 - [x] Spamlist of hosts (per server only)
@@ -149,6 +150,7 @@ If you want to change them - check available options in the help message (`!pm h
 
 * **`!pm spamcheck:mx`** - only accept email from servers which seem prepared to receive it (those having valid MX records) (`true` - enable, `false` - disable)
 * **`!pm spamcheck:spf`** - only accept email from senders which authorized to send it (those matching SPF records) (`true` - enable, `false` - disable)
+* **`!pm spamcheck:rbl`** - reject incoming emails from hosts listed in DNS blocklists (`true` - enable, `false` - disable)
 * **`!pm spamcheck:dkim`** - only accept correctly authorized emails (without DKIM signature at all or with valid DKIM signature) (`true` - enable, `false` - disable)
 * **`!pm spamcheck:smtp`** - only accept email from servers which seem prepared to receive it (those listening on an SMTP port) (`true` - enable, `false` - disable)
 

bot/access.go

@@ -189,28 +189,6 @@ func (b *Bot) BanAuth(ctx context.Context, addr net.Addr) {
 	}
 }
 
-// Ban an address listed in DNS Blacklists automatically
-func (b *Bot) BanDNSBL(ctx context.Context, addr net.Addr) {
-	if !b.cfg.GetBot(ctx).BanlistEnabled() {
-		return
-	}
-
-	if !b.cfg.GetBot(ctx).BanlistDNSBL() {
-		return
-	}
-
-	if b.IsTrusted(addr) {
-		return
-	}
-	b.log.Debug().Str("addr", addr.String()).Msg("attempting to automatically ban")
-	banlist := b.cfg.GetBanlist(ctx)
-	banlist.Add(addr)
-	err := b.cfg.SetBanlist(ctx, banlist)
-	if err != nil {
-		b.log.Error().Err(err).Str("addr", addr.String()).Msg("cannot update banlist")
-	}
-}
-
 // Ban an address manually
 func (b *Bot) BanManually(ctx context.Context, addr net.Addr) {
 	if !b.cfg.GetBot(ctx).BanlistEnabled() {

bot/command.go

@@ -35,7 +35,6 @@ const (
 	commandBanlistTotals  = "banlist:totals"
 	commandBanlistAuto    = "banlist:auto"
 	commandBanlistAuth    = "banlist:auth"
-	commandBanlistDNSBL   = "banlist:dnsbl"
 	commandBanlistAdd     = "banlist:add"
 	commandBanlistRemove  = "banlist:remove"
 	commandBanlistReset   = "banlist:reset"
@@ -256,6 +255,12 @@ func (b *Bot) initCommands() commandList {
 			sanitizer:   utils.SanitizeBoolString,
 			allowed:     b.allowOwner,
 		},
+		{
+			key:         config.RoomSpamcheckRBL,
+			description: "reject incoming emails from hosts listed in DNS blocklists (`true` - enable, `false` - disable)",
+			sanitizer:   utils.SanitizeBoolString,
+			allowed:     b.allowOwner,
+		},
 		{allowed: b.allowOwner, description: "mailbox anti-spam"}, // delimiter
 		{
 			key:         commandSpamlist,
@@ -337,11 +342,6 @@ func (b *Bot) initCommands() commandList {
 			description: "Enable/disable automatic banning of IP addresses when they try to auth with invalid credentials",
 			allowed:     b.allowAdmin,
 		},
-		{
-			key:         commandBanlistDNSBL,
-			description: "Enable/disable automatic banning of IP addresses when they are listed in DNS Blacklists",
-			allowed:     b.allowAdmin,
-		},
 		{
 			key:         commandBanlistAuto,
 			description: "Enable/disable automatic banning of IP addresses when they try to send invalid emails",
@@ -439,8 +439,6 @@ func (b *Bot) handle(ctx context.Context) {
 		b.runBanlist(ctx, commandSlice)
 	case commandBanlistAuth:
 		b.runBanlistAuth(ctx, commandSlice)
-	case commandBanlistDNSBL:
-		b.runBanlistDNSBL(ctx, commandSlice)
 	case commandBanlistAuto:
 		b.runBanlistAuto(ctx, commandSlice)
 	case commandBanlistTotals:

bot/command_admin.go

@@ -380,33 +380,6 @@ func (b *Bot) runBanlistAuth(ctx context.Context, commandSlice []string) { //nol
 	b.lp.SendNotice(ctx, evt.RoomID, "auth banning has been updated", linkpearl.RelatesTo(evt.ID))
 }
 
-func (b *Bot) runBanlistDNSBL(ctx context.Context, commandSlice []string) { //nolint:dupl // not in that case
-	evt := eventFromContext(ctx)
-	cfg := b.cfg.GetBot(ctx)
-	if len(commandSlice) < 2 {
-		var msg strings.Builder
-		msg.WriteString("Currently: `")
-		msg.WriteString(cfg.Get(config.BotBanlistDNSBL))
-		msg.WriteString("`\n\n")
-
-		if !cfg.BanlistDNSBL() {
-			msg.WriteString("To enable automatic banning by using DNS Blacklists, send `")
-			msg.WriteString(b.prefix)
-			msg.WriteString(" banlist:dnsbl true` (banlist itself must be enabled!)\n\n")
-		}
-
-		b.lp.SendNotice(ctx, evt.RoomID, msg.String(), linkpearl.RelatesTo(evt.ID))
-		return
-	}
-	value := utils.SanitizeBoolString(commandSlice[1])
-	cfg.Set(config.BotBanlistDNSBL, value)
-	err := b.cfg.SetBot(ctx, cfg)
-	if err != nil {
-		b.Error(ctx, "cannot set bot config: %v", err)
-	}
-	b.lp.SendNotice(ctx, evt.RoomID, "dns blacklists banning has been updated", linkpearl.RelatesTo(evt.ID))
-}
-
 func (b *Bot) runBanlistAuto(ctx context.Context, commandSlice []string) { //nolint:dupl // not in that case
 	evt := eventFromContext(ctx)
 	cfg := b.cfg.GetBot(ctx)

bot/config/bot.go

@@ -23,7 +23,6 @@ const (
 	BotBanlistEnabled      = "banlist:enabled"
 	BotBanlistAuto         = "banlist:auto"
 	BotBanlistAuth         = "banlist:auth"
-	BotBanlistDNSBL        = "banlist:dnsbl"
 	BotGreylist            = "greylist"
 	BotMautrix015Migration = "mautrix015migration"
 )
@@ -85,11 +84,6 @@ func (s Bot) BanlistAuth() bool {
 	return utils.Bool(s.Get(BotBanlistAuth))
 }
 
-// BanlistDNSBL option
-func (s Bot) BanlistDNSBL() bool {
-	return utils.Bool(s.Get(BotBanlistDNSBL))
-}
-
 // Greylist option (duration in minutes)
 func (s Bot) Greylist() int {
 	return utils.Int(s.Get(BotGreylist))

bot/config/room.go

@@ -39,10 +39,11 @@ const (
 	RoomNoSubject   = "nosubject"
 	RoomNoThreads   = "nothreads"
 
+	RoomSpamcheckRBL  = "spamcheck:rbl"
 	RoomSpamcheckDKIM = "spamcheck:dkim"
-	RoomSpamcheckMX   = "spamcheck:mx"
 	RoomSpamcheckSMTP = "spamcheck:smtp"
 	RoomSpamcheckSPF  = "spamcheck:spf"
+	RoomSpamcheckMX   = "spamcheck:mx"
 
 	RoomSpamlist = "spamlist"
 )
@@ -147,6 +148,10 @@ func (s Room) NoInlines() bool {
 	return utils.Bool(s.Get(RoomNoInlines))
 }
 
+func (s Room) SpamcheckRBL() bool {
+	return utils.Bool(s.Get(RoomSpamcheckRBL))
+}
+
 func (s Room) SpamcheckDKIM() bool {
 	return utils.Bool(s.Get(RoomSpamcheckDKIM))
 }

cmd/cmd.go

@@ -108,6 +108,9 @@ func initMatrix(cfg *config.Config) {
 	if err != nil {
 		log.Fatal().Err(err).Msg("cannot initialize SQL database")
 	}
+	if cfg.DB.Dialect == "sqlite" {
+		db.SetMaxOpenConns(1)
+	}
 
 	lp, err := linkpearl.New(&linkpearl.Config{
 		Homeserver:        cfg.Homeserver,

e2e/send

@@ -1,3 +1,3 @@
 #!/bin/bash
 
-ssmtp -v aine@gelato.casa < $1
+ssmtp -v test@localhost < $1

email/options.go

@@ -5,6 +5,7 @@ type IncomingFilteringOptions interface {
 	SpamcheckDKIM() bool
 	SpamcheckSMTP() bool
 	SpamcheckSPF() bool
+	SpamcheckRBL() bool
 	SpamcheckMX() bool
 	Spamlist() []string
 }

smtp/dnsbl.go

@@ -51,7 +51,7 @@ type DNSBLResult struct {
 }
 
 // CheckDNSBLs checks if the given IP address is listed in any of the DNSBLs, and returns a decision, based on the results
-func CheckDNSBLs(ctx context.Context, log *zerolog.Logger, addr net.Addr, optionalTimeout ...time.Duration) bool {
+func CheckDNSBLs(ctx context.Context, log *zerolog.Logger, addr net.Addr, optionalTimeout ...time.Duration) (blocked bool, reasons []string) {
 	ttl := DNSBLTimeout
 	if len(optionalTimeout) > 0 {
 		ttl = optionalTimeout[0]
@@ -77,6 +77,7 @@ func CheckDNSBLs(ctx context.Context, log *zerolog.Logger, addr net.Addr, option
 		}
 		if r.Listed {
 			listed++
+			reasons = append(reasons, r.Reasons)
 			listedRBLs = append(listedRBLs, r.RBL)
 		} else {
 			unlisted++
@@ -95,7 +96,7 @@ func CheckDNSBLs(ctx context.Context, log *zerolog.Logger, addr net.Addr, option
 		Bool("blocked", decision).
 		Msg("DNSBL results")
 
-	return decision
+	return decision, reasons
 }
 
 // check checks if the given IP address is listed in any of the DNSBLs

smtp/errors.go

@@ -0,0 +1,65 @@
+package smtp
+
+import (
+	"errors"
+	"strings"
+
+	"github.com/emersion/go-smtp"
+)
+
+const (
+	// NoUserCode SMTP code
+	NoUserCode = 550
+	// BannedCode SMTP code
+	BannedCode = 554
+	// GreylistCode SMTP code
+	GreylistCode = 451
+	// RBLCode SMTP code
+	RBLCode = 450
+)
+
+var (
+	// NoUserEnhancedCode enhanced SMTP code
+	NoUserEnhancedCode = smtp.EnhancedCode{5, 5, 0}
+	// BannedEnhancedCode enhanced SMTP code
+	BannedEnhancedCode = smtp.EnhancedCode{5, 5, 4}
+	// GreylistEnhancedCode is GraylistCode in enhanced code notation
+	GreylistEnhancedCode = smtp.EnhancedCode{4, 5, 1}
+	// RBLEnhancedCode is RBLCode in enhanced code notation
+	RBLEnhancedCode = smtp.EnhancedCode{4, 5, 0}
+	// ErrBanned returned to banned hosts
+	ErrBanned = &smtp.SMTPError{
+		Code:         BannedCode,
+		EnhancedCode: BannedEnhancedCode,
+		Message:      "please, don't bother me anymore, kupo.",
+	}
+	// ErrNoUser returned when no such mailbox found
+	ErrNoUser = &smtp.SMTPError{
+		Code:         NoUserCode,
+		EnhancedCode: NoUserEnhancedCode,
+		Message:      "no such user here, kupo.",
+	}
+	// ErrGreylisted returned when the host is graylisted
+	ErrGreylisted = &smtp.SMTPError{
+		Code:         GreylistCode,
+		EnhancedCode: GreylistEnhancedCode,
+		Message:      "You have been greylisted, try again a bit later.",
+	}
+	// ErrRBL returned when the host is blacklisted
+	ErrRBL = &smtp.SMTPError{
+		Code:         RBLCode,
+		EnhancedCode: RBLEnhancedCode,
+		Message:      "You are blacklisted, kupo.",
+	}
+	// ErrInvalidEmail for invalid emails :)
+	ErrInvalidEmail = errors.New("please, provide valid email address")
+)
+
+// extendErrRBL extends the RBL error with reasons returned by the DNSBLs
+func extendErrRBL(reasons []string) *smtp.SMTPError {
+	return &smtp.SMTPError{
+		Code:         RBLCode,
+		EnhancedCode: RBLEnhancedCode,
+		Message:      "You are blacklisted, kupo. Details: " + strings.Join(reasons, "; "),
+	}
+}

smtp/listener.go

@@ -17,14 +17,12 @@ type Listener struct {
 	tlsMu    sync.Mutex
 	listener net.Listener
 	isBanned func(context.Context, net.Addr) bool
-	banDNSBL func(context.Context, net.Addr)
 }
 
 func NewListener(
 	port string,
 	tlsConfig *tls.Config,
 	isBanned func(context.Context, net.Addr) bool,
-	banDNSBL func(context.Context, net.Addr),
 	log *zerolog.Logger,
 ) (*Listener, error) {
 	actual, err := net.Listen("tcp", ":"+port)
@@ -38,7 +36,6 @@ func NewListener(
 		tls:      tlsConfig,
 		listener: actual,
 		isBanned: isBanned,
-		banDNSBL: banDNSBL,
 	}, nil
 }
 
@@ -69,15 +66,6 @@ func (l *Listener) Accept() (net.Conn, error) {
 			continue
 		}
 
-		log.Info().Msg("checking dns blacklists...")
-		if CheckDNSBLs(ctx, l.log, conn.RemoteAddr()) {
-			//nolint:gocritic // TODO
-			// conn.Close()
-			// l.banDNSBL(ctx, conn.RemoteAddr())
-			log.Info().Msg("should rejected connection (DNS Blacklist); but won't do it for now (for testing purposes)")
-			continue
-		}
-
 		log.Info().Msg("accepted connection")
 
 		if l.tls != nil {

smtp/manager.go

@@ -67,7 +67,6 @@ type matrixbot interface {
 	IsTrusted(net.Addr) bool
 	BanAuto(context.Context, net.Addr)
 	BanAuth(context.Context, net.Addr)
-	BanDNSBL(context.Context, net.Addr)
 	GetMapping(context.Context, string) (id.RoomID, bool)
 	GetIFOptions(context.Context, id.RoomID) email.IncomingFilteringOptions
 	IncomingEmail(context.Context, *email.Email) error
@@ -174,7 +173,7 @@ func (m *Manager) Stop() {
 }
 
 func (m *Manager) listen(port string, tlsConfig *tls.Config) {
-	lwrapper, err := NewListener(port, tlsConfig, m.bot.IsBanned, m.bot.BanDNSBL, m.log)
+	lwrapper, err := NewListener(port, tlsConfig, m.bot.IsBanned, m.log)
 	if err != nil {
 		m.log.Error().Err(err).Str("port", port).Msg("cannot start listener")
 		m.errs <- err

smtp/server.go

@@ -10,32 +10,6 @@ import (
 	"gitlab.com/etke.cc/postmoogle/email"
 )
 
-const (
-	// NoUserCode SMTP code
-	NoUserCode = 550
-	// BannedCode SMTP code
-	BannedCode = 554
-)
-
-var (
-	// NoUserEnhancedCode enhanced SMTP code
-	NoUserEnhancedCode = smtp.EnhancedCode{5, 5, 0}
-	// BannedEnhancedCode enhanced SMTP code
-	BannedEnhancedCode = smtp.EnhancedCode{5, 5, 4}
-	// ErrBanned returned to banned hosts
-	ErrBanned = &smtp.SMTPError{
-		Code:         BannedCode,
-		EnhancedCode: BannedEnhancedCode,
-		Message:      "please, don't bother me anymore, kupo.",
-	}
-	// ErrNoUser returned when no such mailbox found
-	ErrNoUser = &smtp.SMTPError{
-		Code:         NoUserCode,
-		EnhancedCode: NoUserEnhancedCode,
-		Message:      "no such user here, kupo.",
-	}
-)
-
 type mailServer struct {
 	bot     matrixbot
 	log     *zerolog.Logger

smtp/session.go

@@ -3,7 +3,6 @@ package smtp
 import (
 	"bytes"
 	"context"
-	"errors"
 	"io"
 	"net"
 	"net/url"
@@ -22,22 +21,14 @@ import (
 )
 
 const (
-	// GraylistCode SMTP code
-	GraylistCode = 451
 	// Incoming is the direction of the email
 	Incoming = "incoming"
 	// Outgoing is the direction of the email
 	Outoing = "outgoing"
 )
 
-var (
+// ensure that session implements smtp.AuthSession
-	// ErrInvalidEmail for invalid emails :)
+var _ smtp.AuthSession = (*session)(nil)
-	ErrInvalidEmail = errors.New("please, provide valid email address")
-	// GraylistEnhancedCode is GraylistCode in enhanced code notation
-	GraylistEnhancedCode = smtp.EnhancedCode{4, 5, 1}
-	// ensure that session implements smtp.AuthSession
-	_ smtp.AuthSession = (*session)(nil)
-)
 
 type session struct {
 	log      *zerolog.Logger
@@ -95,27 +86,38 @@ func (s *session) authPlain(_, username, password string) error {
 
 func (s *session) Mail(from string, _ *smtp.MailOptions) error {
 	if s.dir == Outoing {
-		if err := s.validateOutgoingMail(from); err != nil {
+		return s.validateOutgoingMail(from)
-			return err
-		}
-	} else {
-		if !email.AddressValid(from) {
-			s.log.Debug().Str("from", from).Msg("address is invalid")
-			s.bot.BanAuto(s.ctx, s.conn.Conn().RemoteAddr())
-			return ErrBanned
-		}
-		s.from = email.Address(from)
-		s.log.Debug().Str("from", from).Msg("incoming mail")
 	}
+
+	// incoming mail
+	if !email.AddressValid(from) {
+		s.log.Debug().Str("from", from).Msg("address is invalid")
+		s.bot.BanAuto(s.ctx, s.conn.Conn().RemoteAddr())
+		return ErrBanned
+	}
+	s.from = email.Address(from)
+	s.log.Debug().Str("from", from).Msg("incoming mail")
 	return nil
 }
 
 func (s *session) Rcpt(to string, _ *smtp.RcptOptions) error {
 	s.tos = append(s.tos, to)
 	s.log.Debug().Str("to", to).Msg("mail")
-	if s.dir != Outoing {
+	if s.dir == Outoing {
-		if err := s.validateIncomingRcpt(to); err != nil {
+		return nil
-			return err
+	}
+	if err := s.validateIncomingRcpt(to); err != nil {
+		return err
+	}
+
+	if s.bot.GetIFOptions(s.ctx, s.roomID).SpamcheckRBL() {
+		s.log.Info().Msg("checking dns blacklists...")
+		if listed, reasons := CheckDNSBLs(s.ctx, s.log, s.conn.Conn().RemoteAddr()); listed {
+			s.log.Info().Strs("reasons", reasons).Msg("rejected incoming email (DNS Blacklist)")
+			if len(reasons) > 0 {
+				return extendErrRBL(reasons)
+			}
+			return ErrRBL
 		}
 	}
 
@@ -173,11 +175,7 @@ func (s *session) incomingData(r io.Reader) error {
 		return ErrBanned
 	}
 	if s.bot.IsGreylisted(s.ctx, addr) {
-		return &smtp.SMTPError{
+		return ErrGreylisted
-			Code:         GraylistCode,
-			EnhancedCode: GraylistEnhancedCode,
-			Message:      "You have been greylisted, try again a bit later.",
-		}
 	}
 	if validations.SpamcheckDKIM() {
 		results, verr := dkim.Verify(reader)