Add optional inbound relay (backup-MX) behind INBOUND_RELAY_ENABLE.

Port 25 accepts only configured domains and listed recipients, then forwards to an upstream; the outbound path is unchanged when the flag is off.

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/inbound/service.go

@@ -0,0 +1,156 @@
+// Package inbound owns backup-MX / relay-forwarder domains: the SQLite
+// registry and the Postfix lookup tables (relay_domains, transport_maps,
+// relay_recipient_maps, smtp_tls_policy_maps). It does not listen on port 25
+// itself — postfix-config.sh does that when INBOUND_RELAY_ENABLE is true.
+package inbound
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/mixeme/selfpost/internal/postfix"
+	"github.com/mixeme/selfpost/internal/store"
+)
+
+// Maps is the slice of the Postfix manager the inbound service needs.
+type Maps interface {
+	RebuildInboundMaps(routes []postfix.InboundRoute) error
+}
+
+// Service coordinates inbound-domain state across SQLite and the Postfix maps.
+type Service struct {
+	store *store.Store
+	maps  Maps
+}
+
+// NewService builds the inbound service over the shared store and Postfix maps.
+func NewService(st *store.Store, maps Maps) *Service {
+	return &Service{store: st, maps: maps}
+}
+
+// List returns every inbound domain.
+func (s *Service) List() ([]store.InboundDomain, error) {
+	return s.store.ListInboundDomains()
+}
+
+// Get returns one inbound domain by id.
+func (s *Service) Get(id int64) (store.InboundDomain, error) {
+	return s.store.GetInboundDomain(id)
+}
+
+// Add validates the domain name, inserts it, and rebuilds the maps.
+func (s *Service) Add(name string) (store.InboundDomain, error) {
+	name = normalizeDomain(name)
+	if err := checkDomain(name); err != nil {
+		return store.InboundDomain{}, err
+	}
+	d, err := s.store.AddInboundDomain(name)
+	if err != nil {
+		return store.InboundDomain{}, err
+	}
+	if err := s.Resync(); err != nil {
+		_ = s.store.DeleteInboundDomain(d.ID)
+		return store.InboundDomain{}, err
+	}
+	return d, nil
+}
+
+// SetTransport validates and saves the upstream, then rebuilds the maps.
+func (s *Service) SetTransport(id int64, host, portRaw, tlsMode string) error {
+	if _, err := s.store.GetInboundDomain(id); err != nil {
+		return err
+	}
+	host = normalizeHost(host)
+	if err := checkHost(host); err != nil {
+		return err
+	}
+	port, err := parsePort(portRaw)
+	if err != nil {
+		return err
+	}
+	if err := checkTLSMode(tlsMode); err != nil {
+		return err
+	}
+	if err := s.store.UpdateInboundTransport(id, host, port, tlsMode); err != nil {
+		return err
+	}
+	return s.Resync()
+}
+
+// SetRecipients validates the mode and, in list mode, every address, then
+// rebuilds the maps.
+func (s *Service) SetRecipients(id int64, mode string, rawAddresses []string) error {
+	d, err := s.store.GetInboundDomain(id)
+	if err != nil {
+		return err
+	}
+	if err := checkRecipientMode(mode); err != nil {
+		return err
+	}
+	var addrs []string
+	if mode == store.RecipientModeList {
+		addrs, err = parseRecipientAddresses(rawAddresses, d.Name)
+		if err != nil {
+			return err
+		}
+	}
+	if err := s.store.UpdateInboundRecipients(id, mode, addrs); err != nil {
+		return err
+	}
+	return s.Resync()
+}
+
+// Delete removes the domain and rebuilds the maps.
+func (s *Service) Delete(id int64) error {
+	if err := s.store.DeleteInboundDomain(id); err != nil {
+		return err
+	}
+	return s.Resync()
+}
+
+// Resync rebuilds the inbound Postfix maps from SQLite.
+func (s *Service) Resync() error {
+	list, err := s.store.ListInboundDomains()
+	if err != nil {
+		return err
+	}
+	routes := make([]postfix.InboundRoute, 0, len(list))
+	for _, d := range list {
+		full, err := s.store.GetInboundDomain(d.ID)
+		if err != nil {
+			return err
+		}
+		routes = append(routes, postfix.InboundRoute{
+			Domain:        full.Name,
+			Host:          full.Host,
+			Port:          full.Port,
+			TLSMode:       full.TLSMode,
+			RecipientMode: full.RecipientMode,
+			Recipients:    full.Recipients,
+		})
+	}
+	return s.maps.RebuildInboundMaps(routes)
+}
+
+func parseRecipientAddresses(raw []string, domain string) ([]string, error) {
+	seen := make(map[string]bool)
+	out := make([]string, 0, len(raw))
+	for _, r := range raw {
+		addr := strings.ToLower(strings.TrimSpace(r))
+		if addr == "" {
+			continue
+		}
+		if err := checkMailbox(addr, domain); err != nil {
+			return nil, err
+		}
+		if seen[addr] {
+			continue
+		}
+		seen[addr] = true
+		out = append(out, addr)
+	}
+	if len(out) == 0 {
+		return nil, fmt.Errorf("listed-recipients mode requires at least one address")
+	}
+	return out, nil
+}

internal/inbound/service_test.go

@@ -0,0 +1,111 @@
+package inbound
+
+import (
+	"errors"
+	"path/filepath"
+	"testing"
+
+	"github.com/mixeme/selfpost/internal/postfix"
+	"github.com/mixeme/selfpost/internal/store"
+)
+
+type fakeMaps struct {
+	routes  []postfix.InboundRoute
+	err     error
+	rebuild int
+}
+
+func (f *fakeMaps) RebuildInboundMaps(routes []postfix.InboundRoute) error {
+	f.rebuild++
+	f.routes = append([]postfix.InboundRoute(nil), routes...)
+	return f.err
+}
+
+func testService(t *testing.T) (*Service, *store.Store, *fakeMaps) {
+	t.Helper()
+	st, err := store.Open(filepath.Join(t.TempDir(), "test.db"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { st.Close() })
+	m := &fakeMaps{}
+	return NewService(st, m), st, m
+}
+
+func TestAddAndSetTransport(t *testing.T) {
+	s, _, m := testService(t)
+	d, err := s.Add("Lists.Example.COM")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if d.Name != "lists.example.com" {
+		t.Fatalf("name = %q", d.Name)
+	}
+	if m.rebuild != 1 {
+		t.Fatalf("rebuild after add = %d", m.rebuild)
+	}
+	// Empty host is omitted from maps.
+	if len(m.routes) != 1 || m.routes[0].Host != "" {
+		t.Fatalf("routes after add: %+v", m.routes)
+	}
+
+	if err := s.SetTransport(d.ID, "10.0.0.8", "25", store.TLSModeEncrypt); err != nil {
+		t.Fatal(err)
+	}
+	if m.routes[0].Host != "10.0.0.8" || m.routes[0].TLSMode != store.TLSModeEncrypt {
+		t.Fatalf("routes after transport: %+v", m.routes[0])
+	}
+}
+
+func TestSetRecipientsValidatesDomain(t *testing.T) {
+	s, _, _ := testService(t)
+	d, err := s.Add("lists.example.com")
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = s.SetRecipients(d.ID, store.RecipientModeList, []string{"staff@other.com"})
+	if err == nil {
+		t.Fatal("expected foreign-domain error")
+	}
+	err = s.SetRecipients(d.ID, store.RecipientModeList, nil)
+	if err == nil {
+		t.Fatal("expected empty-list error")
+	}
+	if err := s.SetRecipients(d.ID, store.RecipientModeList, []string{"staff@lists.example.com"}); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestRejectsUnsafeHost(t *testing.T) {
+	s, _, _ := testService(t)
+	d, err := s.Add("lists.example.com")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := s.SetTransport(d.ID, "10.0.0.8; rm", "25", store.TLSModeMay); err == nil {
+		t.Fatal("expected unsafe host to be rejected")
+	}
+}
+
+func TestDeleteResyncs(t *testing.T) {
+	s, _, m := testService(t)
+	d, err := s.Add("lists.example.com")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := s.Delete(d.ID); err != nil {
+		t.Fatal(err)
+	}
+	if !errors.Is(mustGet(t, s, d.ID), store.ErrInboundDomainNotFound) {
+		t.Fatal("domain still present")
+	}
+	if len(m.routes) != 0 {
+		t.Fatalf("maps after delete: %+v", m.routes)
+	}
+}
+
+func mustGet(t *testing.T, s *Service, id int64) error {
+	t.Helper()
+	_, err := s.Get(id)
+	return err
+}

internal/inbound/validate.go

@@ -0,0 +1,131 @@
+package inbound
+
+import (
+	"fmt"
+	"net"
+	"strconv"
+	"strings"
+)
+
+func normalizeDomain(name string) string {
+	return strings.ToLower(strings.TrimSpace(name))
+}
+
+func normalizeHost(host string) string {
+	host = strings.ToLower(strings.TrimSpace(host))
+	if strings.HasPrefix(host, "[") && strings.HasSuffix(host, "]") {
+		host = host[1 : len(host)-1]
+	}
+	return host
+}
+
+func checkDomain(name string) error {
+	if name == "" {
+		return fmt.Errorf("domain is required")
+	}
+	if len(name) > 253 {
+		return fmt.Errorf("domain must be at most 253 characters")
+	}
+	labels := strings.Split(name, ".")
+	if len(labels) < 2 {
+		return fmt.Errorf("domain must include at least one dot (e.g. example.com)")
+	}
+	for _, label := range labels {
+		if err := checkLabel(label); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func checkHost(host string) error {
+	if host == "" {
+		return fmt.Errorf("host is required")
+	}
+	if len(host) > 253 {
+		return fmt.Errorf("host must be at most 253 characters")
+	}
+	if ip := net.ParseIP(host); ip != nil {
+		return nil
+	}
+	for _, label := range strings.Split(host, ".") {
+		if err := checkLabel(label); err != nil {
+			return fmt.Errorf("host is invalid: %w", err)
+		}
+	}
+	return nil
+}
+
+func checkLabel(label string) error {
+	if len(label) == 0 {
+		return fmt.Errorf("must not contain an empty label")
+	}
+	if len(label) > 63 {
+		return fmt.Errorf("each label must be at most 63 characters")
+	}
+	if label[0] == '-' || label[len(label)-1] == '-' {
+		return fmt.Errorf("labels must not start or end with '-'")
+	}
+	for i := 0; i < len(label); i++ {
+		c := label[i]
+		lower := c >= 'a' && c <= 'z'
+		digit := c >= '0' && c <= '9'
+		if !lower && !digit && c != '-' {
+			return fmt.Errorf("may contain only lower-case letters, digits, '.' and '-'")
+		}
+	}
+	return nil
+}
+
+func parsePort(raw string) (int, error) {
+	raw = strings.TrimSpace(raw)
+	if raw == "" {
+		return 0, fmt.Errorf("port is required")
+	}
+	n, err := strconv.Atoi(raw)
+	if err != nil || n < 1 || n > 65535 {
+		return 0, fmt.Errorf("port must be between 1 and 65535")
+	}
+	return n, nil
+}
+
+func checkTLSMode(mode string) error {
+	switch mode {
+	case "may", "encrypt", "none":
+		return nil
+	default:
+		return fmt.Errorf("invalid TLS mode")
+	}
+}
+
+func checkRecipientMode(mode string) error {
+	switch mode {
+	case "list", "any":
+		return nil
+	default:
+		return fmt.Errorf("invalid recipient mode")
+	}
+}
+
+func checkMailbox(addr, domain string) error {
+	at := strings.LastIndexByte(addr, '@')
+	if at <= 0 || at >= len(addr)-1 {
+		return fmt.Errorf("%q is not a valid email address", addr)
+	}
+	local, host := addr[:at], addr[at+1:]
+	if host != domain {
+		return fmt.Errorf("%q does not belong to domain %s", addr, domain)
+	}
+	if local == "" || local[0] == '.' || local[len(local)-1] == '.' {
+		return fmt.Errorf("%q: invalid local part", addr)
+	}
+	for i := 0; i < len(local); i++ {
+		c := local[i]
+		lower := c >= 'a' && c <= 'z'
+		digit := c >= '0' && c <= '9'
+		if !lower && !digit && c != '.' && c != '-' && c != '_' && c != '+' {
+			return fmt.Errorf("%q: local part contains invalid characters", addr)
+		}
+	}
+	return nil
+}