findings of the security review of stage 1

The review of d254a99..fd29468 (read-only, a separate agent) found all
five fixes sound and nothing above low. Fixed here:

- The M1 e2e step passed on the unfixed code: the stranger's RSET between
  MAIL FROMs ends the transaction, Postfix's mail_reset() calls
  milter_abort(), and the old code released the slot too. The stranger now
  keeps one MAIL FROM open (strangerHoldsMailFrom) while the domain's own
  application sends; under the old code that slot was the domain's one.
- A domain import could still store a report address on the server's own
  name (W1's form rule only): checkDomainImport refuses one that is not
  the domain's own hosted address. Not a mailbox either way, but the
  panel would show an address the server refuses. Cases in
  TestDomainImportIsCheckedLikeTheForms.
- DeleteDomain matches the reports' domain without regard to case.
- A cut that fails after the journal rows were written says the rows were
  written.
- dmarc.Service.Resync and inbound.Service.Resync are serialised like
  app.Service.Resync (W3's shape, outside its diff).

Left as the review's nit: three ApplicationByLogin lookups for a refused
MAIL FROM (a refusal is rare; the store is local).

go test ./internal/dmarc ./internal/inbound ./internal/store; the import
test; GOOS=linux go vet ./test/e2e.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/dmarc/service.go

@@ -5,6 +5,7 @@ package dmarc
 import (
 	"sort"
 	"strings"
+	"sync"
 
 	"github.com/mixeme/selfpost/internal/dnscheck"
 	"github.com/mixeme/selfpost/internal/postfix"
@@ -22,6 +23,10 @@ type Service struct {
 	maps     Maps
 	hostname string
 	enabled  bool
+
+	// resyncMu makes a rebuild's read and write one step, as app.Service's
+	// (security audit 2026-10-17, W3; the review of stage 1).
+	resyncMu sync.Mutex
 }
 
 // NewService builds the DMARC ingest service.
@@ -34,6 +39,8 @@ func (s *Service) Enabled() bool { return s.enabled }
 
 // Resync rebuilds the Postfix allow-list and transport maps from SQLite.
 func (s *Service) Resync() error {
+	s.resyncMu.Lock()
+	defer s.resyncMu.Unlock()
 	if !s.enabled {
 		return s.maps.RebuildDMARCMaps(postfix.DMARCMapsConfig{})
 	}

internal/inbound/service.go

@@ -7,6 +7,7 @@ package inbound
 import (
 	"fmt"
 	"strings"
+	"sync"
 
 	"github.com/mixeme/selfpost/internal/postfix"
 	"github.com/mixeme/selfpost/internal/store"
@@ -21,6 +22,10 @@ type Maps interface {
 type Service struct {
 	store *store.Store
 	maps  Maps
+
+	// resyncMu makes a rebuild's read and write one step, as app.Service's
+	// (security audit 2026-10-17, W3; the review of stage 1).
+	resyncMu sync.Mutex
 }
 
 // NewService builds the inbound service over the shared store and Postfix maps.
@@ -161,6 +166,8 @@ func (s *Service) Delete(id int64) error {
 
 // Resync rebuilds the inbound Postfix maps from SQLite.
 func (s *Service) Resync() error {
+	s.resyncMu.Lock()
+	defer s.resyncMu.Unlock()
 	list, err := s.store.ListInboundDomains()
 	if err != nil {
 		return err

internal/store/domains.go

@@ -144,7 +144,7 @@ func (s *Store) DeleteDomain(id int64) error {
 		return fmt.Errorf("delete domain: begin: %w", err)
 	}
 	defer tx.Rollback() //nolint:errcheck // a no-op after Commit
-	if _, err := tx.Exec(`DELETE FROM dmarc_reports WHERE domain = (SELECT name FROM domains WHERE id = ?)`, id); err != nil {
+	if _, err := tx.Exec(`DELETE FROM dmarc_reports WHERE domain = (SELECT name FROM domains WHERE id = ?) COLLATE NOCASE`, id); err != nil {
 		return fmt.Errorf("delete domain: its DMARC reports: %w", err)
 	}
 	res, err := tx.Exec("DELETE FROM domains WHERE id = ?", id)

internal/store/inboundspam.go

@@ -91,7 +91,7 @@ func (s *Store) countInboundWrites(n int) error {
 	s.inboundWrites.Store(0)
 	// The zero time removes nothing by age: this is the cap alone.
 	if _, err := s.PruneInboundSpam(time.Time{}, inboundCapRows); err != nil {
-		return fmt.Errorf("cut inbound_spam_log to %d rows: %w", inboundCapRows, err)
+		return fmt.Errorf("the rows were written; cutting inbound_spam_log to %d rows: %w", inboundCapRows, err)
 	}
 	return nil
 }

internal/web/handlers/handlers_backup.go

@@ -12,6 +12,7 @@ import (
 	"time"
 
 	"github.com/mixeme/selfpost/internal/backup"
+	"github.com/mixeme/selfpost/internal/dmarc"
 	"github.com/mixeme/selfpost/internal/domain"
 	"github.com/mixeme/selfpost/internal/secretfile"
 	"github.com/mixeme/selfpost/internal/store"
@@ -450,6 +451,13 @@ func (h *Handlers) checkDomainImport(exp *domain.DomainExport) string {
 		if err := validate.Email(exp.DMARCRua); err != nil {
 			return invalid("report address", err)
 		}
+		// As on Domain settings: an address on this server's own name is
+		// only ever the domain's own hosted one (security audit 2026-10-17,
+		// W1; the review of stage 1 found the import path open).
+		if dmarc.IsHostedOnHostname(exp.DMARCRua, h.cfg.Hostname) &&
+			!strings.EqualFold(strings.TrimSpace(exp.DMARCRua), dmarc.HostedReportAddress(h.cfg.Hostname, exp.Domain)) {
+			return "The export's report address is on this server's own name and is not the domain's own hosted address. Edit the file's dmarc_rua, or set it to empty and choose the address on Domain settings after the import."
+		}
 	}
 	limit := func(rl *domain.RateLimitExport) error {
 		if rl == nil {

internal/web/handlers/handlers_import_test.go

@@ -38,6 +38,12 @@ func TestDomainImportIsCheckedLikeTheForms(t *testing.T) {
 	if msg := h.checkDomainImport(&exp); msg != "" {
 		t.Fatalf("a good export refused: %s", msg)
 	}
+	// The domain's own hosted address is its own.
+	own := good()
+	own.DMARCRua = "dmarc-reports+example.com@mail.example.org"
+	if msg := h.checkDomainImport(&own); msg != "" {
+		t.Fatalf("the domain's own hosted address refused: %s", msg)
+	}
 	if got := strings.Join(exp.Applications[0].AuthAllowedIPs, " "); got != "192.0.2.1 2001:db8::1" {
 		t.Errorf("client addresses stored as %q, want as the form stores them", got)
 	}
@@ -64,6 +70,11 @@ func TestDomainImportIsCheckedLikeTheForms(t *testing.T) {
 			"Invalid DKIM selector in export file: selector must be at most 63 characters"},
 		{"report address", func(e *domain.DomainExport) { e.DMARCRua = "not an address" },
 			"Invalid report address in export file: "},
+		// As on Domain settings (security audit 2026-10-17, W1).
+		{"report address on the hostname", func(e *domain.DomainExport) { e.DMARCRua = "ops@MAIL.example.org" },
+			"The export's report address is on this server's own name"},
+		{"another domain's hosted address", func(e *domain.DomainExport) { e.DMARCRua = "dmarc-reports+victim.example@mail.example.org" },
+			"The export's report address is on this server's own name"},
 		{"no window", func(e *domain.DomainExport) { e.RateLimit.WindowSeconds = 0 },
 			"Invalid rate limit for the domain in export file: enter a time window greater than zero seconds"},
 		{"no messages", func(e *domain.DomainExport) { e.RateLimit.MaxMessages = 0 },