fix(mail): relatorios DMARC nao mostravam o clipe de anexo

has_attachments so era definido para mensagens multipart. Um relatorio
agregado DMARC do Google e de parte unica: o corpo E o anexo, um
application/zip sem qualquer parte de texto. Ficava guardado como nao tendo
anexos, ao lado dos relatorios TLS-RPT do mesmo remetente e na mesma pasta,
que trazem uma linha de texto e por isso sao multipart/mixed e apareciam
marcados.

A regra passa a olhar tambem para a parte de topo: uma disposicao explicita
decide (um .txt enviado como a mensagem inteira e anexo, uma parte inline nao
e), e sem ela conta como anexo tudo o que nao seja texto nem multipart -- um
zip, um PDF, uma mensagem reencaminhada.

As mensagens ja guardadas mantinham a marca antiga, e sao justamente aquelas
que o utilizador esta a olhar. Ha um backfill que as re-le uma vez, em segundo
plano, sem atrasar o arranque. So examina as que estao marcadas como sem
anexos: a regra antiga nunca inventou um anexo que nao existisse, portanto uma
marca verdadeira nao precisa de segunda opiniao e a varredura fica do tamanho
do defeito. A tabela backfills guarda o marcador para nao repetir a cada
arranque.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

migrations/0011_backfill_markers.down.sql

@@ -0,0 +1 @@
+DROP TABLE IF EXISTS backfills;

migrations/0011_backfill_markers.up.sql

@@ -0,0 +1,12 @@
+-- Records one-shot data repairs so they run once rather than on every start.
+--
+-- The first user is the attachment flag: has_attachments was only ever set for
+-- multipart messages, so a single-part attachment - a DMARC aggregate report,
+-- whose whole body is a zip - was stored as having none. The fix corrects new
+-- deliveries; the messages already filed need re-reading, and re-reading every
+-- message on every boot is not something to do forever.
+CREATE TABLE IF NOT EXISTS backfills (
+    name         VARCHAR(64) PRIMARY KEY,
+    completed_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    detail       TEXT
+);

services/protocols/cmd/lambdamail-protocols/backfill_attachments.go

@@ -0,0 +1,77 @@
+package main
+
+import (
+	"context"
+	"log"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"lambdamail/protocols/internal/application/usecase"
+	"lambdamail/protocols/internal/infrastructure/diskstorage"
+	"lambdamail/protocols/internal/infrastructure/postgres"
+)
+
+// attachmentBackfillName identifies this repair in the backfills table.
+const attachmentBackfillName = "has_attachments_single_part"
+
+// backfillAttachmentFlags re-reads stored messages and marks the ones whose
+// body is itself an attachment.
+//
+// has_attachments was only set for multipart messages, so a DMARC aggregate
+// report - a single-part application/zip with no text at all - was filed as
+// having none. Correcting the rule fixes new deliveries; the messages already
+// in the mailbox need re-reading, which is what this does, once.
+//
+// It runs in the background and never blocks startup: this is cosmetic
+// metadata, and no message is at risk if it never finishes.
+func backfillAttachmentFlags(ctx context.Context, pool *pgxpool.Pool) {
+	repo := postgres.NewAttachmentBackfill(pool)
+
+	done, err := repo.Done(ctx, attachmentBackfillName)
+	if err != nil {
+		log.Printf("attachment backfill: cannot read the marker, skipping: %v", err)
+		return
+	}
+	if done {
+		return
+	}
+
+	blobs := diskstorage.NewLocalDiskBlobReader(pool)
+
+	// Bounded: a mailbox with a million read messages should not turn a deploy
+	// into an hour of disk reads. What is left is picked up on the next start,
+	// because the marker is only written once a pass changes nothing.
+	const batch = 5000
+	candidates, err := repo.Candidates(ctx, batch)
+	if err != nil {
+		log.Printf("attachment backfill: cannot list candidates: %v", err)
+		return
+	}
+
+	corrected := 0
+	for _, c := range candidates {
+		payload, err := blobs.ReadByID(ctx, c.BlobID)
+		if err != nil {
+			// A blob that cannot be read is not a reason to stop; the flag
+			// stays as it was and the message is untouched.
+			continue
+		}
+		if !usecase.ExtractMessageHeaders(payload).HasAttachments {
+			continue
+		}
+		if err := repo.SetHasAttachments(ctx, c.ID); err != nil {
+			log.Printf("attachment backfill: %v", err)
+			continue
+		}
+		corrected++
+	}
+
+	if len(candidates) < batch {
+		// The whole set fit in one pass, so there is nothing left to do.
+		if err := repo.MarkDone(ctx, attachmentBackfillName,
+			"corrected single-part attachments"); err != nil {
+			log.Printf("attachment backfill: %v", err)
+		}
+	}
+	log.Printf("attachment backfill: examined %d message(s), corrected %d", len(candidates), corrected)
+}

services/protocols/cmd/lambdamail-protocols/main.go

@@ -248,6 +248,11 @@ func run(cfg config) {
 	}
 	router.SetAdminTlsAPI(tlsStatus, cfg.PrimaryMailHost, cfg.TLSMode, cfg.JwtSecret, cfg.CertPollInterval)
 
+	// One-shot repair of has_attachments on messages stored before single-part
+	// attachments were recognised. In the background: it is display metadata,
+	// and nothing waits on it.
+	go backfillAttachmentFlags(ctx, pool)
+
 	// Real-time updates: the outbox relay reads the events delivery wrote in
 	// its own transaction and hands them to the hub, which pushes them to the
 	// browser (PLAN.md sections 9.4 and 14.2).

services/protocols/internal/application/usecase/message_headers.go

@@ -69,18 +69,53 @@ func ExtractMessageHeaders(payload []byte) MessageHeaders {
 	}
 
 	contentType := msg.Header.Get("Content-Type")
-	mediaType, params, err := mime.ParseMediaType(contentType)
-	if err == nil && strings.HasPrefix(mediaType, "multipart/") {
-		// mixed and related carry parts that are not the body; alternative is
-		// just the same text twice, so it does not count as an attachment.
-		out.HasAttachments = mediaType != "multipart/alternative"
-		_ = params
+	mediaType, _, err := mime.ParseMediaType(contentType)
+	if err != nil {
+		mediaType = ""
 	}
+	out.HasAttachments = carriesAttachment(mediaType, msg.Header.Get("Content-Disposition"))
 
 	out.Snippet = buildSnippet(msg, mediaType)
 	return out
 }
 
+// carriesAttachment decides whether a message has something worth a paperclip,
+// from its top-level headers alone.
+//
+// Looking only for multipart/* missed the case where the body IS the
+// attachment: a DMARC aggregate report from Google arrives as a single-part
+// application/zip with no text part at all, so it showed up unmarked next to
+// TLS-RPT reports - which do carry a text part, and so are multipart/mixed -
+// from the same sender in the same folder.
+func carriesAttachment(mediaType, disposition string) bool {
+	// An explicit disposition is the author saying so, and it settles the
+	// question even for a text type: a .txt sent as the whole message is an
+	// attachment, an inline part is not.
+	if disp, _, err := mime.ParseMediaType(disposition); err == nil {
+		switch strings.ToLower(disp) {
+		case "attachment":
+			return true
+		case "inline":
+			return false
+		}
+	}
+
+	switch {
+	case strings.HasPrefix(mediaType, "multipart/"):
+		// mixed and related carry parts that are not the body; alternative is
+		// just the same text twice.
+		return mediaType != "multipart/alternative"
+	case mediaType == "":
+		// No Content-Type means text/plain (RFC 2045 section 5.2). An
+		// unparseable one is treated the same way rather than guessed at.
+		return false
+	default:
+		// Anything that is not text and not multipart is a single part that is
+		// not the body: a zip, a PDF, a forwarded message.
+		return !strings.HasPrefix(mediaType, "text/")
+	}
+}
+
 // buildSnippet takes the opening of the body as a plain-text preview.
 func buildSnippet(msg *mail.Message, mediaType string) string {
 	// Only a flat text body is previewed. Walking MIME parts here would mean

services/protocols/internal/application/usecase/message_headers_test.go

@@ -86,3 +86,59 @@ func TestExtractMessageHeaders_TruncatesWithoutBreakingUTF8(t *testing.T) {
 		}
 	}
 }
+
+// A DMARC aggregate report from Google is a single-part message whose body IS
+// the attachment: Content-Type application/zip, no text part at all. The flag
+// was only ever set for multipart/*, so these arrived without the paperclip
+// while TLS-RPT reports - which do carry a text part, so multipart/mixed - got
+// one. Same folder, same sender, one marked and one not.
+func TestExtractMessageHeaders_SinglePartAttachmentCounts(t *testing.T) {
+	msg := "From: <noreply-dmarc-support@google.com>\r\n" +
+		"To: <dmarc@example.test>\r\n" +
+		"Subject: Report domain: example.test\r\n" +
+		"Content-Type: application/zip; name=\"google.com!example.test!1.zip\"\r\n" +
+		"Content-Disposition: attachment; filename=\"google.com!example.test!1.zip\"\r\n" +
+		"Content-Transfer-Encoding: base64\r\n" +
+		"\r\n" +
+		"UEsDBBQAAAAIAA==\r\n"
+
+	h := ExtractMessageHeaders([]byte(msg))
+
+	if !h.HasAttachments {
+		t.Error("a message whose whole body is a zip was reported as having no attachments")
+	}
+}
+
+func TestExtractMessageHeaders_AttachmentDetection(t *testing.T) {
+	cases := []struct {
+		name    string
+		headers string
+		want    bool
+	}{
+		{"plain text", "Content-Type: text/plain; charset=utf-8\r\n", false},
+		{"html only", "Content-Type: text/html; charset=utf-8\r\n", false},
+		// The same text twice is not an attachment.
+		{"alternative", "Content-Type: multipart/alternative; boundary=b\r\n", false},
+		{"mixed", "Content-Type: multipart/mixed; boundary=b\r\n", true},
+		{"related", "Content-Type: multipart/related; boundary=b\r\n", true},
+		{"bare zip", "Content-Type: application/zip\r\n", true},
+		{"bare pdf", "Content-Type: application/pdf\r\n", true},
+		// A forwarded message carried as the whole body.
+		{"attached message", "Content-Type: message/rfc822\r\n", true},
+		// An explicit disposition wins even over a text type: someone sent a
+		// .txt file as the entire message.
+		{"text as attachment", "Content-Type: text/plain\r\nContent-Disposition: attachment; filename=\"notes.txt\"\r\n", true},
+		{"inline text", "Content-Type: text/plain\r\nContent-Disposition: inline\r\n", false},
+		// No Content-Type at all means text/plain (RFC 2045 section 5.2).
+		{"absent content type", "", false},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			msg := "From: <a@b.test>\r\nSubject: x\r\n" + tc.headers + "\r\nbody\r\n"
+			if got := ExtractMessageHeaders([]byte(msg)).HasAttachments; got != tc.want {
+				t.Errorf("HasAttachments = %v, want %v", got, tc.want)
+			}
+		})
+	}
+}

services/protocols/internal/infrastructure/postgres/attachment_backfill.go

@@ -0,0 +1,87 @@
+package postgres
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// AttachmentBackfill repairs has_attachments on messages already stored.
+//
+// The flag was only ever set for multipart messages, so a single-part
+// attachment - a DMARC aggregate report, whose entire body is a zip - was
+// filed as having none, and showed up without a paperclip beside TLS-RPT
+// reports from the same sender that happened to carry a text part.
+type AttachmentBackfill struct {
+	pool *pgxpool.Pool
+}
+
+func NewAttachmentBackfill(pool *pgxpool.Pool) *AttachmentBackfill {
+	return &AttachmentBackfill{pool: pool}
+}
+
+// Done reports whether this repair has already run.
+func (b *AttachmentBackfill) Done(ctx context.Context, name string) (bool, error) {
+	var exists bool
+	err := b.pool.QueryRow(ctx,
+		`SELECT EXISTS (SELECT 1 FROM backfills WHERE name = $1)`, name).Scan(&exists)
+	if err != nil {
+		return false, fmt.Errorf("read backfill marker %s: %w", name, err)
+	}
+	return exists, nil
+}
+
+func (b *AttachmentBackfill) MarkDone(ctx context.Context, name, detail string) error {
+	_, err := b.pool.Exec(ctx,
+		`INSERT INTO backfills (name, detail) VALUES ($1, $2) ON CONFLICT (name) DO NOTHING`,
+		name, detail)
+	if err != nil {
+		return fmt.Errorf("record backfill marker %s: %w", name, err)
+	}
+	return nil
+}
+
+// Candidate is one message worth re-reading.
+type Candidate struct {
+	ID     uuid.UUID
+	BlobID uuid.UUID
+}
+
+// Candidates lists messages currently flagged as having no attachment.
+//
+// Only those: the old rule never claimed an attachment that was not there, so
+// a true flag needs no second opinion and the scan stays as small as the bug.
+func (b *AttachmentBackfill) Candidates(ctx context.Context, limit int) ([]Candidate, error) {
+	rows, err := b.pool.Query(ctx, `
+		SELECT id, blob_id FROM email_messages
+		 WHERE has_attachments = false AND expunged_at IS NULL
+		 ORDER BY received_at DESC
+		 LIMIT $1
+	`, limit)
+	if err != nil {
+		return nil, fmt.Errorf("list attachment backfill candidates: %w", err)
+	}
+	defer rows.Close()
+
+	out := []Candidate{}
+	for rows.Next() {
+		var c Candidate
+		if err := rows.Scan(&c.ID, &c.BlobID); err != nil {
+			return nil, err
+		}
+		out = append(out, c)
+	}
+	return out, rows.Err()
+}
+
+// SetHasAttachments records the recomputed flag.
+func (b *AttachmentBackfill) SetHasAttachments(ctx context.Context, messageID uuid.UUID) error {
+	_, err := b.pool.Exec(ctx,
+		`UPDATE email_messages SET has_attachments = true WHERE id = $1`, messageID)
+	if err != nil {
+		return fmt.Errorf("set has_attachments for %s: %w", messageID, err)
+	}
+	return nil
+}