added IMAP, LetsEncrypt, update layout

internal/mailstore/store.go

@@ -0,0 +1,109 @@
+package mailstore
+
+import (
+	"crypto/rand"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"time"
+)
+
+// ErrQuotaExceeded is returned by StoreMessage when storing raw would push the
+// mailbox over its quota. No row, file, or used_bytes change occurs in that case.
+var ErrQuotaExceeded = errors.New("mailstore: mailbox quota exceeded")
+
+// StoreMessage encrypts raw with the mailbox's own data encryption key and persists
+// it to disk, then indexes it in esrv_mailbox_messages and updates the mailbox's
+// cached used_bytes. from/subject are cached in the DB in plain text by design (see
+// schema.go) so IMAP LIST/basic SEARCH don't need to decrypt every message.
+func (s *Store) StoreMessage(mailboxID int64, folder string, raw []byte, messageIDHeader, from, subject string) (uid int64, err error) {
+	mbox, err := s.DB.GetMailboxByID(mailboxID)
+	if err != nil {
+		return 0, err
+	}
+	if mbox == nil {
+		return 0, fmt.Errorf("mailstore: mailbox %d not found", mailboxID)
+	}
+	if mbox.UsedBytes+int64(len(raw)) > mbox.QuotaBytes {
+		return 0, ErrQuotaExceeded
+	}
+
+	dek, err := s.UnwrapDEK(mbox.DEKWrapped, mbox.DEKNonce)
+	if err != nil {
+		return 0, err
+	}
+	ciphertext, nonce, err := sealAESGCM(dek, raw)
+	if err != nil {
+		return 0, err
+	}
+
+	now := time.Now()
+	dir := filepath.Join(s.BasePath, sanitizePathSegment(mbox.Email), folder, now.Format("2006-02-Jan"))
+	if err := os.MkdirAll(dir, 0o755); err != nil {
+		return 0, err
+	}
+	name := make([]byte, 8)
+	rand.Read(name)
+	storagePath := filepath.Join(dir, hex.EncodeToString(name)+".eml.enc")
+	if err := os.WriteFile(storagePath, ciphertext, 0o600); err != nil {
+		return 0, err
+	}
+
+	uid, err = s.DB.InsertMessage(mailboxID, folder, messageIDHeader, "", now, int64(len(raw)), storagePath, nonce, from, subject)
+	if err != nil {
+		os.Remove(storagePath)
+		return 0, err
+	}
+	if err := s.DB.AddMailboxUsedBytes(mailboxID, int64(len(raw))); err != nil {
+		return 0, err
+	}
+	return uid, nil
+}
+
+// FetchMessage decrypts a stored message on demand. Plaintext is never written to disk
+// or cached — only returned to the caller.
+func (s *Store) FetchMessage(mailboxID, uid int64) ([]byte, error) {
+	msg, err := s.DB.GetMessageByUID(mailboxID, uid)
+	if err != nil {
+		return nil, err
+	}
+	if msg == nil {
+		return nil, fmt.Errorf("mailstore: message %d not found in mailbox %d", uid, mailboxID)
+	}
+	mbox, err := s.DB.GetMailboxByID(mailboxID)
+	if err != nil {
+		return nil, err
+	}
+	if mbox == nil {
+		return nil, fmt.Errorf("mailstore: mailbox %d not found", mailboxID)
+	}
+	dek, err := s.UnwrapDEK(mbox.DEKWrapped, mbox.DEKNonce)
+	if err != nil {
+		return nil, err
+	}
+	ciphertext, err := os.ReadFile(msg.StoragePath)
+	if err != nil {
+		return nil, err
+	}
+	return openAESGCM(dek, ciphertext, msg.Nonce)
+}
+
+// DeleteMessage removes the on-disk ciphertext, the index row, and frees the quota.
+func (s *Store) DeleteMessage(mailboxID, uid int64) error {
+	msg, err := s.DB.GetMessageByUID(mailboxID, uid)
+	if err != nil {
+		return err
+	}
+	if msg == nil {
+		return nil
+	}
+	if err := os.Remove(msg.StoragePath); err != nil && !os.IsNotExist(err) {
+		return err
+	}
+	if err := s.DB.DeleteMessage(mailboxID, uid); err != nil {
+		return err
+	}
+	return s.DB.AddMailboxUsedBytes(mailboxID, -msg.SizeBytes)
+}