store: host_credentials becomes kind-aware (repo + admin slots)

internal/store/host_credentials.go

@@ -8,13 +8,23 @@ import (
 	"time"
 )
 
+// CredentialKind identifies the role of a host_credentials row.
+type CredentialKind string
+
+const (
+	// CredKindRepo is the append-only credential used for every backup.
+	CredKindRepo CredentialKind = "repo"
+	// CredKindAdmin is the delete-capable credential used for prune.
+	CredKindAdmin CredentialKind = "admin"
+)
+
 // GetHostCredentials returns the AEAD-encrypted repo creds blob for
-// the host, or ("", ErrNotFound) if no credential has ever been set.
+// the host + kind, or ("", ErrNotFound) if no matching row exists.
 // The caller decrypts using host_id as AEAD additional data.
-func (s *Store) GetHostCredentials(ctx context.Context, hostID string) (string, error) {
+func (s *Store) GetHostCredentials(ctx context.Context, hostID string, kind CredentialKind) (string, error) {
 	row := s.db.QueryRowContext(ctx,
-		`SELECT enc_repo_creds FROM host_credentials WHERE host_id = ?`,
-		hostID)
+		`SELECT enc_repo_creds FROM host_credentials WHERE host_id = ? AND kind = ?`,
+		hostID, string(kind))
 	var enc string
 	if err := row.Scan(&enc); err != nil {
 		if errors.Is(err, sql.ErrNoRows) {
@@ -25,22 +35,35 @@ func (s *Store) GetHostCredentials(ctx context.Context, hostID string) (string,
 	return enc, nil
 }
 
-// SetHostCredentials replaces the host's encrypted repo creds blob.
-// The caller has already encrypted using host_id as additional data.
-func (s *Store) SetHostCredentials(ctx context.Context, hostID, encRepoCreds string) error {
+// SetHostCredentials replaces the host's encrypted repo creds blob for
+// the given kind. The caller has already encrypted using host_id as
+// additional data.
+func (s *Store) SetHostCredentials(ctx context.Context, hostID string, kind CredentialKind, encRepoCreds string) error {
 	if encRepoCreds == "" {
 		return fmt.Errorf("store: empty enc_repo_creds")
 	}
 	now := time.Now().UTC().Format(time.RFC3339Nano)
 	_, err := s.db.ExecContext(ctx,
-		`INSERT INTO host_credentials (host_id, enc_repo_creds, updated_at)
-		 VALUES (?, ?, ?)
-		 ON CONFLICT(host_id) DO UPDATE SET
+		`INSERT INTO host_credentials (host_id, kind, enc_repo_creds, updated_at)
+		 VALUES (?, ?, ?, ?)
+		 ON CONFLICT(host_id, kind) DO UPDATE SET
 			enc_repo_creds = excluded.enc_repo_creds,
 			updated_at     = excluded.updated_at`,
-		hostID, encRepoCreds, now)
+		hostID, string(kind), encRepoCreds, now)
 	if err != nil {
 		return fmt.Errorf("store: set host credentials: %w", err)
 	}
 	return nil
 }
+
+// DeleteHostCredentials removes the credential row for the given host
+// and kind. A no-op if the row does not exist.
+func (s *Store) DeleteHostCredentials(ctx context.Context, hostID string, kind CredentialKind) error {
+	_, err := s.db.ExecContext(ctx,
+		`DELETE FROM host_credentials WHERE host_id = ? AND kind = ?`,
+		hostID, string(kind))
+	if err != nil {
+		return fmt.Errorf("store: delete host credentials: %w", err)
+	}
+	return nil
+}