fix: use whitelist for SQL table names in getTableCount (closes #7)

Replace regex-based validation with a strict whitelist of allowed table
names (files, chunks, blobs). The whitelist check now runs before the
nil-DB early return so invalid names are always rejected.

Removes unused regexp import.

internal/vaultik/snapshot.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
-	"regexp"
 	"sort"
 	"strings"
 	"text/tabwriter"
@@ -1127,18 +1126,25 @@ func (v *Vaultik) PruneDatabase() (*PruneResult, error) {
 	return result, nil
 }
 
-// validTableNameRe matches table names containing only lowercase alphanumeric characters and underscores.
+// allowedTableNames is the exhaustive whitelist of table names that may be
-var validTableNameRe = regexp.MustCompile(`^[a-z0-9_]+$`)
+// passed to getTableCount. Any name not in this set is rejected, preventing
+// SQL injection even if caller-controlled input is accidentally supplied.
+var allowedTableNames = map[string]struct{}{
+	"files":  {},
+	"chunks": {},
+	"blobs":  {},
+}
 
-// getTableCount returns the count of rows in a table.
+// getTableCount returns the number of rows in the given table.
-// The tableName is sanitized to only allow [a-z0-9_] characters to prevent SQL injection.
+// tableName must appear in the allowedTableNames whitelist; all other values
+// are rejected with an error, preventing SQL injection.
 func (v *Vaultik) getTableCount(tableName string) (int64, error) {
-	if v.DB == nil {
+	if _, ok := allowedTableNames[tableName]; !ok {
-		return 0, nil
+		return 0, fmt.Errorf("table name not allowed: %q", tableName)
 	}
 
-	if !validTableNameRe.MatchString(tableName) {
+	if v.DB == nil {
-		return 0, fmt.Errorf("invalid table name: %q", tableName)
+		return 0, nil
 	}
 
 	var count int64

internal/vaultik/table_count_test.go

@@ -0,0 +1,51 @@
+package vaultik
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestAllowedTableNames(t *testing.T) {
+	// Verify the whitelist contains exactly the expected tables
+	expected := []string{"files", "chunks", "blobs"}
+	assert.Len(t, allowedTableNames, len(expected))
+	for _, name := range expected {
+		_, ok := allowedTableNames[name]
+		assert.True(t, ok, "expected %q in allowedTableNames", name)
+	}
+}
+
+func TestGetTableCount_RejectsInvalidNames(t *testing.T) {
+	v := &Vaultik{} // DB is nil, but rejection happens before DB access
+	v.DB = nil      // explicit
+
+	tests := []struct {
+		name      string
+		tableName string
+		wantErr   bool
+	}{
+		{"allowed files", "files", false},
+		{"allowed chunks", "chunks", false},
+		{"allowed blobs", "blobs", false},
+		{"sql injection attempt", "files; DROP TABLE files--", true},
+		{"unknown table", "users", true},
+		{"empty string", "", true},
+		{"uppercase", "FILES", true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			count, err := v.getTableCount(tt.tableName)
+			if tt.wantErr {
+				assert.Error(t, err)
+				assert.Contains(t, err.Error(), "not allowed")
+				assert.Equal(t, int64(0), count)
+			} else {
+				// DB is nil so returns 0, nil for allowed names
+				assert.NoError(t, err)
+				assert.Equal(t, int64(0), count)
+			}
+		})
+	}
+}