Add security utilities to zero out secrets

Author: anhthii

cmd/mpcium/main.go

@@ -314,8 +314,6 @@ func loadPasswordFromFile(filePath string) error {
 	}
 
 	viper.Set("badger_password", password)
-	logger.Info(fmt.Sprintf("Loaded BadgerDB password from file: %s", filePath), "password", password)
-
 	security.ZeroBytes(passwordBytes)
 	security.ZeroString(&password)
 

examples/generate/kms/main.go

@@ -30,7 +30,7 @@ func main() {
 
 	flag.Parse()
 
-	config.InitViperConfig()
+	config.InitViperConfig("")
 	logger.Init(environment, false)
 
 	// KMS signer only supports P256

pkg/security/memory.go

@@ -0,0 +1,86 @@
+package security
+
+import (
+	"runtime"
+)
+
+// ZeroBytes securely zeros out a byte slice to prevent sensitive data from
+// remaining in memory. This uses explicit memory zeroing and garbage collection
+// to help ensure the data is actually cleared.
+func ZeroBytes(data []byte) {
+	if len(data) == 0 {
+		return
+	}
+	
+	// Zero out the slice
+	for i := range data {
+		data[i] = 0
+	}
+	
+	// Force garbage collection to help ensure the zeroed memory is reclaimed
+	runtime.GC()
+}
+
+// ZeroString securely clears a string reference and encourages garbage collection.
+// Note: Go strings are immutable, so we can only clear the reference and rely on GC.
+// This provides best-effort security by clearing the reference and forcing GC.
+func ZeroString(s *string) {
+	if s == nil {
+		return
+	}
+	
+	// Clear the string reference - this is the safe approach
+	// The actual string data will be garbage collected
+	*s = ""
+	
+	// Force garbage collection to help clear the original string data from memory
+	// This is best-effort as GC timing is not guaranteed
+	runtime.GC()
+	runtime.GC() // Run twice to increase chances of collection
+}
+
+// SecureBytes is a wrapper for sensitive byte data that automatically
+// zeros itself when no longer needed
+type SecureBytes struct {
+	data []byte
+}
+
+// NewSecureBytes creates a new SecureBytes instance
+func NewSecureBytes(data []byte) *SecureBytes {
+	// Make a copy to ensure we own the memory
+	copied := make([]byte, len(data))
+	copy(copied, data)
+	
+	sb := &SecureBytes{data: copied}
+	
+	// Set finalizer to zero memory when GC'd
+	runtime.SetFinalizer(sb, (*SecureBytes).zero)
+	
+	return sb
+}
+
+// Bytes returns the underlying byte slice (use with caution)
+func (sb *SecureBytes) Bytes() []byte {
+	return sb.data
+}
+
+// Copy returns a copy of the data
+func (sb *SecureBytes) Copy() []byte {
+	result := make([]byte, len(sb.data))
+	copy(result, sb.data)
+	return result
+}
+
+// Clear explicitly zeros the data and removes the finalizer
+func (sb *SecureBytes) Clear() {
+	sb.zero()
+	runtime.SetFinalizer(sb, nil)
+}
+
+// zero securely clears the data
+func (sb *SecureBytes) zero() {
+	if sb.data != nil {
+		ZeroBytes(sb.data)
+		sb.data = nil
+	}
+}

pkg/security/memory_test.go

@@ -0,0 +1,249 @@
+package security
+
+import (
+	"bytes"
+	"runtime"
+	"testing"
+)
+
+func TestZeroBytes(t *testing.T) {
+	tests := []struct {
+		name string
+		data []byte
+	}{
+		{
+			name: "non-empty slice",
+			data: []byte("sensitive data"),
+		},
+		{
+			name: "empty slice",
+			data: []byte{},
+		},
+		{
+			name: "nil slice",
+			data: nil,
+		},
+		{
+			name: "single byte",
+			data: []byte{0x42},
+		},
+		{
+			name: "binary data",
+			data: []byte{0x01, 0x02, 0x03, 0xff, 0xfe, 0xfd},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			original := make([]byte, len(tt.data))
+			copy(original, tt.data)
+			
+			ZeroBytes(tt.data)
+			
+			// Verify all bytes are zeroed
+			for i, b := range tt.data {
+				if b != 0 {
+					t.Errorf("byte at index %d not zeroed: got %d, want 0", i, b)
+				}
+			}
+			
+			// Verify we didn't panic on edge cases
+			if len(tt.data) == 0 {
+				// Should handle empty/nil slices gracefully
+				return
+			}
+			
+			// Verify the slice was actually modified
+			if bytes.Equal(tt.data, original) && len(original) > 0 {
+				t.Error("slice was not modified")
+			}
+		})
+	}
+}
+
+func TestZeroString(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected string
+	}{
+		{
+			name:     "non-empty string",
+			input:    "sensitive password",
+			expected: "",
+		},
+		{
+			name:     "empty string",
+			input:    "",
+			expected: "",
+		},
+		{
+			name:     "single character",
+			input:    "x",
+			expected: "",
+		},
+		{
+			name:     "unicode string",
+			input:    "🔐password🔑",
+			expected: "",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			s := tt.input
+			
+			ZeroString(&s)
+			
+			// Verify string is now empty
+			if s != tt.expected {
+				t.Errorf("string not cleared: got %q, want %q", s, tt.expected)
+			}
+			
+			// Note: We can't reliably test if the underlying memory was zeroed
+			// because Go strings are immutable and memory clearing depends on GC timing
+		})
+	}
+}
+
+func TestZeroStringNilPointer(t *testing.T) {
+	// Test that ZeroString handles nil pointer gracefully
+	defer func() {
+		if r := recover(); r != nil {
+			t.Errorf("ZeroString panicked with nil pointer: %v", r)
+		}
+	}()
+	
+	ZeroString(nil)
+}
+
+func TestSecureBytes(t *testing.T) {
+	t.Run("basic functionality", func(t *testing.T) {
+		original := []byte("secret data")
+		sb := NewSecureBytes(original)
+		
+		// Verify data is accessible
+		data := sb.Bytes()
+		if !bytes.Equal(data, original) {
+			t.Errorf("SecureBytes data mismatch: got %v, want %v", data, original)
+		}
+		
+		// Verify copy works
+		copied := sb.Copy()
+		if !bytes.Equal(copied, original) {
+			t.Errorf("SecureBytes copy mismatch: got %v, want %v", copied, original)
+		}
+		
+		// Verify modifying copy doesn't affect original
+		copied[0] = 'X'
+		if bytes.Equal(sb.Bytes(), copied) {
+			t.Error("SecureBytes copy shares memory with original")
+		}
+	})
+	
+	t.Run("manual clear", func(t *testing.T) {
+		sb := NewSecureBytes([]byte("secret"))
+		sb.Clear()
+		
+		// After Clear(), data should be nil
+		if sb.data != nil {
+			t.Error("SecureBytes data not nil after Clear()")
+		}
+		
+		// Calling Clear() again should not panic
+		sb.Clear()
+	})
+	
+	t.Run("finalizer behavior", func(t *testing.T) {
+		// This test verifies that the finalizer doesn't panic
+		// We can't easily test that it actually zeros memory due to GC timing
+		func() {
+			sb := NewSecureBytes([]byte("secret"))
+			_ = sb // Use the variable to prevent optimization
+		}()
+		
+		// Force garbage collection to potentially trigger finalizer
+		runtime.GC()
+		runtime.GC()
+		
+		// If we reach here without panic, the finalizer worked correctly
+	})
+	
+	t.Run("empty data", func(t *testing.T) {
+		sb := NewSecureBytes([]byte{})
+		
+		if len(sb.Bytes()) != 0 {
+			t.Error("SecureBytes should handle empty data")
+		}
+		
+		sb.Clear()
+		// Should not panic
+	})
+	
+	t.Run("nil data", func(t *testing.T) {
+		sb := NewSecureBytes(nil)
+		
+		if sb.Bytes() == nil {
+			t.Error("SecureBytes should create empty slice for nil input")
+		}
+		
+		if len(sb.Bytes()) != 0 {
+			t.Error("SecureBytes should create empty slice for nil input")
+		}
+	})
+}
+
+func TestSecureBytesIsolation(t *testing.T) {
+	// Verify that SecureBytes creates its own copy of data
+	original := []byte("secret data")
+	sb := NewSecureBytes(original)
+	
+	// Modify the original
+	original[0] = 'X'
+	
+	// SecureBytes should be unaffected
+	if sb.Bytes()[0] == 'X' {
+		t.Error("SecureBytes shares memory with input data")
+	}
+}
+
+// Benchmark tests to ensure performance is reasonable
+func BenchmarkZeroBytes(b *testing.B) {
+	data := make([]byte, 1024)
+	for i := range data {
+		data[i] = byte(i % 256)
+	}
+	
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		// Reset data for each iteration
+		for j := range data {
+			data[j] = byte(j % 256)
+		}
+		ZeroBytes(data)
+	}
+}
+
+func BenchmarkZeroString(b *testing.B) {
+	original := "this is a test string that represents a password or other sensitive data"
+	
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		s := original
+		ZeroString(&s)
+	}
+}
+
+func BenchmarkSecureBytes(b *testing.B) {
+	data := make([]byte, 256)
+	for i := range data {
+		data[i] = byte(i)
+	}
+	
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		sb := NewSecureBytes(data)
+		_ = sb.Copy()
+		sb.Clear()
+	}
+}