DateKeys/codec/internal_test.go

package codec

import (
	"bytes"
	"testing"
)

// The Encoder wipes every buffer it outgrows: an encoding that holds a
// secret leaves no stale copy behind.
func TestEncoderWipesOutgrownBuffers(t *testing.T) {
	secret := bytes.Repeat([]byte{0xab}, 32)
	var e Encoder
	e.Bstr(secret)
	old := e.buf[:cap(e.buf)]
	e.Bstr(make([]byte, 2*cap(e.buf)))
	if bytes.Contains(old, secret[:8]) {
		t.Fatalf("outgrown buffer not wiped: %x", old)
	}
	b, err := e.Out()
	if err != nil || !bytes.Contains(b, secret) {
		t.Fatalf("output lost the data: %v", err)
	}
	// A buffer with room is not replaced.
	e = Encoder{buf: make([]byte, 0, 64)}
	e.Text("fits")
	if cap(e.buf) != 64 {
		t.Fatal("buffer replaced although it had room")
	}
}