raise bcrypt cost factor lower bound to x/crypto/bcrypt default

Signed-off-by: Adam Shannon <[email protected]>

hash_bcrypt.go

@@ -34,6 +34,9 @@ type BCrypt struct {
 }
 
 func (b *BCrypt) Hash(ctx context.Context, data []byte) ([]byte, error) {
+	if b.WorkFactor == 0 {
+		b.WorkFactor = bcrypt.DefaultCost
+	}
 	s, err := bcrypt.GenerateFromPassword(data, b.WorkFactor)
 	if err != nil {
 		return nil, errors.WithStack(err)

hash_bcrypt_test.go

@@ -26,6 +26,7 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"golang.org/x/crypto/bcrypt"
 )
 
 func TestCompare(t *testing.T) {
@@ -110,3 +111,17 @@ func TestHash(t *testing.T) {
 		})
 	}
 }
+
+func TestDefaultWorkFactor(t *testing.T) {
+	b := &BCrypt{}
+	data := []byte("secrets")
+	hash, err := b.Hash(context.TODO(), data)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cost, err := bcrypt.Cost(hash)
+	if cost != bcrypt.DefaultCost {
+		t.Errorf("got cost factor %d", cost)
+	}
+}