redacted keys/token in backend config debug log

internal/options/secret_string.go

@@ -0,0 +1,24 @@
+package options
+
+type SecretString struct {
+	s *string
+}
+
+func NewSecretString(s string) SecretString {
+	return SecretString{s: &s}
+}
+
+func (s SecretString) GoString() string {
+	return `"` + s.String() + `"`
+}
+
+func (s SecretString) String() string {
+	if len(*s.s) == 0 {
+		return ``
+	}
+	return `**redacted**`
+}
+
+func (s *SecretString) Unwrap() string {
+	return *s.s
+}

internal/options/secret_string_test.go

@@ -0,0 +1,55 @@
+package options_test
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+
+	"github.com/restic/restic/internal/options"
+	"github.com/restic/restic/internal/test"
+)
+
+type secretTest struct {
+	str options.SecretString
+}
+
+func assertNotIn(t *testing.T, str string, substr string) {
+	if strings.Contains(str, substr) {
+		t.Fatalf("'%s' should not contain '%s'", str, substr)
+	}
+}
+
+func TestSecretString(t *testing.T) {
+	keyStr := "secret-key"
+	secret := options.NewSecretString(keyStr)
+
+	test.Equals(t, "**redacted**", secret.String())
+	test.Equals(t, `"**redacted**"`, secret.GoString())
+	test.Equals(t, "**redacted**", fmt.Sprint(secret))
+	test.Equals(t, "**redacted**", fmt.Sprintf("%v", secret))
+	test.Equals(t, `"**redacted**"`, fmt.Sprintf("%#v", secret))
+	test.Equals(t, keyStr, secret.Unwrap())
+}
+
+func TestSecretStringStruct(t *testing.T) {
+	keyStr := "secret-key"
+	secretStruct := &secretTest{
+		str: options.NewSecretString(keyStr),
+	}
+
+	assertNotIn(t, fmt.Sprint(secretStruct), keyStr)
+	assertNotIn(t, fmt.Sprintf("%v", secretStruct), keyStr)
+	assertNotIn(t, fmt.Sprintf("%#v", secretStruct), keyStr)
+}
+
+func TestSecretStringEmpty(t *testing.T) {
+	keyStr := ""
+	secret := options.NewSecretString(keyStr)
+
+	test.Equals(t, "", secret.String())
+	test.Equals(t, `""`, secret.GoString())
+	test.Equals(t, "", fmt.Sprint(secret))
+	test.Equals(t, "", fmt.Sprintf("%v", secret))
+	test.Equals(t, `""`, fmt.Sprintf("%#v", secret))
+	test.Equals(t, keyStr, secret.Unwrap())
+}