switch action {
			case clientGrants:
				writeSTSErrorResponse(ctx, w, ErrSTSClientGrantsExpiredToken, err)
			case webIdentity:
				writeSTSErrorResponse(ctx, w, ErrSTSWebIdentityExpiredToken, err)
			}
			return
		case auth.ErrInvalidDuration:
			writeSTSErrorResponse(ctx, w, ErrSTSInvalidParameterValue, err)
			return
		}
		writeSTSErrorResponse(ctx, w, ErrSTSInvalidParameterValue, err)
		return
	}