private boolean isSniEnabledByDefault() {
        try {
            String enableSNI = System.getProperty("jsse.enableSNIExtension", "true");
            if ("true".equalsIgnoreCase(enableSNI)) {
                return true;
            } else if ("false".equalsIgnoreCase(enableSNI)) {
                return false;
            } else {
                throw new RuntimeException(
                        "Can only set \"jsse.enableSNIExtension\" to \"true\" or \"false\"");
            }
        } catch (SecurityException e) {
            return true;
        }
    }
Returns X.509 key manager or null for none.
common/src/main/java/org/conscrypt/SSLParametersImpl.java