private ASN1Sequence getAltnameSequence(final byte[] sanValue) {
        try (val bInput = new ByteArrayInputStream(sanValue);
             val input = new ASN1InputStream(bInput)) {
            return ASN1Sequence.getInstance(input.readObject());
        } catch (final IOException e) {
            LoggingUtils.error(LOGGER, e);
        }
        return null;
    }
Get alt name seq.

@param sanValue subject alternative name value encoded as byte[]
@return ASN1Sequence abstraction representing subject alternative name
@see <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/security/cert/X509Certificate.html#getSubjectAlternativeNames()">
X509Certificate#getSubjectAlternativeNames</a>
support/cas-server-support-x509-core/src/main/java/org/apereo/cas/adaptors/x509/authentication/principal/X509UPNExtractorUtils.java