私はこれに対する解決策を見つけましたが、最もクリーンではありませんが、機能します:
XMLSignature signature = new XMLSignature(sigElement,
null);
KeyInfo keyInfo = signature.getKeyInfo();
NodeList x509Certificates = keyInfo.getElement().getElementsByTagNameNS("http://www.w3.org/2000/09/xmldsig#", "X509Certificate");
ArrayList<X509Certificate> allCertificates = new ArrayList<X509Certificate>();
for (int i = 0; i < x509Certificates.getLength(); i++) {
Node x509CertificateElement = x509Certificates.item(i);
byte[] decodedX509Certificate = Base64.decode(x509CertificateElement.getTextContent());
X509Certificate x509Certificate = (X509Certificate) CertificateFactory.getInstance("X509").generateCertificate(new ByteArrayInputStream(decodedX509Certificate));
allCertificates.add(x509Certificate);
}
// now you have all certificates in allCertificates