xmlsecurity: improve handling of multiple X509Data elements

Combine everything related to a certificate in a new struct X509Data.

The CertDigest is not actually written in the X509Data element but in
xades:Cert, so try to find the matching entry in
XSecController::setX509CertDigest().

There was a confusing interaction with PGP signatures, where ouGpgKeyID
was used for import, but export wrote the value from ouCertDigest
instead - this needed fixing.

The main point of this is enforcing a constraint from xmldsig-core 4.5.4:

  All certificates appearing in an X509Data element MUST relate to the
  validation key by either containing it or being part of a certification
  chain that terminates in a certificate containing the validation key.

Change-Id: I5254aa393f8e7172da59709923e4bbcd625ec713
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/111254
Tested-by: Jenkins
Reviewed-by: Michael Stahl <michael.stahl@allotropia.de>

16 files changed, 460 insertions, 195 deletions

diff --git a/xmlsecurity/inc/xmlsignaturehelper.hxx b/xmlsecurity/inc/xmlsignaturehelper.hxx
index ae0b10c9d239..de7de9908205 100644
--- a/xmlsecurity/inc/xmlsignaturehelper.hxx
+++ b/xmlsecurity/inc/xmlsignaturehelper.hxx
@@ -27,6 +27,9 @@
 #include "xmlsignaturehelper.hxx"
 #include "xsecctl.hxx"
 
+#include <com/sun/star/security/XCertificate.hpp>
+#include <com/sun/star/xml/crypto/XSecurityEnvironment.hpp>
+
 class DateTime;
 class UriBindingHelper;
 
@@ -90,6 +93,15 @@ public:
                 // After signing/verifying, get information about signatures
     SignatureInformation  GetSignatureInformation( sal_Int32 nSecurityId ) const;
     SignatureInformations GetSignatureInformations() const;
+    /// ImplVerifySignature calls this to figure out which X509Data is the
+    /// signing certificate and update the internal state with the result.
+    /// @return
+    ///    A sequence with the signing certificate at the back on success.
+    ///    An empty sequence on failure.
+    std::vector<css::uno::Reference<css::security::XCertificate>>
+    CheckAndUpdateSignatureInformation(
+        css::uno::Reference<css::xml::crypto::XSecurityEnvironment> const& xSecEnv,
+        SignatureInformation const& rInfo);
 
                 // See XSecController for documentation
     void        StartMission(const css::uno::Reference<css::xml::crypto::XXMLSecurityContext>& xSecurityContext);
diff --git a/xmlsecurity/inc/xsecctl.hxx b/xmlsecurity/inc/xsecctl.hxx
index 4576af6ee635..698b1eb72c6f 100644
--- a/xmlsecurity/inc/xsecctl.hxx
+++ b/xmlsecurity/inc/xsecctl.hxx
@@ -262,9 +262,11 @@ private:
         sal_Int32 nDigestID );
     void setReferenceCount() const;
 
-    void setX509IssuerName( OUString const & ouX509IssuerName );
-    void setX509SerialNumber( OUString const & ouX509SerialNumber );
-    void setX509Certificate( OUString const & ouX509Certificate );
+    void setX509Data(SignatureInformation::X509Data const& rData);
+    void setX509CertDigest(
+        OUString const& rCertDigest, sal_Int32 const nReferenceDigestID,
+        std::u16string_view const& rX509IssuerName, std::u16string_view const& rX509SerialNumber);
+
     void setSignatureValue( OUString const & ouSignatureValue );
     void setDigestValue( sal_Int32 nDigestID, OUString const & ouDigestValue );
     void setGpgKeyID( OUString const & ouKeyID );
@@ -273,7 +275,6 @@ private:
 
     void setDate(OUString const& rId, OUString const& ouDate);
     void setDescription(OUString const& rId, OUString const& rDescription);
-    void setCertDigest(const OUString& rCertDigest);
     void setValidSignatureImage(const OUString& rValidSigImg);
     void setInvalidSignatureImage(const OUString& rInvalidSigImg);
     void setSignatureLineId(const OUString& rSignatureLineId);
@@ -302,6 +303,9 @@ public:
 
     SignatureInformation    getSignatureInformation( sal_Int32 nSecurityId ) const;
     SignatureInformations   getSignatureInformations() const;
+    /// only verify can figure out which X509Data is the signing certificate
+    void UpdateSignatureInformation(sal_Int32 nSecurityId,
+            std::vector<SignatureInformation::X509Data> const& rDatas);
 
     static void exportSignature(
         const css::uno::Reference< css::xml::sax::XDocumentHandler >& xDocumentHandler,
diff --git a/xmlsecurity/source/component/documentdigitalsignatures.cxx b/xmlsecurity/source/component/documentdigitalsignatures.cxx
index 10e099dbf432..f3b74de8f752 100644
--- a/xmlsecurity/source/component/documentdigitalsignatures.cxx
+++ b/xmlsecurity/source/component/documentdigitalsignatures.cxx
@@ -540,30 +540,36 @@ DocumentDigitalSignatures::ImplVerifySignatures(
         const SignatureInformation& rInfo = aSignInfos[n];
         css::security::DocumentSignatureInformation& rSigInfo = arInfos[n];
 
-        if (rInfo.ouGpgCertificate.isEmpty()) // X.509
+        if (!rInfo.X509Datas.empty()) // X.509
         {
-            if (!rInfo.ouX509Certificate.isEmpty())
-                rSigInfo.Signer = xSecEnv->createCertificateFromAscii(rInfo.ouX509Certificate);
-            if (!rSigInfo.Signer.is())
-                rSigInfo.Signer = xSecEnv->getCertificate(
-                    rInfo.ouX509IssuerName,
-                    xmlsecurity::numericStringToBigInteger(rInfo.ouX509SerialNumber));
-
-            // On Windows checking the certificate path is buggy. It does name matching (issuer, subject name)
-            // to find the parent certificate. It does not take into account that there can be several certificates
-            // with the same subject name.
-            try
+            std::vector<uno::Reference<XCertificate>> certs(
+                rSignatureHelper.CheckAndUpdateSignatureInformation(
+                    xSecEnv, rInfo));
+            if (certs.empty())
             {
-                rSigInfo.CertificateStatus = xSecEnv->verifyCertificate(
-                    rSigInfo.Signer, Sequence<Reference<css::security::XCertificate>>());
+                rSigInfo.CertificateStatus = css::security::CertificateValidity::INVALID;
             }
-            catch (SecurityException&)
+            else
             {
-                OSL_FAIL("Verification of certificate failed");
-                rSigInfo.CertificateStatus = css::security::CertificateValidity::INVALID;
+                rSigInfo.Signer = certs.back();
+                // get only intermediates
+                certs.pop_back();
+            // On Windows checking the certificate path is buggy. It does name matching (issuer, subject name)
+            // to find the parent certificate. It does not take into account that there can be several certificates
+            // with the same subject name.
+                try
+                {
+                    rSigInfo.CertificateStatus = xSecEnv->verifyCertificate(
+                        rSigInfo.Signer, comphelper::containerToSequence(certs));
+                }
+                catch (SecurityException&)
+                {
+                    SAL_WARN("xmlsecurity.comp", "Verification of certificate failed");
+                    rSigInfo.CertificateStatus = css::security::CertificateValidity::INVALID;
+                }
             }
         }
-        else if (xGpgSecEnv.is()) // GPG
+        else if (!rInfo.ouGpgCertificate.isEmpty() && xGpgSecEnv.is()) // GPG
         {
             // TODO not ideal to retrieve cert by keyID, might
             // collide, or PGPKeyID format might change - can't we
diff --git a/xmlsecurity/source/dialogs/digitalsignaturesdialog.cxx b/xmlsecurity/source/dialogs/digitalsignaturesdialog.cxx
index 1d373417fd27..c848c3ea5049 100644
--- a/xmlsecurity/source/dialogs/digitalsignaturesdialog.cxx
+++ b/xmlsecurity/source/dialogs/digitalsignaturesdialog.cxx
@@ -593,7 +593,7 @@ void DigitalSignaturesDialog::ImplFillSignaturesBox()
                 if (!rInfo.ouGpgCertificate.isEmpty())
                     aType = "OpenPGP";
                 // XML based: XAdES or not.
-                else if (!rInfo.ouCertDigest.isEmpty())
+                else if (!rInfo.X509Datas.empty() && !rInfo.X509Datas.back().CertDigest.isEmpty())
                     aType = "XAdES";
                 else
                     aType = "XML-DSig";
@@ -705,8 +705,8 @@ uno::Reference<security::XCertificate> DigitalSignaturesDialog::getCertificate(c
     uno::Reference<security::XCertificate> xCert;
 
     //First we try to get the certificate which is embedded in the XML Signature
-    if (xSecEnv.is() && !rInfo.ouX509Certificate.isEmpty())
-        xCert = xSecEnv->createCertificateFromAscii(rInfo.ouX509Certificate);
+    if (xSecEnv.is() && !rInfo.X509Datas.empty() && !rInfo.X509Datas.back().X509Certificate.isEmpty())
+        xCert = xSecEnv->createCertificateFromAscii(rInfo.X509Datas.back().X509Certificate);
     else {
         //There must be an embedded certificate because we use it to get the
         //issuer name. We cannot use /Signature/KeyInfo/X509Data/X509IssuerName
@@ -718,8 +718,11 @@ uno::Reference<security::XCertificate> DigitalSignaturesDialog::getCertificate(c
     }
 
     //In case there is no embedded certificate we try to get it from a local store
-    if (!xCert.is() && xSecEnv.is())
-        xCert = xSecEnv->getCertificate( rInfo.ouX509IssuerName, xmlsecurity::numericStringToBigInteger( rInfo.ouX509SerialNumber ) );
+    if (!xCert.is() && xSecEnv.is() && !rInfo.X509Datas.empty())
+    {
+        xCert = xSecEnv->getCertificate(rInfo.X509Datas.back().X509IssuerName,
+            xmlsecurity::numericStringToBigInteger(rInfo.X509Datas.back().X509SerialNumber));
+    }
     if (!xCert.is() && xGpgSecEnv.is())
         xCert = xGpgSecEnv->getCertificate( rInfo.ouGpgKeyID, xmlsecurity::numericStringToBigInteger(u"") );
 
diff --git a/xmlsecurity/source/helper/documentsignaturehelper.cxx b/xmlsecurity/source/helper/documentsignaturehelper.cxx
index 2784298acf8c..92331a41a7e6 100644
--- a/xmlsecurity/source/helper/documentsignaturehelper.cxx
+++ b/xmlsecurity/source/helper/documentsignaturehelper.cxx
@@ -498,6 +498,29 @@ void DocumentSignatureHelper::writeDigestMethod(
     xDocumentHandler->endElement("DigestMethod");
 }
 
+static void WriteXadesCert(
+    uno::Reference<xml::sax::XDocumentHandler> const& xDocumentHandler,
+    SignatureInformation::X509Data const& rData)
+{
+    xDocumentHandler->startElement("xd:Cert", uno::Reference<xml::sax::XAttributeList>(new SvXMLAttributeList()));
+    xDocumentHandler->startElement("xd:CertDigest", uno::Reference<xml::sax::XAttributeList>(new SvXMLAttributeList()));
+    DocumentSignatureHelper::writeDigestMethod(xDocumentHandler);
+    xDocumentHandler->startElement("DigestValue", uno::Reference<xml::sax::XAttributeList>(new SvXMLAttributeList()));
+    assert(!rData.CertDigest.isEmpty());
+    xDocumentHandler->characters(rData.CertDigest);
+    xDocumentHandler->endElement("DigestValue");
+    xDocumentHandler->endElement("xd:CertDigest");
+    xDocumentHandler->startElement("xd:IssuerSerial", uno::Reference<xml::sax::XAttributeList>(new SvXMLAttributeList()));
+    xDocumentHandler->startElement("X509IssuerName", uno::Reference<xml::sax::XAttributeList>(new SvXMLAttributeList()));
+    xDocumentHandler->characters(rData.X509IssuerName);
+    xDocumentHandler->endElement("X509IssuerName");
+    xDocumentHandler->startElement("X509SerialNumber", uno::Reference<xml::sax::XAttributeList>(new SvXMLAttributeList()));
+    xDocumentHandler->characters(rData.X509SerialNumber);
+    xDocumentHandler->endElement("X509SerialNumber");
+    xDocumentHandler->endElement("xd:IssuerSerial");
+    xDocumentHandler->endElement("xd:Cert");
+}
+
 void DocumentSignatureHelper::writeSignedProperties(
     const uno::Reference<xml::sax::XDocumentHandler>& xDocumentHandler,
     const SignatureInformation& signatureInfo,
@@ -514,26 +537,21 @@ void DocumentSignatureHelper::writeSignedProperties(
     xDocumentHandler->characters(sDate);
     xDocumentHandler->endElement("xd:SigningTime");
     xDocumentHandler->startElement("xd:SigningCertificate", uno::Reference<xml::sax::XAttributeList>(new SvXMLAttributeList()));
-    xDocumentHandler->startElement("xd:Cert", uno::Reference<xml::sax::XAttributeList>(new SvXMLAttributeList()));
-    xDocumentHandler->startElement("xd:CertDigest", uno::Reference<xml::sax::XAttributeList>(new SvXMLAttributeList()));
-    writeDigestMethod(xDocumentHandler);
-
-    xDocumentHandler->startElement("DigestValue", uno::Reference<xml::sax::XAttributeList>(new SvXMLAttributeList()));
-    // TODO: this is empty for gpg signatures currently
-    //assert(!signatureInfo.ouCertDigest.isEmpty());
-    xDocumentHandler->characters(signatureInfo.ouCertDigest);
-    xDocumentHandler->endElement("DigestValue");
-
-    xDocumentHandler->endElement("xd:CertDigest");
-    xDocumentHandler->startElement("xd:IssuerSerial", uno::Reference<xml::sax::XAttributeList>(new SvXMLAttributeList()));
-    xDocumentHandler->startElement("X509IssuerName", uno::Reference<xml::sax::XAttributeList>(new SvXMLAttributeList()));
-    xDocumentHandler->characters(signatureInfo.ouX509IssuerName);
-    xDocumentHandler->endElement("X509IssuerName");
-    xDocumentHandler->startElement("X509SerialNumber", uno::Reference<xml::sax::XAttributeList>(new SvXMLAttributeList()));
-    xDocumentHandler->characters(signatureInfo.ouX509SerialNumber);
-    xDocumentHandler->endElement("X509SerialNumber");
-    xDocumentHandler->endElement("xd:IssuerSerial");
-    xDocumentHandler->endElement("xd:Cert");
+    assert(!signatureInfo.X509Datas.empty() || !signatureInfo.ouGpgKeyID.isEmpty());
+    if (!signatureInfo.X509Datas.empty())
+    {
+        for (auto const& it : signatureInfo.X509Datas)
+        {
+            WriteXadesCert(xDocumentHandler, it);
+        }
+    }
+    else
+    {
+        // for PGP, write empty mandatory X509IssuerName, X509SerialNumber
+        SignatureInformation::X509Data temp;
+        temp.CertDigest = signatureInfo.ouGpgKeyID;
+        WriteXadesCert(xDocumentHandler, temp);
+    }
     xDocumentHandler->endElement("xd:SigningCertificate");
     xDocumentHandler->startElement("xd:SignaturePolicyIdentifier", uno::Reference<xml::sax::XAttributeList>(new SvXMLAttributeList()));
     xDocumentHandler->startElement("xd:SignaturePolicyImplied", uno::Reference<xml::sax::XAttributeList>(new SvXMLAttributeList()));
diff --git a/xmlsecurity/source/helper/documentsignaturemanager.cxx b/xmlsecurity/source/helper/documentsignaturemanager.cxx
index 295522775951..d0ac3d0fc11a 100644
--- a/xmlsecurity/source/helper/documentsignaturemanager.cxx
+++ b/xmlsecurity/source/helper/documentsignaturemanager.cxx
@@ -587,6 +587,18 @@ void DocumentSignatureManager::read(bool bUseTempStream, bool bCacheLastSignatur
                                                             bCacheLastSignature);
         maSignatureHelper.EndMission();
 
+        // this parses the XML independently from ImplVerifySignatures() - check
+        // certificates here too ...
+        for (auto const& it : maSignatureHelper.GetSignatureInformations())
+        {
+            if (!it.X509Datas.empty())
+            {
+                uno::Reference<xml::crypto::XSecurityEnvironment> const xSecEnv(
+                    getSecurityEnvironment());
+                getSignatureHelper().CheckAndUpdateSignatureInformation(xSecEnv, it);
+            }
+        }
+
         maCurrentSignatureInformations = maSignatureHelper.GetSignatureInformations();
     }
     else
diff --git a/xmlsecurity/source/helper/ooxmlsecexporter.cxx b/xmlsecurity/source/helper/ooxmlsecexporter.cxx
index 43a89811619b..e9a4e02fb222 100644
--- a/xmlsecurity/source/helper/ooxmlsecexporter.cxx
+++ b/xmlsecurity/source/helper/ooxmlsecexporter.cxx
@@ -201,13 +201,17 @@ void OOXMLSecExporter::Impl::writeKeyInfo()
 {
     m_xDocumentHandler->startElement(
         "KeyInfo", uno::Reference<xml::sax::XAttributeList>(new SvXMLAttributeList()));
-    m_xDocumentHandler->startElement(
-        "X509Data", uno::Reference<xml::sax::XAttributeList>(new SvXMLAttributeList()));
-    m_xDocumentHandler->startElement(
-        "X509Certificate", uno::Reference<xml::sax::XAttributeList>(new SvXMLAttributeList()));
-    m_xDocumentHandler->characters(m_rInformation.ouX509Certificate);
-    m_xDocumentHandler->endElement("X509Certificate");
-    m_xDocumentHandler->endElement("X509Data");
+    assert(!m_rInformation.X509Datas.empty());
+    for (auto const& it : m_rInformation.X509Datas)
+    {
+        m_xDocumentHandler->startElement(
+            "X509Data", uno::Reference<xml::sax::XAttributeList>(new SvXMLAttributeList()));
+        m_xDocumentHandler->startElement(
+            "X509Certificate", uno::Reference<xml::sax::XAttributeList>(new SvXMLAttributeList()));
+        m_xDocumentHandler->characters(it.X509Certificate);
+        m_xDocumentHandler->endElement("X509Certificate");
+        m_xDocumentHandler->endElement("X509Data");
+    }
     m_xDocumentHandler->endElement("KeyInfo");
 }
 
diff --git a/xmlsecurity/source/helper/ooxmlsecparser.cxx b/xmlsecurity/source/helper/ooxmlsecparser.cxx
index a200de60c07a..363b0f7bba59 100644
--- a/xmlsecurity/source/helper/ooxmlsecparser.cxx
+++ b/xmlsecurity/source/helper/ooxmlsecparser.cxx
@@ -185,9 +185,16 @@ void SAL_CALL OOXMLSecParser::endElement(const OUString& rName)
         m_pXSecController->setSignatureValue(m_aSignatureValue);
         m_bInSignatureValue = false;
     }
+    else if (rName == "X509Data")
+    {
+        SignatureInformation::X509Data temp;
+        temp.X509Certificate = m_aX509Certificate;
+        temp.X509IssuerName = m_aX509IssuerName;
+        temp.X509SerialNumber = m_aX509SerialNumber;
+        m_pXSecController->setX509Data(temp);
+    }
     else if (rName == "X509Certificate")
     {
-        m_pXSecController->setX509Certificate(m_aX509Certificate);
         m_bInX509Certificate = false;
     }
     else if (rName == "mdssi:Value")
@@ -202,17 +209,18 @@ void SAL_CALL OOXMLSecParser::endElement(const OUString& rName)
     }
     else if (rName == "X509IssuerName")
     {
-        m_pXSecController->setX509IssuerName(m_aX509IssuerName);
         m_bInX509IssuerName = false;
     }
     else if (rName == "X509SerialNumber")
     {
-        m_pXSecController->setX509SerialNumber(m_aX509SerialNumber);
         m_bInX509SerialNumber = false;
     }
+    else if (rName == "xd:Cert")
+    {
+        m_pXSecController->setX509CertDigest(m_aCertDigest, css::xml::crypto::DigestID::SHA1, m_aX509IssuerName, m_aX509SerialNumber);
+    }
     else if (rName == "xd:CertDigest")
     {
-        m_pXSecController->setCertDigest(m_aCertDigest);
         m_bInCertDigest = false;
     }
     else if (rName == "Object")
diff --git a/xmlsecurity/source/helper/pdfsignaturehelper.cxx b/xmlsecurity/source/helper/pdfsignaturehelper.cxx
index cbeba392a932..6ebdeb0a9c4f 100644
--- a/xmlsecurity/source/helper/pdfsignaturehelper.cxx
+++ b/xmlsecurity/source/helper/pdfsignaturehelper.cxx
@@ -506,8 +506,11 @@ PDFSignatureHelper::GetDocumentSignatureInformations(
         security::DocumentSignatureInformation& rExternal = aRet[i];
         rExternal.SignatureIsValid
             = rInternal.nStatus == xml::crypto::SecurityOperationStatus_OPERATION_SUCCEEDED;
-        if (!rInternal.ouX509Certificate.isEmpty())
-            rExternal.Signer = xSecEnv->createCertificateFromAscii(rInternal.ouX509Certificate);
+        if (!rInternal.X509Datas.empty() && !rInternal.X509Datas.back().X509Certificate.isEmpty())
+        {
+            rExternal.Signer
+                = xSecEnv->createCertificateFromAscii(rInternal.X509Datas.back().X509Certificate);
+        }
         rExternal.PartialDocumentSignature = rInternal.bPartialDocumentSignature;
 
         // Verify certificate.
diff --git a/xmlsecurity/source/helper/xmlsignaturehelper.cxx b/xmlsecurity/source/helper/xmlsignaturehelper.cxx
index 779f95119198..ba6717c32ff0 100644
--- a/xmlsecurity/source/helper/xmlsignaturehelper.cxx
+++ b/xmlsecurity/source/helper/xmlsignaturehelper.cxx
@@ -21,6 +21,7 @@
 #include <xmlsignaturehelper.hxx>
 #include <documentsignaturehelper.hxx>
 #include <xsecctl.hxx>
+#include <biginteger.hxx>
 
 #include <xmlsignaturehelper2.hxx>
 
@@ -45,6 +46,8 @@
 #include <tools/diagnose_ex.h>
 #include <sal/log.hxx>
 
+#include <optional>
+
 #define NS_DOCUMENTSIGNATURES   "http://openoffice.org/2004/documentsignatures"
 #define NS_DOCUMENTSIGNATURES_ODF_1_2 "urn:oasis:names:tc:opendocument:xmlns:digitalsignature:1.0"
 #define OOXML_SIGNATURE_ORIGIN "http://schemas.openxmlformats.org/package/2006/relationships/digital-signature/origin"
@@ -546,4 +549,147 @@ void XMLSignatureHelper::CreateAndWriteOOXMLSignature(const uno::Reference<embed
     xSaxWriter->endDocument();
 }
 
+/** check this constraint from xmldsig-core 4.5.4:
+
+  All certificates appearing in an X509Data element MUST relate to the
+  validation key by either containing it or being part of a certification
+  chain that terminates in a certificate containing the validation key.
+ */
+static auto CheckX509Data(
+    uno::Reference<xml::crypto::XSecurityEnvironment> const& xSecEnv,
+    std::vector<SignatureInformation::X509Data> const& rX509Datas,
+    std::vector<uno::Reference<security::XCertificate>> & rCerts,
+    std::vector<SignatureInformation::X509Data> & rSorted) -> bool
+{
+    assert(rCerts.empty());
+    assert(rSorted.empty());
+    if (rX509Datas.empty())
+    {
+        SAL_WARN("xmlsecurity.comp", "no X509Data");
+        return false;
+    }
+    std::vector<uno::Reference<security::XCertificate>> certs;
+    for (SignatureInformation::X509Data const& it : rX509Datas)
+    {
+        if (!it.X509Certificate.isEmpty())
+        {
+            certs.emplace_back(xSecEnv->createCertificateFromAscii(it.X509Certificate));
+        }
+        else
+        {
+            certs.emplace_back(xSecEnv->getCertificate(
+                it.X509IssuerName,
+                xmlsecurity::numericStringToBigInteger(it.X509SerialNumber)));
+        }
+        if (!certs.back().is())
+        {
+            SAL_WARN("xmlsecurity.comp", "X509Data cannot be parsed");
+            return false;
+        }
+    }
+
+    // first, search one whose issuer isn't in the list, or a self-signed one
+    std::optional<size_t> start;
+    for (size_t i = 0; i < certs.size(); ++i)
+    {
+        for (size_t j = 0; ; ++j)
+        {
+            if (j == certs.size())
+            {
+                if (start)
+                {
+                    SAL_WARN("xmlsecurity.comp", "X509Data do not form a chain: certificate has no issuer but already have start of chain: " << certs[i]->getSubjectName());
+                    return false;
+                }
+                start = i; // issuer isn't in the list
+                break;
+            }
+            if (xmlsecurity::EqualDistinguishedNames(certs[i]->getIssuerName(), certs[j]->getSubjectName()))
+            {
+                if (i == j) // self signed
+                {
+                    if (start)
+                    {
+                        SAL_WARN("xmlsecurity.comp", "X509Data do not form a chain: certificate is self-signed but already have start of chain: " << certs[i]->getSubjectName());
+                        return false;
+                    }
+                    start = i;
+                }
+                break;
+            }
+        }
+    }
+    std::vector<size_t> chain;
+    if (!start)
+    {
+        // this can only be a cycle?
+        SAL_WARN("xmlsecurity.comp", "X509Data do not form a chain: cycle detected");
+        return false;
+    }
+    chain.emplace_back(*start);
+
+    // second, check that there is a chain, no tree or cycle...
+    for (size_t i = 0; i < certs.size(); ++i)
+    {
+        assert(chain.size() == i + 1);
+        for (size_t j = 0; j < certs.size(); ++j)
+        {
+            if (chain[i] != j)
+            {
+                if (xmlsecurity::EqualDistinguishedNames(
+                        certs[chain[i]]->getSubjectName(), certs[j]->getIssuerName()))
+                {
+                    if (chain.size() != i + 1) // already found issuee?
+                    {
+                        SAL_WARN("xmlsecurity.comp", "X509Data do not form a chain: certificate issued 2 others: " << certs[chain[i]]->getSubjectName());
+                        return false;
+                    }
+                    chain.emplace_back(j);
+                }
+            }
+        }
+        if (i == certs.size() - 1)
+        {   // last one: must be a leaf
+            if (chain.size() != i + 1)
+            {
+                SAL_WARN("xmlsecurity.comp", "X509Data do not form a chain: certificate in cycle: " << certs[chain[i]]->getSubjectName());
+                return false;
+            }
+        }
+        else if (chain.size() != i + 2)
+        {   // not issuer of another?
+            SAL_WARN("xmlsecurity.comp", "X509Data do not form a chain: certificate issued 0 others: " << certs[chain[i]]->getSubjectName());
+            return false;
+        }
+    }
+
+    // success
+    assert(chain.size() == rX509Datas.size());
+    for (auto const& it : chain)
+    {
+        rSorted.emplace_back(rX509Datas[it]);
+        rCerts.emplace_back(certs[it]);
+    }
+    return true;
+}
+
+std::vector<uno::Reference<security::XCertificate>>
+XMLSignatureHelper::CheckAndUpdateSignatureInformation(
+    uno::Reference<xml::crypto::XSecurityEnvironment> const& xSecEnv,
+    SignatureInformation const& rInfo)
+{
+    // if the check fails, it's not possible to determine which X509Data
+    // contained the signing certificate - the UI cannot display something
+    // useful in this case, so prevent anything misleading by clearing the
+    // X509Datas.
+
+    std::vector<uno::Reference<security::XCertificate>> certs;
+    std::vector<SignatureInformation::X509Data> datas;
+    CheckX509Data(xSecEnv, rInfo.X509Datas, certs, datas);
+
+    // rInfo is a copy, update the original
+    mpXSecController->UpdateSignatureInformation(rInfo.nSecurityId, datas);
+    return certs;
+}
+
 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/xmlsecurity/source/helper/xsecctl.cxx b/xmlsecurity/source/helper/xsecctl.cxx
index 43b74e2c9250..a05d54ab1755 100644
--- a/xmlsecurity/source/helper/xsecctl.cxx
+++ b/xmlsecurity/source/helper/xsecctl.cxx
@@ -734,7 +734,7 @@ void XSecController::exportSignature(
                     xDocumentHandler->startElement(
                         "PGPKeyID",
                         css::uno::Reference< css::xml::sax::XAttributeList > (new SvXMLAttributeList()));
-                    xDocumentHandler->characters( signatureInfo.ouCertDigest );
+                    xDocumentHandler->characters(signatureInfo.ouGpgKeyID);
                     xDocumentHandler->endElement( "PGPKeyID" );
 
                     /* Write PGPKeyPacket element */
@@ -758,43 +758,47 @@ void XSecController::exportSignature(
             }
             else
             {
-                /* Write X509Data element */
-                xDocumentHandler->startElement(
-                    "X509Data",
-                    css::uno::Reference< css::xml::sax::XAttributeList > (new SvXMLAttributeList()));
+                assert(!signatureInfo.X509Datas.empty());
+                for (auto const& it : signatureInfo.X509Datas)
                 {
-                    /* Write X509IssuerSerial element */
+                    /* Write X509Data element */
                     xDocumentHandler->startElement(
-                        "X509IssuerSerial",
+                        "X509Data",
                         css::uno::Reference< css::xml::sax::XAttributeList > (new SvXMLAttributeList()));
                     {
-                        /* Write X509IssuerName element */
+                        /* Write X509IssuerSerial element */
                         xDocumentHandler->startElement(
-                            "X509IssuerName",
+                            "X509IssuerSerial",
                             css::uno::Reference< css::xml::sax::XAttributeList > (new SvXMLAttributeList()));
-                        xDocumentHandler->characters( signatureInfo.ouX509IssuerName );
-                        xDocumentHandler->endElement( "X509IssuerName" );
+                        {
+                            /* Write X509IssuerName element */
+                            xDocumentHandler->startElement(
+                                "X509IssuerName",
+                                css::uno::Reference< css::xml::sax::XAttributeList > (new SvXMLAttributeList()));
+                            xDocumentHandler->characters(it.X509IssuerName);
+                            xDocumentHandler->endElement( "X509IssuerName" );
 
-                        /* Write X509SerialNumber element */
-                        xDocumentHandler->startElement(
-                            "X509SerialNumber",
-                            css::uno::Reference< css::xml::sax::XAttributeList > (new SvXMLAttributeList()));
-                        xDocumentHandler->characters( signatureInfo.ouX509SerialNumber );
-                        xDocumentHandler->endElement( "X509SerialNumber" );
-                    }
-                    xDocumentHandler->endElement( "X509IssuerSerial" );
+                            /* Write X509SerialNumber element */
+                            xDocumentHandler->startElement(
+                                "X509SerialNumber",
+                                css::uno::Reference< css::xml::sax::XAttributeList > (new SvXMLAttributeList()));
+                            xDocumentHandler->characters(it.X509SerialNumber);
+                            xDocumentHandler->endElement( "X509SerialNumber" );
+                        }
+                        xDocumentHandler->endElement( "X509IssuerSerial" );
 
-                    /* Write X509Certificate element */
-                    if (!signatureInfo.ouX509Certificate.isEmpty())
-                    {
-                        xDocumentHandler->startElement(
-                            "X509Certificate",
-                            css::uno::Reference< css::xml::sax::XAttributeList > (new SvXMLAttributeList()));
-                        xDocumentHandler->characters( signatureInfo.ouX509Certificate );
-                        xDocumentHandler->endElement( "X509Certificate" );
+                        /* Write X509Certificate element */
+                        if (!it.X509Certificate.isEmpty())
+                        {
+                            xDocumentHandler->startElement(
+                                "X509Certificate",
+                                css::uno::Reference< css::xml::sax::XAttributeList > (new SvXMLAttributeList()));
+                            xDocumentHandler->characters(it.X509Certificate);
+                            xDocumentHandler->endElement( "X509Certificate" );
+                        }
                     }
+                    xDocumentHandler->endElement( "X509Data" );
                 }
-                xDocumentHandler->endElement( "X509Data" );
             }
         }
         xDocumentHandler->endElement( "KeyInfo" );
@@ -913,6 +917,15 @@ void XSecController::exportOOXMLSignature(const uno::Reference<embed::XStorage>&
     aExporter.writeSignature();
 }
 
+void XSecController::UpdateSignatureInformation(sal_Int32 const nSecurityId,
+    std::vector<SignatureInformation::X509Data> const& rDatas)
+{
+    SignatureInformation aInf( 0 );
+    int const nIndex = findSignatureInfor(nSecurityId);
+    assert(nIndex != -1); // nothing should touch this between parsing and verify
+    m_vInternalSignatureInformations[nIndex].signatureInfor.X509Datas = rDatas;
+}
+
 SignatureInformation XSecController::getSignatureInformation( sal_Int32 nSecurityId ) const
 {
     SignatureInformation aInf( 0 );
diff --git a/xmlsecurity/source/helper/xsecparser.cxx b/xmlsecurity/source/helper/xsecparser.cxx
index fe138c916448..f09620823ba2 100644
--- a/xmlsecurity/source/helper/xsecparser.cxx
+++ b/xmlsecurity/source/helper/xsecparser.cxx
@@ -243,98 +243,79 @@ class XSecParser::DsX509CertificateContext
     : public XSecParser::Context
 {
     private:
-        OUString m_Value;
+        OUString & m_rValue;
 
     public:
         DsX509CertificateContext(XSecParser & rParser,
-                std::unique_ptr<SvXMLNamespaceMap> pOldNamespaceMap)
+                std::unique_ptr<SvXMLNamespaceMap> pOldNamespaceMap,
+                OUString & rValue)
             : XSecParser::Context(rParser, std::move(pOldNamespaceMap))
+            , m_rValue(rValue)
         {
         }
 
-        virtual void EndElement() override
-        {
-            m_rParser.m_pXSecController->setX509Certificate(m_Value);
-        }
-
         virtual void Characters(OUString const& rChars) override
         {
-            m_Value += rChars;
+            m_rValue += rChars;
         }
 };
 
 class XSecParser::DsX509SerialNumberContext
-    : public XSecParser::ReferencedContextImpl
+    : public XSecParser::Context
 {
     private:
-        OUString m_Value;
+        OUString & m_rValue;
 
     public:
         DsX509SerialNumberContext(XSecParser & rParser,
                 std::unique_ptr<SvXMLNamespaceMap> pOldNamespaceMap,
-                bool const isReferenced)
-            : ReferencedContextImpl(rParser, std::move(pOldNamespaceMap), isReferenced)
-        {
-        }
-
-        virtual void EndElement() override
+                OUString & rValue)
+            : XSecParser::Context(rParser, std::move(pOldNamespaceMap))
+            , m_rValue(rValue)
         {
-            if (m_isReferenced)
-            {
-                m_rParser.m_pXSecController->setX509SerialNumber(m_Value);
-            }
-            else
-            {
-                SAL_INFO("xmlsecurity.helper", "ignoring unsigned X509SerialNumber");
-            }
         }
 
         virtual void Characters(OUString const& rChars) override
         {
-            m_Value += rChars;
+            m_rValue += rChars;
         }
 };
 
 class XSecParser::DsX509IssuerNameContext
-    : public XSecParser::ReferencedContextImpl
+    : public XSecParser::Context
 {
     private:
-        OUString m_Value;
+        OUString & m_rValue;
 
     public:
         DsX509IssuerNameContext(XSecParser & rParser,
                 std::unique_ptr<SvXMLNamespaceMap> pOldNamespaceMap,
-                bool const isReferenced)
-            : ReferencedContextImpl(rParser, std::move(pOldNamespaceMap), isReferenced)
-        {
-        }
-
-        virtual void EndElement() override
+                OUString & rValue)
+            : XSecParser::Context(rParser, std::move(pOldNamespaceMap))
+            , m_rValue(rValue)
         {
-            if (m_isReferenced)
-            {
-                m_rParser.m_pXSecController->setX509IssuerName(m_Value);
-            }
-            else
-            {
-                SAL_INFO("xmlsecurity.helper", "ignoring unsigned X509IssuerName");
-            }
         }
 
         virtual void Characters(OUString const& rChars) override
         {
-            m_Value += rChars;
+            m_rValue += rChars;
         }
 };
 
 class XSecParser::DsX509IssuerSerialContext
-    : public XSecParser::ReferencedContextImpl
+    : public XSecParser::Context
 {
+    private:
+        OUString & m_rX509IssuerName;
+        OUString & m_rX509SerialNumber;
+
     public:
         DsX509IssuerSerialContext(XSecParser & rParser,
                 std::unique_ptr<SvXMLNamespaceMap> pOldNamespaceMap,
-                bool const isReferenced)
-            : ReferencedContextImpl(rParser, std::move(pOldNamespaceMap), isReferenced)
+                OUString & rIssuerName, OUString & rSerialNumber)
+            : XSecParser::Context(rParser, std::move(pOldNamespaceMap))
+            , m_rX509IssuerName(rIssuerName)
+            , m_rX509SerialNumber(rSerialNumber)
         {
         }
 
@@ -344,11 +325,11 @@ class XSecParser::DsX509IssuerSerialContext
         {
             if (nNamespace == XML_NAMESPACE_DS && rName == "X509IssuerName")
             {
-                return std::make_unique<DsX509IssuerNameContext>(m_rParser, std::move(pOldNamespaceMap), m_isReferenced);
+                return std::make_unique<DsX509IssuerNameContext>(m_rParser, std::move(pOldNamespaceMap), m_rX509IssuerName);
             }
             if (nNamespace == XML_NAMESPACE_DS && rName == "X509SerialNumber")
             {
-                return std::make_unique<DsX509SerialNumberContext>(m_rParser, std::move(pOldNamespaceMap), m_isReferenced);
+                return std::make_unique<DsX509SerialNumberContext>(m_rParser, std::move(pOldNamespaceMap), m_rX509SerialNumber);
             }
             // missing: ds:X509SKI, ds:X509SubjectName, ds:X509CRL
             return XSecParser::Context::CreateChildContext(std::move(pOldNamespaceMap), nNamespace, rName);
@@ -358,6 +339,9 @@ class XSecParser::DsX509IssuerSerialContext
 class XSecParser::DsX509DataContext
     : public XSecParser::Context
 {
+    private:
+        SignatureInformation::X509Data m_X509Data;
+
     public:
         DsX509DataContext(XSecParser & rParser,
                 std::unique_ptr<SvXMLNamespaceMap> pOldNamespaceMap)
@@ -365,6 +349,11 @@ class XSecParser::DsX509DataContext
         {
         }
 
+        virtual void EndElement() override
+        {
+            m_rParser.m_pXSecController->setX509Data(m_X509Data);
+        }
+
         virtual std::unique_ptr<Context> CreateChildContext(
             std::unique_ptr<SvXMLNamespaceMap> pOldNamespaceMap,
             sal_uInt16 const nNamespace, OUString const& rName) override
@@ -372,11 +361,11 @@ class XSecParser::DsX509DataContext
             if (nNamespace == XML_NAMESPACE_DS && rName == "X509IssuerSerial")
             {
                 // can't require KeyInfo to be signed so pass in *true*
-                return std::make_unique<DsX509IssuerSerialContext>(m_rParser, std::move(pOldNamespaceMap), true);
+                return std::make_unique<DsX509IssuerSerialContext>(m_rParser, std::move(pOldNamespaceMap), m_X509Data.X509IssuerName, m_X509Data.X509SerialNumber);
             }
             if (nNamespace == XML_NAMESPACE_DS && rName == "X509Certificate")
             {
-                return std::make_unique<DsX509CertificateContext>(m_rParser, std::move(pOldNamespaceMap));
+                return std::make_unique<DsX509CertificateContext>(m_rParser, std::move(pOldNamespaceMap), m_X509Data.X509Certificate);
             }
             // missing: ds:X509SKI, ds:X509SubjectName, ds:X509CRL
             return XSecParser::Context::CreateChildContext(std::move(pOldNamespaceMap), nNamespace, rName);
@@ -968,30 +957,20 @@ class XSecParser::LoSignatureLineContext
 };
 
 class XSecParser::XadesCertDigestContext
-    : public XSecParser::ReferencedContextImpl
+    : public XSecParser::Context
 {
     private:
-        OUString m_Value;
-        sal_Int32 m_nReferenceDigestID = css::xml::crypto::DigestID::SHA1;
+        OUString & m_rDigestValue;
+        sal_Int32 & m_rReferenceDigestID;
 
     public:
         XadesCertDigestContext(XSecParser & rParser,
                 std::unique_ptr<SvXMLNamespaceMap> pOldNamespaceMap,
-                bool const isReferenced)
-            : ReferencedContextImpl(rParser, std::move(pOldNamespaceMap), isReferenced)
-        {
-        }
-
-        virtual void EndElement() override
+                OUString & rDigestValue, sal_Int32 & rReferenceDigestID)
+            : XSecParser::Context(rParser, std::move(pOldNamespaceMap))
+            , m_rDigestValue(rDigestValue)
+            , m_rReferenceDigestID(rReferenceDigestID)
         {
-            if (m_isReferenced)
-            {
-                m_rParser.m_pXSecController->setCertDigest(m_Value/* FIXME , m_nReferenceDigestID*/);
-            }
-            else
-            {
-                SAL_INFO("xmlsecurity.helper", "ignoring unsigned CertDigest");
-            }
         }
 
         virtual std::unique_ptr<Context> CreateChildContext(
@@ -1000,11 +979,11 @@ class XSecParser::XadesCertDigestContext
         {
             if (nNamespace == XML_NAMESPACE_DS && rName == "DigestMethod")
             {
-                return std::make_unique<DsDigestMethodContext>(m_rParser, std::move(pOldNamespaceMap), m_nReferenceDigestID);
+                return std::make_unique<DsDigestMethodContext>(m_rParser, std::move(pOldNamespaceMap), m_rReferenceDigestID);
             }
             if (nNamespace == XML_NAMESPACE_DS && rName == "DigestValue")
             {
-                return std::make_unique<DsDigestValueContext>(m_rParser, std::move(pOldNamespaceMap), m_Value);
+                return std::make_unique<DsDigestValueContext>(m_rParser, std::move(pOldNamespaceMap), m_rDigestValue);
             }
             return XSecParser::Context::CreateChildContext(std::move(pOldNamespaceMap), nNamespace, rName);
         }
@@ -1013,6 +992,12 @@ class XSecParser::XadesCertDigestContext
 class XSecParser::XadesCertContext
     : public XSecParser::ReferencedContextImpl
 {
+    private:
+        sal_Int32 m_nReferenceDigestID = css::xml::crypto::DigestID::SHA1;
+        OUString m_CertDigest;
+        OUString m_X509IssuerName;
+        OUString m_X509SerialNumber;
+
     public:
         XadesCertContext(XSecParser & rParser,
                 std::unique_ptr<SvXMLNamespaceMap> pOldNamespaceMap,
@@ -1021,17 +1006,29 @@ class XSecParser::XadesCertContext
         {
         }
 
+        virtual void EndElement() override
+        {
+            if (m_isReferenced)
+            {
+                m_rParser.m_pXSecController->setX509CertDigest(m_CertDigest, m_nReferenceDigestID, m_X509IssuerName, m_X509SerialNumber);
+            }
+            else
+            {
+                SAL_INFO("xmlsecurity.helper", "ignoring unsigned xades:Cert");
+            }
+        }
+
         virtual std::unique_ptr<Context> CreateChildContext(
             std::unique_ptr<SvXMLNamespaceMap> pOldNamespaceMap,
             sal_uInt16 const nNamespace, OUString const& rName) override
         {
             if (nNamespace == XML_NAMESPACE_XADES132 && rName == "CertDigest")
             {
-                return std::make_unique<XadesCertDigestContext>(m_rParser, std::move(pOldNamespaceMap), m_isReferenced);
+                return std::make_unique<XadesCertDigestContext>(m_rParser, std::move(pOldNamespaceMap), m_CertDigest, m_nReferenceDigestID);
             }
             if (nNamespace == XML_NAMESPACE_XADES132 && rName == "IssuerSerial")
             {
-                return std::make_unique<DsX509IssuerSerialContext>(m_rParser, std::move(pOldNamespaceMap), m_isReferenced);
+                return std::make_unique<DsX509IssuerSerialContext>(m_rParser, std::move(pOldNamespaceMap), m_X509IssuerName, m_X509SerialNumber);
             }
             return XSecParser::Context::CreateChildContext(std::move(pOldNamespaceMap), nNamespace, rName);
         }
diff --git a/xmlsecurity/source/helper/xsecsign.cxx b/xmlsecurity/source/helper/xsecsign.cxx
index 52d39f4f520a..5cf213b6dada 100644
--- a/xmlsecurity/source/helper/xsecsign.cxx
+++ b/xmlsecurity/source/helper/xsecsign.cxx
@@ -193,6 +193,7 @@ void XSecController::signAStream( sal_Int32 securityId, const OUString& uri, boo
     }
 }
 
+// note: this is called when creating a new signature from scratch
 void XSecController::setX509Certificate(
     sal_Int32 nSecurityId,
     const OUString& ouX509IssuerName,
@@ -206,10 +207,12 @@ void XSecController::setX509Certificate(
     if ( index == -1 )
     {
         InternalSignatureInformation isi(nSecurityId, nullptr);
-        isi.signatureInfor.ouX509IssuerName = ouX509IssuerName;
-        isi.signatureInfor.ouX509SerialNumber = ouX509SerialNumber;
-        isi.signatureInfor.ouX509Certificate = ouX509Cert;
-        isi.signatureInfor.ouCertDigest = ouX509CertDigest;
+        isi.signatureInfor.X509Datas.clear();
+        isi.signatureInfor.X509Datas.emplace_back();
+        isi.signatureInfor.X509Datas.back().X509IssuerName = ouX509IssuerName;
+        isi.signatureInfor.X509Datas.back().X509SerialNumber = ouX509SerialNumber;
+        isi.signatureInfor.X509Datas.back().X509Certificate = ouX509Cert;
+        isi.signatureInfor.X509Datas.back().CertDigest = ouX509CertDigest;
         isi.signatureInfor.eAlgorithmID = eAlgorithmID;
         m_vInternalSignatureInformations.push_back( isi );
     }
@@ -217,16 +220,18 @@ void XSecController::setX509Certificate(
     {
         SignatureInformation &si
             = m_vInternalSignatureInformations[index].signatureInfor;
-        si.ouX509IssuerName = ouX509IssuerName;
-        si.ouX509SerialNumber = ouX509SerialNumber;
-        si.ouX509Certificate = ouX509Cert;
-        si.ouCertDigest = ouX509CertDigest;
+        si.X509Datas.clear();
+        si.X509Datas.emplace_back();
+        si.X509Datas.back().X509IssuerName = ouX509IssuerName;
+        si.X509Datas.back().X509SerialNumber = ouX509SerialNumber;
+        si.X509Datas.back().X509Certificate = ouX509Cert;
+        si.X509Datas.back().CertDigest = ouX509CertDigest;
     }
 }
 
 void XSecController::setGpgCertificate(
         sal_Int32 nSecurityId,
-        const OUString& ouCertDigest,
+        const OUString& ouKeyDigest,
         const OUString& ouCert,
         const OUString& ouOwner)
 {
@@ -237,16 +242,17 @@ void XSecController::setGpgCertificate(
         InternalSignatureInformation isi(nSecurityId, nullptr);
         isi.signatureInfor.ouGpgCertificate = ouCert;
         isi.signatureInfor.ouGpgOwner = ouOwner;
-        isi.signatureInfor.ouCertDigest = ouCertDigest;
+        isi.signatureInfor.ouGpgKeyID = ouKeyDigest;
         m_vInternalSignatureInformations.push_back( isi );
     }
     else
     {
         SignatureInformation &si
             = m_vInternalSignatureInformations[index].signatureInfor;
+        si.X509Datas.clear(); // it is a PGP signature now
         si.ouGpgCertificate = ouCert;
         si.ouGpgOwner = ouOwner;
-        si.ouCertDigest = ouCertDigest;
+        si.ouGpgKeyID = ouKeyDigest;
     }
 }
 
diff --git a/xmlsecurity/source/helper/xsecverify.cxx b/xmlsecurity/source/helper/xsecverify.cxx
index ffe1e939a5a0..c630fd361ac2 100644
--- a/xmlsecurity/source/helper/xsecverify.cxx
+++ b/xmlsecurity/source/helper/xsecverify.cxx
@@ -22,6 +22,7 @@
 #include <xsecctl.hxx>
 #include "xsecparser.hxx"
 #include "ooxmlsecparser.hxx"
+#include <biginteger.hxx>
 #include <framework/signatureverifierimpl.hxx>
 #include <framework/saxeventkeeperimpl.hxx>
 #include <gpg/xmlsignature_gpgimpl.hxx>
@@ -240,7 +241,7 @@ void XSecController::setReferenceCount() const
     xReferenceCollector->setReferenceCount( referenceCount );
 }
 
-void XSecController::setX509IssuerName( OUString const & ouX509IssuerName )
+void XSecController::setX509Data(SignatureInformation::X509Data const& rData)
 {
     if (m_vInternalSignatureInformations.empty())
     {
@@ -248,29 +249,8 @@ void XSecController::setX509IssuerName( OUString const & ouX509IssuerName )
         return;
     }
     InternalSignatureInformation &isi = m_vInternalSignatureInformations.back();
-    isi.signatureInfor.ouX509IssuerName = ouX509IssuerName;
-}
-
-void XSecController::setX509SerialNumber( OUString const & ouX509SerialNumber )
-{
-    if (m_vInternalSignatureInformations.empty())
-    {
-        SAL_INFO("xmlsecurity.helper","XSecController::setX509SerialNumber: no signature");
-        return;
-    }
-    InternalSignatureInformation &isi = m_vInternalSignatureInformations.back();
-    isi.signatureInfor.ouX509SerialNumber = ouX509SerialNumber;
-}
-
-void XSecController::setX509Certificate( OUString const & ouX509Certificate )
-{
-    if (m_vInternalSignatureInformations.empty())
-    {
-        SAL_INFO("xmlsecurity.helper","XSecController::setX509Certificate: no signature");
-        return;
-    }
-    InternalSignatureInformation &isi = m_vInternalSignatureInformations.back();
-    isi.signatureInfor.ouX509Certificate = ouX509Certificate;
+    // TODO: ImplVerifySignatures() handles all-empty case?
+    isi.signatureInfor.X509Datas.push_back(rData);
 }
 
 void XSecController::setSignatureValue( OUString const & ouSignatureValue )
@@ -380,13 +360,61 @@ void XSecController::setSignatureBytes(const uno::Sequence<sal_Int8>& rBytes)
     rInformation.signatureInfor.aSignatureBytes = rBytes;
 }
 
-void XSecController::setCertDigest(const OUString& rCertDigest)
+void XSecController::setX509CertDigest(
+    OUString const& rCertDigest, sal_Int32 const /*TODO nReferenceDigestID*/,
+    std::u16string_view const& rX509IssuerName, std::u16string_view const& rX509SerialNumber)
 {
     if (m_vInternalSignatureInformations.empty())
         return;
 
     InternalSignatureInformation& rInformation = m_vInternalSignatureInformations.back();
-    rInformation.signatureInfor.ouCertDigest = rCertDigest;
+    for (auto & it : rInformation.signatureInfor.X509Datas)
+    {
+        if (xmlsecurity::EqualDistinguishedNames(it.X509IssuerName, rX509IssuerName)
+            && it.X509SerialNumber == rX509SerialNumber)
+        {
+            it.CertDigest = rCertDigest;
+            return;
+        }
+    }
+    // fall-back: read the actual certificates
+    for (auto & it : rInformation.signatureInfor.X509Datas)
+    {
+        if (!it.X509Certificate.isEmpty())
+        {
+            try
+            {
+                uno::Reference<xml::crypto::XSecurityEnvironment> const xSecEnv(m_xSecurityContext->getSecurityEnvironment());
+                uno::Reference<security::XCertificate> const xCert(xSecEnv->createCertificateFromAscii(it.X509Certificate));
+                if (!xCert.is())
+                {
+                    SAL_INFO("xmlsecurity.helper", "cannot parse X509Certificate");
+                }
+                else if (xmlsecurity::EqualDistinguishedNames(xCert->getIssuerName(),rX509IssuerName)
+                    && xmlsecurity::bigIntegerToNumericString(xCert->getSerialNumber()) == rX509SerialNumber)
+                {
+                    it.CertDigest = rCertDigest;
+                    // note: testInsertCertificate_PEM_DOCX requires these!
+                    it.X509SerialNumber = rX509SerialNumber;
+                    it.X509IssuerName = rX509IssuerName;
+                    return;
+                }
+            }
+            catch (uno::Exception const&)
+            {
+                SAL_INFO("xmlsecurity.helper", "cannot parse X509Certificate");
+            }
+        }
+    }
+    if (!rInformation.signatureInfor.ouGpgCertificate.isEmpty())
+    {
+        SAL_INFO_IF(rCertDigest != rInformation.signatureInfor.ouGpgKeyID,
+            "xmlsecurity.helper", "PGPKeyID vs CertDigest mismatch");
+    }
+    else
+    {
+        SAL_INFO("xmlsecurity.helper", "cannot find X509Data for CertDigest");
+    }
 }
 
 namespace {
diff --git a/xmlsecurity/source/xmlsec/mscrypt/xmlsignature_mscryptimpl.cxx b/xmlsecurity/source/xmlsec/mscrypt/xmlsignature_mscryptimpl.cxx
index 3bc02d161722..d9b8b1eace68 100644
--- a/xmlsecurity/source/xmlsec/mscrypt/xmlsignature_mscryptimpl.cxx
+++ b/xmlsecurity/source/xmlsec/mscrypt/xmlsignature_mscryptimpl.cxx
@@ -18,6 +18,7 @@
  */
 
 #include <sal/config.h>
+#include <sal/log.hxx>
 #include <rtl/uuid.h>
 #include <xmlsec-wrapper.h>
 
@@ -254,6 +255,7 @@ SAL_CALL XMLSignature_MSCryptImpl::validate(
                  ++nReferenceGood;
         }
     }
+    SAL_INFO("xmlsecurity.xmlsec", "xmlSecDSigCtxVerify status " << pDsigCtx->status << ", references good " << nReferenceGood << " of " << nReferenceCount);
 
     if (rs == 0 && nReferenceCount == nReferenceGood)
     {
diff --git a/xmlsecurity/source/xmlsec/nss/xmlsignature_nssimpl.cxx b/xmlsecurity/source/xmlsec/nss/xmlsignature_nssimpl.cxx
index 32e4335a5207..b41d754f7407 100644
--- a/xmlsecurity/source/xmlsec/nss/xmlsignature_nssimpl.cxx
+++ b/xmlsecurity/source/xmlsec/nss/xmlsignature_nssimpl.cxx
@@ -26,6 +26,8 @@
 
 #include "securityenvironment_nssimpl.hxx"
 
+#include <sal/log.hxx>
+
 #include <com/sun/star/xml/crypto/XXMLSignature.hpp>
 #include <memory>
 
@@ -261,6 +263,7 @@ SAL_CALL XMLSignature_NssImpl::validate(
                     ++nReferenceGood;
             }
         }
+        SAL_INFO("xmlsecurity.xmlsec", "xmlSecDSigCtxVerify status " << pDsigCtx->status << ", references good " << nReferenceGood << " of " << nReferenceCount);
 
         if (rs == 0 && pDsigCtx->status == xmlSecDSigStatusSucceeded && nReferenceCount == nReferenceGood)
         {