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SignatureProvider.SignXmlDsig method (Office)

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Used to sign the XMLDSIG template.

Syntax

expression.SignXmlDsig(QueryContinue, psigsetup, psiginfo, XmlDsigStream)

expression An expression that returns a SignatureProvider object.

Parameters

Name Required/Optional Data type Description
QueryContinue Required IQueryContinue Provides a way to query the host application for permission to continue the verification operation.
psigsetup Required SignatureSetup Specifies configuration information about a signature line.
psiginfo Required SignatureInfo Specifies information captured from the signing ceremony.
XmlDsigStream Required IStream Represents a stream of data containing XML, which represents an XMLDSIG object.

Remarks

XMLDSIG is a standards-based signature format (https://www.w3.org/TR/xmldsig-core/), verifiable by third parties. This is the default format for signatures in Microsoft Office.

Example

The following example, written in C#, shows the implementation of the SignXmlDsig method in a custom signature provider project.

 public void SignXmlDsig(object queryContinue, SignatureSetup sigsetup, SignatureInfo siginfo, object xmldsigStream) 
 { 
 using (COMStream comstream = new COMStream(xmldsigStream)) 
 { 
 XmlDocument xmldsig = new XmlDocument(); 
 xmldsig.PreserveWhitespace = true; 
 xmldsig.Load(comstream); 
 
 XmlNamespaceManager nsmgr = new XmlNamespaceManager(xmldsig.NameTable); 
 nsmgr.AddNamespace("ds", "https://www.w3.org/2000/09/xmldsig#"); 
 
 XmlElement signature = xmldsig.DocumentElement; 
 SignedXml signedXml = new SignedXml(); 
 signedXml.LoadXml(signature); 
 
 // Cert 
 X509Certificate2 cert = TestSignatureProvider.GetSigningCertificate(siginfo); 
 KeyInfo keyInfo = new KeyInfo(); 
 if (cert.PrivateKey is RSA) 
 keyInfo.AddClause(new RSAKeyValue((RSA) cert.PrivateKey)); 
 else if (cert.PrivateKey is DSA) 
 keyInfo.AddClause(new DSAKeyValue((DSA) cert.PrivateKey)); 
 keyInfo.AddClause(new KeyInfoX509Data(cert)); 
 signedXml.SigningKey = cert.PrivateKey; 
 signedXml.KeyInfo = keyInfo; 
 
 // Compute signature 
 signedXml.ComputeSignature(); 
 
 // Copy data from signed signature 
 // REVIEW: Cleaner way to do this? 
 string[] xpathsToCopy = new string[] 
 { 
 "./ds:SignedInfo", 
 "./ds:SignatureValue", 
 "./ds:KeyInfo", 
 }; 
 XmlElement signedSignature = signedXml.GetXml(); 
 foreach (string xpathToCopy in xpathsToCopy) 
 { 
 signature.ReplaceChild( 
 xmldsig.ImportNode(signedSignature.SelectSingleNode(xpathToCopy, nsmgr), true), 
 signature.SelectSingleNode(xpathToCopy, nsmgr)); 
 } 
 
 // Save signature back to stream 
 comstream.SetLength(0); 
 comstream.Position = 0; 
 xmldsig.Save(new XmlTextWriter(comstream, new UTF8Encoding(false))); 
 } 
 }

Note

Signature providers are implemented exclusively in custom COM add-ins created in managed and unmanaged code and cannot be implemented in Microsoft Visual Basic for Applications (VBA).

See also

Support and feedback

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