XmlDsigExcC14NWithCommentsTransform Class

 
System_CAPS_noteNote

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Represents the exclusive C14N XML canonicalization transform for a digital signature as defined by the World Wide Web Consortium (W3C), with comments.

Namespace:   System.Security.Cryptography.Xml
Assembly:  System.Security (in System.Security.dll)

System::Object
  System.Security.Cryptography.Xml::Transform
    System.Security.Cryptography.Xml::XmlDsigExcC14NTransform
      System.Security.Cryptography.Xml::XmlDsigExcC14NWithCommentsTransform

[HostProtectionAttribute(SecurityAction::LinkDemand, MayLeakOnAbort = true)]
public ref class XmlDsigExcC14NWithCommentsTransform : XmlDsigExcC14NTransform

NameDescription
System_CAPS_pubmethodXmlDsigExcC14NWithCommentsTransform()

Initializes a new instance of the XmlDsigExcC14NWithCommentsTransform class.

System_CAPS_pubmethodXmlDsigExcC14NWithCommentsTransform(String^)

Initializes a new instance of the XmlDsigExcC14NWithCommentsTransform class specifying a list of namespace prefixes to canonicalize using the standard canonicalization algorithm.

NameDescription
System_CAPS_pubpropertyAlgorithm

Gets or sets the Uniform Resource Identifier (URI) that identifies the algorithm performed by the current transform.(Inherited from Transform.)

System_CAPS_pubpropertyContext

Gets or sets an XmlElement object that represents the document context under which the current Transform object is running. (Inherited from Transform.)

System_CAPS_pubpropertyInclusiveNamespacesPrefixList

Gets or sets a string that contains namespace prefixes to canonicalize using the standard canonicalization algorithm. (Inherited from XmlDsigExcC14NTransform.)

System_CAPS_pubpropertyInputTypes

Gets an array of types that are valid inputs to the LoadInput method of the current XmlDsigExcC14NTransform object.(Inherited from XmlDsigExcC14NTransform.)

System_CAPS_pubpropertyOutputTypes

Gets an array of types that are possible outputs from the GetOutput methods of the current XmlDsigExcC14NTransform object.(Inherited from XmlDsigExcC14NTransform.)

System_CAPS_pubpropertyPropagatedNamespaces

Gets or sets a Hashtable object that contains the namespaces that are propagated into the signature. (Inherited from Transform.)

System_CAPS_pubpropertyResolver

Sets the current XmlResolver object.(Inherited from Transform.)

NameDescription
System_CAPS_pubmethodEquals(Object^)

Determines whether the specified object is equal to the current object.(Inherited from Object.)

System_CAPS_protmethodFinalize()

Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)

System_CAPS_pubmethodGetDigestedOutput(HashAlgorithm^)

Returns the digest associated with a XmlDsigExcC14NTransform object.(Inherited from XmlDsigExcC14NTransform.)

System_CAPS_pubmethodGetHashCode()

Serves as the default hash function. (Inherited from Object.)

System_CAPS_protmethodGetInnerXml()

Returns an XML representation of the parameters of a XmlDsigExcC14NTransform object that are suitable to be included as subelements of an XMLDSIG <Transform> element.(Inherited from XmlDsigExcC14NTransform.)

System_CAPS_pubmethodGetOutput()

Returns the output of the current XmlDsigExcC14NTransform object(Inherited from XmlDsigExcC14NTransform.)

System_CAPS_pubmethodGetOutput(Type^)

Returns the output of the current XmlDsigExcC14NTransform object as an object of the specified type.(Inherited from XmlDsigExcC14NTransform.)

System_CAPS_pubmethodGetType()

Gets the Type of the current instance.(Inherited from Object.)

System_CAPS_pubmethodGetXml()

Returns the XML representation of the current Transform object.(Inherited from Transform.)

System_CAPS_pubmethodLoadInnerXml(XmlNodeList^)

Parses the specified XmlNodeList object as transform-specific content of a <Transform> element and configures the internal state of the current XmlDsigExcC14NTransform object to match the <Transform> element.(Inherited from XmlDsigExcC14NTransform.)

System_CAPS_pubmethodLoadInput(Object^)

When overridden in a derived class, loads the specified input into the current XmlDsigExcC14NTransform object.(Inherited from XmlDsigExcC14NTransform.)

System_CAPS_protmethodMemberwiseClone()

Creates a shallow copy of the current Object.(Inherited from Object.)

System_CAPS_pubmethodToString()

Returns a string that represents the current object.(Inherited from Object.)

The XmlDsigExcC14NWithCommentsTransform class represents the exclusive C14N XML canonicalization transform with comments. This class is similar to the XmlDsigExcC14NTransform class, which allows a signer to create a digest using the canonical form of an XML document. However, the XmlDsigExcC14NWithCommentsTransform class excludes ancestor context from a canonicalized subdocument.

Use the XmlDsigExcC14NWithCommentsTransform class when you need to canonicalize an XML subdocument so that it is independent from its XML context. For example, applications such as Web services that use signed XML within complex communication protocols often need to canonicalize XML in this manner. Such applications often envelop XML within various dynamically constructed elements, which can substantially change the document and cause XML signature verification to fail. The XmlDsigExcC14NWithCommentsTransform class solves this problem by excluding such ancestor context from the canonical subdocument.

Note that you cannot directly create a new instance of a canonicalization transform class. To specify a canonicalization transform, pass the Uniform Resource Identifier (URI) that describes the transform to the CanonicalizationMethod property, which is accessible from the SignedInfo property. To acquire a reference to the canonicalization transform, use the CanonicalizationMethodObject property, which is accessible from the SignedInfo property.

The URI that describes the XmlDsigExcC14NWithCommentsTransform class is defined by the XmlDsigExcC14NWithCommentsTransformUrl field.

For more information about the exclusive C14N transform, see the XMLDSIG specification, which is available from the World Wide Web Consortium (W3C) at www.w3.org/TR/xmldsig-core/. The canonicalization algorithm is defined in the W3C Canonical XML specification, which is available at www.w3.org/2001/10/xml-exc-c14n.

The following code example shows how to sign and verify an XML document using the XmlDsigExcC14NWithCommentsTransform class. This example creates an envelope signature.

//
// This example signs an XML file using an
// envelope signature. It then verifies the 
// signed XML.
//
#using <System.Xml.dll>
#using <System.Security.dll>
#using <System.dll>

using namespace System;
using namespace System::Security::Cryptography;
using namespace System::Security::Cryptography::X509Certificates;
using namespace System::Security::Cryptography::Xml;
using namespace System::Text;
using namespace System::Xml;

// Sign an XML file and save the signature in a new file.
static void SignXmlFile( String^ FileName, String^ SignedFileName, RSA^ Key )
{

   // Create a new XML document.
   XmlDocument^ doc = gcnew XmlDocument;

   // Format the document to ignore white spaces.
   doc->PreserveWhitespace = false;

   // Load the passed XML file using it's name.
   doc->Load( gcnew XmlTextReader( FileName ) );

   // Create a SignedXml object.
   SignedXml^ signedXml = gcnew SignedXml( doc );

   // Add the key to the SignedXml document. 
   signedXml->SigningKey = Key;

   // Specify a canonicalization method.
   signedXml->SignedInfo->CanonicalizationMethod = SignedXml::XmlDsigExcC14NWithCommentsTransformUrl;

   // Set the InclusiveNamespacesPrefixList property.
   XmlDsigExcC14NWithCommentsTransform^ canMethod = dynamic_cast<XmlDsigExcC14NWithCommentsTransform^>(signedXml->SignedInfo->CanonicalizationMethodObject);
   canMethod->InclusiveNamespacesPrefixList = L"Sign";

   // Create a reference to be signed.
   Reference^ reference = gcnew Reference;
   reference->Uri = L"";

   // Add an enveloped transformation to the reference.
   XmlDsigEnvelopedSignatureTransform^ env = gcnew XmlDsigEnvelopedSignatureTransform;
   reference->AddTransform( env );

   // Add the reference to the SignedXml object.
   signedXml->AddReference( reference );

   // Add an RSAKeyValue KeyInfo (optional; helps recipient find key to validate).
   KeyInfo^ keyInfo = gcnew KeyInfo;
   keyInfo->AddClause( gcnew RSAKeyValue( dynamic_cast<RSA^>(Key) ) );
   signedXml->KeyInfo = keyInfo;

   // Compute the signature.
   signedXml->ComputeSignature();

   // Get the XML representation of the signature and save
   // it to an XmlElement object.
   XmlElement^ xmlDigitalSignature = signedXml->GetXml();

   // Append the element to the XML document.
   doc->DocumentElement->AppendChild( doc->ImportNode( xmlDigitalSignature, true ) );
   if ( dynamic_cast<XmlDeclaration^>(doc->FirstChild) )
   {
      doc->RemoveChild( doc->FirstChild );
   }


   // Save the signed XML document to a file specified
   // using the passed string.
   XmlTextWriter^ xmltw = gcnew XmlTextWriter( SignedFileName,gcnew UTF8Encoding( false ) );
   doc->WriteTo( xmltw );
   xmltw->Close();
}


// Verify the signature of an XML file and return the result.
static Boolean VerifyXmlFile( String^ Name )
{

   // Create a new XML document.
   XmlDocument^ xmlDocument = gcnew XmlDocument;

   // Format using white spaces.
   xmlDocument->PreserveWhitespace = true;

   // Load the passed XML file into the document. 
   xmlDocument->Load( Name );

   // Create a new SignedXml object and pass it
   // the XML document class.
   SignedXml^ signedXml = gcnew SignedXml( xmlDocument );

   // Find the "Signature" node and create a new
   // XmlNodeList object.
   XmlNodeList^ nodeList = xmlDocument->GetElementsByTagName( L"Signature" );

   // Load the signature node.
   signedXml->LoadXml( dynamic_cast<XmlElement^>(nodeList->Item( 0 )) );

   // Check the signature and return the result.
   return signedXml->CheckSignature();
}


// Create example data to sign.
static void CreateSomeXml( String^ FileName )
{

   // Create a new XmlDocument object.
   XmlDocument^ document = gcnew XmlDocument;

   // Create a new XmlNode object.
   XmlNode^ node = document->CreateNode( XmlNodeType::Element, L"", L"MyXML", L"Don't_Sign" );

   // Append the node to the document.
   document->AppendChild( node );

   // Create a new XmlNode object.
   XmlNode^ subnode = document->CreateNode( XmlNodeType::Element, L"", L"TempElement", L"Sign" );

   // Add some text to the node.
   subnode->InnerText = L"Here is some data to sign.";

   // Append the node to the document.
   document->DocumentElement->AppendChild( subnode );

   // Save the XML document to the file name specified.
   XmlTextWriter^ xmltw = gcnew XmlTextWriter( FileName,gcnew UTF8Encoding( false ) );
   document->WriteTo( xmltw );
   xmltw->Close();
}

int main()
{
   try
   {

      // Create an XML file to sign.
      CreateSomeXml( L"Example.xml" );
      Console::WriteLine( L"New XML file created." );

      // Sign the XML that was just created and save it in a 
      // new file.
      //SignXmlFile("Example.xml", "SignedExample.xml", Key);
      Console::WriteLine( L"XML file signed." );

      // Verify the signature of the signed XML.
      Console::WriteLine( L"Verifying signature..." );
      bool result = VerifyXmlFile( L"SignedExample.xml" );

      // Display the results of the signature verification to 
      // the console.
      if ( result )
      {
         Console::WriteLine( L"The XML signature is valid." );
      }
      else
      {
         Console::WriteLine( L"The XML signature is not valid." );
      }
   }
   catch ( CryptographicException^ e ) 
   {
      Console::WriteLine( e->Message );
   }

   return 1;
}

.NET Framework
Available since 2.0

Any public static ( Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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