XmlDsigEnvelopedSignatureTransform Class
Represents the enveloped signature transform for an XML digital signature as defined by the W3C.
Assembly: System.Security (in System.Security.dll)
The XmlDsigEnvelopedSignatureTransform class removes the <Signature> element from an XML document before the digest is computed. With this transform, you can sign and verify all elements of an XML document except the XML digital signature elements.
Although you can create and insert a signature into an XML document, verifying the modified document using the embedded signature will fail because the document now has additional elements. This transform removes the <Signature> element and allows you to verify the document using its original form.
Use the XmlDsigEnvelopedSignatureTransform class whenever you create an enveloped signature.
For more information about the enveloped signature transform, see Section 6.6.4 of the XMLDSIG specification, which is available from the W3C at www.w3.org/TR/xmldsig-core/.
This section contains two code examples. The first example demonstrates how to sign an XML file using an envelope signature. The second example demonstrates how to use members of the XmlDsigEnvelopedSignatureTransform class.
Example #1
' ' This example signs an XML file using an ' envelope signature. It then verifies the ' signed XML. ' Imports System Imports System.Security.Cryptography Imports System.Security.Cryptography.X509Certificates Imports System.Security.Cryptography.Xml Imports System.Text Imports System.Xml Public Class SignVerifyEnvelope Overloads Public Shared Sub Main(args() As [String]) Try ' Generate a signing key. Dim Key As New RSACryptoServiceProvider() ' Create an XML file to sign. CreateSomeXml("Example.xml") Console.WriteLine("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("XML file signed.") ' Verify the signature of the signed XML. Console.WriteLine("Verifying signature...") Dim result As Boolean = VerifyXmlFile("SignedExample.xml") ' Display the results of the signature verification to \ ' the console. If result Then Console.WriteLine("The XML signature is valid.") Else Console.WriteLine("The XML signature is not valid.") End If Catch e As CryptographicException Console.WriteLine(e.Message) End Try End Sub ' Sign an XML file and save the signature in a new file. Public Shared Sub SignXmlFile(FileName As String, SignedFileName As String, Key As RSA) ' Create a new XML document. Dim doc As New XmlDocument() ' Format the document to ignore white spaces. doc.PreserveWhitespace = False ' Load the passed XML file using it's name. doc.Load(New XmlTextReader(FileName)) ' Create a SignedXml object. Dim signedXml As New SignedXml(doc) ' Add the key to the SignedXml document. signedXml.SigningKey = Key ' Create a reference to be signed. Dim reference As New Reference() reference.Uri = "" ' Add an enveloped transformation to the reference. Dim env As New 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). Dim keyInfo As New KeyInfo() keyInfo.AddClause(New RSAKeyValue(CType(Key, RSA))) signedXml.KeyInfo = keyInfo ' Compute the signature. signedXml.ComputeSignature() ' Get the XML representation of the signature and save ' it to an XmlElement object. Dim xmlDigitalSignature As XmlElement = signedXml.GetXml() ' Append the element to the XML document. doc.DocumentElement.AppendChild(doc.ImportNode(xmlDigitalSignature, True)) If TypeOf doc.FirstChild Is XmlDeclaration Then doc.RemoveChild(doc.FirstChild) End If ' Save the signed XML document to a file specified ' using the passed string. Dim xmltw As New XmlTextWriter(SignedFileName, New UTF8Encoding(False)) doc.WriteTo(xmltw) xmltw.Close() End Sub ' Verify the signature of an XML file and return the result. Public Shared Function VerifyXmlFile(Name As [String]) As [Boolean] ' Create a new XML document. Dim xmlDocument As New 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. Dim signedXml As New SignedXml(xmlDocument) ' Find the "Signature" node and create a new ' XmlNodeList object. Dim nodeList As XmlNodeList = xmlDocument.GetElementsByTagName("Signature") ' Load the signature node. signedXml.LoadXml(CType(nodeList(0), XmlElement)) ' Check the signature and return the result. Return signedXml.CheckSignature() End Function ' Create example data to sign. Public Shared Sub CreateSomeXml(FileName As String) ' Create a new XmlDocument object. Dim document As New XmlDocument() ' Create a new XmlNode object. Dim node As XmlNode = document.CreateNode(XmlNodeType.Element, "", "MyElement", "samples") ' Add some text to the node. node.InnerText = "Example text to be signed." ' Append the node to the document. document.AppendChild(node) ' Save the XML document to the file name specified. Dim xmltw As New XmlTextWriter(FileName, New UTF8Encoding(False)) document.WriteTo(xmltw) xmltw.Close() End Sub End Class
Example #2
Imports System Imports System.IO Imports System.Xml Imports System.Security.Cryptography Imports System.Security.Cryptography.Xml Imports System.Security.Cryptography.X509Certificates Public Class Form1 Inherits System.Windows.Forms.Form Private certificatePath As String = "..\\my509.cer" ' Event handler for Run button. Private Sub Button1_Click( _ ByVal sender As System.Object, _ ByVal e As System.EventArgs) Handles Button1.Click tbxOutput.Cursor = Cursors.WaitCursor tbxOutput.Text = "" ' Encrypt an XML message Dim productsXml As XmlDocument = LoadProducts() ShowTransformProperties(productsXml) SignDocument(productsXml) ShowTransformProperties(productsXml) ' Use XmlDsigEnvelopedSignatureTransform to resolve a Uri. Dim baseUri As New Uri("http://www.contoso.com") Dim relativeUri As String = "xml" Dim absoluteUri As Uri = ResolveUris(baseUri, relativeUri) ' Align interface and conclude application. WriteLine(vbCrLf + "This sample completed successfully;" + _ " press Exit to continue.") ' Reset the cursor. tbxOutput.Cursor = Cursors.Default End Sub ' Encrypt the text in the specified XmlDocument. Private Sub ShowTransformProperties(ByVal xmlDoc As XmlDocument) Dim xmlTransform As New XmlDsigEnvelopedSignatureTransform ' Ensure the transform is using the proper algorithm. xmlTransform.Algorithm = _ SignedXml.XmlDsigEnvelopedSignatureTransformUrl ' Retrieve the XML representation of the current transform. Dim xmlInTransform As XmlElement = xmlTransform.GetXml() WriteLine(vbCrLf + "Xml representation of the current transform: ") WriteLine(xmlInTransform.OuterXml) ' Retrieve the valid input types for the current transform. Dim validInTypes() As Type = xmlTransform.InputTypes ' Verify the xmlTransform can accept the XMLDocument as an ' input type. For i As Int16 = 0 To validInTypes.Length Step 1 If (validInTypes(i).Equals(xmlDoc.GetType())) Then ' Load the document into the transfrom. xmlTransform.LoadInput(xmlDoc) Dim IncludeComments As Boolean = True ' This transform is created for demonstration purposes. Dim secondTransform As _ New XmlDsigEnvelopedSignatureTransform(IncludeComments) Dim classDescription As String = secondTransform.ToString() ' This call does not perform as expected. ' An enveloped signature has no inner XML elements secondTransform.LoadInnerXml(xmlDoc.SelectNodes("//.")) Exit For End If Next Dim validOutTypes() As Type = xmlTransform.OutputTypes For i As Int16 = validOutTypes.Length - 1 To 0 Step -1 If (validOutTypes(i).Equals(GetType(System.Xml.XmlDocument))) Then Try Dim xmlDocumentType As Type xmlDocumentType = GetType(System.Xml.XmlDocument) Dim xmlDocumentOutput As XmlDocument xmlDocumentOutput = CType( _ xmlTransform.GetOutput(xmlDocumentType), _ XmlDocument) ' Display to the console the Xml before and after ' encryption. WriteLine("Result of the GetOutput method call from " + _ "the current transform: " + _ xmlDocumentOutput.OuterXml) Catch ex As Exception WriteLine("Unexpected exception caught: " + ex.ToString()) End Try Exit For ElseIf (validOutTypes(i).Equals( _ GetType(System.Xml.XmlNodeList))) Then Try Dim xmlNodeListType As Type xmlNodeListType = GetType(System.Xml.XmlNodeList) Dim xmlNodes As XmlNodeList xmlNodes = CType( _ xmlTransform.GetOutput(xmlNodeListType), _ System.Xml.XmlNodeList) ' Display to the console the Xml before and after ' encryption. WriteLine("Encoding the following message: " + _ xmlDoc.InnerText) WriteLine("Nodes of the XmlNodeList retrieved from " + _ "GetOutput:") For j As Int16 = 0 To xmlNodes.Count - 1 Step 1 WriteLine("Node " + j.ToString() + " has the " + _ "following name: " + xmlNodes.Item(j).Name + _ " and the following InnerXml: " + _ xmlNodes.Item(j).InnerXml) Next Catch ex As Exception WriteLine("Unexpected exception caught: " + ex.ToString()) End Try Exit For Else Dim outputObject As Object = xmlTransform.GetOutput() End If Next End Sub Private Function LoadProducts() As XmlDocument Dim xmlDoc As New XmlDocument Dim contosoProducts As String = "<PRODUCTS>" contosoProducts += "<PRODUCT><ID>123</ID>" contosoProducts += "<DESCRIPTION>Router</DESCRIPTION></PRODUCT>" contosoProducts += "<PRODUCT><ID>456</ID>" contosoProducts += "<DESCRIPTION>Keyboard</DESCRIPTION></PRODUCT>" contosoProducts += "<PRODUCT><ID>789</ID>" contosoProducts += "<DESCRIPTION>Monitor</DESCRIPTION></PRODUCT>" contosoProducts += "</PRODUCTS>" xmlDoc.LoadXml(contosoProducts) Return xmlDoc End Function ' Create a signature and add it to the specified document. Private Sub SignDocument(ByRef xmlDoc As XmlDocument) ' Generate a signing key. Dim Key As New RSACryptoServiceProvider ' Create a SignedXml object. Dim signedXml As New SignedXml(xmlDoc) ' Add the key to the SignedXml document. signedXml.SigningKey = Key ' Create a reference to be signed. Dim reference As New Reference Reference.Uri = "" ' Add an enveloped transformation to the reference. Reference.AddTransform(New XmlDsigEnvelopedSignatureTransform) ' Add the reference to the SignedXml object. SignedXml.AddReference(Reference) Try ' Create a new KeyInfo object. Dim keyInfo As New keyInfo ' Load the X509 certificate. Dim MSCert As X509Certificate MSCert = X509Certificate.CreateFromCertFile(certificatePath) ' Load the certificate into a KeyInfoX509Data object ' and add it to the KeyInfo object. keyInfo.AddClause(New KeyInfoX509Data(MSCert)) ' Add the KeyInfo object to the SignedXml object. signedXml.KeyInfo = keyInfo Catch ex As FileNotFoundException WriteLine("Unable to load the following file: " + certificatePath) End Try ' Compute the signature. signedXml.ComputeSignature() ' Add the signature branch to the original tree so it is enveloped. xmlDoc.DocumentElement.AppendChild(signedXml.GetXml()) End Sub ' Resolve the specified base and relative Uri's . Private Function ResolveUris( _ ByVal baseUri As Uri, _ ByVal relativeUri As String) As Uri Dim xmlResolver As New XmlUrlResolver xmlResolver.Credentials = _ System.Net.CredentialCache.DefaultCredentials Dim xmlTransform As New XmlDsigEnvelopedSignatureTransform xmlTransform.Resolver = xmlResolver Dim absoluteUri As Uri = xmlResolver.ResolveUri(baseUri, relativeUri) If Not absoluteUri Is Nothing Then WriteLine(vbCrLf + "Resolved the base Uri and relative Uri " + _ "to the following:") WriteLine(absoluteUri.ToString()) Else WriteLine("Unable to resolve the base Uri and relative Uri") End If Return absoluteUri End Function ' Write specified message and carriage return to the output textbox. Private Sub WriteLine(ByVal message As String) tbxOutput.AppendText(Message + vbCrLf) End Sub ' Event handler for Exit button. Private Sub Button2_Click( _ ByVal sender As System.Object, _ ByVal e As System.EventArgs) Handles Button2.Click Application.Exit() End Sub #Region " Windows Form Designer generated code " Public Sub New() MyBase.New() 'This call is required by the Windows Form Designer. InitializeComponent() 'Add any initialization after the InitializeComponent() call End Sub 'Form overrides dispose to clean up the component list. Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean) If disposing Then If Not (components Is Nothing) Then components.Dispose() End If End If MyBase.Dispose(disposing) End Sub 'Required by the Windows Form Designer Private components As System.ComponentModel.IContainer 'NOTE: The following procedure is required by the Windows Form Designer 'It can be modified using the Windows Form Designer. 'Do not modify it using the code editor. Friend WithEvents Panel2 As System.Windows.Forms.Panel Friend WithEvents Panel1 As System.Windows.Forms.Panel Friend WithEvents Button1 As System.Windows.Forms.Button Friend WithEvents Button2 As System.Windows.Forms.Button Friend WithEvents tbxOutput As System.Windows.Forms.RichTextBox <System.Diagnostics.DebuggerStepThrough()> _ Private Sub InitializeComponent() Me.Panel2 = New System.Windows.Forms.Panel Me.Button1 = New System.Windows.Forms.Button Me.Button2 = New System.Windows.Forms.Button Me.Panel1 = New System.Windows.Forms.Panel Me.tbxOutput = New System.Windows.Forms.RichTextBox Me.Panel2.SuspendLayout() Me.Panel1.SuspendLayout() Me.SuspendLayout() ' 'Panel2 ' Me.Panel2.Controls.Add(Me.Button1) Me.Panel2.Controls.Add(Me.Button2) Me.Panel2.Dock = System.Windows.Forms.DockStyle.Bottom Me.Panel2.DockPadding.All = 20 Me.Panel2.Location = New System.Drawing.Point(0, 320) Me.Panel2.Name = "Panel2" Me.Panel2.Size = New System.Drawing.Size(616, 64) Me.Panel2.TabIndex = 1 ' 'Button1 ' Me.Button1.Dock = System.Windows.Forms.DockStyle.Right Me.Button1.Font = New System.Drawing.Font( _ "Microsoft Sans Serif", _ 9.0!, _ System.Drawing.FontStyle.Regular, _ System.Drawing.GraphicsUnit.Point, _ CType(0, Byte)) Me.Button1.Location = New System.Drawing.Point(446, 20) Me.Button1.Name = "Button1" Me.Button1.Size = New System.Drawing.Size(75, 24) Me.Button1.TabIndex = 2 Me.Button1.Text = "&Run" ' 'Button2 ' Me.Button2.Dock = System.Windows.Forms.DockStyle.Right Me.Button2.Font = New System.Drawing.Font( _ "Microsoft Sans Serif", _ 9.0!, _ System.Drawing.FontStyle.Regular, _ System.Drawing.GraphicsUnit.Point, _ CType(0, Byte)) Me.Button2.Location = New System.Drawing.Point(521, 20) Me.Button2.Name = "Button2" Me.Button2.Size = New System.Drawing.Size(75, 24) Me.Button2.TabIndex = 3 Me.Button2.Text = "E&xit" ' 'Panel1 ' Me.Panel1.Controls.Add(Me.tbxOutput) Me.Panel1.Dock = System.Windows.Forms.DockStyle.Fill Me.Panel1.DockPadding.All = 20 Me.Panel1.Location = New System.Drawing.Point(0, 0) Me.Panel1.Name = "Panel1" Me.Panel1.Size = New System.Drawing.Size(616, 320) Me.Panel1.TabIndex = 2 ' 'tbxOutput ' Me.tbxOutput.AccessibleDescription = _ "Displays output from application." Me.tbxOutput.AccessibleName = "Output textbox." Me.tbxOutput.Dock = System.Windows.Forms.DockStyle.Fill Me.tbxOutput.Location = New System.Drawing.Point(20, 20) Me.tbxOutput.Name = "tbxOutput" Me.tbxOutput.Size = New System.Drawing.Size(576, 280) Me.tbxOutput.TabIndex = 1 Me.tbxOutput.Text = "Click the Run button to run the application." ' 'Form1 ' Me.AutoScaleBaseSize = New System.Drawing.Size(6, 15) Me.ClientSize = New System.Drawing.Size(616, 384) Me.Controls.Add(Me.Panel1) Me.Controls.Add(Me.Panel2) Me.Name = "Form1" Me.Text = "XmlDsigEnvelopedSignatureTransform" Me.Panel2.ResumeLayout(False) Me.Panel1.ResumeLayout(False) Me.ResumeLayout(False) End Sub #End Region End Class ' ' This sample produces the following output: ' ' Xml representation of the current transform: ' <Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature" ' xmlns="http://www.w3.org/2000/09/xmldsig#" /> ' Result of the GetOutput method call from the current transform: <PRODUCTS> ' <PRODUCT><ID>123</ID><DESCRIPTION>Router</DESCRIPTION></PRODUCT><PRODUCT> ' <ID>456</ID><DESCRIPTION>Keyboard</DESCRIPTION></PRODUCT><PRODUCT><ID>789 ' </ID><DESCRIPTION>Monitor</DESCRIPTION></PRODUCT></PRODUCTS> ' Unable to load the following file: ..\\my509.cer ' ' Xml representation of the current transform: ' <Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature" ' xmlns="http://www.w3.org/2000/09/xmldsig#" /> ' Result of the GetOutput method call from the current transform: <PRODUCTS> ' <PRODUCT><ID>123</ID><DESCRIPTION>Router</DESCRIPTION></PRODUCT><PRODUCT> ' <ID>456</ID><DESCRIPTION>Keyboard</DESCRIPTION></PRODUCT><PRODUCT><ID>789 ' </ID><DESCRIPTION>Monitor</DESCRIPTION></PRODUCT><Signature xmlns= ' "http://www.w3.org/2000/09/xmldsig#"><SignedInfo><CanonicalizationMethod ' Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315" /> ' <SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1" /> ' <Reference URI=""><Transforms><Transform Algorithm="http://www.w3.org/2000 ' /09/xmldsig#enveloped-signature" /></Transforms><DigestMethod Algorithm= ' "http://www.w3.org/2000/09/xmldsig#sha1" /><DigestValue>KvPW6HUiIUMEDS0YSoTg ' po2JPbA=</DigestValue></Reference></SignedInfo><SignatureValue>c/njCGDru/aWA ' mWG83I+mWO040xOzxvmNx0b0o8ZyPc9j5VwApdAt103OGBtB1H6EkOvt7Ekw+PVuUo8m5LzLPyaT ' xUDMbb2kZZ5itSkGD4rmMUMUMuzrkAoquJZjxeOydBJ2CMehV2rE3RMPLIwRX176DZVy5JKU6Cb7 ' PR2Rpw=</SignatureValue></Signature></PRODUCTS> ' ' Resolved the base Uri and relative Uri to the following: ' http://www.contoso.com/xml ' ' This sample completed successfully; press Exit to continue.
System.Security.Cryptography.Xml.Transform
System.Security.Cryptography.Xml.XmlDsigEnvelopedSignatureTransform
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.