如何：验证 XML 文档的数字签名

项目
08/12/2011

可以使用 System.Security.Cryptography.Xml 命名空间中的类验证数字签名的 XML 数据。使用 XML 数字签名 (XMLDSIG)，您可以验证签名后的数据没有被更改。有关 XMLDSIG 标准的更多信息，请参见位于 http://www.w3.org/TR/xmldsig-core/ 上的 WWW 联合会 (W3C) 规范。

此过程中的代码示例演示了如何验证包含在 <Signature> 元素中的 XML 数字签名。该示例从密钥容器中检索 RSA 公钥，然后用该密钥验证签名。

有关如何创建可以用此技术验证的数字签名的信息，请参见如何：使用数字签名为 XML 文档签名。

验证 XML 文档的数字签名

若要验证文档，必须使用与签名时所使用的非对称密钥相同的密钥。创建 CspParameters 对象，并指定签名时使用的密钥容器的名称。

Dim cspParams As New CspParameters()
cspParams.KeyContainerName = "XML_DSIG_RSA_KEY"

CspParameters cspParams = new CspParameters();
cspParams.KeyContainerName = "XML_DSIG_RSA_KEY";

使用 RSACryptoServiceProvider 类检索公钥。当您将 CspParameters 对象传递给 RSACryptoServiceProvider 类的构造函数时，该密钥将自动按名称从密钥容器中加载。
```
Dim rsaKey As New RSACryptoServiceProvider(cspParams)
```
```
RSACryptoServiceProvider rsaKey = new RSACryptoServiceProvider(cspParams);
```

通过从磁盘加载 XML 文件创建 XmlDocument 对象。 XmlDocument 对象包含要验证的已签名的 XML 文档。

Dim xmlDoc As New XmlDocument()

' Load an XML file into the XmlDocument object.
xmlDoc.PreserveWhitespace = True
xmlDoc.Load("test.xml")

XmlDocument xmlDoc = new XmlDocument();

// Load an XML file into the XmlDocument object.
xmlDoc.PreserveWhitespace = true;
xmlDoc.Load("test.xml");

创建一个新的 SignedXml 对象，并将 XmlDocument 对象传递给它。

Dim signedXml As New SignedXml(Doc)

SignedXml signedXml = new SignedXml(Doc);

找到 <signature> 元素，并创建新的 XmlNodeList 对象。

Dim nodeList As XmlNodeList = Doc.GetElementsByTagName("Signature")

XmlNodeList nodeList = Doc.GetElementsByTagName("Signature");

将第一个 <signature> 元素的 XML 加载到 SignedXml 对象中。

signedXml.LoadXml(CType(nodeList(0), XmlElement))

signedXml.LoadXml((XmlElement)nodeList[0]);

使用 CheckSignature 方法和 RSA 公钥检查签名。此方法将返回指示成功或失败的布尔值。
```
Return signedXml.CheckSignature(Key)
```
```
return signedXml.CheckSignature(Key);
```

示例

Imports System
Imports System.Security.Cryptography
Imports System.Security.Cryptography.Xml
Imports System.Xml



Module VerifyXML


    Sub Main(ByVal args() As String)
        Try
            ' Create a new CspParameters object to specify
            ' a key container.
            Dim cspParams As New CspParameters()
            cspParams.KeyContainerName = "XML_DSIG_RSA_KEY"
            ' Create a new RSA signing key and save it in the container. 
            Dim rsaKey As New RSACryptoServiceProvider(cspParams)
            ' Create a new XML document.
            Dim xmlDoc As New XmlDocument()

            ' Load an XML file into the XmlDocument object.
            xmlDoc.PreserveWhitespace = True
            xmlDoc.Load("test.xml")
            ' Verify the signature of the signed XML.
            Console.WriteLine("Verifying signature...")
            Dim result As Boolean = VerifyXml(xmlDoc, rsaKey)

            ' 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 Exception
            Console.WriteLine(e.Message)
        End Try

    End Sub





    ' Verify the signature of an XML file against an asymmetric 
    ' algorithm and return the result.
    Function VerifyXml(ByVal Doc As XmlDocument, ByVal Key As RSA) As [Boolean]
        ' Check arguments.
        If Doc Is Nothing Then
            Throw New ArgumentException("Doc")
        End If
        If Key Is Nothing Then
            Throw New ArgumentException("Key")
        End If
        ' Create a new SignedXml object and pass it
        ' the XML document class.
        Dim signedXml As New SignedXml(Doc)
        ' Find the "Signature" node and create a new
        ' XmlNodeList object.
        Dim nodeList As XmlNodeList = Doc.GetElementsByTagName("Signature")
        ' Throw an exception if no signature was found.
        If nodeList.Count <= 0 Then
            Throw New CryptographicException("Verification failed: No Signature was found in the document.")
        End If

        ' This example only supports one signature for
        ' the entire XML document.  Throw an exception 
        ' if more than one signature was found.
        If nodeList.Count >= 2 Then
            Throw New CryptographicException("Verification failed: More that one signature was found for the document.")
        End If

        ' Load the first <signature> node.  
        signedXml.LoadXml(CType(nodeList(0), XmlElement))
        ' Check the signature and return the result.
        Return signedXml.CheckSignature(Key)
    End Function
End Module

using System;
using System.Security.Cryptography;
using System.Security.Cryptography.Xml;
using System.Xml;

public class VerifyXML
{

    public static void Main(String[] args)
    {
        try
        {
            // Create a new CspParameters object to specify
            // a key container.
            CspParameters cspParams = new CspParameters();
            cspParams.KeyContainerName = "XML_DSIG_RSA_KEY";

            // Create a new RSA signing key and save it in the container. 
            RSACryptoServiceProvider rsaKey = new RSACryptoServiceProvider(cspParams);

            // Create a new XML document.
            XmlDocument xmlDoc = new XmlDocument();

            // Load an XML file into the XmlDocument object.
            xmlDoc.PreserveWhitespace = true;
            xmlDoc.Load("test.xml");

            // Verify the signature of the signed XML.
            Console.WriteLine("Verifying signature...");
            bool result = VerifyXml(xmlDoc, rsaKey);

            // Display the results of the signature verification to 
            // the console.
            if (result)
            {
                Console.WriteLine("The XML signature is valid.");
            }
            else
            {
                Console.WriteLine("The XML signature is not valid.");
            }

        }
        catch (Exception e)
        {
            Console.WriteLine(e.Message);
        }
    }




    // Verify the signature of an XML file against an asymmetric 
    // algorithm and return the result.
    public static Boolean VerifyXml(XmlDocument Doc, RSA Key)
    {
        // Check arguments.
        if (Doc == null)
            throw new ArgumentException("Doc");
        if (Key == null)
            throw new ArgumentException("Key");

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

        // Find the "Signature" node and create a new
        // XmlNodeList object.
        XmlNodeList nodeList = Doc.GetElementsByTagName("Signature");

        // Throw an exception if no signature was found.
        if (nodeList.Count <= 0)
        {
            throw new CryptographicException("Verification failed: No Signature was found in the document.");
        }

        // This example only supports one signature for
        // the entire XML document.  Throw an exception 
        // if more than one signature was found.
        if (nodeList.Count >= 2)
        {
            throw new CryptographicException("Verification failed: More that one signature was found for the document.");
        }

        // Load the first <signature> node.  
        signedXml.LoadXml((XmlElement)nodeList[0]);

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

此示例假定一个名为 "test.xml" 的文件与编译的程序在同一目录中。 "test.xml" 文件必须用如何：使用数字签名为 XML 文档签名中描述的技术签名。

编译代码

若要编译此示例，您需要包括对 System.Security.dll 的引用。
包括以下命名空间：System.Xml、System.Security.Cryptography 和 System.Security.Cryptography.Xml。

安全性

不要用纯文本存储或传输非对称密钥对的私钥。有关对称和非对称加密密钥的更多信息，请参见生成加密和解密的密钥。

不要将私钥直接嵌入到源代码中。可以通过使用 Ildasm.exe（MSIL 反汇编程序），或通过在诸如记事本的文本编辑器中打开程序集，从程序集轻松读取嵌入的密钥。

请参见

通过

如何：验证 XML 文档的数字签名

验证 XML 文档的数字签名

示例

编译代码

安全性

请参见

任务

参考

其他资源

其他资源