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问题:
Is there a way to sign an XML file with RSA and to have the namespace prefix "ds:Signature" instead of "Signature"? I spent many hourstrying to solve this and from what I can see there is no solution.
It seems that it is hard-coded in the class System.Security.Cryptography.Xml.Signature.
XmlElement element = document.CreateElement("Signature", "http://www.w3.org/2000/09/xmldsig#");
If anyone knows a solution, I need to sign it like that cause the software importing it verifies it with "ds:signature", so with "ds" prefix the software verifies it like this:
public static bool VerifySignature(XmlDocument doc, RSA key, string prefix)
{
SignedXml xml = new SignedXml(doc);
string str = "Signature";
if (!string.IsNullOrEmpty(prefix))
{
str = string.Format("{0}:{1}", prefix, str);
}
XmlNodeList elementsByTagName = doc.GetElementsByTagName(str);
xml.LoadXml((XmlElement)elementsByTagName[0]);
return xml.CheckSignature(key);
}
VerifySignature(xmlDoc, rsa, "ds");
normally it signs like this:
<kk>blabla<Signature xmlns="http://www.w3.org/2000/09/xmldsig#"><SignedInfo><CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#" /><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>rVL2nKjPTBhL9IDHYpu69OiE8gI=</DigestValue></Reference></SignedInfo><SignatureValue>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</SignatureValue></Signature></kk>
and I need it to do it like this:
<kk>blabla<ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#"><ds:SignedInfo><ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#" /><ds:SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1" /><ds:Reference URI=""><ds:Transforms><ds:Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature" /></ds:Transforms><ds:DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1" /><ds:DigestValue>rVL2nKjPTBhL9IDHYpu69OiE8gI=</ds:DigestValue></ds:Reference></ds:SignedInfo><ds:SignatureValue>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</ds:SignatureValue></ds:Signature></kk>
回答1:
if anyone know a solution, i need to sign it like that cause the software importing it verifies it with "ds:signature" , so with "ds" prefix
The prefix should be unimportant - all that should matter is what namespace the element is in. It shouldn't matter how that namespace is expressed. If it does, that shows brokenness in the verifying code, I'd say.
However, if you really want to do this, is there any reason you don't want to just replace the element with one with the same contents, but using the prefix you want? It shouldn't be hard to do that in LINQ to XML.
回答2:
i found the solution here
using System;
using System.Reflection;
using System.Security.Cryptography.Xml;
using System.Security.Cryptography;
using System.Collections.Generic;
using System.Text;
using System.Xml;
namespace mysign
{
public class PrefixedSignedXML : SignedXml
{
public PrefixedSignedXML(XmlDocument document)
: base(document)
{ }
public PrefixedSignedXML(XmlElement element)
: base(element)
{ }
public PrefixedSignedXML()
: base()
{ }
public void ComputeSignature(string prefix)
{
this.BuildDigestedReferences();
AsymmetricAlgorithm signingKey = this.SigningKey;
if (signingKey == null)
{
throw new CryptographicException("Cryptography_Xml_LoadKeyFailed");
}
if (this.SignedInfo.SignatureMethod == null)
{
if (!(signingKey is DSA))
{
if (!(signingKey is RSA))
{
throw new CryptographicException("Cryptography_Xml_CreatedKeyFailed");
}
if (this.SignedInfo.SignatureMethod == null)
{
this.SignedInfo.SignatureMethod = "http://www.w3.org/2000/09/xmldsig#rsa-sha1";
}
}
else
{
this.SignedInfo.SignatureMethod = "http://www.w3.org/2000/09/xmldsig#dsa-sha1";
}
}
SignatureDescription description = CryptoConfig.CreateFromName(this.SignedInfo.SignatureMethod) as SignatureDescription;
if (description == null)
{
throw new CryptographicException("Cryptography_Xml_SignatureDescriptionNotCreated");
}
HashAlgorithm hash = description.CreateDigest();
if (hash == null)
{
throw new CryptographicException("Cryptography_Xml_CreateHashAlgorithmFailed");
}
this.GetC14NDigest(hash, prefix);
this.m_signature.SignatureValue = description.CreateFormatter(signingKey).CreateSignature(hash);
}
public XmlElement GetXml(string prefix)
{
XmlElement e = this.GetXml();
SetPrefix(prefix, e);
return e;
}
//Invocar por reflexión al método privado SignedXml.BuildDigestedReferences
private void BuildDigestedReferences()
{
Type t = typeof(SignedXml);
MethodInfo m = t.GetMethod("BuildDigestedReferences", BindingFlags.NonPublic | BindingFlags.Instance);
m.Invoke(this, new object[] { });
}
private byte[] GetC14NDigest(HashAlgorithm hash, string prefix)
{
//string securityUrl = (this.m_containingDocument == null) ? null : this.m_containingDocument.BaseURI;
//XmlResolver xmlResolver = new XmlSecureResolver(new XmlUrlResolver(), securityUrl);
XmlDocument document = new XmlDocument();
document.PreserveWhitespace = true;
XmlElement e = this.SignedInfo.GetXml();
document.AppendChild(document.ImportNode(e, true));
//CanonicalXmlNodeList namespaces = (this.m_context == null) ? null : Utils.GetPropagatedAttributes(this.m_context);
//Utils.AddNamespaces(document.DocumentElement, namespaces);
Transform canonicalizationMethodObject = this.SignedInfo.CanonicalizationMethodObject;
//canonicalizationMethodObject.Resolver = xmlResolver;
//canonicalizationMethodObject.BaseURI = securityUrl;
SetPrefix(prefix, document.DocumentElement); //establecemos el prefijo antes de se que calcule el hash (o de lo contrario la firma no será válida)
canonicalizationMethodObject.LoadInput(document);
return canonicalizationMethodObject.GetDigestedOutput(hash);
}
private void SetPrefix(string prefix, XmlNode node)
{
foreach (XmlNode n in node.ChildNodes)
SetPrefix(prefix, n);
node.Prefix = prefix;
}
}
}
回答3:
I tried these solutions, but they didn't worked out. However, by looking at .NET source code (http://referencesource.microsoft.com/) we can see that this can be acomplished easily by providing a derived XmlDocument class to SignedXml, where namespace can be added. However, having the "ds" prefix within 'SignedInfo' and descendants will cause siganture to fail. Here is the best I could do without breaking the signature:
XmlDsigDocument.cs
using System;
using System.Collections.Generic;
using System.Security.Cryptography.Xml;
using System.Text;
using System.Xml;
namespace CustomSecurity
{
class XmlDsigDocument : XmlDocument
{
// Constants
public const string XmlDsigNamespacePrefix = "ds";
/// <summary>
/// Override CreateElement function as it is extensively used by SignedXml
/// </summary>
/// <param name="prefix"></param>
/// <param name="localName"></param>
/// <param name="namespaceURI"></param>
/// <returns></returns>
public override XmlElement CreateElement(string prefix, string localName, string namespaceURI)
{
// CAntonio. If this is a Digital signature security element, add the prefix.
if (string.IsNullOrEmpty(prefix))
{
// !!! Note: If you comment this line, you'll get a valid signed file! (but without ds prefix)
// !!! Note: If you uncomment this line, you'll get an invalid signed file! (with ds prefix within 'Signature' object)
//prefix = GetPrefix(namespaceURI);
// The only way to get a valid signed file is to prevent 'Prefix' on 'SignedInfo' and descendants.
List<string> SignedInfoAndDescendants = new List<string>();
SignedInfoAndDescendants.Add("SignedInfo");
SignedInfoAndDescendants.Add("CanonicalizationMethod");
SignedInfoAndDescendants.Add("InclusiveNamespaces");
SignedInfoAndDescendants.Add("SignatureMethod");
SignedInfoAndDescendants.Add("Reference");
SignedInfoAndDescendants.Add("Transforms");
SignedInfoAndDescendants.Add("Transform");
SignedInfoAndDescendants.Add("InclusiveNamespaces");
SignedInfoAndDescendants.Add("DigestMethod");
SignedInfoAndDescendants.Add("DigestValue");
if (!SignedInfoAndDescendants.Contains(localName))
{
prefix = GetPrefix(namespaceURI);
}
}
return base.CreateElement(prefix, localName, namespaceURI);
}
/// <summary>
/// Select the standar prefix for the namespaceURI provided
/// </summary>
/// <param name="namespaceURI"></param>
/// <returns></returns>
public static string GetPrefix(string namespaceURI)
{
if (namespaceURI == "http://www.w3.org/2001/10/xml-exc-c14n#")
return "ec";
else if (namespaceURI == SignedXml.XmlDsigNamespaceUrl)
return "ds";
return string.Empty;
}
}
}
This is used on the SignedXml Creation:
// Create a new XML document.
XmlDsigDocument doc = new XmlDsigDocument();
// Load the passed XML file using its name.
doc.Load(new XmlTextReader(FileName));
// Create a SignedXml object.
SignedXml signedXml = new SignedXml(doc);
You can see full source files at:
https://social.msdn.microsoft.com/Forums/en-US/cd595379-f66a-49c8-8ca2-62acdc58b252/add-prefixds-signedxml?forum=xmlandnetfx
回答4:
May be correctly SetPrefix code looks like this:
private void SetPrefix(String prefix, XmlNode node) {
foreach (XmlNode n in node.ChildNodes)
{
SetPrefix(prefix, n);
n.Prefix = prefix;
}
}
回答5:
I agree that Prefix should not be important, but...
XML becomes much easier in C# if you use XPath:
var s = signedXml.GetXml();
XmlNodeList nodes = s.SelectNodes("descendant-or-self::*");
foreach (XmlNode childNode in nodes)
{
childNode.Prefix = "dsig";
}
回答6:
The code George Dima provide works.
I will explain how it works.
When you call the ComputeSignature method this will generate the Signature Value by digesting the value of the SignedInfo node.
The code provided by George Dima adds the Prefix to the SignedInfo node and its children BEFORE getting the digest value. This won't add the prefix to the whole xml structure
this is the method that generates the digest value of the signedinfo node
private byte[] GetC14NDigest(HashAlgorithm hash, string prefix)
{
XmlDocument document = new XmlDocument();
document.PreserveWhitespace = true;
XmlElement e = this.SignedInfo.GetXml();
document.AppendChild(document.ImportNode(e, true));
Transform canonicalizationMethodObject = this.SignedInfo.CanonicalizationMethodObject;
SetPrefix(prefix, document.DocumentElement); //HERE'S WHERE THE PREFIX IS ADDED TO GET THE DIGEST VALUE
canonicalizationMethodObject.LoadInput(document);
return canonicalizationMethodObject.GetDigestedOutput(hash);
}
So you now have the digest value of the SignedInfo node WITH the prefix, and this value will be use to get the Signature Value, but you still DON'T have the xml with the prefix yet, so if you just do this
signedXml.GetXml();
you will get the xml without the prefix and of course because the signature value was calculated considering the ds prefix you will have an invalid signature so what you have to do is call the GetXml passing it the value of the prefix, in this case "ds" like this
signedXml.GetXml("ds");
