I'm trying to protect against malicious XXE injections in the XMLs processed by my app. Therefore I'm using XDocument instead of XmlDocument.
The XML represents the payload of a web request so I call XDocument.Parse on its string content. However, I'm seeing the XXE references contained in the XML (&XXE) being replaced in the result with the actual value of ENTITY xxe.
Is it possible to parse the XML with XDocument without replacing &xxe ?
Thanks
EDIT:
I managed to avoid the replacement of xxes in the XML using XmlResolver=null for XDocument.Load
Instead of Parse try to use Load with a pre-configured reader:
var xdoc = XDocument.Load(new XmlTextReader(
new StringReader(xmlContent)) { EntityHandling = EntityHandling.ExpandCharEntities });
From MSDN:
When EntityHandling is set to ExpandCharEntities, the reader expands character entities and returns general entities as EntityReference nodes.
Use the following example to stop resolving XXE (schemas and DTD).
Dim objXmlReader As System.Xml.XmlTextReader = Nothing
objXmlReader = New System.Xml.XmlTextReader(_patternFilePath)
objXmlReader.XmlResolver = Nothing
patternDocument = XDocument.Load(objXmlReader)
Related
I am returning an object from a web service. It arrives in XML format -
<DailyTracker xmlns="http://schemas.datacontract.org/2004/07/MSI.Web.MSINet.BusinessEntities">
<ClientId>2147483647</ClientId>
<ClientRosterId>2147483647</ClientRosterId>
<Dept>
<DepartmentID>2147483647</DepartmentID>
<DepartmentName>String content</DepartmentName>
<EmailAddress>String content</EmailAddress>
<Location>2147483647</Location>
<PayCode>String content</PayCode>
</Dept>
etc, etc...
</DailyTracker>
This is coming from an asp.net website using c#. I am returning an object of type DailyTracker.
how can I add an attribute to one of the elements? Is that possible?
Thanks!
Instantiate an XDocument using the XML returned from the service. Get the XElement that you want, then add a new XAttribute to it:
XDocument document = new XDocument(xmlString);
XElement element = document.Element("myElement");
element.Add(new XAttribute("MyAttr", "My Value"));
You can override the Serialization process and add custom attributes to the Serialized XML content similar to the one that is described here
I have an XML file that already contains a reference to an XSLT file.
I'm looking at converting this XML file, according to the referenced transformation rules, so that I can then create a nice PDF file.
It appears that I can perform the actual transform via System.Xml.Xsl.XslCompiledTransform, but it requires that I manually associate an XSLT before I perform the transform.
Based on what I've seen, I must now manually pull the XSLT reference from the XDocument (rough start below):
xmlDocument.Document.Nodes()
.Where(n => n.NodeType == System.Xml.XmlNodeType.ProcessingInstruction)
However, since the XSLT is already referenced within the XML file itself, I assume I'm doing too much work, and there's a more efficient way to apply the transform.
Is there, or is this what one has to do?
There is no more efficient way to do that. You have to retrieve href to xslt from your xml before transforming it.
Similar question here : XslTransform with xml-stylesheet
I wrote the following runtime extention to help with this.
I haven't tested using a reference xsl in the xml yet, but otherwise it should be good.
<Runtime.CompilerServices.Extension()>
Public Function XslTransform(XDocument As XDocument, xslFile As String) As XDocument
If String.IsNullOrWhiteSpace(xslFile) Then
Try
Dim ProcessingInstructions As IEnumerable(Of XElement) = From Node As XNode In XDocument.Nodes
Where Node.NodeType = Xml.XmlNodeType.ProcessingInstruction
Select Node
xslFile = ProcessingInstructions.Value
Catch ex As Exception
ex.WriteToLog(EventLogEntryType.Warning)
End Try
End If
XslTransform = New XDocument
Try
Dim XslCompiledTransform As New Xml.Xsl.XslCompiledTransform()
XslCompiledTransform.Load(xslFile)
Using XmlWriter As Xml.XmlWriter = XslTransform.CreateWriter
Using XMLreader As Xml.XmlReader = XDocument.CreateReader()
XslCompiledTransform.Transform(XMLreader, XmlWriter)
XmlWriter.Close()
End Using
End Using
Return XslTransform
Catch ex As Exception
ex.WriteToLog
XslTransform = New XDocument()
Throw New ArgumentException("XDocument failted to transform using " & xslFile, ex)
End Try
End Function
Is there anything built in to determine if an XML file is valid. One way would be to read the entire content and verify if the string represents valid XML content. Even then, how to determine if string contains valid XML data.
Create an XmlReader around a StringReader with the XML and read through the reader:
using (var reader = XmlReader.Create(something))
while(reader.Read())
;
If you don't get any exceptions, the XML is well-formed.
Unlike XDocument or XmlDocument, this will not hold an entire DOM tree in memory, so it will run quickly even on extremely large XML files.
You can try to load the XML into XML document and catch the exception.
Here is the sample code:
var doc = new XmlDocument();
try {
doc.LoadXml(content);
} catch (XmlException e) {
// put code here that should be executed when the XML is not valid.
}
Hope it helps.
Have a look at this question:
How to check for valid xml in string input before calling .LoadXml()
I am developing window phone 7 application. I am new to the window phone 7 application. I am referring to the following link for XML Serialization & Deserialization.
http://www.codeproject.com/KB/windows-phone-7/wp7rssreader.aspx
In the above link the LoadFromIso() function is used for XML Deserialization. I want to load the xml file after deserialization in the above link. In simple one case we can do this as in the following code. Similar to the following code I want "doc" in the above link. In the following code we can perform the various opeations on the XML file by using LINQ to XML with following statement
doc = XDocument.Load(isfStream);
The complete code is as follows
IsolatedStorageFile isfData = IsolatedStorageFile.GetUserStoreForApplication();
XDocument doc = null;
IsolatedStorageFileStream isfStream = null;
if (isfData.FileExists(strXMLFile))
{
isfStream = new IsolatedStorageFileStream(strXMLFile, FileMode.Open, isfData);
doc = XDocument.Load(isfStream);
isfStream.Close();
}
In the similar way I want the instance of the XDocument after deserializing the object so that I can perform the various operations on the XML file by using LINQ to XML. Can you please provide me any code or link through which I can obtain the instance of the XDocument so that I can load the XML file & perform the various operation on the XML file by using the LINQ to XML ?
The variable doc in your code is an XDocument of the deserialized content.
You can perform your operations on/with doc.
A simple WP7 project demonstrating loading XML using XDocument and LINQ and data binding to a listbox here. As Matt advises the work gets done on your XDocument instance.
binding a Linq datasource to a listbox
I am trying to access this webservice, The problem is that sometimes XDocument.Parse is not able to process and generates an error System.Xml.XmlException: Root element is missing. on the line:
XDocument xmlDoc = XDocument.Parse(xmlData);
Even though the XML sent is correct according to my logs.
I was wondering, Is it possible that the StreamReader is not working properly
using (StreamReader reader = new StreamReader(context.Request.InputStream))
{
xmlData = reader.ReadToEnd();
}
XDocument xmlDoc = XDocument.Parse(xmlData);
By the way this is all under a Custom HttpHandler.
Can someone please me guide in the right direction for this.
Thanks
Does it work any more consistently if you use
XDocument.Load(new StreamReader(context.Request.InputStream))
instead of XDocument.Parse?
Your code sample doesn't include logging of the read inputstream. The problem is prior to this point.