|
//---------------------------------------------------------------------------
//
// <copyright file=ConstrainedDataObject.cs company=Microsoft>
// Copyright (C) Microsoft Corporation. All rights reserved.
// </copyright>
//
//
// Description: Internal class implemented to primarily disable the XAML cut and paste of content from a
// partial trust source to a full trust target
//
// See spec at http://team/sites/Avalon/Specs/Rich%20Clipboard%20in%20Sandbox%20Spec.doc
//
// History:
// 09/08/2002 : akaza Created
//
//---------------------------------------------------------------------------
namespace MS.Internal
{
using System;
using System.Collections.Generic;
using System.Security;
using System.Security.Permissions;
using System.Windows;
// PreSharp uses message numbers that the C# compiler doesn't know about.
// Disable the C# complaints, per the PreSharp documentation.
#pragma warning disable 1634, 1691
#region ConstrainedDataObject Class
/// <summary>
/// Implements a wrapper class the helps prevent the copy paste of xaml content from partial trust to full trust
/// This class is instantiated and returned in the case of copy from a partial trust source to a full trust or >partial trust
/// target. The core functionality here is to strip and deny any requests for XAML content or ApplicationTrust Content in a DataObject
/// Please note it is by intent that we create a blocked list versus an allowed list of allowed types so as to not block of scenarios like
/// inking from getting their content in a full trust application if they want to.
/// </summary>
internal sealed class ConstrainedDataObject : System.Windows.IDataObject
{
//------------------------------------------------------
//
// Constructors
//
//------------------------------------------------------
#region Constructors
/// <summary>
/// Initializes a new instance of the class, containing the specified data.
/// </summary>
/// <SecurityNote>
/// Critical: This acts as a cannister to store a dataobject that will contain XAML and ApplicationTrust format.
/// The intent is to prevent that from being exposed. We mark this critical to ensure that this is called an created
/// only from known locations. Also some of the interface methods that it implements have inheritance demand.
/// </SecurityNote>
[SecurityCritical]
internal ConstrainedDataObject(System.Windows.IDataObject data)
{
// This check guarantees us that we can never create a Constrained data Object with a null dataobject
Invariant.Assert(data != null);
_innerData = data;
}
#endregion Constructors
//------------------------------------------------------
//
// Public Methods
//
//------------------------------------------------------
#region Public Methods
/// <summary>
/// Retrieves the data associated with the specified data
/// format, using an automated conversion parameter to determine whether to convert
/// the data to the format.
/// </summary>
/// <SecurityNote>
/// Critical: This accesses the _innerDataObject.
/// TreatAsSafe: It filters for the risky information and fails in the case where consumer queries for Xaml or ApplicationTrust
/// </SecurityNote>
[SecurityCritical, SecurityTreatAsSafe]
public object GetData(string format, bool autoConvert)
{
if (format == null)
{
throw new ArgumentNullException("format");
}
if (IsCriticalFormat(format))
{
return null;
}
return _innerData.GetData(format, autoConvert);
}
/// <summary>
/// Retrieves the data associated with the specified data
/// format.
/// </summary>
public object GetData(string format)
{
if (format == null)
{
throw new ArgumentNullException("format");
}
return GetData(format, true);
}
/// <summary>
/// Retrieves the data associated with the specified class
/// type format.
/// </summary>
public object GetData(Type format)
{
if (format == null)
{
throw new ArgumentNullException("format");
}
return GetData(format.FullName);
}
/// <summary>
/// Determines whether data stored in this instance is
/// associated with, or can be converted to, the specified
/// format.
/// </summary>
public bool GetDataPresent(Type format)
{
if (format == null)
{
throw new ArgumentNullException("format");
}
return (GetDataPresent(format.FullName));
}
/// <summary>
/// Determines whether data stored in this instance is
/// associated with the specified format, using an automatic conversion
/// parameter to determine whether to convert the data to the format.
/// </summary>
/// <SecurityNote>
/// Critical: This accesses the _innerDataObject.
/// TreatAsSafe: It filters for the risky information and fails in the case where consumer queries for Xaml or ApplicationTrust
/// </SecurityNote>
[SecurityCritical, SecurityTreatAsSafe]
public bool GetDataPresent(string format, bool autoConvert)
{
bool dataPresent = false;
if (format == null)
{
throw new ArgumentNullException("format");
}
if (!IsCriticalFormat(format))
{
dataPresent = _innerData.GetDataPresent(format, autoConvert);
}
return dataPresent;
}
/// <summary>
/// Determines whether data stored in this instance is
/// associated with, or can be converted to, the specified
/// format.
/// </summary>
public bool GetDataPresent(string format)
{
if (format == null)
{
throw new ArgumentNullException("format");
}
return GetDataPresent(format, true);;
}
/// <summary>
/// Gets a list of all formats that data stored in this
/// instance is associated with or can be converted to, using an automatic
/// conversion parameter <paramref name="autoConvert"/> to
/// determine whether to retrieve all formats that the data can be converted to or
/// only native data formats.
/// </summary>
/// <SecurityNote>
/// Critical: This code touches _innerData which can expose information about formats we do not want to publicly expose
/// for the partial trust to full trust paste scenario.
/// </SecurityNote>
[SecurityCritical, SecurityTreatAsSafe]
public string[] GetFormats(bool autoConvert)
{
string[] formats = _innerData.GetFormats(autoConvert);
if (formats != null)
{
StripCriticalFormats(formats);
}
return formats;
}
/// <summary>
/// Gets a list of all formats that data stored in this instance is associated
/// with or can be converted to.
/// </summary>
public string[] GetFormats()
{
return GetFormats(true);
}
/// <summary>
/// Stores the specified data in
/// this instance, using the class of the data for the format.
/// </summary>
/// <SecurityNote>
/// Critical: This code touches _innerData
/// TreatAsSafe: It does not expose it and relies on the protection in DataObject
/// to block illegitimate conditions
/// </SecurityNote>
[SecurityCritical,SecurityTreatAsSafe]
public void SetData(object data)
{
_innerData.SetData(data);
}
/// <summary>
/// Stores the specified data and its associated format in this
/// instance.
/// </summary>
/// <SecurityNote>
/// Critical: This code touches _innerData
/// TreatAsSafe: It does not expose it and relies on the protection in DataObject
/// to block illegitimate conditions
/// </SecurityNote>
[SecurityCritical, SecurityTreatAsSafe]
public void SetData(string format, object data)
{
_innerData.SetData(format, data);
}
/// <summary>
/// Stores the specified data and
/// its associated class type in this instance.
/// </summary>
/// <SecurityNote>
/// Critical: This code touches _innerData
/// TreatAsSafe: It does not expose it and relies on the protection in DataObject
/// to block illegitimate conditions
/// </SecurityNote>
[SecurityCritical, SecurityTreatAsSafe]
public void SetData(Type format, object data)
{
_innerData.SetData(format, data);
}
/// <summary>
/// Stores the specified data and its associated format in
/// this instance, using the automatic conversion parameter
/// to specify whether the
/// data can be converted to another format.
/// </summary>
/// <SecurityNote>
/// Critical: This code touches _innerData
/// TreatAsSafe: It does not expose it and relies on the protection in DataObject
/// to block illegitimate conditions
/// </SecurityNote>
[SecurityCritical, SecurityTreatAsSafe]
public void SetData(string format, Object data, bool autoConvert)
{
_innerData.SetData(format, data, autoConvert);
}
#endregion Public Methods
//------------------------------------------------------
//
// Internal Methods
//
//------------------------------------------------------
#region Internal Methods
/// <summary>
/// Return true if the format string are equal(Case-senstive).
/// </summary>
private static bool IsFormatEqual(string format1, string format2)
{
return (String.CompareOrdinal(format1, format2) == 0);
}
/// <summary>
/// This code looks for Xaml and ApplicationTrust strings in an array of strings and removed them. The reason for that is
/// that since the only scenario this class is used in is when the target application has more permissions than the source then
/// we want to ensure that the target application cannot get to xaml and application trust formats if they come out of a partial trust source.
/// </summary>
private string[] StripCriticalFormats(string[] formats)
{
List<string> resultList = new List<string>();
for (uint currentFormat = 0; currentFormat < formats.Length; currentFormat++)
{
if (!IsCriticalFormat(formats[currentFormat]))
{
resultList.Add(formats[currentFormat]);
}
}
return resultList.ToArray();
}
/// <SecurityNote>
/// Critical: This code is used to determine whether information returned is secure or not
/// TreatAsSafe: This function is critical only for tracking purposes
/// </SecurityNote>
/// <param name="format"></param>
[SecurityCritical, SecurityTreatAsSafe]
private bool IsCriticalFormat(string format)
{
return (IsFormatEqual(format, DataFormats.Xaml) ||
IsFormatEqual(format, DataFormats.ApplicationTrust));
}
#endregion Private Methods
//------------------------------------------------------
//
// Private Fields
//
//------------------------------------------------------
#region Private Fields
// Inner data object of IDataObject.
/// <SecurityNote>
/// This member holds a reference to a dataobject which if exposed allows client code in an app to get to the XAML
/// content on the clipboard. This is deisabled for the scenario where target application has more permissions than source of
/// data object and that is the only scenario where we create an instance of this class.
/// </SecurityNote>
[SecurityCritical]
private System.Windows.IDataObject _innerData;
#endregion Private Fields
}
#endregion ConstrainedDataObject Class
}
|