sharepoint - Mejor patrón para AllowUnsafeUpdates

spweb spsite

Question

Hasta ahora, en mi investigación he visto que no es prudente establecer AllowUnsafeUpdates en la operación de solicitud GET para evitar la creación de scripts entre sitios. Pero, si se requiere permitir esto, ¿cuál es la forma correcta de manejar la situación para mitigar cualquier exposición?

Aquí está mi mejor estimación sobre un patrón confiable si es absolutamente necesario permitir actualizaciones web o del sitio en una solicitud GET.

¿Mejores prácticas?

protected override void OnLoad(System.EventArgs e)
{
if(Request.HttpMethod == "POST")
{
SPUtility.ValidateFormDigest();
// will automatically set AllowSafeUpdates to true
}
// If not a POST then AllowUnsafeUpdates should be used only
// at the point of update and reset immediately after finished
// NOTE: Is this true? How is cross-site scripting used on GET
// and what mitigates the vulnerability?
}
// Point of item update
using(SPSite site = new SPSite(SPContext.Current.Site.Url, SPContext.Current.Site.SystemAccount.UserToken))
{
using (SPWeb web = site.RootWeb)
{
bool allowUpdates = web.AllowUnsafeUpdates; //store original value
web.AllowUnsafeUpdates = true;
//... Do something and call Update() ...
web.AllowUnsafeUpdates = allowUpdates; //restore original value
}
}

Comentarios sobre el mejor patrón se aprecia.

Answer 1

No estoy tan seguro de que valga la pena recordar el valor anterior de permitir actualizaciones no seguras.

Me gustaría envolver la llamada en torno a la cantidad mínima posible de código, para que las llamadas anidadas no se produzcan.

Luego puedes convertirlo en falso después.

Answer 2

Uso una clase contenedora para manejar la mayoría de la manipulación de objetos SPWeb. Esto me ayuda a recordar cerrar la web, y alivia los problemas de la configuración de actualizaciones inseguras. Está un poco hinchado, ya que he parchado a los nuevos constructores y miembros. pero entonces de nuevo; también lo es la clase SPWeb.

Uso:

using (WebWrapper wrapper = new WebWrapper("http://localhost"))
{
wrapper.AllowUnsafeUpdates();
//Do work on wrapper.
}

La definición de clase:

using System;
using System.Collections.Specialized;
using System.Data;
using System.Diagnostics;
using System.Globalization;
using System.Runtime.Serialization;
using Microsoft.SharePoint;
using Microsoft.SharePoint.Administration;
namespace Skaar.SharePoint.Customization
{
/// <summary>
/// A wrapper for a <see cref="SPWeb"/> object.
/// <remarks>Closes web object on Dispose if applicable.</remarks>
/// </summary>
[Serializable]
[DebuggerDisplay("{Uri} Unsafe:{AllowUnsafeUpdatesSetting} Update:{UpdatePending}")]
public sealed class WebWrapper : IDisposable, IDeserializationCallback, IEquatable<WebWrapper>
{
[NonSerialized] private bool unsafeUpdatesSetting;
[NonSerialized] private SPWeb web;
/// <summary>
/// Determines if the inner web object should be closed.
/// </summary>
[NonSerialized] private bool webShouldBeClosed;
/// <summary>
/// This value is used in serialization to restore <see cref="Web"/>.
/// </summary>
private string webUrl;
/// <summary>
/// Creates a new wrapper object.
/// </summary>
/// <param name="web">A web that should be closed/disposed when done.</param>
public WebWrapper(SPWeb web) : this(web, true)
{
}
/// <summary>
/// Creates a new wrapper object.
/// </summary>
/// <param name="web">An inner web object</param>
/// <param name="webShouldBeClosed">If true, the web object is closed in the <see cref="Dispose()"/> method.</param>
public WebWrapper(SPWeb web, bool webShouldBeClosed)
{
setWeb(web, webShouldBeClosed);
}
/// <summary>
/// Creates a new wrapper object.
/// </summary>
/// <param name="webAddress">The address to a web.</param>
public WebWrapper(Uri webAddress)
{
using (SPSite site = new SPSite(webAddress.ToString()))
{
string relativeUrl = renderWebRootRelativeUrl(webAddress);
if (relativeUrl == null)
{
setWeb(site.OpenWeb(), true);
}
else
{
setWeb(site.OpenWeb(relativeUrl), true);
}
}
}
private string renderWebRootRelativeUrl(Uri address)
{
for (int i = 0; i < address.Segments.Length; i++)
{
string segment = address.Segments[i];
if (string.Equals(segment, "_layouts/"))
{
string newUrl=string.Join(null, address.Segments, 0, i).Trim(''/'');
return newUrl;
}
}
return null;
}
/// <summary>
/// If true, <see cref="SPWeb.Update"/> will be called in <see cref="Dispose()"/>.
/// </summary>
public bool UpdatePending { get; private set; }
/// <summary>
/// The setting of the inner web (<see cref="SPWeb.AllowUnsafeUpdates"/>)
/// </summary>
public bool AllowUnsafeUpdatesSetting
{
get { return Web.AllowUnsafeUpdates; }
}
/// <summary>
/// The inner object.
/// </summary>
/// <exception cref="ObjectDisposedException">Exception is thrown if <see cref="IsDisposed"/> is true.</exception>
public SPWeb Web
{
get
{
if(IsDisposed)
{
throw new ObjectDisposedException("Web wrapper is disposed.");
}
return web;
}
}
/// <summary>
/// The address of the <see cref="Web"/> wrapped as a <see cref="Uri"/> object.
/// </summary>
public Uri Uri
{
get { return new Uri(Web.Url); }
}
/// <summary>
/// The address of the <see cref="Web"/> wrapped as a <see cref="Uri"/> object.
/// </summary>
public Uri GetUri(SPUrlZone zone)
{
return Site.WebApplication.GetResponseUri(zone, Uri.AbsolutePath);
}
/// <summary>
/// Creates a wrapper around the context web.
/// <remarks>The web will not be closed when wrapper is disposed. Returns null if context is unavailable.</remarks>
/// </summary>
public static WebWrapper Context
{
get
{
return SPContext.Current==null?null:new WebWrapper(SPContext.Current.Web, false);
}
}
/// <summary>
/// This is a static property wrapping of
/// the <see cref="CloneOf(SPWeb)"/> method, using
/// the <see cref="SPContext"/> current web as
/// parameter.
/// <remarks>Returns null if context is unavailable.</remarks>
/// </summary>
public static WebWrapper CloneOfContext
{
get
{
if (SPContext.Current != null)
{
SPWeb contextWeb = SPContext.Current.Web;
return CloneOf(contextWeb);
}
return null;
}
}
/// <summary>
/// Returns the <see cref="SPWeb.Exists"/> property of the <see cref="Web"/> object.
/// </summary>
public bool Exists
{
get { return Web != null && Web.Exists; }
}
/// <summary>
/// Gets the <see cref="SPSite"/> object of <see cref="Web"/>.
/// </summary>
/// <remarks>This object should not be closed by user code.</remarks>
public SPSite Site
{
get { return web.Site; }
}
/// <summary>
/// Gets the owner defined in <see cref="SPSite.Owner"/>.
/// </summary>
public SPUser Owner
{
get
{
return Site.Owner;
}
}
/// <summary>
/// Returns a context of the inner <see cref="Web"/>.
/// </summary>
public SPContext ContextOfWeb
{
get { return SPContext.GetContext(web); }
}
/// <summary>
/// Gets the language of <see cref="Web"/>.
/// </summary>
public CultureInfo Locale
{
get { return Web.Locale; }
}
/// <summary>
/// Gets the language of the root web.
/// </summary>
public CultureInfo LocaleOfRoot
{
get
{
using (WebWrapper root = Root)
{
return root.Locale;
}
}
}
/// <summary>
/// Returns a new <see cref="WebWrapper"/> wrapping the root <see cref="SPWeb"/> of this.
/// </summary>
public WebWrapper Root
{
get
{
if (webShouldBeClosed)
using (SPSite site = Site)
{
return new WebWrapper(site.RootWeb);
}
return new WebWrapper(Site.RootWeb);
}
}
/// <summary>
/// A wrapper for <see cref="SPWeb.Title"/>.
/// </summary>
public string Title
{
get { return Web.Title; }
set { Web.Title = value; }
}
/// <summary>
/// A wrapper for <see cref="SPWeb.ID"/>.
/// </summary>
public Guid ID
{
get { return Web.ID; }
}
#region Web Properties
[NonSerialized] private bool updatePropertiesPending;
/// <summary>
/// A wrapper method to <see cref="Web"/> object''s <see cref="SPWeb.Properties"/> indexer.
/// </summary>
/// <param name="key">The key to use when fetching property value.</param>
/// <returns>A string containing the value.</returns>
public string GetProperty(string key)
{
return Web.Properties[key];
}
/// <summary>
/// Sets the value in the <see cref="Web"/> object''s <see cref="SPWeb.Properties"/>. Creates a new key, or updates an existing as needed.
/// </summary>
/// <param name="key">The key to use when storing the property value.</param>
/// <param name="value">The value to set in the key.</param>
/// <remarks>The property <see cref="UpdatePending"/> is set to true.</remarks>
public void SetProperty(string key, string value)
{
if (!Web.Properties.ContainsKey(key))
{
Web.Properties.Add(key, value);
}
else
{
Web.Properties[key] = value;
}
updatePropertiesPending = true;
}
#endregion
#region IDeserializationCallback Members
///<summary>
///Runs when the entire object graph has been deserialized.
///</summary>
///
///<param name="sender">The object that initiated the callback. The functionality for this parameter is not currently implemented. </param>
public void OnDeserialization(object sender)
{
using (SPSite site = new SPSite(webUrl))
{
setWeb(site.OpenWeb(), true);
}
}
#endregion
#region IDisposable Members
///<summary>
///Closes inner web object if appropriate.
///</summary>
///<filterpriority>2</filterpriority>
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
public void Dispose(bool isDisposing)
{
if (IsDisposed) return;
if (isDisposing)
{
doDisposeOfWeb();
IsDisposed = true;
}
}
#endregion
/// <summary>
/// Value is true if <see cref="Dispose()"/> method has been called. Object is not in a usable state.
/// </summary>
internal bool IsDisposed
{
get; private set;
}
#region IEquatable<WebWrapper> Members
/// <summary>
/// This tests whether the two objects wraps the same web. It may however be two different instances of the same web.
/// </summary>
/// <param name="other">Another wrapper object.</param>
/// <returns>True if <see cref="Uri"/> equals, false otherwise.</returns>
public bool Equals(WebWrapper other)
{
if (other == null)
{
return false;
}
return Uri.Equals(other.Uri);
}
#endregion
/// <summary>
/// Reopens the inner <see cref="SPWeb"/> object. May be used when web object needs to be rereferenced in a new security context.
/// </summary>
public void ReOpen()
{
bool unsafeSetting = AllowUnsafeUpdatesSetting;
using (SPSite site = new SPSite(Web.Url))
{
SPWeb newWeb = site.OpenWeb();
doDisposeOfWeb();
web = newWeb;
web.AllowUnsafeUpdates = unsafeSetting;
unsafeUpdatesSetting = false;
webShouldBeClosed = true;
}
}
private void doDisposeOfWeb()
{
if (Web == null) return;
Update(true);
if (webShouldBeClosed)
{
Web.Close();
}
else if (Web.Exists)
{
Web.AllowUnsafeUpdates = unsafeUpdatesSetting;
}
web = null;
}
/// <summary>
/// Calls <see cref="SPWeb.Update"/> on the <see cref="Web"/> object.
/// </summary>
public void Update()
{
Update(false);
}
/// <summary>
/// Sets <see cref="UpdatePending"/> to <c>true</c>.
/// </summary>
public void SetUpdatePending()
{
UpdatePending = true;
}
/// <summary>
/// Calls <see cref="SPWeb.Update"/> on the <see cref="Web"/> object.
/// <param name="onlyIfPending">If true, update will depend on state of the <see cref="UpdatePending"/> property.</param>
/// </summary>
public void Update(bool onlyIfPending)
{
if (onlyIfPending)
{
if (updatePropertiesPending)
{
Web.Properties.Update();
updatePropertiesPending = false;
}
if (UpdatePending)
{
Web.Update();
UpdatePending = false;
}
}
else
{
Web.Update();
UpdatePending = false;
}
}
/// <summary>
/// Returns the list from <see cref="Web"/> with <see cref="SPList.Title"/> equal to <see cref="title"/>.
/// </summary>
/// <param name="title">The <see cref="SPList.Title"/> of an existing list.</param>
/// <returns>The first list found with the given title, or null, if no list is found.</returns>
public SPList GetList(string title)
{
foreach (SPList list in Web.Lists)
{
if (list.Title == title)
{
return list;
}
}
return null;
}
/// <summary>
/// A wrapper method to the <see cref="Web"/> object''s <see cref="SPWeb.Lists"/> indexer.
/// </summary>
/// <param name="id">The id of the list to return.</param>
/// <returns>The list with the supplied id.</returns>
public SPList GetList(Guid id)
{
return Web.Lists[id];
}
private void setWeb(SPWeb innerWeb, bool shouldBeClosed)
{
if (innerWeb == null || !innerWeb.Exists)
{
throw new ArgumentException("Web does not exist", "innerWeb");
}
web = innerWeb;
webShouldBeClosed = shouldBeClosed;
unsafeUpdatesSetting = innerWeb.AllowUnsafeUpdates;
AllowUnsafeUpdates();
webUrl = web.Url;
}
/// <summary>
/// Creates a new <see cref="SPWeb"/> object using the
/// url of the <see cref="web"/> parameter and wraps it
/// in a new wrapper object. The web will be
/// closed when the wrapper is disposed.
/// The cloning is done using the <see cref="SPWeb.Url"/>, thus no security context is transferred to the new web.
/// </summary>
/// <remarks>Use this to create a clone of the context web.</remarks>
/// <param name="web">The web to clone.</param>
/// <returns>A new wrapper object.</returns>
public static WebWrapper CloneOf(SPWeb web)
{
using (SPSite site = new SPSite(web.Url))
{
return new WebWrapper(site.OpenWeb());
}
}
/// <summary>
/// Creates a new <see cref="SPWeb"/> object using the
/// <see cref="Web"/> of the <see cref="web"/> parameter and wraps it
/// in a new wrapper object. The web will be
/// closed when the wrapper is disposed.
/// </summary>
/// <remarks>Use this to create a clone of the context web.</remarks>
/// <param name="web">The wrapper to clone.</param>
/// <returns>A new wrapper object.</returns>
public static WebWrapper CloneOf(WebWrapper web)
{
return CloneOf(web.Web);
}
/// <summary>
/// Sets the AllowUnsafeUpdates property to true on the
/// wrapped web object.
/// <remarks>
/// The setting is resat back in the dispose method, unless the
/// web itself is closed.
/// </remarks>
/// </summary>
public void AllowUnsafeUpdates()
{
Web.AllowUnsafeUpdates = true;
}
/// <summary>
/// Returns the url of the inner web.
/// </summary>
/// <returns>A value that equals <see cref="Web"/> <see cref="SPWeb.Url"/> property.</returns>
public override string ToString()
{
return webUrl;
}
/// <summary>
/// Returns a new <see cref="WebWrapper"/> object wrapping a new copy of the inner <see cref="Web"/> object.
/// The cloning is done using the <see cref="SPWeb.Url"/>, thus no security context is transferred to the new web.
/// </summary>
/// <remarks>The static method <see cref="CloneOf(SPWeb)"/> is used on the <see cref="Web"/> property.</remarks>
/// <returns>A new wrapper.</returns>
public WebWrapper Clone()
{
return CloneOf(Web);
}
/// <summary>
/// Implicitly wraps the web object in a <see cref="WebWrapper"/> object.
/// </summary>
/// <param name="web">The web to wrap.</param>
/// <returns>A new wrapper object. The original web may be accessed through the <see cref="Web"/> property.</returns>
public static implicit operator WebWrapper(SPWeb web)
{
return new WebWrapper(web, false);
}
/// <summary>
/// Explicitly extracts the <see cref="Web"/> value from the <see cref="wrapper"/>.
/// </summary>
/// <param name="wrapper">The object wrapping the <see cref="SPWeb"/> to extract.</param>
/// <returns>The inner <see cref="Web"/> of <see cref="wrapper"/>.</returns>
/// <remarks>The returned <see cref="SPWeb"/> object should be properly disposed after use.</remarks>
public static explicit operator SPWeb(WebWrapper wrapper)
{
wrapper.DoNotDisposeInnerWeb();
return wrapper.Web;
}
/// <summary>
/// Wrapper method for <see cref="SPWeb.GetList"/> on <see cref="Web"/> object.
/// </summary>
/// <param name="uri">A site relative uri to the list.</param>
/// <returns>A list if found.</returns>
public SPList GetList(Uri uri)
{
return web.GetList(uri.ToString());
}
/// <summary>
/// Wrapper method for <see cref="SPWeb.GetSiteData"/> on <see cref="Web"/> object.
/// </summary>
/// <returns>The results of the query,</returns>
public DataTable GetSiteData(SPSiteDataQuery query)
{
return Web.GetSiteData(query);
}
/// <summary>
/// Creates a new <see cref="SPWeb"/> as a sub web to this.
/// </summary>
/// <param name="url">The proposed local url of the new web. The nearest available is selected.</param>
/// <param name="name">The title of the new web.</param>
/// <param name="description">The description of the new web.</param>
/// <param name="language">The language of the new web. <remarks>If the language is not supported, the language of this is used.</remarks></param>
/// <param name="template">The site template to use.</param>
/// <returns>The new web wrapped in a new <see cref="WebWrapper"/> object.</returns>
[DebuggerStepThrough]
//debugger step through is to prevent this method to break when debugging, as it throws exceptions by [poor] design.
public WebWrapper CreateSubWeb(string url, string name, string description, uint language,
string template)
{
SPWeb newWeb;
try
{
newWeb = Web.Webs.Add(findSuitableWebUrl(url), name, description, language, template, true, false);
}
catch (SPException err)
{
if (err.ErrorCode == -2130575266)
{
//language not supported. Fallback to parent web language
newWeb = Web.Webs.Add(findSuitableWebUrl(url), name, description, Web.Language, template, true,
false);
}
else
throw;
}
return new WebWrapper(newWeb);
}
private string findSuitableWebUrl(string proposedName)
{
StringCollection names = new StringCollection();
names.AddRange(Web.Webs.Names);
int suffixIndex = 0;
const int maxIterations = 100000;
string name = proposedName;
while (names.Contains(name) && suffixIndex < maxIterations)
{
name = string.Format("{0}_{1}", proposedName, suffixIndex++);
}
return name;
}
/// <summary>
/// Calling this method will inhibit the default behaviour of closing the web on disposal.
/// </summary>
/// <remarks>Use with caution.</remarks>
internal void DoNotDisposeInnerWeb()
{
webShouldBeClosed = false;
}
}
}

Answer 3

Me gustaría modificar ligeramente el delegado de Trent para aceptar la web para actualizar:

public static void DoUnsafeUpdate(this SPWeb web, Action<SPWeb> action)
{
try
{
web.AllowUnsafeUpdates = true;
action(web);
}
finally
{
web.AllowUnsafeUpdates = false;
}
}

Y luego extienda HttpContext para encapsular la verificación del resumen del formulario, con una opción para elevarlo usando la técnica que se describe aquí :

public static void DoUnsafeUpdate(this HttpContext context, Action<SPWeb> action, bool elevated)
{
SPWeb web = SPControl.GetContextWeb(context);
if (!context.Request.HttpMethod.Equals("POST", StringComparison.Ordinal)
|| web.ValidateFormDigest())
throw new SPException("Error validating postback digest");
if (elevated)
web.RunAsSystem(w => w.DoUnsafeUpdate(action));
else
web.DoUnsafeUpdate(action);
}

Uso:

protected override void OnLoad(System.EventArgs e)
{
Context.DoUnsafeUpdate(web =>
{
// Update elevated web
}, true);
}

Answer 4

Otra forma limpia de implementar sería usar una combinación de métodos de extensión y delegados anónimos como tales:

public static void DoUnsafeUpdate(this SPWeb web, Action action)
{
bool allowUnsafeUpdates = web.AllowUnsafeUpdates;
web.AllowUnsafeUpdates = true;
action();
web.AllowUnsafeUpdates = allowUnsafeUpdates;
}

Con el método de extensión anterior, puede realizar su acción de "actualización insegura" de la siguiente manera:

var web = SPContext.Current.Web;
web.DoUnsafeUpdate(delegate()
{
// Put your "unsafe update" code here
});

Answer 5

Para AllowUnsafeUpdates, sigo este proceso:

if( HttpContext.Current is null )
{
Do nothing, no need to set AllowUnsafeUpdates to true nor
to call ValidateFormDigest() because update will be carried out
}
else // HttpContext.Current is NOT null
{
if( SPContext.Current is null )
{
Need to set AllowUnsafeUpdates to true
}
else // SPContext.Current is NOT null
{
Call ValidateFormDigest()
}
}

Answer 6

Si está realizando alguna operación que modifique algo, cualquiera que pueda convencer al usuario de que haga clic en un enlace puede realizar esa operación. Por ejemplo, supongamos que tiene una solicitud GET para una página que permite al usuario agregar un administrador a un sitio, y el usuario hace clic en un enlace a una página que hace un Response.Redirect (" http: // yourserver / _layouts / admin.aspx? operation = addAdministrator & username = attackerNameHere ").

Aunque normalmente un POST no ofrece mucha protección contra esto (nada impedirá que alguien tenga un <form method = "post" action = "http: //yourserver/_layouts/admin.aspx">), SharePoint tiene un concepto de forma resúmenes, que contienen información sobre la solicitud anterior que está generando la publicación posterior (incluido el nombre del usuario). Esto reduce significativamente la huella para este tipo de ataque.

El único momento en que no es un problema de seguridad para AllowUnsafeUpdates en un GET es si no está recibiendo información del usuario. Por ejemplo, si tiene un elemento web que también registra visitas a una lista, entonces no hay vulnerabilidad de seguridad expuesta.

Editar : si va a utilizar AllowUnsafeUpdates, no es necesario restablecerlo a su valor anterior. No persiste. Es solo algo que necesita establecer en un objeto SPWeb antes de realizar actualizaciones desde un GET (u otros casos)