How to decode viewstate - asp.net

Question

I need to see the contents of the viewstate of an asp.net page. I looked for a viewstate decoder, found Fridz Onion's ViewState Decoder but it asks for the url of a page to get its viewstate. Since my viewstate is formed after a postback and comes as a result of an operation in an update panel, I cannot provide a url. I need to copy & paste the viewstate string and see what's inside. Is there a tool or a website exist that can help viewing the contents of viewstate?

Answer 1

Here's an online ViewState decoder:
http://ignatu.co.uk/ViewStateDecoder.aspx
Edit: Unfortunatey, the above link is dead - here's another ViewState decoder (from the comments):
http://viewstatedecoder.azurewebsites.net/

Answer 2

Use Fiddler and grab the view state in the response and paste it into the bottom left text box then decode.

Answer 3

Here is the source code for a ViewState visualizer from Scott Mitchell's article on ViewState (25 pages)
using System;
using System.Collections;
using System.Text;
using System.IO;
using System.Web.UI;
namespace ViewStateArticle.ExtendedPageClasses
{
/// <summary>
/// Parses the view state, constructing a viaully-accessible object graph.
/// </summary>
public class ViewStateParser
{
// private member variables
private TextWriter tw;
private string indentString = " ";
#region Constructor
/// <summary>
/// Creates a new ViewStateParser instance, specifying the TextWriter to emit the output to.
/// </summary>
public ViewStateParser(TextWriter writer)
{
tw = writer;
}
#endregion
#region Methods
#region ParseViewStateGraph Methods
/// <summary>
/// Emits a readable version of the view state to the TextWriter passed into the object's constructor.
/// </summary>
/// <param name="viewState">The view state object to start parsing at.</param>
public virtual void ParseViewStateGraph(object viewState)
{
ParseViewStateGraph(viewState, 0, string.Empty);
}
/// <summary>
/// Emits a readable version of the view state to the TextWriter passed into the object's constructor.
/// </summary>
/// <param name="viewStateAsString">A base-64 encoded representation of the view state to parse.</param>
public virtual void ParseViewStateGraph(string viewStateAsString)
{
// First, deserialize the string into a Triplet
LosFormatter los = new LosFormatter();
object viewState = los.Deserialize(viewStateAsString);
ParseViewStateGraph(viewState, 0, string.Empty);
}
/// <summary>
/// Recursively parses the view state.
/// </summary>
/// <param name="node">The current view state node.</param>
/// <param name="depth">The "depth" of the view state tree.</param>
/// <param name="label">A label to display in the emitted output next to the current node.</param>
protected virtual void ParseViewStateGraph(object node, int depth, string label)
{
tw.Write(System.Environment.NewLine);
if (node == null)
{
tw.Write(String.Concat(Indent(depth), label, "NODE IS NULL"));
}
else if (node is Triplet)
{
tw.Write(String.Concat(Indent(depth), label, "TRIPLET"));
ParseViewStateGraph(((Triplet) node).First, depth+1, "First: ");
ParseViewStateGraph(((Triplet) node).Second, depth+1, "Second: ");
ParseViewStateGraph(((Triplet) node).Third, depth+1, "Third: ");
}
else if (node is Pair)
{
tw.Write(String.Concat(Indent(depth), label, "PAIR"));
ParseViewStateGraph(((Pair) node).First, depth+1, "First: ");
ParseViewStateGraph(((Pair) node).Second, depth+1, "Second: ");
}
else if (node is ArrayList)
{
tw.Write(String.Concat(Indent(depth), label, "ARRAYLIST"));
// display array values
for (int i = 0; i < ((ArrayList) node).Count; i++)
ParseViewStateGraph(((ArrayList) node)[i], depth+1, String.Format("({0}) ", i));
}
else if (node.GetType().IsArray)
{
tw.Write(String.Concat(Indent(depth), label, "ARRAY "));
tw.Write(String.Concat("(", node.GetType().ToString(), ")"));
IEnumerator e = ((Array) node).GetEnumerator();
int count = 0;
while (e.MoveNext())
ParseViewStateGraph(e.Current, depth+1, String.Format("({0}) ", count++));
}
else if (node.GetType().IsPrimitive || node is string)
{
tw.Write(String.Concat(Indent(depth), label));
tw.Write(node.ToString() + " (" + node.GetType().ToString() + ")");
}
else
{
tw.Write(String.Concat(Indent(depth), label, "OTHER - "));
tw.Write(node.GetType().ToString());
}
}
#endregion
/// <summary>
/// Returns a string containing the <see cref="IndentString"/> property value a specified number of times.
/// </summary>
/// <param name="depth">The number of times to repeat the <see cref="IndentString"/> property.</param>
/// <returns>A string containing the <see cref="IndentString"/> property value a specified number of times.</returns>
protected virtual string Indent(int depth)
{
StringBuilder sb = new StringBuilder(IndentString.Length * depth);
for (int i = 0; i < depth; i++)
sb.Append(IndentString);
return sb.ToString();
}
#endregion
#region Properties
/// <summary>
/// Specifies the indentation to use for each level when displaying the object graph.
/// </summary>
/// <value>A string value; the default is three blank spaces.</value>
public string IndentString
{
get
{
return indentString;
}
set
{
indentString = value;
}
}
#endregion
}
}
And here's a simple page to read the viewstate from a textbox and graph it using the above code
private void btnParse_Click(object sender, System.EventArgs e)
{
// parse the viewState
StringWriter writer = new StringWriter();
ViewStateParser p = new ViewStateParser(writer);
p.ParseViewStateGraph(txtViewState.Text);
ltlViewState.Text = writer.ToString();
}

Answer 4

As another person just mentioned, it's a base64 encoded string. In the past, I've used this website to decode it:
http://www.motobit.com/util/base64-decoder-encoder.asp

Answer 5

JavaScript-ViewState-Parser:
http://mutantzombie.github.com/JavaScript-ViewState-Parser/
https://github.com/mutantzombie/JavaScript-ViewState-Parser/
The parser should work with most non-encrypted ViewStates. It doesn’t
handle the serialization format used by .NET version 1 because that
version is sorely outdated and therefore too unlikely to be
encountered in any real situation.
http://deadliestwebattacks.com/2011/05/29/javascript-viewstate-parser/
Parsing .NET ViewState
A Spirited Peek into ViewState, Part I:
http://deadliestwebattacks.com/2011/05/13/a-spirited-peek-into-viewstate-part-i/
A Spirited Peek into ViewState, Part II:
http://deadliestwebattacks.com/2011/05/25/a-spirited-peek-into-viewstate-part-ii/

Answer 6

Here's another decoder that works well as of 2014: http://viewstatedecoder.azurewebsites.net/
This worked on an input on which the Ignatu decoder failed with "The serialized data is invalid" (although it leaves the BinaryFormatter-serialized data undecoded, showing only its length).

Answer 7

This is somewhat "native" .NET way of converting ViewState from string into StateBag
Code is below:
public static StateBag LoadViewState(string viewState)
{
System.Web.UI.Page converterPage = new System.Web.UI.Page();
HiddenFieldPageStatePersister persister = new HiddenFieldPageStatePersister(new Page());
Type utilClass = typeof(System.Web.UI.BaseParser).Assembly.GetType("System.Web.UI.Util");
if (utilClass != null && persister != null)
{
MethodInfo method = utilClass.GetMethod("DeserializeWithAssert", BindingFlags.NonPublic | BindingFlags.Static);
if (method != null)
{
PropertyInfo formatterProperty = persister.GetType().GetProperty("StateFormatter", BindingFlags.NonPublic | BindingFlags.Instance);
if (formatterProperty != null)
{
IStateFormatter formatter = (IStateFormatter)formatterProperty.GetValue(persister, null);
if (formatter != null)
{
FieldInfo pageField = formatter.GetType().GetField("_page", BindingFlags.NonPublic | BindingFlags.Instance);
if (pageField != null)
{
pageField.SetValue(formatter, null);
try
{
Pair pair = (Pair)method.Invoke(null, new object[] { formatter, viewState });
if (pair != null)
{
MethodInfo loadViewState = converterPage.GetType().GetMethod("LoadViewStateRecursive", BindingFlags.Instance | BindingFlags.NonPublic);
if (loadViewState != null)
{
FieldInfo postback = converterPage.GetType().GetField("_isCrossPagePostBack", BindingFlags.NonPublic | BindingFlags.Instance);
if (postback != null)
{
postback.SetValue(converterPage, true);
}
FieldInfo namevalue = converterPage.GetType().GetField("_requestValueCollection", BindingFlags.NonPublic | BindingFlags.Instance);
if (namevalue != null)
{
namevalue.SetValue(converterPage, new NameValueCollection());
}
loadViewState.Invoke(converterPage, new object[] { ((Pair)((Pair)pair.First).Second) });
FieldInfo viewStateField = typeof(Control).GetField("_viewState", BindingFlags.NonPublic | BindingFlags.Instance);
if (viewStateField != null)
{
return (StateBag)viewStateField.GetValue(converterPage);
}
}
}
}
catch (Exception ex)
{
if (ex != null)
{
}
}
}
}
}
}
}
return null;
}

Answer 8

You can ignore the URL field and simply paste the viewstate into the Viewstate string box.
It does look like you have an old version; the serialisation methods changed in ASP.NET 2.0, so grab the 2.0 version

Answer 9

Best way in python is use this link.
A small Python 3.5+ library for decoding ASP.NET viewstate.
First install that: pip install viewstate
>>> from viewstate import ViewState
>>> base64_encoded_viewstate = '/wEPBQVhYmNkZQ9nAgE='
>>> vs = ViewState(base64_encoded_viewstate)
>>> vs.decode()
('abcde', (True, 1))

Answer 10

Online Viewstate Viewer made by Lachlan Keown:
http://lachlankeown.blogspot.com/2008/05/online-viewstate-viewer-decoder.html

Answer 11

Normally, ViewState should be decryptable if you have the machine-key, right? After all, ASP.net needs to decrypt it, and that is certainly not a black box.