How to decode viewstate

59

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?

This question is tagged with asp.net viewstate

~ Asked on 2008-08-22 16:38:49

11 Answers


38

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

~ Answered on 2008-08-22 16:40:16


39

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/

~ Answered on 2011-02-07 11:35:37


14

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();
        }

~ Answered on 2012-05-15 16:26:58


7

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

~ Answered on 2008-08-22 16:49:45


5

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).

~ Answered on 2014-07-16 23:21:19


4

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


~ Answered on 2013-03-10 18:07:43


3

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;
    }

~ Answered on 2013-06-28 18:05:33


2

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

~ Answered on 2008-08-22 16:50:35


1

~ Answered on 2013-03-10 18:16:26


0

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.

~ Answered on 2008-08-22 17:15:06


0

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))

~ Answered on 2020-08-13 13:13:32


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