How to decode viewstate

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  amp  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

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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  gt  gt  gt  from viewstate import ViewState  gt  gt  gt  base64 encoded viewstate     wEPBQVhYmNkZQ9nAgE    gt  gt  gt  vs   ViewState base64 encoded viewstate   gt  gt  gt  vs decode     abcde    True  1

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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            lt summary gt          Parses the view state  constructing a viaully-accessible object graph           lt  summary gt      public class ViewStateParser                  private member variables         private TextWriter tw          private string indentString                    region Constructor              lt summary gt              Creates a new ViewStateParser instance  specifying the TextWriter to emit the output to               lt  summary gt          public ViewStateParser TextWriter writer                        tw   writer                     endregion           region Methods          region ParseViewStateGraph Methods              lt summary gt              Emits a readable version of the view state to the TextWriter passed into the object s constructor               lt  summary gt               lt param name  viewState  gt The view state object to start parsing at  lt  param gt          public virtual void ParseViewStateGraph object viewState                        ParseViewStateGraph viewState  0  string Empty                               lt summary gt              Emits a readable version of the view state to the TextWriter passed into the object s constructor               lt  summary gt               lt param name  viewStateAsString  gt A base-64 encoded representation of the view state to parse  lt  param gt          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                               lt summary gt              Recursively parses the view state               lt  summary gt               lt param name  node  gt The current view state node  lt  param gt               lt param name  depth  gt The  depth  of the view state tree  lt  param gt               lt param name  label  gt A label to display in the emitted output next to the current node  lt  param gt          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  lt    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               lt summary gt              Returns a string containing the  lt see cref  IndentString   gt  property value a specified number of times               lt  summary gt               lt param name  depth  gt The number of times to repeat the  lt see cref  IndentString   gt  property  lt  param gt               lt returns gt A string containing the  lt see cref  IndentString   gt  property value a specified number of times  lt  returns gt          protected virtual string Indent int depth                        StringBuilder sb   new StringBuilder IndentString Length   depth               for  int i   0  i  lt  depth  i                    sb Append IndentString                return sb ToString                       endregion           region Properties              lt summary gt              Specifies the indentation to use for each level when displaying the object graph               lt  summary gt               lt value gt A string value  the default is three blank spaces  lt  value gt          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

User · Answer

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

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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

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

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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

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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  amp  amp  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

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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

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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

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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

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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

[asp.net] How to decode viewstate

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