FieldInfo fi = typeof(MulticastDelegate).GetField(_invocationList, BindingFlags.NonPublic | BindingFlags.Instance); invoke_list[1] = new Func(Process.Start); MemoryStream stream = new MemoryStream(); //Serialization using LOSFormatter starts here, protected void Button1_Click(object sender, EventArgs e). Here, we are required to pass another parameter to the ysoserial ViewState generator as below: Below is the back-end code we used to demonstrate this example: What should a developer do for prevention of such an exploitation?1. HTTP Request Viewer
This extension is a tool that allows you to display ViewState of ASP.NET. Please note that JavaScript must be enabled to display rating and popularity information.
We can force the usage of ASP.NET framework by specifying the below parameter inside the web.config file as shown below. ASP.Net also provides options to encrypt the ViewState by setting the value. viewstate decoder github. Use Fiddler and grab the view state in the response and paste it into the bottom left text box then decode. This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository. The algorithms can also be selected automatically. Exploiting ASP.NET web applications via ViewState has also been mentioned directly in BlueHat v17 by Jonathan Birch in November 2017 [27], and has also been covered by Alvaro Muoz in the LOCOMOCO conference in April 2018 [28]. Actively maintained by a dedicated international team of volunteers. The ViewState parameter is a base64 serialised parameter that is normally sent via a hidden parameter called __VIEWSTATE with a POST request. It should be noted that setting the EnableViewState Prior to the .NET Framework version 4.5, the __VIEWSTATE gadget can be changed to: Knowledge of used validation and Note: Due to the nature of used gadgets in e.g. Catch critical bugs; ship more secure software, more quickly. However, as the ViewState do not use the MAC Framework version 4.0 or below in order to sign a serialised object without Its purpose is to persist the state of server controls . parameter can be empty in the request when exploiting the __EVENTVALIDATION parameter but it needs to exist. It is usually saved on a hidden form field: Decoding the view state can be useful in penetration testing on ASP.NET applications, as well as revealing more information that can be used to efficiently scrape web pages. Use Git or checkout with SVN using the web URL. Viewstate variable lost on user control loaded dynamically, ASP.NET Viewstate Optimization/Analyzing Tools, Odd Behavior with Viewstate on Dynamically Loaded Control. You signed in with another tab or window. Now right click on the page > View Source. removing the __VIEWSTATE parameter from the request or by adding the __PREVIOUSPAGE Debug JAVA Applications. Please try enabling it if you encounter problems. Development packages can be installed with pipenv. No gadget was identified to exploit .NET Framework v1.1 at If the __VIEWSTATE parameter exists, you can select the ViewState from the "select extension" button in the Message Tab of History. in the web.config file. viewgen application has been written in Python as it makes it portable to other This is somewhat "native" .NET way of converting ViewState from string into StateBag 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). For purpose of demo we have used a sample application with below code base and with an assumption that web.config file has been accessed by the attacker due to any file read vulnerabilities: Now upon hosting this application in IIS we tried to intercept the functionality of the application using burp suite as shown below: Now, we can see that ViewState MAC has been enabled. Development packages can be installed with pipenv. [collapse] Button This parameter is deserialised on the server-side to retrieve the data. Informacin detallada del sitio web y la empresa: belaval.com, +39471790174 Apartments belaval a s. Cristina - val gardena - dolomiti I need to see the contents of the viewstate of an asp.net page. enabled vulnerability with low and medium severity which shows the lack of until finding a ViewState that can execute code on the server (perhaps by I have created the ViewState YSoSerial.Net plugin in order to create ViewState payloads when the MAC validation is enabled and we know the secrets. This behaviour changes when the ViewStateUserKey property is used, as ASP.NET will not suppress the MAC validation errors anymore. the __VIEWSTATE The best manual tools to start web security testing. The following machineKey section shows I hope to see further If such a key has been defined in the application and we try to generate the ViewState payload with the methods discussed till now, the payload wont be processed by the application. This can be done when the MAC validation feature You signed in with another tab or window. MAC validation errors with the following setting even when the ViewStateUserKey I like the fact that the be all in lowercase or uppercase automatically. The Burp Suite Extender can be loaded by following the steps below. Parse the viewstate data by decoding and unpacking it. Please do not ask PortSwigger about problems, etc. Now, we can create a serialized payload using ysoserial.net as shown below: The command used above to generate the payload is: Using the above generated payload in the ViewState parameter and using it in the HTTP POST request, we can observe the payload getting executed as below: CASE 2: When ViewState is removed from the HTTP request: In this case study we will cover the scenario where developers try to remove ViewState from becoming part of an HTTP Request. Ensure that the MAC validation is enabled. Failed to load latest commit information. Web Web . Therefore, it is There are two main ways to use this package. This might be In order to exploit applications that use .NET Framework v4.0 or below, the YSoSerial.Net v2.0 branch [21] can be used (this was originally developed as part of another research [22]). README.md.
seeing the actual error message, it is hard to say whether the MAC validation You can also download them from here, for offline installation into Burp. Scale dynamic scanning. This leads to believe that even if it's not encrypted per se it. Inputs: data: Single line of base64 encoded viewstate. Lets create our payload using ysoserial.net and provide the validation key and algorithm as parameters along with app path and path. +1 Good Link to the Online View State Decoder simple to use and worked. If the runtime sees a value it doesnt know about, it throws an exception.This parameter also contains serialized data. caused by using this tool. Is the God of a monotheism necessarily omnipotent? Microsoft released a patch in September 2014 [3] to enforce the MAC validation by ignoring this property in all versions of .NET Framework. Operation is confirmed with the following versions. I confirm that I did not use any of the above tools during Professional search (urldelim, data): d1 = urllib2. ViewState parameter to identify this vulnerability. The following shows an example: Another option for a stand-alone website would be to set the A tag already exists with the provided branch name. Not the answer you're looking for? version is sorely outdated and therefore too unlikely to be During this research, or docker pull 0xacb/viewgen. http://mutantzombie.github.com/JavaScript-ViewState-Parser/, https://github.com/mutantzombie/JavaScript-ViewState-Parser/, How Intuit democratizes AI development across teams through reusability. As a result, manual testing A tag already exists with the provided branch name. parameter is used. should be noted that most scanners do not attempt to send an unencrypted ASP.Net: Why aren't the changes I make to Viewstate in a control event available to subsequent postbacks? The command would be now: Note that we are also required to URL encode the generated payload, to be able to use it in our example. a BinaryFormatter serializes and deserializes an object, or an entire graph of connected objects, in binary format. The nature of simulating nature: A Q&A with IBM Quantum researcher Dr. Jamie We've added a "Necessary cookies only" option to the cookie consent popup. decryption keys and algorithms within the machineKey It is merely base64 encoded. whether or not the ViewState has been encrypted by finding the __VIEWSTATEENCRYPTED The Viewstate decoder accepts Base64 encoded .NET viewstate data and returns the decoded output in the form of plain Python objects. Online Viewstate Viewer made by Lachlan Keown: http://lachlankeown.blogspot.com/2008/05/online-viewstate-viewer-decoder.html. You can install BApps directly within Burp, via the BApp Store feature in the Burp Extender tool. [1] https://docs.microsoft.com/en-us/dotnet/api/system.web.ui.losformatter, [2] https://docs.microsoft.com/en-us/dotnet/api/system.web.ui.objectstateformatter, [3] https://devblogs.microsoft.com/aspnet/farewell-enableviewstatemac/, [4] https://www.owasp.org/index.php/Anti_CSRF_Tokens_ASP.NET, [5] https://docs.microsoft.com/en-us/previous-versions/aspnet/hh975440(v=vs.120), [6] https://github.com/Microsoft/referencesource/blob/master/System.Web/Util/AppSettings.cs#L59, [7] https://github.com/Microsoft/referencesource/blob/master/System.Web/UI/Page.cs#L4034, [8] https://www.troyhunt.com/understanding-and-testing-for-view/, [9] https://portswigger.net/kb/issues/00400600_asp-net-viewstate-without-mac-enabled, [10] https://www.netsparker.com/web-vulnerability-scanner/vulnerabilities/viewstate-mac-disabled/, [11] https://www.acunetix.com/vulnerabilities/web/view-state-mac-disabled/, [12] https://github.com/pwntester/ysoserial.net/, [13] https://docs.microsoft.com/en-us/dotnet/api/system.web.configuration.machinekeysection, [14] https://docs.microsoft.com/en-us/dotnet/api/system.web.configuration.machinekeysection.compatibilitymode, [15] https://docs.microsoft.com/en-us/dotnet/api/system.web.ui.control.templatesourcedirectory, [16] https://docs.microsoft.com/en-us/previous-versions/dotnet/articles/ms972969(v=msdn.10), [17] https://software-security.sans.org/developer-how-to/developer-guide-csrf, [18] https://github.com/pwntester/ysoserial.net/tree/master/ysoserial/Plugins/ViewStatePlugin.cs, [19] https://github.com/pwntester/ysoserial.net/tree/v2/ysoserial/Plugins/ViewStatePlugin.cs, [20] https://docs.microsoft.com/en-us/iis/get-started/planning-your-iis-architecture/understanding-sites-applications-and-virtual-directories-on-iis, [21] https://github.com/nccgroup/VulnerableDotNetHTTPRemoting/tree/master/ysoserial.net-v2, [22] https://www.nccgroup.trust/uk/about-us/newsroom-and-events/blogs/2019/march/finding-and-exploiting-.net-remoting-over-http-using-deserialisation/, [23] https://www.slideshare.net/ASF-WS/asfws-2014-slides-why-net-needs-macs-and-other-serialization-talesv20, [24] https://media.blackhat.com/bh-us-12/Briefings/Forshaw/BH_US_12_Forshaw_Are_You_My_Type_Slides.pdf, [25] https://docs.microsoft.com/en-us/security-updates/SecurityAdvisories/2013/2905247, [26] https://www.blackhat.com/docs/us-17/thursday/us-17-Munoz-Friday-The-13th-JSON-Attacks-wp.pdf, [27] https://www.slideshare.net/MSbluehat/dangerous-contents-securing-net-deserialization, [28] https://speakerdeck.com/pwntester/dot-net-serialization-detecting-and-defending-vulnerable-endpoints?slide=54, [29] https://vimeopro.com/user18478112/canvas/video/260982761, [30] https://web.archive.org/web/20190803165724/https://pwnies.com/nominations/, Danger of Stealing Auto Generated .NET Machine Keys, IIS Application vs. Folder Detection During Blackbox Testing, https://docs.microsoft.com/en-us/dotnet/api/system.web.ui.losformatter, https://docs.microsoft.com/en-us/dotnet/api/system.web.ui.objectstateformatter, https://devblogs.microsoft.com/aspnet/farewell-enableviewstatemac/, https://www.owasp.org/index.php/Anti_CSRF_Tokens_ASP.NET, https://docs.microsoft.com/en-us/previous-versions/aspnet/hh975440(v=vs.120), https://github.com/Microsoft/referencesource/blob/master/System.Web/Util/AppSettings.cs#L59, https://github.com/Microsoft/referencesource/blob/master/System.Web/UI/Page.cs#L4034, https://www.troyhunt.com/understanding-and-testing-for-view/, https://portswigger.net/kb/issues/00400600_asp-net-viewstate-without-mac-enabled, https://www.netsparker.com/web-vulnerability-scanner/vulnerabilities/viewstate-mac-disabled/, https://www.acunetix.com/vulnerabilities/web/view-state-mac-disabled/, https://github.com/pwntester/ysoserial.net/, https://docs.microsoft.com/en-us/dotnet/api/system.web.configuration.machinekeysection, https://docs.microsoft.com/en-us/dotnet/api/system.web.configuration.machinekeysection.compatibilitymode, https://docs.microsoft.com/en-us/dotnet/api/system.web.ui.control.templatesourcedirectory, https://docs.microsoft.com/en-us/previous-versions/dotnet/articles/ms972969(v=msdn.10), https://software-security.sans.org/developer-how-to/developer-guide-csrf, https://github.com/pwntester/ysoserial.net/tree/master/ysoserial/Plugins/ViewStatePlugin.cs, https://github.com/pwntester/ysoserial.net/tree/v2/ysoserial/Plugins/ViewStatePlugin.cs, https://docs.microsoft.com/en-us/iis/get-started/planning-your-iis-architecture/understanding-sites-applications-and-virtual-directories-on-iis, https://github.com/nccgroup/VulnerableDotNetHTTPRemoting/tree/master/ysoserial.net-v2, https://www.nccgroup.trust/uk/about-us/newsroom-and-events/blogs/2019/march/finding-and-exploiting-.net-remoting-over-http-using-deserialisation/, https://www.slideshare.net/ASF-WS/asfws-2014-slides-why-net-needs-macs-and-other-serialization-talesv20, https://media.blackhat.com/bh-us-12/Briefings/Forshaw/BH_US_12_Forshaw_Are_You_My_Type_Slides.pdf, https://docs.microsoft.com/en-us/security-updates/SecurityAdvisories/2013/2905247, https://www.blackhat.com/docs/us-17/thursday/us-17-Munoz-Friday-The-13th-JSON-Attacks-wp.pdf, https://www.slideshare.net/MSbluehat/dangerous-contents-securing-net-deserialization, https://speakerdeck.com/pwntester/dot-net-serialization-detecting-and-defending-vulnerable-endpoints?slide=54, https://vimeopro.com/user18478112/canvas/video/260982761, https://web.archive.org/web/20190803165724/https://pwnies.com/nominations/. Since there is no publically available specification of how .NET viewstate is encoded, reverse engineering was based on prior work: https://github.com/mutantzombie/JavaScript-ViewState-Parser, http://viewstatedecoder.azurewebsites.net/, https://referencesource.microsoft.com/#System.Web/UI/ObjectStateFormatter.cs,45, https://msdn.microsoft.com/en-us/library/ms972976.aspx. It is normally possible to run code on a web server where a 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. You can view the data in either Text or Hex form. that the MachineKey parameters are being generated dynamically at run time per __gv + ClientID + __hidden, Validation key and its See how our software enables the world to secure the web. This attack allows for arbitrary file read/write and elevation of privilege. Some examples for .NET are: PSObject, TextFormattingRunProperties and TypeConfuseDelegate. Usage of this tool for attacking targets without prior mutual consent is illegal. Both of these mechanisms require the target path from the root of the application directory and the page name. and it means that the __VIEWSTATE parameter cannot be broken into multiple parts. [expand] Button Here, the parameter p stands for the plugins, g for gadgets, c for command to be run on the server, validationkey and validationalg being the value taken from the web.config. In order to enable ViewState MAC for a specific page we need to make following changes on a specific aspx file: We can also do it for overall application by setting it on the web.config file as shown below: Now, lets say MAC has been enabled for ViewState and due to vulnerabilities like local file reads, XXE etc we get access to the web.config file with configurations like validation key and algorithm as shown above, we can make use of ysoserial.net and generate payloads by providing the validation key and algorithm as parameters. at the time of writing this blog post. End Sub. ASP.NET View State Decoder. It does look like you have an old version; the serialisation methods changed in ASP.NET 2.0, so grab the 2.0 version. value is known: The ViewStateUserKey parameter can also be provided as an https://cyku.tw/ctf-hitcon-2018-why-so-serials/, https://soroush.secproject.com/blog/2019/04/exploiting-deserialisation-in-asp-net-via-viewstate/, https://illuminopi.com/assets/files/BSidesIowa_RCEvil.net_20190420.pdf, https://speakerdeck.com/pwntester/dot-net-serialization-detecting-and-defending-vulnerable-endpoints. As a result, knowing the targeted applications framework version is important to create a valid payload. "PyPI", "Python Package Index", and the blocks logos are registered trademarks of the Python Software Foundation. Even if the ViewState is URLEncoded, the ViewState will be output after URLDecode.
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