In Scott Guthries blog on the ASP.NET Security vulnerability noted here he says that for ASP.NET 3.5 SP1+ the following attribute should be set in the custom errors section
redirectMode="ResponseRewrite"
What is the significance of this in relation to the vulnerability and why only 3.5 SP1 and above?
I've just read on the net about a newly discovered security vulnerability in ASP.NET. You can read the details here. The problem lies in the way that ASP.NET implements the AES encryption algorithm to protect the integrity of the cookies these applications generate to store information during user sessions.This is a bit vague, but here is a more frightening part: The first stage of the attack takes a few thousand requests, but once it succeeds and the attacker gets the secret keys, it's totally stealthy.The cryptographic knowledge required is very basic.
All in all, I'm not familiar enough with the security/cryptograpy subject to know if this is really that serious.So, should all ASP.NET developers fear this technique that can own any ASP.NET website in seconds or what?How does this issue affect the average ASP.NET developer? Does it affect us at all?
In real life, what are the consequences of this vulnerability? And, finally: is there some workaround that prevents this vulnerability?EDIT: I'd like to summarize the responses I got so far.So, this is basically a "padding oracle" type of attack. @Sri provided a great explanation about what does this type of attack mean. Here is a shocking video about the issue!About the seriousness of this vulnerability: Yes, it is indeed serious. It lets the attacker to get to know the machine key of an application. Thus, he can do some very unwanted things.
In posession of the app's machine key, the attacker can decrypt authentication cookies.
Even worse than that, he can generate authentication cookies with the name of any user. Thus, he can appear as anyone on the site. The application is unable to differentiate between you or the hacker who generated an authentication cookie with your name for himself.It also lets him to decrypt (and also generate) session cookies, although this is not as dangerous as the previous one.Not so serious: He can decrypt the encrypted ViewState of pages. (If you use ViewState to store confidental data, you shouldn't do this anyways!)Quite unexpected: With the knowledge of the machine key, the attacker can download any arbitrary file from your web application, even those that normally can't be downloaded! (Including Web.Config, etc.)
Here is a bunch of good practices I got that don't solve the issue but help improve the general security of a web application.You can encrypt sensitive data with Protected Configuration Use HTTP Only cookies Prevent DoS attacksNow, let's focus on this issue.Scott Guthrie published an entry about it on his blogScottGu's FAQ blog post about the vulnerabilityScottGu's update on the vulnerabilityMicrosoft has a security advisory about itUnderstanding the vulnerabilityAdditional information about the vulnerabilityhe solutionEnable customErrors and make a single error page to which all errors are redirected. Yes, even 404s.
ScottGu said that differentiating between 404s and 500s are essential for this attack.) Also, into your Application_Error or Error.aspx put some code that makes a random delay. (Generate a random number, and use Thread.Sleep to sleep for that long.) This will make it impossible for the attacker to decide what exactly happened on your server.Some people recommended switching back to 3DES. In theory, if you don't use AES, you don't encounter the security weakness in the AES implementation. As it turns out, this is not recommended at all.Some other
This question is somewhat of a follow up to How serious is this new ASP.NET security vulnerability and how can I workaround it? So if my question seems to be broken read over this question and its accepted solution first and then take that into the context of my question.Can someone explain why returning the same error page and same status code for custom errors matters? I find this to be immaterial especially if this is advocated as part of the work around to it.Isn't it just as easy for the script/application to execute this attack and not specifically care whether or not it gets a http status code and more on the outcome? Ie doing this 4000 times you get redirected to an error page where on 4001 you stay on the same page because it didn't invalidate the padding?
I see why adding the delay to the error page is somewhat relevant but doesn't this also just add another layer to fool the script into thinking the site is an invalid target?What could be done to prevent this if the script takes into account that since the site is asp.net it's running the AES encryption that it ignores the timing of error pages and watches the redirection or lack of redirection as the response vector? If a script does this will that mean there's NO WAY to stop it?Edit: I accept the timing attack reduction but the error page part is what really seems bogus. This attack vector puts their data into viewstate. There's only 2 cases. Pass. Fail.
Either Fail, they're on a page and the viewstate does not contain their data. No matter what you do here there is no way to remove the fail case because the page just will never contain their inserted data unless they successfully cracked the key. This is why I can't justify the custom errors usage having ANY EFFECT AT ALL.Or Pass, they're on a page and the viewstate contains their inserted data.Summary of this vulnerability
The cipher key from the WebResoure.axd / ScriptResource.axd is taken and the first guess of the validation key is used to generate a value of potential key with the ciphered text.This value is passed to the WebResource.axd / ScriptResource.axd at this point if the decryption key was guessed correctly their response will be accepted but since the data is garbage that it's looking for the WebResource.axd / ScriptResource.axd will return a 404 error.If the decryption key was not successfully guessed it will get a 500 error for the padding invalid exception. At this point the attack application knows to increment the potential decryption key value and try again repeating until it finds the first successful 404 from the WebResource.axd / ScriptResource.axd
Just reading about this ASP.NET security vurnerability. Just wondering if this could be used to attack a WCF service hosted under IIS to get to its web.config or if its a pure ASP.NET vurnerability
View 3 RepliesWhy does the recent ASP.NET security vurnerability specify an html error page to redirect to pre ASP.NET 3.5 SP1 but an aspx page for later versions?
View 1 RepliesSince installing the security patch for the ASP.NET Oracle Padding vunerability any user that was keeping themselves logged in to our site is getting error messages when hitting any page.
The errors logged on the server are
System.Web.UI.ViewStateException: Invalid viewstate.
Client IP: xxx.xxx.xxx.xxx
Port: 55796
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9) Gecko/2008052906 Firefox/3.0
ViewState: l4nsXEvWcOwlDpmdbxw916bpHoPiqdBP7Syb+zCQAv44xv/r3oLtETKTL28/Gts6
Referer: Path: /product/4795/fender-usa-deluxe-stratocaster-mn-olympic-white-pearl
With custom errors switched off a user sees the following information
Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: System.Web.HttpException: Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.
Source Error:
An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.
Stack Trace: [ViewStateException: Invalid viewstate.
Client IP: xxx.xxx.xxx.xxx
Port: 3588
User-Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; GTB6.5; .NET CLR 2.0.50727; OfficeLiveConnector.1.3; OfficeLivePatch.0.0; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)
ViewState: s0toPCu7bxkB7a3G+KTxawY3ILf1qunZyIqNBKg8xSoqY2BkWIUCJAHKFKo2RnJw
Referer:
Path: /]
[HttpException (0x80004005): Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.]
System.Web.UI.ViewStateException.ThrowError(Exception inner, String persistedState, String errorPageMessage, Boolean macValidationError) +118
System.Web.UI.ViewStateException.ThrowMacValidationError(Exception inner, String persistedState) +13
System.Web.UI.ObjectStateFormatter.Deserialize(String inputString) +238
System.Web.UI.ObjectStateFormatter.System.Web.UI.IStateFormatter.Deserialize(String serializedState) +5
System.Web.Mvc.AntiForgeryDataSerializer.Deserialize(String serializedToken) +90
to delete all cookies and log back in, but obviously an average user, won't know to do this and I'm worried they will just think our site is broken.
We recently discovered that our web app was vulnerable to cross site scripting (XSS) attacks. We managed to manipulate our inputs to produce the following HTML:
[Code]....
Which executes an alert window when clicked.
After HTMLEncoding using the AntiXSS the web app successfully encodes the output to look like this:
<a href="javascript:__doPostBack('ctl00$ContentPlaceHolder1$CtlSearchList1$CtlListView1$DataGrid1$ctl03$ctl00','')">'); onclick=alert('This
is an XSS vulernability. An attacker could do anything here (redirect to another website, virus etc)');('.txt</a>
but the alert window still fires! What am I doing wrong?
2nd in an occasional series:
Here's the first one
Is CAT.NET correct that the following is a genuine vulnerability in ASP.NET or is it a false positive?
var myInt = Int32.Parse(txtUserInput.Text);
Response.Redirect(string.Format("myPage.aspx?myId={0}", myInt);
CAT.NET is reporting this as a redirect vulnerability needing remediation via encoding myInt.
Considering the recent ASP.NET vulnerability, what should I look for in my httphandlers that would cause such a Padding Oracle vulnerability?
Asked in another way... what did MSFT do wrong and what did they fix in their handlers?
I have to invoke SSIS packages from web service in the most secure way. I think that windows authentication will be secure but i am not sure. I do not have much knowledge about how to achieve this and the information on the internet is very distributed.
View 1 RepliesWe use Sharepoint to control our websites. We build the sites, then load them into the sharepoint server. My question is if I use windows authentication, how can I get my role security in my web config file to coencide with the asp.net controls that use the Forms authentication. Is there a differenence? Our security uses a session variable for security but there is no where to set up their permissions except in active directory. I hope this makes sense because I would like to implement the LoginView with Role groups but how can I give them the role="administrator"? Do I have to go into active directory and give them these permissions(would take awhile due to the size of the company)? Or do I have to set up priveladges in the web.config file for each user(difficult I think)?
View 5 RepliesI'm writing a simple Intranet application using windows authentication. I want to restrict access to Safe/UCantSeeMe.aspx. I am aware of the AuthorizeAttribute, but this only works on methods. I also found a good post on doing this with the MVC pattern, but I'm not using MVC. This can be done with roles in forms based security. I read on MSDN that using windows based security means roles are based on groups, but it doesn't go into any detail. how can I restrict access to Safe/UCantSeeMe.aspx?
View 1 RepliesI am getting an error incase user submits incorect security question's answer. I gave text in 'QuestionFailureText'. But its not working.
Below is the error getting.
'
Security Exception Description:The application attempted to perform an operation not allowed by the security policy. To grant this application the required permission please contact your system administrator or change the application's trust level in the configuration file.
Exception Details: System.Security.SecurityException: The source was not found, but some or all event logs could not be searched. Inaccessible logs: Security.
Source Error:
[Code]....
Source File: c:WindowsMicrosoft.NETFramework64v2.0.50727Temporary ASP.NET Filespng.webe16ed3ec284df543App_Web_rvfjstqa.5.cs Line: 0 Stack Trace:
[Code]....
We are using membership provider for LDAP authentication. It is working as it should.
But what all configuration settings I have to do so that
all the future requests to this application run under the security context of the Logged in user account not through the some default user set in IIS.
We need to have this working because all the permissions on the database are based on the logged in user.
We are using form authentication for LDAP authentication. And having impersonation = true in web.config.
I have implemented role based security in my asp.net 2.0 vb.net application using windows authentication and the windowstokenroleprovider and limiting access to certain pages using the location tag to specific active directory groups.
The issue is that when a user tries to access a page they are not authorized to view it brings up a login prompt and when it does not pass it takes them to the default page that tells them they are not authorized to view the page. I am wondering if there is a way to throw up a custom page that tells them they are not athorized to view the page that I can incorporate into the site itself with the header and so forth? if this page could come up in lieu of the sign in box popping up as well.
[ASP.NET 3.5, FormsAuthentication, SQL Server]
In the Roles table there is Role, and RoleType.
I have 3different roles, 2 of which have sub-roles.
Example
Role----------------------Type
Adminstrator
Subscriber---Basic
Subscriber---Business
I need to implement Code Access Security, and URL based security using the roles & types...
For instance, the (Subscriber/Basic) would need to view a different set of pages, and have different access to things then a (Subscriber/Business).
I think I can handle the Code Access security with a custom attribute, but I am unsure to how enforce a User be apart of 2 roles in the URL Authorization.
I am currently using the web.config to deny/allow access to the directories/pages.
e.g.
/Areas/Admin/web.config
[Code]....
Is it possible to force the user to be apart of 2 roles with this technique?
i used security in login page which restricts all users who have not logged in to all pages. I need to restrict specific users to specific pages. I'm not using AspSqlService provider. So i cannot create roles and restrict automatically. And the pictures i use in login page are not visible @ runtime.
View 1 RepliesI'm working on a website where it should be possible for registered users to upload word documents. The administration of users is done through Membership and Profiles. When the documents have been uploaded, the following needs to be achieved:Non-registered users should not be allowed to download documents I should be able to control which users that has access to which documents I should be able to register which user downloads which documents I should be able to track how many times a document has been downloaded
Can this be achieved be using Membership and Profiles?
I have identity impersonate = true in the Web.config file. I have integrated security = true in the DB connection string in the Web.config file.Before identity impersonate was true,users were able to access the DB through the web service account (seemingly).Now I get an error which says " Login failed for ... " because I am aware there is no specific account for that user in the permissions for that DB instance.I needed to set identity impersonate = true because the web service does not have access to the Active Directory,which I need to retrieve certain user information.
My question is,does identity impersonate = true override the integrated security and attempt to user the authenticated user's account to connect to the DB? Is there a simple way to prevent this in the Web.config itself?If not,would programatically impersonating the user within the Active Directory query functions and setting identity impersonate = false do the trick here?
I am using Itext sharp to create a pdf. I am adding an image and I keep getting this error
Request for the permission of type 'System.Security.Permissions.FileIOPermission, mscorlib, ersion=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed.
it is this bit of code that is causing this
[Code]....
If i comment this out, the PDF builds and no errors are thrown (there is just no image)
I don't understand cause I am am trying to do is read a file.
Error:Â
Security Exception
Description: The application attempted to perform an operation not allowed by the security policy.  To grant this application the required permission please contact your system administrator or change the application's trust level in the configuration file. Exception Details: System.Security.SecurityException: Request for the permission of type 'System.Web.AspNetHostingPermission, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed.Local its run fine. when i place in iis. it throw this exception.
I have created user web control library project and these controls i'm using in my web application. These User controls just works fine in my local machine but when i moved this project(including Library) to our Local server , it is throwing security exception
Error 1 Cannot register assembly "LocalServerLibraryDemoLibraryDemoLibraryinDebugLibrary.dll". Request for the permission of type 'System.Web.AspNetHostingPermission, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed. Library
Anybody knows why this error occuring...?
My website security is configured with "Windows Integrated Security" only (anonymous is disabled).
I also want to set a specific account to run the w3wp.exe process using the
Application Pool Identity to a domain account.
Running directly from the server works without any problem but from remote computers I always get the authenticaion window then the 401.1 error (after 3 attempts).
It seems that its the combination of "Windows Integrated Security" along with the "Application Pool Identity" that causes the problem. When I disable one of the two it works properly.
My server is Windows Server 2003 R2, running IIS 6.0.
I have an application that has a user Login Control (provided by ASP). I am just now working with the integration of a dataBase created in MS visual studio 2010, to a developed website created in MS visual web developer 2010. My main goal is to create an authentication ticket that enables a user to be able to see a dataBase information only after that user has been successfully authenticated.
Up to now I'm able to see the dataBase when i run the website even if I'm not log-in, how i can create a home page that tells the user to log-in and once that user has successfully log-in it redirects the user to another page where the user can see the database and how I can add information to that dataBase only to specific members
I simply want to know how to manually check if the value a user has provided for the answer to their security question matches their current answer on record. I want to use the build in support of the membership and membershipuser objects.
I see that via the passwordrecovery control that the actual answer can be returned. However I am currently not using this control and it would take a good bit to integrate it as it does not meet our user's requirements.
In a worst case scenario, getting the actual answer (like the passwordrecovery control does) and manually checking it in our application would be acceptable.
A best case scenario is some sort of API where I can pass in the user name and the answer to their security question that was provided and simply get an indication of whether answer was correct or not.