I have read the section on header injections as described here: http://guides.rubyonrails.org/security.html. But I can't seem to walk through a step by step example of this in my head. Could someone walk me through an example of how exploiting the referer header could cause issues in an application?
It is very simple:
A malicious user can insert due to a vulnerability in earlier versions of Ruby and RoR a secuence of URL encoded characters “%0d%0a” that are the equivalent for “\r\n” which is a carriage-return and line-feed.
In this way a new lines in the header can be injected with new information as cookies, redirections, referers and any other information that can be used to help the attacker to commit his purpose.
As example maybe the one in the link you sent is not exactly the best, but think about a cookie validation to access a private site. Some sites use to locate a cookie to a value like "true" or "1" once the user pass trough the validation process. If you insert into the header the cookie value without passing the validation process you should access the private pages without the need of login into the application.
Related
I am running an MVC site along side Umbraco. The MVC site handles its own authentication completely separate to Umbraco, and ASP.NET Forms authentication for that matter. It sets a cookie and uses that internally to keep track of things.
Everything works fine for the most part, but if I am logged into my MVC site with the aforementioned cookie set, I try to login to the Umbraco admin section using the correct Umbraco credentials, it authenticates me and redirects me to the admin section but the WebAPI calls start to fail. The first is a call to: /umbraco/backoffice/UmbracoApi/UpdateCheck/GetCheck which returns a 417 Missing token null HTTP error response.
If I delete my custom cookie and refresh the page everything works fine.
I don't understand how my cookie can interfere with Umbraco's. It's not using ASP.NET Forms authentication or anything.
This error occurs because your request is not sending up the required angular CSRF headers + cookie. I'm not sure why this would be the case but it does seems strange if it is a fault of your custom cookie. Perhaps you can tell us some more information about your issue: Cookie name/value, steps to reproduce, specific version of Umbraco, hosting environment, etc....
Some info as to what is going on, the code that returns this error is here:
https://github.com/umbraco/Umbraco-CMS/blob/dev-v7/src/Umbraco.Web/WebApi/Filters/AngularAntiForgeryHelper.cs#L94
This is where the CSRF cookies are set:
https://github.com/umbraco/Umbraco-CMS/blob/dev-v7/src/Umbraco.Web/WebApi/Filters/SetAngularAntiForgeryTokensAttribute.cs
and this attribute is applied to two actions, one for login and one when we retrieve the current user data:
https://github.com/umbraco/Umbraco-CMS/blob/dev-v7/src/Umbraco.Web/Editors/AuthenticationController.cs#L103
https://github.com/umbraco/Umbraco-CMS/blob/dev-v7/src/Umbraco.Web/Editors/AuthenticationController.cs#L84
This is where the header is set in the JS:
https://github.com/umbraco/Umbraco-CMS/blob/5b9a98ad6ae9e63322c26f7b162204e34f7fcb54/src/Umbraco.Web.UI.Client/src/init.js#L11
Depending on your hosting environment/setup there has been strange reports of some firewalls stripping/changing data, for example:
http://our.umbraco.org/forum/umbraco-7/using-umbraco-7/47340-Umbraco-7-plus-ISA-Server-2006
Hopefully given the info above you might be able to pinpoint where the problem starts.
My initial thought is that you by accident used a key value for your cookie that is reserved by Umbraco, which could result in the wrong cookie being read, causing issues. The solution to this would be to simply rename your cookie.
If this is not the case I have another theory:
HTTP requests will always include all cookies which path/domain matches the domain of the resource you are requesting. They are sorted by path length primarily, and secondarily by creation time. If Umbraco backend for some reason finds the cookie used for authentication by its index number (wouldn't even be surprised) in the list, rather than key value, your custom cookie would cause the index to shift, thus making Umbraco look at the wrong cookie
So, if renaming the cookie didn't do anything, a fun thing to try could be to set path of the cookie to the shortest possible path, which would make your browser put the cookie further down the list, so the index won't shift.
It's just a theory though, so I'm interested in hearing how it goes :)
I have to implement a web site (MVC4/Single Page Application + knockout + Web.API) and I've been reading tons of articles and forums but I still can't figure out about some points in security/authentication and the way to go forward when securing the login page and the Web.API.
The site will run totally under SSL. Once the user logs on the first time, he/she will get an email with a link to confirm the register process. Password and a “salt” value will be stored encrypted in database, with no possibility to get password decrypted back. The API will be used just for this application.
I have some questions that I need to answer before to go any further:
Which method will be the best for my application in terms of security: Basic/ SimpleMembership? Any other possibilities?
The object Principal/IPrincipal is to be used just with Basic Authentication?
As far as I know, if I use SimpleMembership, because of the use of cookies, is this not breaking the RESTful paradigm? So if I build a REST Web.API, shouldn't I avoid to use SimpleMembership?
I was checking ThinkTecture.IdentityModel, with tokens. Is this a type of authentication like Basic, or Forms, or Auth, or it's something that can be added to the other authentication types?
Thank you.
Most likely this question will be closed as too localized. Even then, I will put in a few pointers. This is not an answer, but the comments section would be too small for this.
What method and how you authenticate is totally up to your subsystem. There is no one way that will work the best for everyone. A SPA is no different that any other application. You still will be giving access to certain resources based on authentication. That could be APIs, with a custom Authorization attribute, could be a header value, token based, who knows! Whatever you think is best.
I suggest you read more on this to understand how this works.
Use of cookies in no way states that it breaks REST. You will find ton of articles on this specific item itself. Cookies will be passed with your request, just the way you pass any specific information that the server needs in order for it to give you data. If sending cookies breaks REST, then sending parameters to your API should break REST too!
Now, a very common approach (and by no means the ONE AND ALL approach), is the use of a token based system for SPA. The reason though many, the easiest to explain would be that, your services (Web API or whatever) could be hosted separately and your client is working as CORS client. In which case, you authenticate in whatever form you choose, create a secure token and send it back to the client and every resource that needs an authenticated user, is checked against the token. The token will be sent as part of your header with every request. No token would result in a simple 401 (Unauthorized) or a invalid token could result in a 403 (Forbidden).
No one says an SPA needs to be all static HTML, with data binding, it could as well be your MVC site returning partials being loaded (something I have done in the past). As far as working with just HTML and JS (Durandal specifically), there are ways to secure even the client app. Ultimately, lock down the data from the server and route the client to the login screen the moment you receive a 401/403.
If your concern is more in the terms of XSS or request forging, there are ways to prevent that even with just HTML and JS (though not as easy as dropping anti-forgery token with MVC).
My two cents.
If you do "direct" authentication - meaning you can validate the passwords directly - you can use Basic Authentication.
I wrote about it here:
http://leastprivilege.com/2013/04/22/web-api-security-basic-authentication-with-thinktecture-identitymodel-authenticationhandler/
In addition you can consider using session tokens to get rid of the password on the client:
http://leastprivilege.com/2012/06/19/session-token-support-for-asp-net-web-api/
I am using MVC3. I have a couple of pages which does not require authentication but these pages have querystrings which could be tampered. I am planning to encrypt these urls when sending to users and decrypting it back when they hit it, what is the best way to encrypt and decrypt query strings in MVC3? Send me a pointer If there is any module that I can reuse...
Why dont you trust in another kind of storage mechanism instead of a query string?. You could pass the information over a POST operation, there are several ways to do that, such as cache or other. Post automatically puts that information on the request header, and its hidden to the ussers, also if your site is over SSL connection, that information is encripted.
You could improve security to your site against malware petitions with integrated MVC security features, such #Html.AntiForgeryToken(), this prevents that a malitious site tries to bypass your system impersonating a real petition. In a nut shell this means that a unique ID is printed on the form header when the form is sent to the client, and if the ID does not equals the one that the server expects, simply the request is ignored.
Heres an interesting post that could help you.
https://sites.google.com/site/muazkh/asp-net-mvc-security-and-hacking-defense-in-depth
Best regards!
I have a problem with the anti CRSF MVC mechanism. The cookie and the form input returned does not match. I'm getting an error every single time, only in one specific page. In the rest of the application it works well.
The server is returning HTTP 500 Internal Server Error and I can see on the log this exception:
[System.Web.Mvc.HttpAntiForgeryException]: {"A required anti-forgery
token was not supplied or was invalid."}
This is the hidden input that the server is generating is:
<input name="__RequestVerificationToken" type="hidden" value="QK8P7rjyZE6Vm5seY7Fr704YCOoFGdTIMzl1W7R0ZFpXSMjGKLG2T05DfFSYTxvtQCEx7DDT69DGsDB2+ZXFHY8oAjiKz0gw8BhDFywgmfIpoXnGpj7fONNzIIfvbrDrE9WJsMu6Io/0bDLM5WfKs0zktiNjyOWpfYrmnfINYmjW8NLOZFoz74xTcgTptAld">
And this is the Cookie returned:
Set-Cookie:__RequestVerificationToken_L2VGbG93=skmTAVI8HCbfxDS+xhioIMIISL3UOBI7qJM1JbHjTtAqKl4W70pDUcTKMm0p3R3mrHDziE8vXw0C0OO4HArzWO1/e6py+v/cFdbe9maFgjl4jMiZ9Wc4YIhC6+IUXkk6yqJDJ8dCIr8qtGaYcD9IX+m7/SlVhu521KQSWJYRcaY=; path=/; HttpOnly
When I examine what the server is sending, the cookie is exactly the same, but the payload has different encoding I think:
__RequestVerificationToken:QK8P7rjyZE6Vm5seY7Fr704YCOoFGdTIMzl1W7R0ZFpXSMjGKLG2T05DfFSYTxvtQCEx7DDT69DGsDB2%2BZXFHY8oAjiKz0gw8BhDFywgmfIpoXnGpj7fONNzIIfvbrDrE9WJsMu6Io%2F0bDLM5WfKs0zktiNjyOWpfYrmnfINYmjW8NLOZFoz74xTcgTptAld
The differences are in two characters that appear encoded:
/ -> %2F
+ -> %2B
Those are the only differences I can find between the hidden input field, and the post payload.
What could be the problem that is causing that ValidateAntiForgeryToken fails in verify the token?
Regards.
I've had and resolved several issues with ValidateAntiForgeryToken lately, so I'll share my findings with you.
Salt: Since you mention this only happens on a single page, my best guess is that you are using different salt values in your calls to Html.AntiForgeryToken(salt) and ValidateAntiForgeryToken(salt) calls.
AJAX: as another answer has said, using AJAX may require extra work to ensure the token is included in the POST. Here is my favorite simple, automatic solution to add the token to all AJAX POST requests.
In your question though, you state that you have verified that the token is sending. Have you verified that you're only sending the token once? I found out that an AJAX call of mine was sending the token twice, which combined the values, and caused it to fail.
Machine Key and Cookies: this issue is ugly, easy to spot (causes exceptions), but not very intuitive. The validation cookies and tokens are encoded and decoded using a unique "machine key". This means that if you have a server farm, or change your server, your cookie will no longer be valid. Closing your browser fixes the issue (because the cookie is a session cookie). However, some people leave their browser windows open in the background for a long time!
The solution is to set a "machine key" in your config file. This will tell MVC to use the same key on all servers, ensuring that the cookie will be decryptable everywhere.
Encoding Bugs: using a testing utility called jMeter, we attempted to load-test our pages, only to find out that it had a bug that caused our token to have 2 extra " around the value.
The solution is to lower your trust in your tools! Test in a browser, and if that works, create a test that extracts the token and cookie values, and set a breakpoint to verify the results.
If none of these things work for you, then I'd recommend taking a look at the MVC source code for ValidateAntiForgeryTokenAttribute, specifically the OnAuthorization method. It will help you see the different steps where validation could fail. You might even inspect your error's Exception.StackTrace to determine which part is failing.
As a side note, I really dislike the implementation of ValidateAntiForgeryToken in MVC, because:
There are about 5 verification steps that can fail, but there is only one generic error message.
The class is sealed, so it cannot be extended with additional functionality.
The encryption method is weird - it initializes a Page and creates an artificial ViewState to encrypt the tokens and cookies. Seems overkill.
So, I grabbed the source code, and created my own specialized subclass, which also turned out to be very helpful in debugging its issues, because I could set breakpoints on the validation methods, and it was really easy to determine which validation step was failing.
If this is being sent as an Ajax request, then the current setup of the framework isn't build to do this naturally.
Luckly Phil Haak wrote a nice blog post on dealing with CSRF and Ajax -> Preventing CSRF With Ajax which goes into some good detail about how to use the existing framework and modify it to work for Ajax/Json.
From my recent findings ...
If you set content type as "application/x-www-form-urlencoded" in the ajax request then you must put the AFRT in the data
If you set the content type to "application/json" then the token goes in the ajax "headers" property as described by haack.
On the server if you are checking for the form type token then using the vanilla AntiForgeryRequestTokenAttribute is ok but if you want to validate tokens sent in the header then you need to call the AntiForgeryToken.OnAuthorize ... or whatever, passing the token from the cookie (http context).
It aint easy but if it was everybody would be doing it :)
How does one protect against XSRF attacks in Grails. I see that forms support the notion of useToken which (I think should suffice). However, remoteForm or other AJAX related request don't support this feature.
Also, is there a way to invert the functionality of useToken so that it is always used rather than enabled on a case by case basis?
You could try looking at the source code of the <g:form> tag. It uses a SynchronizerToken to create a token and store it in the session. Based on the resolution of this issue it should be possible to use the same token for all forms on the same page. I did not try this, but theoretically you would just need to manually create a hidden field on the form and generate the token in that field.
We have inject a hidden value to the request object in a before filter and encrypt the value with a specific key. We then inject that request.token value to every form on the site and when we receive a POST we have a before filter to verify that that hidden field is present and its value can be decoded by that same secret key.
If that hidden value is not present or if it is stale -- we use a timestamp as payload -- we give the client an error status.
This is an alternative way to what was described above and we use this, because we do not use sessions on our sites to make it easier to load balance.