AFAIK it's not possible to set a header field when a form is submited, it can only be done in ajax requests
This questions also points that it's not possible:
How to set a Header field on POST a form?
Custom HTTP Request headers in HTML
But reading Cross-Site Request Forgery (CSRF) Prevention Cheat Sheet it's mentioned that:
Encrypted Token Pattern
Overview
The Encrypted Token Pattern leverages an encryption, rather than
comparison, method of Token-validation. After successful
authentication, the server generates a unique Token comprised of the
user's ID, a timestamp value and a nonce, using a unique key available
only on the server. This Token is returned to the client and embedded
in a hidden field. Subsequent AJAX requests include this Token in the
request-header, in a similar manner to the Double-Submit pattern.
Non-AJAX form-based requests will implicitly persist the Token in its hidden field, although I recommend persisting this data in a
custom HTTP header in such cases. On receipt of this request, the
server reads and decrypts the Token value with the same key used to
create the Token.
This sentence confuses me:
I recommend persisting this data in a custom HTTP header in such cases
Could anyone shed some light on it?
Yes, the sentence implies that the POST operation is invoked by a custom JavaScript handler in order to inject the AUTH header. I've corrected the OWASP description to reflect this oversight.
Related
I'm creating a TODO list app with nodejs and I need an option to delete a todo record. So I've created an HTML form that contains a delete button but I can only use POST as the method. actually my code is working fine but are there any problems with using POST to DELETE records?
No there isn't. Apart from GET and POST requests, most of the other HTTP method serve only semantic purposes. Except for some notable examples such as OPTIONS which is use to communicate supported methods. Using correct HTTP verbs will make your application / API easier to understand.
The same goes for HTTP status code. Functionality-wise, it doesn't really matter if you send a 200 (OK), 201(Created), or 202 (Accepted) for a successful request. However, sending the correct status code can avoid necessary confusion.
As far as I know, no. There're no hazards of using HTTP post method instead of DELETE. You can see how it's used in deletion here
One difference is that users might be tricked into making the POST request and inadvertently deleting an entry, if they are lured onto a malicious web page that contains an auto-submitting HTML form
<form method="POST" action="<your deletion endpoint>">
(Whether that is possible depends on the content type that your deletion endpoint expects.)
A DELETE request, however, cannot be forged in such a way. A malicious web page could create a DELETE request only with fetch or XMLHttpRequest, and because of the CORS protocol the browser would refuse to carry that out (unless your server explicitly allows it through a suitable CORS preflight response).
I got a (Flask) backend powering an API that serves JSON to an Angular app.
I love the fact that my backend (algorithms, database) is totally disconnected from my frontend (design, UI) as it could literally run from two distinct servers. However since the view is entirely generated client side everyone can access the JSON data obviously. Say the application is a simple list of things (the things are stored in a JSON file).
In order to prevent direct access to my database through JSON in the browser console I found these options :
Encrypting the data (weak since the decrypting function will be freely visible in the javascript, but not so easy when dealing with minified files)
Instead of $http.get the whole database then filtering with angular, $http.get many times (as the user is scrolling a list for example) so that it is programmatically harder to crawl
I believe my options are still weak. How could I make it harder for a hacker to crawl the whole database ? Any ideas ?
As I understand this question - the user should be permitted to access all of the data via your UI, but you do not want them to access the API directly. As you have figured out, any data accessed by the client cannot be secured but we can make accessing it a little more of PITA.
One common way of doing this is to check the HTTP referer. When you make a call from the UI the server will be given the page the request is coming from. This is typically used to prevent people creating mashups that use your data without permission. As with all the HTTP request headers, you are relying on the caller to be truthful. This will not protect you from console hacking or someone writing a scraper in some other language. #see CSRF
Another idea is to embed a variable token in the html source that bootstraps your app. You can specify this as an angular constant or a global variable and include it in all of your $http requests. The token itself could be unique for each session or be a encrypted expiration date that only the server can process. However, this method is flawed as well as someone could parse the html source, get the code, and then make a request.
So really, you can make it harder for someone, but it is hardly foolproof.
If users should only be able to access some of the data, you can try something like firebase. It allows you to define rules for who can access what.
Security Considerations When designing web applications, consider
security threats from:
JSON vulnerability XSRF Both server and the client must cooperate in
order to eliminate these threats. Angular comes pre-configured with
strategies that address these issues, but for this to work backend
server cooperation is required.
JSON Vulnerability Protection A JSON vulnerability allows third party
website to turn your JSON resource URL into JSONP request under some
conditions. To counter this your server can prefix all JSON requests
with following string ")]}',\n". Angular will automatically strip the
prefix before processing it as JSON.
For example if your server needs to return:
['one','two'] which is vulnerable to attack, your server can return:
)]}', ['one','two'] Angular will strip the prefix, before processing
the JSON.
Cross Site Request Forgery (XSRF) Protection XSRF is a technique by
which an unauthorized site can gain your user's private data. Angular
provides a mechanism to counter XSRF. When performing XHR requests,
the $http service reads a token from a cookie (by default, XSRF-TOKEN)
and sets it as an HTTP header (X-XSRF-TOKEN). Since only JavaScript
that runs on your domain could read the cookie, your server can be
assured that the XHR came from JavaScript running on your domain. The
header will not be set for cross-domain requests.
To take advantage of this, your server needs to set a token in a
JavaScript readable session cookie called XSRF-TOKEN on the first HTTP
GET request. On subsequent XHR requests the server can verify that the
cookie matches X-XSRF-TOKEN HTTP header, and therefore be sure that
only JavaScript running on your domain could have sent the request.
The token must be unique for each user and must be verifiable by the
server (to prevent the JavaScript from making up its own tokens). We
recommend that the token is a digest of your site's authentication
cookie with a salt for added security.
The name of the headers can be specified using the xsrfHeaderName and
xsrfCookieName properties of either $httpProvider.defaults at
config-time, $http.defaults at run-time, or the per-request config
object.
Please Kindly refer the below link,
https://docs.angularjs.org/api/ng/service/$http
From AngularJS DOCs
JSON Vulnerability Protection
A JSON vulnerability allows third party website to turn your JSON resource URL into JSONP request under some conditions. To counter this your server can prefix all JSON requests with following string ")]}',\n". Angular will automatically strip the prefix before processing it as JSON.
There are other techniques like XSRF protection and Transformations which will further add security to your JSON communications. more on this can be found in AngularJS Docs https://docs.angularjs.org/api/ng/service/$http
You might want to consider using JSON Web Tokens for this. I'm not sure how to implement this in Flask but here is a decent example of how it can be done with a Nodejs backend. This example at least shows how you can implement it in Angularjs.
http://www.kdelemme.com/2014/03/09/authentication-with-angularjs-and-a-node-js-rest-api/
Update: JWT for Flask:
https://github.com/mattupstate/flask-jwt
I know differences and advantages of each command, my question is could I replace POST requests with GET everywhere? And which these commands calls by default while sending request from html form?
could I replace POST requests with GET everywhere
No (and it would be a terrible idea to try).
Things that a form can do with POST that you can't do with GET include:
Sending lots of data
Sending files
There are other things that would simply be stupid to do with GET.
From http://www.w3.org/TR/html5/forms.html#attr-fs-method :
The method and formmethod content attributes are enumerated attributes
with the following keywords and states:
The keyword get, mapping to the state GET, indicating the HTTP GET
method. The keyword post, mapping to the state POST, indicating the
HTTP POST method. The invalid value default for these attributes is
the GET state. (There is no missing value default.)
When using GET to transfer data from the client to the server, the data is added to the URL, there is not BODY of the request. There is usually a limit on how long a URL can be, in the old days this was 1024 characters but that really depends on the server software and server middleware and even the browser.
This means if you want to transfer loads or data or upload a file to the server, you can not do it with GET.
I know that there are two methods of submitting a form: 'GET' and 'POST'. We can also use request method for accessing the content of the submitted.
I want to know whether there is any other method of submitting the form. As far as my knowledge there are only two methods. But some one asked me this question in a interview that there are 5 method of submitting the form.
If any one has any idea about this please tell me.
The question was probably about HTTP request methods. There 9 request methods:
HTTP defines nine methods (sometimes referred to as "verbs")
indicating the desired action to be performed on the identified
resource. What this resource represents, whether pre-existing data or
data that is generated dynamically, depends on the implementation of
the server. Often, the resource corresponds to a file or the output of
an executable residing on the server.
HEAD: Asks for the response identical to the one that would
correspond to a GET request, but without the response body. This is
useful for retrieving meta-information written in response headers,
without having to transport the entire content.
GET: Requests a representation of the specified resource. Requests
using GET (and a few other HTTP methods) "SHOULD NOT have the
significance of taking an action other than retrieval". The W3C has
published guidance principles on this distinction, saying, "Web
application design should be informed by the above principles, but
also by the relevant limitations." See safe methods below.
POST: Submits data to be processed (e.g., from an HTML form) to
the identified resource. The data is included in the body of the
request. This may result in the creation of a new resource or the
updates of existing resources or both.
PUT: Uploads a representation of the specified resource.
DELETE: Deletes the specified resource.
TRACE: Echoes back the received request, so that a client can see
what (if any) changes or additions have been made by intermediate
servers.
OPTIONS: Returns the HTTP methods that the server supports for
specified URL. This can be used to check the functionality of a web
server by requesting '*' instead of a specific resource.
CONNECT: Converts the request connection to a transparent TCP/IP
tunnel, usually to facilitate SSL-encrypted communication (HTTPS)
through an unencrypted HTTP proxy.
PATCH: Is used to apply partial modifications to a resource.
HTTP servers are required to implement at least the GET and HEAD
methods
The HTML form element's method only accepts two parameters, GET and POST. Evidenced by this entry on the W3 Standards site:
method (GET|POST) GET -- HTTP method used to submit the form--
They may have been asking you about ways to submit the data. In which case there are many more, like AJAX, Flash, P2P types, etc.
However if they specifically said FORM, as in the HTML FORM element -- then no. POST and GET.
Addendum: Here is a StackOverflow question asked on a similar topic. In that the answerer highlights other methods which can be submitted via AJAX. Again, though, note that these are down through AJAX and not strictly through the FORM element.
In regards to this Haacked blog, I'm hesitant to implement the proposed anti-JSON GET hijacking solutions since
The recommended solutions to mitigating JSON hijacking involve non-REST-full JSON POSTs to GET data
The alternate solution (object wrapping) causes problems with 3rd party controls I don't have source-code access to.
I can't find a community-vetted implementation that implements the Alternative Solution (listed below) on how to compose the security token, or securely deliver it within the webpage. I also won't claim to be enough of an expert to roll my own implementation.
Referrer headers can't be relied upon
Background
This blog describes a CSRF issue regarding JSON Hijacking and recommends using JSON POSTs to GET data. Since using a HTTP POST to GET data isn't very REST-full, I'd looking for a more RESTfull solution that enables REST actions per session, or per page.
Another mitigation technique is to wrap JSON data in an object as described here. I'm afraid this may just delay the issue, until another technique is found.
Alternative Implementation
To me, it seems natural to extend the use ASP.NET MVC's AntiForgeryToken with jQuery HTTP GETs for my JSON.
For example if I GET some sensitive data, according to the Haacked link above, the following code is vulnerable:
$.getJSON('[url]', { [parameters] }, function(json) {
// callback function code
});
I agree that it isn't RESTfull to GET data using the recommended POST workaround. My thought is to send a validation token in the URL. That way the CSRF-style attacker won't know the complete URL. Cached, or not cached, they won't be able to get the data.
Below are two examples of how a JSON GET query could be done. I'm not sure what implementation is most effective, but may guess that the first one is safer from errant proxies caching this data, thus making it vulnerable to an attacker.
http://localhost:54607/Home/AdminBalances/ENCODEDTOKEN-TOKEN-HERE
or
http://localhost:54607/Home/AdminBalances?ENCODEDTOKEN-TOKEN-HERE
... which might as well be MVC3's AntiForgeryToken, or a variant (see swt) thereof. This token would be set as an inline value on whatever URL format is chosen above.
Sample questions that prevent me from rolling my own solution
What URL format (above) would you use to validate the JSON GET (slash, questionmark, etc) Will a proxy respond to http://localhost:54607/Home/AdminBalances with http://localhost:54607/Home/AdminBalances?ENCODEDTOKEN-TOKEN-HERE data?
How would you deliver that encoded token to the webpage? Inline, or as a page variable?
How would you compose the token? Built in AntiforgeryToken, or by some other means?
The AntiForgeryToken uses a cookie. Would a backing cookie be used/needed in this case? HTTP Only? What about SSL in conjunction with HTTP Only?
How would you set your cache headers? Anything special for the Google Web Accelerator (for example)
What are the implications of just making the JSON request SSL?
Should the returned JSON array still be wrapped in an object just for safety's sake?
How will this solution interop with Microsoft's proposed templating and databinding features
The questions above are the reasons I'm not forging ahead and doing this myself. Not to mention there likely more questions I haven't thought of, and yet are a risk.
The Asp.net MVC AntiForgeryToken won't work through HTTP GET, because it relies on cookies which rely on HTTP POST (it uses the "Double Submit Cookies" technique described in the OWASP XSRF Prevention Cheat Sheet). You can also additionally protect the cookies sent to the client by setting the as httponly, so they cannot be spoofed via a script.
In this document you can find various techniques that can be used to prevent XSRF. It seems the you described would fall into the Approach 1. But we have a problem on how to retrieve the session on the server when using Ajax HTTP GET request since the cookies are not sent with the request. So you would also have to add a session identifier to you action's URL (aka. cookieless sessions, which are easier to hijack). So in order to perform an attack the attacker would only need to know the correct URL to perform the GET request.
Perhaps a good solution would be to store the session data using some key from the users SSL certificate (for example the certs thumb-print). This way only the owner of the SSL certificate could access his session. This way you don't need to use cookies and you don't need to send session identifiers via query string parameters.
Anyway, you will need to roll out your own XSRF protection if you don't want to use HTTP POST in Asp.net MVC.
I came to this problem and the solution was not so trivial however there is a fantastic blog to get you started this can be used with get and post ajax.
http://johan.driessen.se/posts/Updated-Anti-XSRF-Validation-for-ASP.NET-MVC-4-RC
If you place the following in the global name space all your post/gets can take advantage having an anti forgery token and you don't have to modify your ajax calls. Create an input element in a common page.
<form id="__AjaxAntiForgeryForm" action="#" method="post">#Html.AntiForgeryToken()</form>
The following javascript will read the anti forgery tokken and add it to the request header.
// Wire up the global jQuery ajaxSend event handler.
$(document).ajaxSend(namespace.ajax.globalSendHandler);
// <summary>
// Global handler for all ajax send events.
// </summary>
namespace.ajax.globalSendHandler = function (event, xhr, ajaxOptions) {
// Add the anti forgery token
xhr.setRequestHeader('__RequestVerificationToken', $("#__AjaxAntiForgeryForm input[name=__RequestVerificationToken]").val());
};
I think it is legitimate to use AntiforgeryToken (AFT) within an ajax http GET request provided that it is embedded in a form that already provides the AFT and associated cookie. The ajax handler can then do the validate on the server just how it would in a normal form post.