From my understanding, when CSRF is enabled on server side, the server creates a token (say token1) and injects it in to the form and saves the same in the cookie of the client browser.
When the client sends the form request to the server, it sends the csrf token (token1) from browser cookie and also send the same token as in the form. The server validates the request by checking that the token in cookie and the token in form match and then processes the request.
Now, if i open the same form in another tab, will the server generate another token (token2) and inject it in to the form and cookie. Then, in the cookie, token1 will be overwritten by token2. So the submission of the form in first tab will not work in this case? But from experience i see that the submission of form in tab 1 still succeeds.
So can some one explain how it's succeeding in the above scenario??
Since you have added the Spring Security tag, I will describe how Spring Security uses the Synchronizer Token Pattern to protect against CSRF attacks.
the server creates a token (say token1) and injects it in to the form and saves the same in the cookie of the client browser.
That's not exactly what happens. The server will create a CSRF token (token1) and store that token in the HttpSession. The CSRF token (token1) is also be embedded in the form on the client side. The client is also given a Session ID (session-id1) which is stored in a cookie.
When the client submits the form, it sends token1 and session-id1. The server will then use session-id1 to look up the HttpSession and get the expected CSRF token for that session. It will compare the expected CSRF token to token1 and if the values do not match, the HTTP request will be rejected.
If you open the same form in another tab, the browser will still have access to the Session ID (session-id1). That form will get the same token (token1) that was associated with session-id1.
In the end, there is only one CSRF token (token1) that is used in both tabs.
You can find more information about protection against CSRF attacks in the Spring Security reference documentation.
Related
I confuse session id and CSRF token. so I search about that and understand a little bit.
Session IDs are used to verify a user. CSRF tokens are used to verify request itself.
My question is when server send CSRF token to user?
For example
when client visit www.sample.com first time, sever send session id to client.(is that right?) client want to change his password. so he come to www.sample.com/change where client can change password and is located change button(post). And that time(when client visit www.sample.com/change) sever send CSRF token to client? or when client post their data then middleware send CSRF and compare before server got post data?
The server sends the CSRF token when the client visit the www.sample.com/change page. Usually, the CSRF token is embedded in the HTML file as a hidden html element such as <meta> tag or hidden <input> tag. Therefore, when the client sends a GET request to retrieve the www.sample.com/change page, the CSRF token will be returned as part of the HTML page.
Resources:
https://portswigger.net/web-security/csrf/tokens
Additional Consideration
Let's say we take the "middleware" approach described in your question. In that case, the CSRF token will be generated in the server upon receiving a POST/PUT request. Then, the server cannot discern whether the request is generated by the legitimate site (www.sample.com) or the impersonating site (www.malicious.com) because both requests can look exactly the same (note here that the malicious site can spoof request headers such as origin). Therefore this approach cannot prevent CSRF attack. The CSRF token needs to be sent from the client so that the server can identify the requests originating from the legitimate website.
This question is not about how CSRF tokens works, but is rather about they are stored on the server side.
In short, CSRF tokens are generated by server and injected in to the web page/form. When the form is submitted the csrf token is extracted by the server and compared to the one saved on the server. So far so good.
From this earlier posting - CSRF token value when same page is opened in two tabs on same machine?
Here's the excellent answer which explains that -
The server will create a CSRF token (token1) and store that token in
the HttpSession. The CSRF token (token1) is also be embedded in the
form on the client side. The client is also given a Session ID
(session-id1) which is stored in a cookie.
When the client submits the form, it sends token1 and session-id1. The
server will then use session-id1 to look up the HttpSession and get
the expected CSRF token for that session. It will compare the expected
CSRF token to token1 and if the values do not match, the HTTP request
will be rejected.
and
If you open the same form in another tab, the browser will still have
access to the Session ID (session-id1). That form will get the same
token (token1) that was associated with session-id1.
In the end, there is only one CSRF token (token1) that is used in both
tabs.
Bit more info can be found in the quoted reference, but it fails to explain the server side part.
The above leads to more questions -
If another form (form2) is opened by user in a different tab - then what CSRF token will it get, will it be same as that for the first form(form1) ?
To explore and unsderstand better, I want to know where and how the CSRF tokens are stored in the backend when using spring security (unlike Session Cookies which are generated by Servlet Container, I am assuming that CSRF tokens are generated by Spring Security module). Is there just one CSRF token per session, which is used accross every form and every tab or there are several CSRF tokens.
Please clarify as much as you can... every drop counts
I'm creating a React Js website with a Node.js backend. I've been attempting to figure out a user authentication implementation to prevent CSRF attacks however I'm really confused about where to store Anti-CSRF tokens.
My thought process of a secure implementation is as follows...
User submits request to login with credentials.
Credentials are authenticated.
Server creates session.
Server creates JWT to use as Anti-CSRF token.
Server stores JWT (Anti-CSRF token) in session storage.
Server sends response to client.
Response has header to store session ID in HttpOnly cookie on client-side.
Response payload includes JWT (Anti-CSRF token).
Client receives response.
HttpOnly cookie holding session ID is stored on client-side.
Client stores JWT (Anti-CSRF token) in localStorage.
I figure when a user needs to request information, the client can send the JWT (Anti-CSRF token) via a header or payload, and the session ID will be sent automatically due to it being a cookie. Then, the server can check if the JWT (Anti-CSRF token) exists in the session storage.
I know that the JWT (Anti-CSRF token) will need to be refreshed at some point.
My confusion is due to storing the JWT (Anti-CSRF token) on the client side. I keep reading that it should only be stored on the server. But if it's only stored on the server it doesn't seem to be doing anything at all.
I thought of using both cookies and localStorage because it seems that if a request to the server needs both a HttpOnly cookie and something from localStorage to send back an "authorized" response, an attacker would need to both successfully ride a session and successfully implement an XSS attack to get the Anti-CSRF token.
I just started learning about CSRF and XSS recently so I could be completely wrong and there could be a huge flaw in my implementation that I'm missing. But my main question is... don't Anti-CSRF tokens need to be stored on the client AND the server?
They are also called "CSRF Tokens". When a client requests for a form (e.g. bank login page), server generates the tokens and passes them to client and when the client fills the form, client passes CSRF token along with the completed form. Server verifies the token value and if it matches, request is fulfilled. CSRF tokens are stored on server-side in synchronizer token pattern.
I am working on csrf and using spring 5. Spring 5 automatically provide supports for csrf and on enabling csrf protection on the server side I am getting
403: Invalid X-CSRF token
So this means a token needs to come from frontend?
My understanding is that backend generates csrf token and sends as a response to frontend browser and then it uses this token and send it as cookies to the backend server and then backend will validate it. is my understanding is correct?
when manually generating the hidden token for csrf, How backend will know it is a valid csrf token?
Second Scenario: Suppose two users are logged in to my website and frontend is sending this token to backend then how the application will differentiate which token is for which user?
Also please explain how it works internally means we enabled csrf protection in the backend and manually generated a token on the front end then what it does behind the scenes?
consider my frontend is JS pages
Is there is any specialty of Spring 5 which take care's of sessions for each user and validate tokens automagically for each user?. I tried finding it on the official website but didn't get it anywhere
Hi Zaib the csrf token is generated from back-end as you stated, once it is generated is automatically sent to the front-end which must take care to retrieve from the model and re-post for each "POST" requests.
You can share the csrf token via different way mostly i used header or html parameter.
A token is related to a specific session so is not really important if you have a logged user or not , even not authenticated users must send the csrf token for "POST".
The csrf token is validated via a filter placed in the front of the filter chain defined by Spring security itself, if you search in the documentation there is a table showing you the position of each "default" filter enabled by Spring security. Moreover if you enable debug on Spring ( </debug> is enough in your xml configuration) you will have printed all the filters used while processing an http request.
So each time a request with "POST" method pass through that filter , it will check if in the parameters there is the csrf token or header.
I never used as cookie so it may a different case for you if specifically need that but it does not differ on how it works.
Here is the details of csrf implementation on Spring:
https://docs.spring.io/spring-security/site/docs/5.0.7.RELEASE/reference/htmlsingle/#csrf-configure
I said "POST" method but actually the token is checked for any method that is related to a change of state , you can refer to doc here:
https://docs.spring.io/spring-security/site/docs/4.2.5.RELEASE/apidocs/org/springframework/security/web/csrf/CsrfFilter.html
Hope this help clarifying a bit the usage of the csrf token.
I'm using spring security in my spring boot application. I have a front end single page app that logs in via rest. I have no problem logging in, but once I've logged in, my session token changes, BUT THE CSRF TOKEN DOES NOT.
Is there any way to force spring security to set the csrf token since the old token associated with the un-authenticated session token will not work with the new authenticated session token?
I'm storing the CSRF token in a cookie, and sending it back from the client in the header of every state altering request. I can't login and logout without an intervening request (non-post) to retrieve the csrf token. This seems like a crock.
SO a simple solution is to redirect the login request once it's successful. This puts the request through another loop through the security filter chain ensuring a new CSRF is added to the new session token. A good night sleep does wonders.