I have recently been reading about session ID's and how websites track users.
I was wondering how session ID's are safe inside cookies. Couldn't a website read another website's cookies and get your session ID?
Cookies are stored on the client's browser with cookie name, value and the expiry. But multiple websites may have cookie with same name so cookies are grouped with respect to domains. See the Firefox's cookies screenshot bellow.
Suppose sites A and B have cookies with name ABC. Browser will provide the cookie data for site A from site A only.
Related
According to Wikipedia, cookies are :
Cookies were designed to be a reliable mechanism for websites to
remember stateful information (such as items added in the shopping
cart in an online store) or to record the user's browsing activity
(including clicking particular buttons, logging in, or recording which
pages were visited in the past).
Session ID is:
a session identifier, session ID or session token is a piece of data
that is used in network communications (often over HTTP) to identify a
session, a series of related message exchanges.
My question is when the client send the cookies to the server the, how the server know it is a valid cookies? Does the server store a copy of the cookies to compare with the cookies sent by the client, so if they match then it is valid, otherwise not?
And how the server store the cookies of all the clients, are they in a database or in memory? If in database, what is the key to search the database, is it session ID?
Background: I have a javaee webapp deployed on tomcat which uses form based authentication. When the web server receives a login request, it sends the request to a dedicated authentication service which validates user login (User id and password). After successful authentication user's session is maintained in the web server.
Problem: I have written a simple webpp source code here, to simulate the scenario. On successful login the current HttpSession instance is invalidated and new instance is created. For each request for a post login page, the session is validated. A new JSESSIONID cookie is set which is used to identify the user during the session until session is expired or user logs out. This cookie can easily viewed in browser's dev tools. If I copy the cookie and set this in a different browser via JavaScript (document.cookie="JSESSIONID=xyzz") and then try to access a post login page, the server identifies it as a valid request and session is validated successfully. The post login page is served without user being challenged for user Id and password.
POC: User opens chrome and enter the URL http://localhost:8080/mywebapp/ and logs in with admin and pass1234. On successful log in the home page http://localhost:8080/mywebapp/home is shown. Now the JSESSIONID cookie is copied and set in FireFox. User enters http://localhost:8080/mywebapp/home in Firefox and is shown the home page without being challenged for userId and password.
Question: How can this be prevented wherein same session is getting replicated over multiple browsers?
You can't prevent this specific case of simply copying the cookie from your own browser (or by copying the cookie value from a HTTP payload copypaste/screenshot posted by an ignorant somewhere on the Internet). You can at most prevent the cookie getting hijacked by XSS or man-in-middle attacks.
This all is elaborated in Wikipedia page on the subject Session Hijacking of which I snipped away irrelevant parts (either already enforced by Servlet API, or are simply not applicable here).
Prevention
Methods to prevent session hijacking include:
Encryption of the data traffic passed between the parties by using SSL/TLS; in particular the session key (though ideally all traffic for the entire session[11]). This technique is widely relied-upon by web-based banks and other e-commerce services, because it completely prevents sniffing-style attacks. However, it could still be possible to perform some other kind of session hijack. In response, scientists from the Radboud University Nijmegen proposed in 2013 a way to prevent session hijacking by correlating the application session with the SSL/TLS credentials[12]
(snip, not relevant)
(snip, not relevant)
Some services make secondary checks against the identity of the user. For example, a web server could check with each request made that the IP address of the user matched the one last used during that session. This does not prevent attacks by somebody who shares the same IP address, however, and could be frustrating for users whose IP address is liable to change during a browsing session.
Alternatively, some services will change the value of the cookie with each and every request. This dramatically reduces the window in which an attacker can operate and makes it easy to identify whether an attack has taken place, but can cause other technical problems (for example, two legitimate, closely timed requests from the same client can lead to a token check error on the server).
(snip, not relevant)
In other words:
Use HTTPS instead of HTTP to prevent man-in-middle attacks.
Add a checkbox "Lock my IP" to login form and reject requests from different IP associated with same session in a servlet filter. This only works on users who know themselves they have a fixed IP.
Change session cookie on every request. Interesting at first sight, but breaks when user has same website open in multiple browser tabs/windows in same "session".
Not mentioned, but make sure you don't have a XSS hole anywhere, else it's very easy stealing cookies.
Last but not least, I'd like to make clear that this problem is absolutely not specifically related to Servlet API and the JSESSIONID cookie. All other stateful server side languages/frameworks such as PHP (PHPSESSID) and ASP (ASPSESSIONID) also expose exactly the same security problem. The JSESSIONID was previously (decade ago orso) only a bit more in news because by default it was possible to pass the session identifier along in the URL (which was done to support HTTP session in clients who have cookies disabled). Trouble started when ignorant endusers copypasted the full URL with JSESSIONID inside to share links with others. Since Servlet 3.0 you can turn off JSESSIONID in URLs by enforcing a cookie-only policy.
<session-config>
<tracking-mode>COOKIE</tracking-mode>
</session-config>
See also:
How do servlets work? Instantiation, sessions, shared variables and multithreading
How to prevent adding jsessionid at the end of redirected url
remove jsessionid in url rewrite in spring mvc
What you have stated is called session hijacking. There are many good answers on how to prevent it.
Using same Jsession ID to login into other machine
we can use Encryption or hide JSESSIONID using Browser control.
Thanks
Which is the difference between sessions and cookies. I know that sessions are server side, and managed by the server, and the cookies are client side and managed by the browser.
I don't know why, but I see those things as rendundant. Which data have to be keept in a session variable and which on cookies?
Session is implemented with cookies. You would normally save in a cookie things like the user id, or some identifier that will allow you to know who the user is, and use that information as a key for your session variable on the server side.
Most importantly, you wouldn't want any secret information being stored on the client side, since cookies can easily be stolen (from a security point of view).
Don't forget that HTTP is stateless, so cookies are just a way to bypass this.
In short, cookies are more persistent than sessions. As soon as you close your browser, the session information is gone. Therefore a session has no way to store information about a website/user pair. Cookies do, and are used for things like allowing you to stay logged in to a website, or storing preferences for that website (e.g. language).
The main difference between cookies and sessions is that cookies are stored in the user's browser, and sessions are not. This difference determines what each is best used for.
see http://php.about.com/od/learnphp/qt/session_cookie.htm
Cookies are for small data. They can only hold strings.
In session variables you're able to store objects in the server memory.
We have an implementation understanding with a merchant to create our domain cookies when user is on his site. Now in FF assuming that third party cookies acceptance is set we are able to create the cookies and flow works fine. But the issue is that after the cookie is created and third party cookie is disabled later - the request to load an image from merchant site page to ours site - we do not receive the cookie details.
Is it an expected behavior or we need some special mechanism to get the cookie?
Please help.
You may already know this but cookies are domain based. You can only access cookies on requests for the same domain.
If your image is displayed on sample.com and your the url of the image is sample.com/img.jpg then when the request is made for the image the cookies will be sent along with the request.
On the other hand if the image is displayed on sample.com and the image url is yoursite.com/img.jpg then you won't receive the cookies for sample.com.
Also, dev.sample.com and sample.com are different domain names.
Hopefully this helps clarify why you can't receive cookies. This behavior is mainly security related to prevent websites from sniffing cookies from other sites.
If I have a site (e.g. foo.com) and on the home page of foo.com, there is an image request where the src=bar.com..., will the cookies on the bar.com domain be sent to the bar.com servers?
Yes. HTTP doesn't distinguish between one kind of resource or another (image vs html).
The cookie will typically be included in any type of request, but the scenario you describe is what's known as a third-party cookie (that is, the cookie is set on a domain that is different than the domain of the loaded page) and most browsers offer a privacy setting to block third-party cookies.
A third-party cookie allows the owners of bar.com to place an image (say a banner ad) on foo.com and track the users of foo.com even though those users have never visited bar.com. This is a privacy concern and many users elect to block such cookies.
This question is old, but was the first result on Google for me, so I think it's worth clarifying how this works nowadays (2021).
When bar.com sets the cookie, they can specify a SameSite attribute.
If the cookie is set with SameSite=Lax (or the SameSite attribute is not specified), then the cookie will not be sent for requests for images/iframes/etc hosted on bar.com, but will be sent if the user clicks a link on your foo.com homepage that takes them to bar.com
If the cookie is set with SameSite=Strict, the cookie will not be included in requests to bar.com that originate from another webiste, including if the user clicks a bar.com link on foo.com.
If the cookie is set with SameSite=None, the cookie will be sent to bar.com, including requests for images.
If third-party-cookies are not blocked by the user then most modern browsers will set or send cookies of the third party domain when a request is made to the third party web site. IE 6 has a different kind of blocking mechanism called leashing. wiki: A leashed cookie is a third-party cookie that is sent by the browser only when accessing a third-party document via the same first-party.
Yes cookies are sent on all requests.
This includes "img" and "script" as well as XMLHttpRquest calls from javascript and can be a security issue on script tags as scripts loaded by one website can load scripts from another site and will send their authentication cookies too. This can be exploited to steal data.
Yes, aspx/js/css/image requestion need the cookie verification.