I'm writing a GWT application where users login and interact with their profile. I understand that each form entry needs to be validated on the server, however, I am unsure about potential security issues once the user has logged in.
Let me explain. My application (the relevant parts) works as follows:
1 - user enters email/pass
2 - this info is sent back to the server, a DB is queried, passwords are checked (which are salted and hashed)
3. if the passwords match the profile associated w/ the email, this is considered success
Now I am unsure whether or not it is safe to pass the profile ID back to the client, which would then be used to query the DB for information relevant to the user to be displayed on the profile page.
Is there a possibility for a potential user to manually provide this profile ID and load a profile that way? My concern is that somebody w/ bad intentions could, if they knew the format of the profile ID, load an arbitrary amount of information from my DB without providing credentials.
-Nick
What you are dealing with here is a session management issue. Ideally, you want a way to keep track of logged in users (using random values as the session key), know how long they have been idle, be able to extend sessions as the user is using the site, and expire sessions.
Simply passing the profile ID to the client, and relying on it to send it back for each request is not sufficient - you are correct with your concern.
You want to keep a list of sessions with expiration times in a database. Every time an action is executed that needs user permissions (which should be pretty much everything), check to see if the session is still valid, if it is, extend it by however long you want. If it is expired, kill the session completely and log the user out.
You can store your session keys in a cookie (you have to trust the client at some point), but make sure they are non-deterministic and have a very large keyspace so it cannot be brute forced to get a valid session.
Since you're logging a user in, you must be using a backend that supports sessions (PHP, .Net, JAVA, etc), as Stefan H. said. That means that you shouldn't keep any ids on your client side, since a simple id substitution might grant me full access to another user's account (depending on what functionality you expose on your client, of course).
Any server request to get sensitive info (or for any admin actions) for the logged in user should look something like getMyCreditCard(), setMyCreditCard(), etc (note that no unique ids are passed in).
Is there a possibility for a potential user to manually provide this profile ID and load a profile that way? My concern is that somebody w/ bad intentions could, if they knew the format of the profile ID, load an arbitrary amount of information from my DB without providing credentials.
Stefan H is correct that you can solve this via session management if your session keys are unguessable and unfixable.
Another way to solve it is to use crypto-primitives to prevent tampering with the ID.
For example, you can store a private key on your server and use it to sign the profile ID. On subsequent requests, your server can trust the profile ID if it passes the signature check.
Rule 1 - Avoid cooking up your own security solution and use existing tested approaches.
Rule 2 - If your server side is java then you should be thinking along the lines of jsessionid. Spring Security will give you a good starting point to manage session ids with additional security features. There will be similar existing frameworks across php too (i did not see server side language tags in the question).
Rule 3 - With GWT you come across javascript based security issues with Google Team documents and suggests XSRF and XSS security prevention steps. Reference - https://developers.google.com/web-toolkit/articles/security_for_gwt_applications
Related
Hello fellow developers
I have obviously under estimated a thing when developing my first complex web site, where user creation and login is required.
It appears that cookies can be edited and modified by the user logged in, by using some developer tools i.e. in Google Chrome. That, I never gave a thought.
So, here is my issue.
When the user is logged in, I store the user name in a cookie.
If username-cookie is not blank, and I can find a user file with that name, the user is logged in, per se. Otherwise, no user is logged in.
When the user logs out, I simply expires the cookie, which works fine.
Now, the problem is, that a user obviously can edit the content of a cookie, outside the web application, or with javascript.
What would be the correct approach here to ensure, that the username cookie is not compromised in any way, other by my web application?
Making them read-only is not possible, I assume. Encrypting the cookie and then decrypting might work, I guess. Then, the cookie would be nonsense to the user, and if modified, result in a logout, as no valid username can be found upon decrypting the edited cookie.
I have stalked Googles cookies, and it appears that there are a lot of xxID cookies, which contains garbage. Does that mean, that encrypting/decrypting is the only way to make it work? I also considered some kind of login-ticket, but that would require a table lookup every time a user interacts with my web page.
Can anyone give me a hint as to what would be the correct approach?
Thanks in advance
Best regards,
Karsten Heitmann
You should look up session management for the language you are using.
The traditional approach is that when a user logs on, your application generates a long, cryptographically random token called the "session id" and sets that into a cookie. It stores data like who is logged in on the server side identified by the random value, so when a logged on user comes back, the browser sends the cookie with the random session id and the application can look up session data on the server side. This way an attacker has no way to guess a valid session id for a logged on user, assuming the session id is cryptographically random and long enough (which more precisely means it has enough entropy). Logging out means deleting the session data on the server side, and also removing the cookie, but that is not the most important part - the session will be invalid anyway.
Note that you should not code this yourself. You did not mention the language and environment you are developing in, but session management is rather tricky business if you want to secure it, and it is already provided by most languages / frameworks.
Just for curiosity, the encryption approach you mention is by the way a valid one. Some frameworks actually do that, but you should not attempt to code that either, because it is very easy to get it wrong, lots of things need to be taken care of to make it secure enough. Unfortunately an answer here is not the right format to go into details I'm afraid.
Btw you mention looking at Google. They use their own single sign-on solution, it is very complex compared to simple session management, so it's probably not the best example for you to look at. Find simple websites, most of those work the traditional way.
So I just noticed that one of the internet banks websites is passing session id as url parameter. ( See image below )
I didn't previously see anywhere that ';' in url, in this case it is after 'private;'.
1) What is the use of this ';'?
2) And why internet bank, which needs to be securest place in the internet is passing session id as url parameter?
At first, I thought they are doing it because some of the users disallow use of cookies, but then again, if they allow it, use cookies, if not - url, but I do allow use of cookies, so obviously thats not the case.
3) I guess then they should have some other security measures? What they could be?
4) And what one can possibly do if he knows others valid session id?
As I know, you can quite easily log into others peoples session if you know that id, because its not hard to edit cookies and its much easier to pass that session id as url parameter, especially if you have something like:
session_id($_GET[sessionid]);
Thanks!
1) You should ask whoever designed the application your red box is covering. URL can be anything you want; the convention of key=value&key2=value2 is just that - a convention. In this case, it's Java, and it commonly uses the convention of ;jsessionid=.... for its SID.
2) It's not that big of a deal. Normal users can't copy-paste cookies like they can copy-paste a GET parameter, but power users can do whatever they want (using Mechanize, wget, curl and other non-browser means, or even browser extensions). And if you allow it for some users and disallow for some, it's not really much of a security precaution, is it? Basically, cookie SID will make the attack a bit harder, but it's like putting your front door key under the mat - definitely doesn't keep your door secure. Additionally, cookies are shared between tabs: if a site wants you to be logged in with two accounts at once, you can't do it with cookies.
3) Serverside security, yes. One effective countermeasure is one-time SIDs (each time you visit a page, the server reads the session from the current SID, then starts a new session with a new SID for the next request). A less effective but still good method is to validate other information for consistency (e.g. - still same IP? Still same browser?)
4) Yes, if you know someone's valid SID, and the server does not adequately protect against session fixation, you can "become" that person. This might enable the attacker to, say, pay his bills with your money, for instance.
So, #Amadan correctly covered #1 and #4. But there's a bit more that needs expansion.
Using Session identifiers in a URL can be a major problem. There are a few cases where it's critically bad:
Session Hijacking:
If a user copy-pastes a URL into an email.
In this case, the attacker can simply read the email, and steal the session identifier (thereby resuming the session).
You could partially defend against this by making session lifetimes short, and validating things like IP addresses or User Agents in the session. Note that none of these are foolproof, they just make it "slightly" harder to attack.
If the connection is ever downgraded to HTTP.
If they are not using Http-Strict-Transport-Security (HSTS), then an attacker may be able to successfully downgrade the session to HTTP only (via MITM style attack). If the server isn't setup perfectly, this can cause the URL to leak to the attacker, and hence the session identifier.
Session Fixation Attacks
An attacker can craft a session identifier, and send the user a forged link with that session identifier. The user then logs in to the site, and the session is now tied to their account.
You can mitigate this by strictly rotating session identifiers every time the session changes (log in, log out, privilege upgrade or downgrade, etc). But many servers don't do this, and hence are susceptible to fixation style attacks.
The reason that cookie sessions are seen as more secure is not because they are harder to edit. It's because they are more resistant to fixation attacks (you can't create a URL or link or form or js or anything that sends a fraudulent cookie on behalf of the user).
Why the bank uses a URL parameter? I have two guesses:
Because they want to support those who don't allow cookies.
Which is sigh worthy.
They don't know any better.
Seriously. If it's not in a compliance doc or NIST recommendation, then they likely don't do it. Hell, there are implemented NIST recommendations that are known to be insecure, yet are still followed because it's in writing.
What is the use of this ;?
This is just a query string separator. & isn't the only sub-delim specified in the URL specification (RFC 3986).
And why internet bank, which needs to be securest place in the internet is passing session id as url parameter?
It could be that this session ID is never used, and the actual session identifier user is passed in cookies or in POST data between each navigated page. The only way to verify this is to try copying the URL into another browser to see if your session is resumed, however then again they may be checking things like User Agent - not real security but would dissuade casual attacks. Do not try this on a live system you do not have permission to do so on as it would be illegal. If you want to learn about security download something like Hacme Bank and try on there.
I guess then they should have some other security measures? What they could be?
No doubt they will, otherwise this would be a huge security threat. The URL could be leaked in the referer header if there are any external links on the page. The types of security a bank uses for their website is too large to list here, however they should be meeting certain industry standards such as ISO/IEC 27001 that will cover the types of threat that their site would need to be secure against.
And what one can possibly do if he knows others valid session id? As I know, you can quite easily log into others peoples session if you know that id, because its not hard to edit cookies and its much easier to pass that session id as url parameter, especially if you have something like:
As the ID is displayed on the screen it might be possible to read it (although IDs are generally long). A more realistic attack is Session Fixation. This is where an attacker can set the Session ID of their victim. For example, sending them a link that includes the attacker's Session ID. When the victim follows it and then logs in, as the attacker has the same session, they are logged in too.
Storing the Session information in a cookie or in a URL are both viable methods. A combination may used as
Security session management and (Server) Session management are separate aspects:
The fundamental difference is that cookies are shared between browser windows/tabs, the url not.
If you want your user to be logged on when navigating to the same site in different tab, sharing the security session (=without a new logon procedure) then cookies are a good way.
To differentiate "sessions" per tab and associate distinct server sessions with distinct tabs (Think of the user running two "stateful" transactions in two different tabs in parallel), managing a sessionId on the client which can be different per tab is required. Cookies won't work here.
Putting it in the URL is one way to assure this information is routinely added to requests fired from the page (referrer header). Alternative methods would require specific code to add this information explicitly to each request which is more work.
See How to differ sessions in browser-tabs?
I'm currently working on a web application which deals with multiple users. Whilst it currently works, it relies on some real bad practises which I'll outline in a minute.
We're using MySQL as the database system, since we're updating our current application, we want to ensure everything is backwards compatible. Otherwise I'd look at MongoDB etc.
Our users are stored in a table aptly named login. This contains their username, email, hashed password etc and a field which contains a JSON encoded object of their preferences. There is no real reason for doing this over using a meta table.
So the bad practises:
We're storing the entire users login row, excluding their password (although this is an internal-only app) in a cookie. It's JSON encoded.
Once the user logs in we have a secure HTTP cookie, readable only via Node.js for their username and their password so that we can continue to keep the user logged in automatically.
We have a app.get('*') route which constantly ensures that the user has their three cookies and updates their acc cookie with new preferences. This means that every time the user switches page or accesses a new AJAX item (all under the same routes) they have an updated cookie.
Every time a user performs an action we do this to get their user id: JSON.parse(res.cookies.acc).agent_id yuck!
Now, each user is able to perform actions to certain elements on the page, this effects everyone as the application is internal and anybody can work on the data inside of it.
I know what I want to achieve and how it should be done in say PHP, but I can't figure out the most effective way in Node.js.
I've started creating a User module which would allow us to get the user who performed the action and neatly update their preferences etc. You can see this here bearing in mind that it's a WIP. The issue I'm having with the module is that it doesn't have access to the users cookies, since it's not "a part of" Express. Which explains the last bad practise.
What would be the best way to handle such a system and remain bad-practise free?
I doubt it meets all of your requirements but its worth checking out out Drywall; A website and user system for Node.js
Hopefully it (or parts of it) could be helpful to you.
http://jedireza.github.io/drywall/
So lets say i have a member base website and when the user signs in i put put a cookie (or a session) with a key value pair remembering who the user is. But its just come to my attention which information i should use to remember the user so that its secure. I cant use username=username or user_id = user_id (because my user_id will be 1), because people then can just simply guess what the cookie values are and logged in as that user. So what key/value pair should i use to be able to identify users and still connect their information to the database securely? Thanks.
Ben, there are a few different types of attacks you need to be concerned with. For example simply encrypting the identifier with a private key doesn't prevent someone who can intercept the encrypted value from simply replaying it to your server (and appear to be the user). Some common security risks are detailed here (and in associated links at bottom of this page):
https://www.owasp.org/index.php/Session_hijacking_attack
Session management can be quite complex and depending on the level of security you require, it is not something you want to tackle yourself, because likely your development environment / framework already has a solution that has been vetted moreso than a homebrew solution. Here is a link detailing some things to consider, unfortunately this topic has more to it than a simple Stack Overflow post:
https://www.owasp.org/index.php/Session_Management
If you dont prefer encryption for whatever reason, then a simpler solution could be to use a GUID to identify the user. This way, a hacker would have to launch a denial of service kind-of attack on your application to be able to run through even a very small fraction of the GUIDs.
If you want to do this properly, then you should have a look at http://jaspan.com/improved_persistent_login_cookie_best_practice also.
I'm definitely not an expert in security, but I have recently implemented user management tool and I have done the following.
Don't use encryption, its slow and most of the time for simple implementation its just a waste of time.
Here is what you do need to store on the server - in order to authenticate each request.
UserId (obvious)
CookieHash (made out of userId, some secret private key and crypto randomly generated number)
LastLogin
SessionRenewed (useful for when to cancel someone's session eg. renew cookieHash every 10 min, otherwise log out user)
LastIP
What I store in cookie is following
UserId
CookieHash
How to use this basic security
Simply when user logs in you check username/password etc. (just the usual) If everything is fine then log in user and generate new cookiehash and fill those values given above.
Every request check UserId against its hash. If someone gave UserId = 4 but hash didnt match then automatically drop a session and forward user to login screen. Possible log is good to see how often people try to play around with your hard work.
I hope this helps.
You can just encrypt the user id with a private encryption key that you keep on the server. There are a few things to watch out for with this approach:
Every call to the server will require you to decrypt the cookie to get the id of the user. This will add overhead to each request.
If the key is ever compromised, you will be forced to abandon the current name for the cookie you use and use another encryption key when assigning to the new cookie name; this will cause the user to have to re-login, of course.
While I don't think that these are major hurdles, they might be to you, and you would have to evaluate the impact on your site for yourself.
I'm writing a GWT application, and I've been asked to implement the user management portion of the website. I know a little bit about salting, hashing, encrypting, and user tokens, but I've never read any books or studied papers on the subject.
I'm planning on doing a stateless implementation which means keeping user identifiers and submitting them to the server on every request. No server-side session data will be used. I'm looking at Apache Shiro, and I like the low level of integration so that I don't need to hook up to complex frameworks.
My biggest concern is with having a user token that doesn't expire. If I give them a token and they never log off, then I want the token to persist and be valid so that they can leave the web browser open overnight, and not have any session problems.
Does this plan leave the site vulnerable?
There is always some state that you'll have to keep on the servers if you want to perform any kind of user login. The only question is: Where does that state reside?
In the application server or
In the database (or maybe some other storage)
Obviously, the user name and password will be saved in the database. A session token is usually kept in the application server's memory - but it doesn't have to be. You could just as well save it in the database.
Because your implementation is stateless, with your current solution you'll have to retrieve the user name and password from the database for every request. You could easily change this to retrieve a token and timestamp instead. The only significant change is, that there may be multiple sessions per user, so you'll need a 1:N relation for users/tokens.
First:
If you want to write secure web pages read the OWASP Top Ten. This is comprehensive summary of most web applications vulnerabilities.
Second:
The main problem with your solution is the expiriation time of that token. If attacker will find out its value he will be able to impersonate real user for a long time. Also it is vulnerable for a brute force attack, when attacker will try to guess a token value. It would be wise to ask the real user for a password once in a few days and then change the token value.
I'm planning on doing a stateless
implementation which means keeping
user identifiers and submitting them
to the server on every request. No
server-side session data will be used.
I'm looking at Apache Shiro, and I
like the low level of integration so
that I don't need to hook up to
complex frameworks.
What happens when I copy someone's cookie?
What happens when I decipher the identifier and change it? (is it a int value?)