how do you check if a user already has logged in?
so that if a user in another browser cant log in with the same account.
also, is this a good solution or should i let the user log in in the other browser and then log out the current user and display a message (you are logged in from another location) just like messenger does?
Using sessions is a good way to do this, and is a very common method for controlling authentication.
The flow usually looks something like this:
User visits site, and session_start() is called. A unique session identifier is set for that visitor (ie. a cookie).
User submits his login credentials to a login form
Login credentials are verified, and this fact is stored in the session data with $_SESSION['logged_in'] = true, or something similar
For the rest of the user's time on the site, you can check $_SESSION['logged_in'] to see if the user has logged in.
In order to control a user's logins, you could simply have a field in a database (users table is fine) indicating what the current session id is (retrieved with session_id()) for the user, and if it doesn't match the cookie value you just received, then you immediately call session_destroy() for that id, and consider the user as logged out.
Using $_SESSION means you don't have to worry about generating your own tokens, and gives you the power of the built-in superglobals to facilitate storing information about the user's authentication status.
Personally, I would allow multiple sessions to be active for a user for most web sites, as there's usually not a good reason not to, but it obviously depends on the nature of the site. However, storing the current active session id as mentioned above is a pretty simple way to accomplish this.
Generate a random token upon signing in (or use the sessionid), and store this in the database and in the users cookie. With each page access, ensure that the users token matches the database entry. If the two don't match, alert the user that they've logged in elsewhere.
You could also store the login time, which subsequently would be the time the token was assigned, and require 30 minutes before permitting another user to login with the same ID.
The first half of the question was answered well with how to detect the multiple users but how to treat them I think still needs a bit of work.
First if a user logs in correctly let them in, don't prevent them if they are logged on some other place. If you really don't want the user to have two open sessions then log out the old one or simply update the session id that you are saving so you can bounce out the old connection. You can inform if you want but I would only message the session that you invalidated. If you message the user logging in it becomes annoying when you are only dealing with the case of a user switching computers and they forgot to log out of the old session.
Well All solutions mentioned above will work but if on every page access you are making a call to database and checking for the session token to see weather its the same token assigned to user .. will kill your response time. what i'll suggest is use a caching mechanism instead of database in above said solutions. storing session token into database will add extra field to your database which is actually not required. Use open source caching solution like memcache.
you can make a table like userLoginStatus with fields like clockIn time & clockOut time,
and insert current time in clockIn when user is do login, leave clockOut time blank at that time, it should be updated only when user do clock over logout button,
so you can check specific user's current status, where clockOut is empty that user should be logged in. because it updated only when user do logout.
Related
When starting a session, an authentication is made to the database through a query. If this authentication is granted, one or more session variables are filled with data. This allows the user to transfer through multiple pages without having to re-authenticate - which is great. However, if a session variable that is being used is changed within the database, i.e. username change, access privileges change, the changes are not rippled through to the session (obviously).
How is it possible to get the database changes to trigger, or ripple to, the PHP session variables.
An example is being logged into a website where you have access privileges x that allows you to access pages 1,2,3. Your privileges are now taken away for some reason and you now have access privileges y which allows you to only access page 1. If the user is already authenticated within the site, these changes will not affect the users current session, and will still be able to access pages 2 and 3. This could be an issue in many situations.
Currently my solution to the problem is to re-authenticate the user every page, and update the session variables accordingly. This definitively seems the wrong way to accomplish this task from my limited understanding of how sessions (should) work.
Essentially, I would like a way for database updates to trigger a re-authenticate of the current logged in user. i.e. if user john12 has his database row altered, then his session should require re-authentication.
At the moment I can't think of any way to accomplish this without querying the database every time a page is loaded.
Any tips or solutions would be greatly appreciated.
How I usually do it is by having 4 fields for authentication is my database.
Username
Password (usually hashed)
Token
Logged IP
I remember the user's auth data in cookies. When user has entered the right username and password the website generates a new token and sets two cookies - username and token. On every page load you check if the username, token and logged IP match (to prevent token steal).If one of them isn't right remove all of them and redirect to login page.
In your case if you want to relogin on password change just delete the token when it has been changed.
The only con here is that only one machine can be logged at a given time.
I don't see why you don't want to query the database for user permissions, SQL databases are incredibly fast even with lots of records especially if searching by primary key.
I am looking at the possibilty to set up a option to keep users logged in. Now I understand a session could be used to allow a user to navigate around without re-entering login information on each page only until the browser is closed and the session is lost. A cookie would be stored client side and has a duration until it expires or the user deletes the cookie.
I was thinking that I could use a combination of both
Create a db table (id,user_id,cookie_token,is_active)
User logs in which creates a row in the db table connecting the user to the cookie_token which is stored on the client browser (system) as well.
Each time a token is created, check to see if the user the token is being created for has any active tokens in the system already and set those to inactive before a new one is created.
Only one token can be active per user
So every time the user visits the site, the system looks up that token and checks is_active fields,
If the user_token is found and is_active = 1 or true, the user data is retrieved (id,name,etc) and this then creates the session and the session variables.
I am not able to find any questions or answers that use a combination of both so it could be that this is just overkill or a very bad idea, I just started to read up on sessions and cookies and have been trying to figure out a system that I could implement myself so would be nice to know if this is good or bad.
I can't reply as a comment anymore, because my reply would be too long...
I've implemented something like follows. Unfortunately I can't remember it precisely, but it would give you a pretty good idea:
Visit before manual login:
Start a session.
At successful login, store a user identification into this session and store a token value into the dB and into the cookie.
Next time the browser visits the page:
(re)Start the session.
Check if a user identification is set in this session.
If so, auto-login the user which matches the identification.
If not (session expired due time restriction or browser close), check if a token value is stored in the cookie and if this value matches a token value stored in the dB.
If an (unexpired) match found, auto-login the user and remove old tokens.
If the user identification is invalid and the token value is invalid/expired:
logout the user (which contains all actions to go back to "public" mode like destroying the session, removing tokens, cookies, etc.).
I have a website which has a login/logout feature. How can I ensure, 100%, also in a stable technique, that a user won't be a able to login to the same account from two different computers?
Javascript can't be used for this, since it's easy to disable it.
For example, .NET has a Session_End function that executes when a user aborts the connection with the server. How that can be done with PHP?
Thanks, Guy
Note: This technique would effectively logout the account on the first computer when logging in on a 2nd.
When a user logs in, log the session id for the user to the database or equivalent. On each page request, ensure the session id of the user matches the session id stored in the store for their account. Requests from a logged in account with a mismatched session id should be rejected and the user should be logged out.
It depends on how in depth you want to go. Most commonly:
Create a unique session id cookie on login and saved it in the database
All web pages check the session cookie to make sure it's valid
if the session isn't valid, the user is redirected to the login page
When another user tries to log in, it overwrites the previous session
This essentially kicks out the first user
Large companies will also store the IP address in the database as well (so session cookies can't be stolen)
i have a user login system which works off of sessions such that when the user logs in a session variable of user is populated with his/her username, then each page she loads checks this session, if it is not populated then the page is redirected to the login page. apon logout the session is destroyed.
But this still allows a user to open 2 different browsers at the same time and login. I want to stop this, such that if a user logs in and then trys to login using a different browser or pc, they get an error saying the user is already logged in.
So my first thought was to use a data base write, but then how do i know to unset that value if the browser is closed?
all my pages are php, and i use ajax and php scripts to update dynamic content.
So whats the best way to go about this?
they get an error saying the user is already logged in.
That's wrong approach, causing terrible user's experience.
Make it opposite: let that latter in, but make previous one logged out.
You only need to store current session ID in the user's table. If it doesn't match - ask for login.
If you find in DB that user is already logged in simply ask if he/she wants to go on and overwrite old session info. Another way may be adding a time-ticket to your database information (e.g. inserting time) and check how long is elapsed since inserted.
Regards
If I have understood your question properly, I think you can make use of cookie. Once user is logged in, you can create a cookie and set an expiry to browser session time. Before fetching data from DB, you need to check for cookie presence.
I would make another session variable that checks the browser type, if it is different call a view method to output what you said
I am developing the user management portion of a website that will host a webcast. The goal is to prrevent the same user nam (email address) from being used concurrently. That is, we don't want two individuals using one login to view the event.
I've already setup a table that holds the user registration data with regID as primary key. My thought is to create a login history table with username as primary key, foreign key to user name in registration table. The login history table would simply timestamp when the user logs into the site. However, this won't accomplsih my goal of preventing more than one individual from using the same login name.
Instead, would it be better to have a login status field either in the login history or user table that is set to 1 for logged in and 0 for logged out? It would need a stored procedure to update the value at login and at logout, and would need to be validated when a user logs in such that if login status = 1, user already logged in and cannot login a second time. Is this a feasible approach?
Please share other methods you've used to prevent the same login credential from being shared amongst multiple individuals.
Thanks,
Sid
If it is OK to logout an already logged in user if someone else logs in with the same credentials then you could do the following: when a user logs in generate a random ID in your database for that user and the same in a cookie session. The two must match to authenticate.
Without rolling your own session handler, you could do a little parallel tracking. When a user logs in, you can store the user's session ID and login time in the database (maybe inside the user information table). The login script could then check for the existence if this sessionID and allow/deny login based on the presence of the session ID. If the ID's null/blank, then the user logs in. If there's a session ID present, and it's more than X minutes old, allow the login. Otherwise deny them.
Of course, you'd probably want to roll your own session cleanup handler at that point, so that when stale session files get deleted, you can remove the associated IDs from the database at the same time.
The problem here is detecting the user is logged in (i.e. whether he didn't logout).
One possible way is to register in the database the time of his last activity and the time of his explicit logout. You could then deny a login if it this was attempted less than say 5 minutes ago relatively to his latest activity and if he didn't login in between.
You could force "activity" by having the website pages periodically poll the server with Javascript.
It's easy to determine when someone logs in. It's much harder to determine when someone logs out. If you have a mechanism of killing the webcast streaming to a particular user quickly, you might want to have something which pops up asking the user if they want to kill their other session if you think there might be one active.
How are you doing user sessions on the server? If you store them in the db, you could query the active sessions anytime someone attempts to log in and see if they're already in there. Of course you'd probably also have to check some kind of timestamp since you're not guaranteed that sessions will disappear at session.gc_maxlifetime.
You might want to consider making a global variable in php to store a hash array with login status. This has the benefit that if the application has to be restarted for some reason, the user isn't stuck in the wrong state in the database.
You can store a mapping from user ID to IP or session cookie and redirect requests that come with different information to the login page. If the user logs in, the other session would be invalidated and further requests in the last session forward to the login page.