I successfully use mycrypt to encrypt id's in an admin panel as they are often seen in the URL. I have previously added a key manually as I code, but this time I plan to use the users account id which is kept in a session. Is this a good way, or should I keep with a fixed key throughout the site.
Thanks
Never pass SESSION IDs over URLs, even if encrypted (though it's weird and still quite unsafe). Transferring SESSION IDs has been deprecated long time ago by PHP (session.use_trans_id=0). Session ID is transferred automatically by browser, you don't need to take care of it at all.
The only use case might be if you want forcibly allow browsers with disabled cookies, then you would need to append such a parameter to all links (mimicking deprecated bahaviour). However:
it would be still great security risk, since mostly attackers and malicious webbots disable cookies,
encrypting in any ways makes no sense coz string can be still hijacked and server will decrypt into original session ID
So you just pull out userID stored in session and don't worry about transferring session ID over URL.
Related
Lately I have stumbled upon some articles that suggest using a cookie to store session data.
I liked the idea and extended my session storage by adding a CookieStorage class which works fine (note that per user I use a unique hash key for sigining and encrypting data)
However, there are a lot of other articles that suggest against storing sensitive data in a cookie, even though you encrypt and sign the value.
Personally, I find no reason why not do it especially when encrypting and signing the value with a different key for each user. The risk of the data being compromised is the same as with normal sessions, no? Not to mention that if you use SSL then the risk for hijacking is eleiminated.
What I see as a benefit with such an approach, if the session data are not large, is fewer IO operations on the server for opening/reading/writing session data, whether the storage is file, db, memory based
I would appreciate your feedback on the matter
Thanks
If you're using pure cookie storage with no server-side component at all, then the user is in control of the data. The only thing keeping him from it is your encryption/signing method; but that can be attacked. If you're not using encryption/signing keys specific to the user's session (i.e. you're not using a server-side session), then you're pretty much limited to a static secret. Someone could attack that offline, trying to brute force it. Once they did, they could spoof their entire session.
If you are using more secure one-time random secrets stored in a server-side session... you're already storing data in a server-side session! Why not keep it simple and store everything there? It would also reduce the bandwidth needs required to transfer all the cookies back and forth with every single request.
If you're doing this mainly to save I/O operations on the server: use a more efficient session store like a memcache based store.
Although nowadays session id transferred only via cookies, initially there was other ways, which are still supported and can be used.
Sometimes server needs to know or alter the session info.
That point from #CBroe on the cookie size.
So it seems like Opera Dragonfly is able to cache cookies as well as session info. In particular the PHPSSID my question is. Would there be a way to hide PHPSSID from being shown by any time of debugger/developer tool?
I don't mind cookies since they are secured. As the data in them is hashed with double salt as well as few other things so forging them is no a problem for me.
But I want to assure PHP sessions are not seen. How would I be able to achieve this?
In short the answer is: You can't, that is not session id's work.
The point of a session id is that is a very random number, often called a cryptographic nonce. This value is intended to be very difficult to guess, it is then used to reference state about that session on the server side. This could be in a database or by default PHP uses the file /tmp/THE_SESSION_ID. The data stored in $_SESSION is stored in this file and the user cannot obtain this data.
In PHP to keep attackers from stealing a user's session id you should set session.cookie_secure=On in your php.ini. This forces the session to be over HTTPS.
If you are using HTTPS, then the session id will be obscured from attackers on that network. By using HTTPS session id's cannot be hijacked with tools like Wireshark or Firesheep. Not using HTTPS is a violation of OWASP A9: Insufficient Transport Layer Protection. However a user can still see his own session id by looking at his cookies javascript:document.cookie or by using TamperData.
I'm bit confused. I've been building my sites with my own session system, but i'm not sure how secure the php's own session system is. My session system usually just has user id and quite harsh hash, which does not include user name or password for generation. I save the hash in the user database and as a cookie to confirm the user session on every page load. So my question is can i trust php sessions or keep using my own?
PHP saves a unique session id in a cookie, and all values related to the session in it's own text file on the server. You have to get the session id to steal the session, which means you have to steal the session cookie from the victim's computer. PHP's own system is at least as safe as your homebuilt system
The difference may be how hard it is to find an active session by brute force. That is entirely up to the hashing algorithm and the random number generator.
You can configure PHP to use different hashing algorithms or you could even use your own algorithm to create the session ids for PHP's session system if you don't trust PHP to do it properly.
Storing data in cookies versus using PHP's sessions is very different. Cookies store data on the client-side; sessions store data server-side, which has a number of benefits:
The user can't see it
The user can't modify it
The browser doesn't need to send the data to the server with every request
Normally PHP sessions do store the session key as a cookie (although they don't have to), but none of the data you actually care about is ever sent to the user, it's stored on the server and looked up using the session key
i'm not sure how secure the php's own session system is
And the rest of the world is not sure how secure your's is. A lot of people have looked at the session handler in PHP and not found any flaws in implementation. Its also well characterizied and integrated but supports the notion of user defined handlers.
I'd recommend using the standard session code - but you might want to write your own handler functions.
C.
I know about all the issues with session fixation and hijacking. My question is really basic: I want to create an authentication system with PHP. For that, after the login, I would just store the user id in the session.
But: I've seen some people do weird things like generating a GUID for each user and session and storing that instead of just the user id in the session. Why?
The content of a session cannot be obtained by a client - or can it?
You're correct. The client just sees a randomly generated session id token. There are ways this token can be misused (hijacked, etc.), but having a GUID on top adds nothing. In contrast, options like session.cookie_httponly (JavaScript can't see session cookie) session.cookie_secure (Cookie can only be transmitted over HTTPS) protect against certain attack scenarios.
The short answer is that $_SESSION is safe and you do not need to worry about its contents being leaked to a user or attacker.
The content of the session is not normally be accessible to the user. You should be able to store the user's primary key and you'll be fine. There are cases where the session can be leaked, on a normal linux system the session folder is in /tmp, however this could be changed in your php.ini to the web root (/var/www/tmp) and then could be accessible. The only other way is if the user is able to get access to the $_SESSION super global by hijacking a call to eval() or by the variable being printed normally.
If you are running on a shared host and using an old version of PHP and/or your server is misconfigured it might be possible for another user on this system to read or even modify a session file stored in /tmp/. I don't know of a single application that takes this attack into consideration. If this is a problem you can store the information in a session table in the database.
Sometimes, for added security, developers may assign a long string to the user's session in order to make hijacking even more difficult. By setting a cookie with this new string at the time of session creation, the app can check for the correct string on subsequent requests to better ensure it is the person who actually logged in.
It's just adding one more thing a wannabe hijacker would have to guess. However, it can be a false sense of security as it does little to protect the session if sniffing is involved because the new cookie is sent right along with the php session cookie. Also, session id's are very hard to guess as it is (as I'm sure you know, just don't place it in the url but, rather, in the cookie).
Session info is stored on the harddrive so it's not obtainable by clients without application intervention.
I've never seen GUIDs being used for sessions, but there are a couple of additional methods I have seen that do add a little more security.
Storing the user's IP - if you need to force a session change based on locations (sometimes geoIP stuff will do this)
Storing the user's HTTP_USER_AGENT header string. Can provide a bit of security against hijacking if the hijacker happens to be using a different browser.
There's a great article on session hijacking countermeasures on Wikipedia, actually.
That being said, I would imagine that anyone storing a GUID as part of a session to use in session security might be failing to see a better solution (such as session regeneration). I can see other uses for a GUID to be stored (maybe it's part of a random generator for a game), but not for use with session security.
ive heard a few timse that sessions need to be cleaned with mysql_real_escape_string or htmlspecial chars because they can be modified. what im wondering is how are they modified because when i look at a websites session named PHPSESSID the value it contains is always encrypted.
first of all what encryption method is it using and how is it modified. the reason i want to know this is to better understand how to secure myself based on what methods people are using out there to high-jack sessions
thanks.
They cannot be modified, they're stored on the server. The PHPSESSID is just an identifier, it's not encrypted but randomly generated (so it's unique to each user). People hijack sessions by stealing the PHPSESSID cookie, usually through a cross site scripting attack. Read the answer to this for a nice summary of sessions in php - What do i need to store in the php session when user logged in
Sessions are stored on the server. That means all data is stored in temporary files and are deleted after an x amount of time. The browser does not store session data. It stores an ID of the session, which the server uses to get the right temporary file.
So the user never actually has access to variables stored in a session. But has a reference to their session. It is possible to get someone else's session ID. This way you can pretend to be another user. If sessions are used for validation.
Read up on session hijacking here.
The thing that can get modified is the session id send to you by the client. So, as with all user supplied data, this needs to be 'cleaned' before you use it anywhere, like for example with mysql_real_escape_string before inserting it into a MySQL database.