I'm setting some cookie values where the values are slightly sensitive, but nothing too serious.
Basically I would like to encrypt the value, but just a very quick, basic method.
I'm thinking base64 but that seems to return a really long string.
It just needs to be really quick and simple. Quick being low processing time.
Something like this is too much: http://crackstation.net/hashing-security.htm
I'm using Symfony2 but I don't think there's anything in there to help me (e.g. built-in cookie encryption).
The NelmioSecurityBundle can encrypt cookies. https://github.com/nelmio/NelmioSecurityBundle#encrypted-cookies
If the data you want to store in the cookie are sensitive, you should not store them in cookies in the first place.
I recommend using sessions. This way the data will not be transferred to the user but will still be accessible by your PHP scripts on the server.
Related
I would like to know if it is a good idea to sign cookies with hash to check it's integrity? First of all, I do realize that I should not store any sensitve data in cookies and use sessions instead. That's exactly what i do. But still I am feeling not comfortable with user being able to modify even not so important data. (I'm kind of security paranoic :) )
I came up with the following solution. Let's say we have cookies for:
PHPSESSID
site_lang
recently_viewed
Now whenever I update cookie value I recalculate hash for cookie with key of let's say cookie_hash and value of let's say md5(serialize($_COOKIE)+$secret)
the only thing that I am not using PHPSESSID for calculation and validating hash because it is not being managed by CookieManager class (my custom class) and might be refreshed with new session id and corrupt hash.
My concern is what if some third-party package sets it's own cookie bypassing my CookieManager of course. it will collapse hash. So is it a good idea at all?
MD5 is weak for this, and the scheme you proposed (hash(data||secret)) is flawed anyway. Cryptography is hard, please don't try to come up with your own. :)
What you may be looking for is invented already, it's called message authentication. Have a look at things like HMAC, which is one proper way to do something very similar.
In most cases, authenticating cookie values doesn't make sense in a web application and provides no additional security, but there are cases, when it does. Your examples above don't seem so. :) For example the session id is cryptographically random already, and the other two usually present no harm if changed by a user (but in very special cases, they probably may, though I can't come up with a reasonable example). If something matters and should not be changed by the client (user), that should probably be stored in a server-side session.
However, you may decide to store application state on the client in encrypted and/or authenticated cookies, one reason for that may be a stateless application on the server (see the default session management in Ruby on Rails for example), and in that case, something like your idea (but done correctly) is indeed the solution, but it has its own set of risks (as do server-side sessions).
Note that anytime you store state on the client, one threat that comes up besides secrecy and authenticity is replay. This affects your idea as well. Say it is a problem in your application if the user can change the last_viewed cookie, but you still don't want to put it in the session. You properly authenticate the cookie, maybe even encrypt it, the client has no access. But what if at some point, the user saves the cookie, and in a different session replays it? (Okay, your example tries to protect all cookies at once, which may make this a little bit more difficult, but you get the idea, replay is still a potential problem.)
So in short, you most probably don't need this, but if you do, then use proper message authentication (something like an authenticated encryption, or a proper MAC like HMAC).
I don't know how deep you digged in PHP and Webdevelopment, so please forgive me if the level of my answear is to low.
If you are paranoid you should read more about PHP, sessions, cookies, hashing algorithms and more.
For example:
PHP session handling
PHP session configuration
PHP session security
With this you can modify your sessions & your handling a little bit to serve your paranoia.
By the way you shouldn't use something like md5 in reference to make your web application more secure.
If i understand what you want to do, you want to write a hash of your serialized session array plus a secret/salt into the session to verify the integrity of the session and its data.
If this is your motivation, you really should rethink, at least in my opinion.
A session is just a file on your server (on the users system it's a database entry in a sqlite database of firefox or something else, but without the data you write to the cookie array, that data are just writen to the server) and the session ID is a file name/path to this data on the server, except your sessions are saved on a database.
So with your approach you would just save the value to verify the integrity of the data in the same data (on the server) you want to verify.
And where you want to save the secret?
I think it's a little bit useless.
Depending on your needs and the needs of your application you could search about the key word session TAN, you could set a additional cookie with a random value you save on the session to verify each other, you could save and check the IP (depending on the law of your country and the way your users connect), shorten the session lifetime and more.
You could also set ini directives like session.cookie_httponly (that's one i recommend if you don't want to access your session cookie by a script language like JavaScript) you can find on the links above and more.
Something is a matter of faith, something evident.
Digg in deeper and understand how the technology works under the hood and you can make your decision more easy by yourself.
A user logs in using default Laravel authentication, which puts an encrypted cookie in the browser, and saves the session in the database.
The user moves to a classic asp page, where I check the cookie value, get the hash, and call the laravel app back passing the session id hash.
Then I use that in laravel to see if there's an active session for that id, and if so I return true, so the user can be logged in, in classic asp.
On each page request in the classic app, I check the last_updated_time in the db and update it on each page. All logging in and out is done in laravel, and classic relies on the database to see if a session is active.
I would also call a public url to get sessions variables and add session variables using laravel, since it's all encrypted and using classic asp for this would be hard.
The only risk I see is session highjacking, but I don't think it's a higher risk than usual.
Is it important to lockdown the laravel URL I call to check if it's a valid session?
Am I missing a security hole here?
Is this method secure?
From what you've stated you probably haven't opened up any security holes. The session cookie is not itself encrypted on the users machine, but you are making sure it is encrypted between their machines and yours, as well as between each of your machines. You should make sure you've set the Secure Flag to help prevent the cookie being accidentally sent over traditional unencrypted transport (HTTP), but as stated, this doesn't effect storing the cookie itself.
That being said, you are essentially hijacking your own users sessions. While a hole might not be introduced now, you are potentially weakening the overall system, which could lead to hole in the future.
Is there a better way to do it?
This might well be a dumb question, but are you sure you need the session? If you're juggling credentials between servers, it sounds more like you want to use Access Tokens and scrap the session.
Using Access Tokens is similar to using sessions, but you need to make your services stateless. This means your no longer storing information about the logged in user any specific machine so you'll need to pull anything you need from the database every time they hit a server requiring that information.
This is a good thing in the long run as it's much easier to scale your services when you don't need to worry so much about where the session is and what's inside it.
OAuth 2.0 is widely used standard (Facebook, Twitter, Google), and was specifically designed to be easy to use. The RFC is complex, but there's a log of good guides out there don't worry.
The one slight down side (if you can call it that) to OAuth 2, is that it MUST happen over an encrypted connection. If your use case can not guarantee encryption over SSL or (preferably) TLS, then you should use OAuth 1.0 (WITH revision A) instead.
This is due to the fact that OAuth 2.0 exposes it's "secret" token in requests, where as OAuth 1.0 only ever uses it to provide a signature hash. If you take this route it's advisable to use someone else's library as the hash is very, specific.
Further Improvement
(Note: This section added after the answer was accepted)
One system I've been exploring recently is Json Web Tokens. These store information about the user to save each machine repeatedly looking it up in a database. Because the token is hashed with a secret, you can be sure that, so long as your secret isn't exposed, a valid token represents a successfully logged in user, without having to touch the database.
You should avoid putting anything too personal in the tokens if possible. If you must store private or secret information in the token, you can encrypt it, or you can use a reverse caching proxy to exchange the JWT for a traditional security token. This may initially seem to defeat the purpose, but it means some of your services may not need database access at all.
I'm no security expert but I don't see an issue with this. The packaged Laravel database session handler works the same way. The cookie contains a hash that references a record in the database. The session data is base64 encoded but that's neither here nor there. I think you could actually avoid rolling your own and just use Laravel's DatabaseSessionHandler.
Illuminate/Session/DatabaseSessionHandler
... I just read a little deeper into your question and noticed the part about the public URL to set and retrieve session data. I think this is a really bad idea. Mostly because it will provide an open door to the end user allowing them to read and write session data. This can only end badly.
Like I said above, the data is only base64 encoded so I believe you'll be able to parse, read and write that to your hearts content within asp.
Edit
Ok... I think this is the last edit. The data is php serialized and then base64 encoded. This question looks like it may help you to that end. If it doesn't and an API endpoint is the only way, find some way to block the end user from accessing it.
Aside from session-hijacking, no. This is the standard way applications interact on a internal basis. Of course there might be a better way to get at the data if you choose a different type of session store other than your database, Memcached for instance.
There are couple of things that can be done.
Make the channel HTTPS. It will make almost impossible to sniff on your transport layer.
Rather than making interactions with your cookie, you could use a JWT to get this task done. Which will help you to use the existing functionality in your system while connecting with ASP system as well. You can write a small REST web service which allows ASP to connect. You could use this lib. You can refer this article which will give you an idea how it should be done.
Please let me know if you need more information.
I have a ColdFusion website that is currently running well with login/register modules. I want to use my ColdFusion session in PHP. Can this be achieved?
As mentioned in the comments, no it's not really possible. CF and PHP cannot share in memory sessions variables. However, there are other alternatives such as using cookies.
I used that approach once because a client wanted to share sessions with PHP Forum software. I simply grabbed it using cookies, by finding what cookies were being set ie <cfdump var="#cookies#">. Then converted those cookies into sessions variables. (If you need it the other way around, try doing it in reverse.)
Another possibility is sending data securely by using encrypted URL variables. But we need to know more about your goal. Can you explain exactly what you are doing?
Assume that there is a PHP variable:
$variable = 'username';
cookie value = 'username'
Which one is better to access? get_cookie() or just use $variable?
I have a lot of code using get_cookie('cookie_name') (a CodeIgniter function) instead of using variables.
Will it increase performance if I change it to access $variable instead of cookie?
Cookies are passed from the user's browser to the server every page load, whether you use them or not.
There's really going to be very little performance difference.
What you may want to investigate is whether the data that is being stored in cookies (if you say it's a lot) should be there or not. Many people have cookies turned off, so you only want to store nonessential information (and information that doesn't have to be secure) in them.
Yes, it will, but the increase will be infinitesimally small.
Not only the $variable is somewhat faster, but also consider that a user may simply not accept cookies of any kind, so in general the $variable approach is much better.
I've been developing web apps for a couple of years and never had have to use cookies for anything. I know a lot of people would not agree with me on this, but I've been doing great for now without them.
Regards.
How can I encrypt, and later decrypt, a cookie value in PHP? How secure will the encryption be?
There a variety of different ways to encrypt information in cookies and elsewhere. The strength of the encryption will vary by the method you choose to do the actual encryption. mycrypt is a good place to start. See this answer for an example of using mcrypt.
I don't recommend putting anything sensitive in a cookie, even if it is going to be encrypted. Way too tempting for someone to crack. Try sticking to sessions if you can.
I am in full agreement with the other answers: If the data is truly sensitive it should be stored server side in a session, not in a cookie.
As far as ways to encrypt cookie contents, the Suhosin PHP extension provides the ability to transparently encrypt all cookies. If you have the ability to install PHp extensions this may or may not be easier for you than writing your own encryption scheme.
If the cookie is encrypted securely (for example, with a server-stored secret that changes on a regular basis) I see no problem with storing useful data in the cookie. Why store it on the server? Make the client do some work for a change -- especially if it is preferences. Why should the server have to constantly store and retrieve data from a session file? What if you have hundreds of thousands of users pounding your site? Now you have to maintain hundreds of thousands of session files.
I can think of a reasonable use for this. Suppose you have a large server farm, you're going to have a bottleneck at the database and/or memcached server for handling session requests.. "is this user logged in?"
If you were to store the users session data as an encrypted value in the cookie, then you can prevent having to do quite a few read/writes and allow for an unlimited sized cookie store since there is 0 impact on your side other than being CPU bound for encryption/decryption of the cookie data.
Ruby on Rails by default does this - although it only signs the data and does not encrypt it. There is an alternative implementation which encrypts the data with its own key and signature so you the user is not able to see what data you store in their session.
I can not simply think of a situation where encrypting data in the cookie is useful. If you want to retain secret data about the user or his preferences, information, whatever, then store it on the server in files, in the session or in the database, but not in the client's computer.
On the other hand, if you creating an authentication, then you should use sessions instead of creating secret encrypted cookie values. Sessions weren't implemented for nothing, they are the way to go.