I use cookie to store user credentials. I have two questions:
1- Is hashing cookies necessary? Using for example md5
2- Should I store passwords with usernames or storing username is enough to authenticate the user?
Cookies can be edited by the user, as a penetration tested, I would say storing any user specific data used for authentication is a bad idea.
The best way to store this is in sessions, that way it is server side and the data is only in the scope of that user/connection.
Don't store credentials in cookies or sessions or anywhere other than as hashes in a database.
What you're supposed to use is a session id cookie. PHP creates one automatically when you call session_start. The session will contain all the data pertaining to identification of the user, like the user-id (you probably just need the user-id, nothing more).
Sessions are stored on the server, so they're tamper-safe.
Cookies are stored by the client so they're wholly unreliable. Use cookies for preference things like language selection or "yes I've seen your popup ad".
salt + md5 is not strong enough to store passwords. Use the built in PHP functions that deal specifically with passwords. See http://php.net/manual/en/function.password-hash.php for more info.
Related
I just built a simple login system that uses sessions. When the script verifies that the username and password are both correct, it sets $_SESSION[username] and $_SESSION[role], and then on every page of the site it just checks whether these 2 session variables are set.
Considering that the server handles the sessions, this should be a secure solution, right? Or should I set $_SESSION[md5(password)] as well when logging in, and then check on each page of the site whether all session variables match the user data in the database?
Storing the password in your session is a bad idea, it also doesn't add any security to your website, since sessions are managed by the server.
You are however still vulnerable for session hijacking. Take a look at this question to learn more about how to prevent it.
Don't store passwords outside your database. Don't even return passwords from your database. All you should need to get for session storage is the userID. store that in the session and use it to lookup role level and name data when required. If you are concerned about someone hacking the session data and changing the userID number then you can store a hash of the userID number in the session aswell (I recommend using something a bit more secure than a simple md5 though, there are plenty of rainbow tables around for that nowadays) and compare the hash in the session to the hash of the userID at lookup and verify nothing untoward has been happening.
I've started learning PHP by myself, and in the beginning, I would often choose the simplest way to do a task instead of the best way. Now that I'm developing important websites that need to be 100% secure, I hit this dillema,
I'm using cookies on my main page, to store the login session. Basically, the username and the hashed password is stored in a cookie and is loaded and checked against the database any time the user visits a mustbeloggedin page. For my main page, I'm using md5. Not because I want to, but because I have to. I know that poses a great security risk for the user because a keylog attack can basically freely take his password.
On this new website, I'm gonna use sha256, so that shouldn't be an issue.
Here's my question: what other security issues does storing this kind of data in a cookie and not in a session pose?
Here's mine:
Anyone with physical access to the computer can get the user's hash and store it for later use, by manually setting his cookie.
Any infected computer does the same as the above
Data is loaded, parsed, checked every load (not a security issue but still optimization-wise, it's not very good, but I don't mind that)
Anything else?
Does the domain variable inside the cookie make it secure enough not to be read by any other site?
Edit:: I'm also reading about someone intercepting the data being sent from a client to the server. How are sessions different than this? If I store a session , can't the identifier cookie still be hijacked and used by someone else? Would also adding an ip address to the cookie, then when validating the cookie, also check the IP address and if it's different then print the login form again help?
It seems you are trying to make some improvements, but not enough really.
There should never be a need to store passwords in a cookie, session, array, or anything else.
The password should be in the database and not be taken out to chance further access to it, or manipulation of the data holder in some way.
Otherwise, your highly secured database with hashes and salts on passwords, is only as secure as the framework/scripts and variable or cookie you store the password in (which is less secure than the aforementioned DB setup)!
From your comment:
Your question and statement makes no sense, you're describing a login
page and I'm describing about how the website knows you're logged in.
The cookie has the username and the hashed password, not plain text
password
So you store Bob's password in a cookie, with hash etc.
I steal Bob's password cookie. It's hashed, so safe right?
Ok, so I (James) use it on your site. How does you site know I am James, not Bob? It cannot.
It checks the cookie I stole, and password hash/salt/whatever you do match in your checks (otherwise it wouldn't for Bob either so would be useless).
It thinks I am Bob.
So now you start to check other things, if I have another cookie, perhaps username.
I have already stolen that.
So now your site looks at my cookies, sees a username and password, checks them, and says "welcome Bob, here's your personal/sensitive details, do as you wish...".
Passwords stay in the database!
You could try checking user agent, IP, and a load of other arguably less than useful/sometimes useful things etc, but these are things you can do "as well" as password+has+salt, and at the same time not store passwords in cookies or Sessions.
If your only methods to stop a hacker from using that stolen golden password cookie (hashed or not) is to check user agent, IP, and something else that can easily be faked, then your site is not secure.
Also, anytime the user needs to do something like change their password or email address, or check their whatever sensitive data on your site, you ask them to re-type their password.
Possibly resetting their cookies/hash/hash+salt stored in the DB, but depends on scenario really.
EDIT {
Use a cookie to store the Session reference, and any sensitive data in the Session.
Again, what you should store in the session depends on what data it is, if you run your own server, or shared, etc. Shared hosting can have bad config, opening up other security issues, even extending Session security issues.
(Info is in the links below - as said in comments, reading is your friend ATM - and then some evaluating and considerations of your specific needs)
}
Here is some serious reading for you:
First, your MD5 and even SHA256 are not secure:
http://php.net/manual/en/faq.passwords.php#faq.passwords.fasthash
Hashing algorithms such as MD5, SHA1 and SHA256 are designed to be
very fast and efficient. With modern techniques and computer
equipment, it has become trivial to "brute force" the output of these
algorithms, in order to determine the original input.
Because of how quickly a modern computer can "reverse" these hashing
algorithms, many security professionals strongly suggest against their
use for password hashing.
Also read the link for that quote - the bit about how you should hash, and the bit about salts.
Also, importantly, read about how to correctly store salts and hashes. There is a LOT of BAD advice out there which is misleading to the point you end up with barely any more security than if you just used MD5.
Storing the salt in the DB with the hashed password is fine, just also use unique salts etc (it's all there in the link, about mcrypt/blowfish etc)
A must read, even if you only take bits from it (and even if you ignore the rest of my answer):
The definitive guide to form-based website authentication
Faking Session/Cookies?
More reading:
What is the best way to prevent session hijacking?
Also read about:
Session fixation; Session sidejacking; Cross-site scripting;
And again, given you stated this:
Now that I'm developing important websites that need to be 100% secure
You should really spend a lot of time reading about all these things.
Cookie/session hijacking is real, and generally simple (script kiddie stuff).
If you want to produce secure websites and applications, you really need to learn about quite a few attack methods, preventions, etc.
Best way is read the links I've given, then any "branches" which stem from that read about them too.
Eventually you'll have a larger picture of the vast range of security concerns and resolves to them.
Some takeaways for cookies.
You want to limit any sensitive information saved within as it is not secure.
Cookies are perfect for session ids which you can then use to query your database and check if it is expired, matches an ip, matches user-agent and any other security/validation checks you want to do before you route to relogin or resume session.
http://php.net/manual/en/features.cookies.php
You mentioned user authentication. Most encryption protocols can be broken by using and md5 is considered 'broken' at this point due to completeness of lookup tables with all the hashes and the slight variations between hashes.
How can I make MD5 more secure? Or is it really necessary?
Salting your hash is crucial which adds another layer of security as is additional cdn/server restrictions to block/restrict brute force attacks:
https://crackstation.net/hashing-security.htm
http://www.cs.virginia.edu/~csadmin/gen_support/brute_force.php
If one is overly paranoid you can implement two factor authentication ( expensive? ):
https://isc.sans.edu/forums/diary/Implementing+two+Factor+Authentication+on+the+Cheap/9580/
http://www.twilio.com/docs/howto/two-factor-authentication
Don't store any credentials in cookies. There is session cookie and that is enough. In your database you can create a table where you will store PHP session ID together with user id. It is enough to check user's login and password once, at the logging, to establish a session.
I was doing the same as you do: storing login, password and session id in cookies and had many problems - occasionally for unknown reasons the browser was not deleting one of those cookies, or I had problems with paths of those cookies. I had to develop very complicated methodology for assuring that those cookies are properly set and that all of them are present in a given moment - I tinkered with removing and adding those cookies manually in the browser and had to come up with new ways of preventing the problems arising from such activities, but I was always able to make up new way of breaking that down and had to come up with new mechanism for preventing that.
All of this mess stopped when I finally decided to leave only one cookie - session ID, which I authenticate before every session_start() call - you can check if such a session exists and even compare current browser footprint with previously saved one. It is then very simple to foresee bad scenarios - when somebody deletes this cookie, session is over, garbage collection will clean it up. If somebody changes it or adds fake one - you can compare it against your sessions table and not start a session. To have better control over the sessions, use session_set_save_handler functionality.
There is a lot wrong with your chosen implementation.
the username and the hashed password is stored in a cookie
Don't do that. You should consider the content of cookies insecure.
and is loaded and checked against the database any time the user visits a mustbeloggedin page
There is no need to do that at all, if you know the user is already logged in (session).
I'm using md5
Using md5 at all precludes any semblance of security.
On this new website, I'm gonna use sha256
That will make almost no difference if credentials are still stored in a cookie.
So what should you do?
When a user authenticates themselves store their user info in the session. Any time you need to check if the current visitor has already authenticated check the session data. The session's data is stored on the server - it is secure. There's no need to call the db to find out who the user is on each page load, if the user's data is stored in the session.
Do not use cookies to store user credentials, especially if you're storing the password hash as stored in the db.
Don't use md5 - and if you're "forced" to do so change it at the very first opportunity.
How do you guys store login information?
Probably, store logged status at session. And username at cookies. But what are the safest practices to protect such crucial information, from falling into wrong hands.
Do not store the username in a cookie if you use it for identification. Because cookies are a client side storage and can be manipulated. Store it in the session instead that is a server side storage.
Normally, when authentication was successful, you store the user identification information in the session and only pass the session ID to the client. With that the user information stays protected on the server side.
Store the username as well in a session variable. Sessions are stored on the server, with only an identification number in a cookie.
If you need to protect the session number as well, encrypt the HTTP connection using HTTPS/SSL. This will however require you to buy a SSL certificate from an approved issuer.
If you're storing login information you need to take steps to avoid session hijacking. Store the session id in your database along with things like the users IP and browser useragent string and check that things match each time.
If you're storing passwords too then look at hashing them first - usually with some basic obfuscation like salting them first to avoid rainbow table attacks.
Store the user ID in a session variable; if you need to cache stuff like permission level, store that there too. Store the session ID in a cookie; use HttpOnly. If security/privacy is very important, use SSL for everything (and use an SSL-only cookie; also, have a look at the Strict-Transport-Security header, soon to be usable in Firefox). Otherwise, it is preferable to send at least the login through SSL. (Unfortunately, SSL requires a certificate from a provider trusted by mainstream browsers, which might be expensive to obtain.) Make sure a new session is started at login to prevent session fixation.
Use a salted hash to store passwords; preferably something slow like Blowfish, or SHA-256 repeated a few thousand times. (If you need your code to be extremely portable or run on old versions of PHP, MD5/SHA1 is fine too, but it will make ignorant people complain that you are using a hash that has been "broken".)
I'm creating a login system in PHP, and I want to know how to best protect the user information string in my cookie. I was thinking of encrypting the string with a key somehow? Is this the best way? I'm kinda new to this.
Thanks in advance.
Don't store sensitive information in cookies. Store a session ID hash to connect the logged in user with their account.
Aaron Harun has the right answer for you. There's basically no need to encrypt such data as long as you store it in a session, because that data never reaches the client/browser/user, as it is all server-side. When you create a session on PHP, it handles the cookie stuff for you, so you don't have to worry about that. In most cases, there is no need to deal with cookies. In security, dealing with cookies is detrimental.
I've seen some sloppy sites that actually store the username in a hidden field on a form, which allows anybody to simply edit their local copy of that form and take actions as whichever user they like. This seems like an obvious problem, but cookies are no better.
If you truly think it's a good idea to design a homebrew authentication system, you need to design the database first. Don't store plaintext passwords, store a hash instead (like md5, sha-1, etc) and at that point there's no harm in generating a salt for each password (a random string that you append to the user's password before hashing it, and store that salt with the password hash because you'll need it later--this prevents dictionary hash attacks, ie rainbow tables).
You should never store secure information in a cookie. Cookies are saved in textformat on the user computer, and there are many reason why you should never stock sensitive informations in them :
Cookies are basically text files, which can be opened by anyone on the computer, with any text editor.
The cookies are stored on the user computer, this mean he have no time limit, no connection limit, no processing limit, so he can try to brute force any data as much as he want without being worried of getting ip banned/kicked...
You should only stock things like a username to remember or a session id.
If you absolutely MUST store information in a cookie instead of the user's session, consider signing it with HMAC. The hash_hmac function is a builtin in modern PHP versions.
If you're storing a user login for a "remember me" feature, store both the user's ID and a hash of information that is only available in your database. For example, hashing together the login name and password and storing that with the user's ID in the cookie is reasonably secure. If the user ever changes their password, all the machines he's logged in to with that method would be invalidated, and there's no way to simply change the ID in the cookie and still get logged in, because the username/password hash won't match.
You get sessions for free! That is data stored server side, automatically handled by PHP/framework-of-your-choice. You just put data into the session, which is associated with a random UID stored in clients' sessions. On the clients' side, this is the session cookie. This ID is automatically generated, you can fine grain the behavior manually.
Data stored client side is never safe, no real encryption available. Sessions you will need anyhow for keep track of logged in users. If you have lots of data, you can use the ID to identify associated data from other datastores (DB, XML etc.)
I've been told that it is insecure to store things such as passwords, usernames, and user ID's in cookies, and that instead you should store a sessionID in a cookie. Here's where I get lost.
My objective is to have a basic 'remember me' feature. Normally I would store user login information in a cookie, but as this is unsafe, I'm wondering what the alternative is. I understand that each time I create a session it creates a cookie which creates a unique ID, but expires when I close my browser. So how do I get access to this session information after the browser has closed?
All help is appreciated.
Possibly the best approach, as has been suggested and what most third-party apps do, is to create a "user_sessions" database table with the following fields:
session_id (var_char)
user_id (int)
ip_address (var_char)
last_logged_in (unix timestamp)
Then use a cookie to store an md5 hash of whatever you like, possibly:
md5($username.$ip); //since md5 has a lot of reverse look ups now you should use a number of fields to validate. You could use a different crypto function to make it more difficult to crack, but md5 is the simplest version available in all php versions.
EDIT: You will then compare the stored hash from the cookie with the database session_id to see if they have already logged in. The reason to combine a couple of fields in the md5 function is to create a less "guessable" hashing format. It makes it less likely someone will be able to edit a cookie and login as someone else.
This could be done for all users (this way you can track who is online) and just set a "persistant" login variable in the cookie. eg.
p_login=true || p_login=false
That way you'll know whether to auto login or force login.
note: You may be able to look at http://www.openwall.com/articles/PHP-Users-Passwords for a different way to hash passwords, session_ids and users.
This could be a fairly steep learning curve. Have you considered using a pre-existing CMS or other solution for what you're wanting to achieve, or even a framework that might include this functionality?
For a 'remember me' feature you can send out cookies containing the user ID and a hash of that user's hashed password hashed again with some known, but secret, token. That solution doesn't allow you to remotely expire someone's login, however, without resetting someone's password.
Another approach therefore is to generate a unique token for that person's login and have another database table relating that unique token to a particular user and expiry date.