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?

Reputation: 1144

Is using cookies instead of a session for storing username and password wrong?

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?

Upvotes: 2

Answers (4)

James

Reputation: 4793

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.

Upvotes: 3

n-dru

Reputation: 9430

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.

Upvotes: 1

Vladimir Ramik

Reputation: 1930

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

Upvotes: 1

AD7six

Reputation: 66319

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.

Upvotes: 0

Is using cookies instead of a session for storing username and password wrong?

Answers (4)

Here is some serious reading for you:

So what should you do?

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