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User's content is encrypted, but needs to be decrypted. There are multiple files that need decryption to be viewed, and they will definitely not be viewed at the same time.
I am currently encrypting by using the user's plaintext password to encrypt a randomly-generated key, which encrypts the user's data. The password is hashed and verified normally before doing anything. I am using PHP's aes-128-gcm openssl_encrypt() function.
My current system requires a password every time the user wants to read a file.
I have thought about decrypting all of the content at one, but this doesn't scale well. I have also thought about storing the user's key as a cookie, but I'm worried about security.
Is there a standard way to do this?
Thanks!
The first thing to do is separate the users password out of this. You'll have to decrypt and re-encrypt all their files. There may be other ways around this such as allowing only new files to use this system. But that is very use case specific, such as how long do you keep their files, what is the turn over on them etc..
In any case this is a way to do that:
Encrypt the files they submit using a password you generate.
Store this password in another file we'll call it key.txt for now. Encrypt this file using the users password.
When user logs in (if they don't have it stored) take their password, decrypt key.txt and get the generated password.
Now you can save this generated password anywhere you want, without affecting the users account.
What they see (the end user experience) will look like always they go to downlaod a file, put their password in and get the file. They wont ever know you did this, which is nice for them.
So problem one is fixed.
Now where should we store this?
You could simply store it on the server in the DB. This sort of depends on how confidential the data is, and how secure your server is. Your ultimately responsible for the security of someone else's data, at least this way you can control it.
Make a table with these fields
user_id | ip | password | last_access
When a user goes to download a file, check their last access time and IP address to invalidate the password and make them refresh it. This is very easy to setup and totally under your control. If you save the encryption key, it will always have some level of vulnerability at least this way its all under your control.
Even if you don't want to store it in your DB, the biggest disadvantage here is if someone gets a hold of that table, but if they do that and your storing important data you probably have plenty of problems already.
At least use the first part as that solves a big problem with tying this to their actual account password. Even if a hacker gets the file password from the client (stolen cookies etc.) because it's separate, having that alone wont let them login to your site like the account password would. I am assuming here, a user must login to even get to the download part. Using the same password for both gives them them access to both the means of the getting this data and the method to download it.
To be clear, their is an argument to be made about storing it on the client side. Then if your site is compromised there is less chance someone could get a hold of the password as it (depending how you do it) only exist in memory on both the client and server etc. It puts the responsibility on them.
ASYMMETRIC ENCRYPTION
You could also use asymmetric encryption. Currently it looks you are using AES, which is fine, but it's a Symmetric Key block cypher. Basically there are three common forms of "encryption" (in vernacular):
Hashing (which really isn't encryption) - md5, sha1, sha256 - these are one way, can't be decoded. They have fixed lengths, and always encrypt to the same thing. It's common to see this for file checksum (for validating the contents of the file), Block Chain, Passwords or anything else where you need to compare two "encrypted" values.
Symmetric - AES, 3DES, Blowfish, Twofish - anything you need to encrypt and decrypt. The same key can do both. Generally these will encrypt the same thing to different values each time, because of the IV.
Asymmetric - SSL, DSA, RSA, PGP, used in Crypto currency wallets, TLS etc. With these you have 2 keys, a public one and a private one. The keys cannot decrypt their own encrypted data, only the other key can. So with this if you have one key on the server and the client has the other. You can encrypt their files using your key (decryptable by only their key) and you don't have to worry so much about someone getting your key as it won't allow them to decrypt the files. You can give one key to the client, who can use that key to decrypt their data you encrypted (even without your key). These also encrypt to different "Stuff" each time you use them.
So you can see Asymmetric form has a few advantages to use in a two(or more) party system. It also has the benefit that you don't need their key to encrypt a file. All you need is your part of the pair. So for example if you generate data for them and wan't to encrypt and later have them decrypt it with the same system, you can do that with no issues. This probably eliminates a step, as you would need to ask them, or keep track of their Symmetric anytime you wanted to encrypt something. Here you just need your part of the key pair.
It really isn't much harder to implement (on the server), its just harder to understand what it does. That's why I decided to add this, without this knowledge (which you may or may not already know) it's hard to use these terms and have them make sense. The only real disadvantage for you (if you call it that) if you used Asymmetric encryption, is if a client loses their key you would have no way to decrypt the file. So I would make sure they know to back them up in a secure place. It's the same problem that you see in the news when it comes to losing a crypto currency wallet which is encrypted Asymmetrically
As I said most of my knowledge has to do with encrypting and dealing with data on a server. So I am not sure how to tie that in to the "client experience". I do know for example how to use RSA keys for password less login for SSH etc. Which is kind of the same thing but not quite.
Hope it helps!
they will definitely not be viewed at the same time
Wouldn't the most secure answer here be to simply require the password every time? I would assume (although I'm sure this isn't the answer you're looking for) that simply asking for the password each time might be the best solution.
Although it may be tedious for the user, I would also assume it imparts some sense of security - since it's not quite as simple as logging in (as the files are encrypted).
From my perspective, I would argue that encrypted files should not be mass decrypted anyways?
Sorry, I know this isn't the answer you're looking for - but if you have more information about your motivation, maybe then a more reasonable solution can be found?
Don't do decryption on the server-side - do it client side. It is safe to keep the user's password in memory on their own device.
First off, my understanding of encrypting and hashing:
Encrypting - can be decrypted
Hashing - can NOT be unhashed
When building a web application, I should:
Encrypt the email address (will be used to login) with encryption key. It's nice to be able to decrypt email addresses for later use (e.g. emailing users)
Hash the password with a salt. No one should be able to see user's password, so hashing (since it is one-way) is good.
If the above 2 points are right, where should I store the encryption key and salt?
If I store it in the DB, the seems a bit pointless should the DB ever be compromised. The benefit, though, is that I can assign a unique encryption key and salt for each user.
Should I store the encryption key and salt in my application's configuration? If the DB is ever compromised, at least the encryption key and salt are not also compromised (hopefully). The problem with this is that it probably means that everyone shares the same encryption key and salt.
Suggestions on what to do?
If you encrypt the email at all, you need to do it with a common salt/key. Otherwise, how are you going to select a user by his email address from the db to check whether the hashed password is correct? You can't decrypt every email address every time.
Overall, I think there's very little to be gained from encrypting email addresses. Use MySQL database encryption if you want, but don't worry about this at the application level.
The salt for hashing the password should/needs to be unique and can be stored in the database, in fact it can be part of the hash itself. See http://www.openwall.com/phpass/ for a good implementation.
Your understanding seems correct to me.
Password: Only the hash of a password should be stored, together with a user specific salt. The salt can be stored plaintext, the reason for the salt is, that an attacker cannot use one single rainbowtable for all users (building a rainbowtable is expensive). It's recommended to use the hash_hmac() function.
EMail: I think it's a good idea to encrypt these adresses, but however you do it, if the attacker has control over the server, he will be able to recover these addresses. I would put a secret key in a separate directory, which is outside the web root (cannot be accessed directly from the web). Don't write it in a file that can be delivered without interpreting, the extension *.php is better than *.inc . If you have no access to such a directory, at least make one and protect it with .htaccess Deny from all.
If you need to find an email address in the DB you can additionally store a hash, this allows to search case insensitive (first turn to lowercase, then generate the hash).
The salt should be per-user, and can be indeed in the database; thus the point of a salt is that someone with a copy of your db can't work on cracking all the passwords at once, but each separately.
As for the encryption key, that's a much harder issue - definitely don't store it in the database; if your platform offers any kind of protected storage, you may want to use that. See e.g. this for useful answers: What's the best method to use / store encryption keys in MySQL
I have read about using MySQL AES_ENCRYPT/AES_DECRYPT (two-way encryption) is less secure than using PHP - hash() (one-way encryption).
http://bytes.com/topic/php/answers/831748-how-use-aes_encrypt-aes_decrypt
Is it true that it is more secure that 'Rather than send the User his password, simply send him a link that he can click on to reset his password, instead.'?
And on top of that, if I am using MySQL AES_ENCRYPT/AES_DECRYPT (which I quite keen on...), how do I define the key which can be accepted by MySQL? for instance, is the length of the key important? or can I simple use '123123#123123' as my key?
thanks!
There is a fundamental difference between the two concepts, hashing and encryption:
Encryption can be reversed, hashing can't (at least that's the idea).
If a malicious user gains access to the passwords in a database and knows the key you used to encrypt them, they will be able to recover said passwords. If they are hashed, they won't be able to do that.
That's why passwords should be always be hashed (and salted), never encrypted.
for instance, is the length of the key important? or can I simple use '123123#123123' as my key?
AFAIK MySQL's AES_ENCRYPT can take keys of arbitrary length; but obviously shorter keys will make it easier for an attacker to bruteforce it (ie: try all possible combinations)
Two way encryption is inherently less secure because the real data is stored somewhere. That is, you have a password "hello." Then you hash it, you get 5d41402abc4b2a76b9719d911017c592. This is meaningless to a normal person and they will not know how to decrypt it without knowing the correct encryption algorithm. They cannot use this either because only the original password is used. You check a password by hashing it and comparing it to the hash (also stored). 5d41402abc4b2a76b9719d911017c592 hashed is 69a329523ce1ec88bf63061863d9cb14, so they don't match. Even if a user knows the hashed password, he can't get anything out of it.
So you can store the encrypted data, but if you decrypt it when you are pulling it out then anyone can use it.
The security of sending a user a link compared to giving them the password is a different issue. If you email the password, it is printed out in plain text for all to see (and use). Giving them a link to allow them to input a new password means no one will see it which is a bit more secure, but if someone committing fraud has access to that link anyway it is going to cause problems.
About AES, I can't find out too much on it at a glance, but it looks like it doesn't matter what you encrypt. So if you use AES_DECRYPT(AES_ENCRYPT('x', 'b'), 'b'); it will return 'x'. You have to keep track of the key.
If you are storing passwords on your server with symmetric encryption, you have to decode the stored password to test it against a user-submitted password. That means the key also has to be stored on the server. Which means anyone who compromises your webapp can retrieve and decrypt every user's password. (And use them to compromise other accounts where the user has used the same password.)
Hashing a password means that you can't leak the password to an attacker because you don't even know what it is yourself. You can still check whether a submitted password is the same as the original password by hashing it using the same algorithm and salt, so you can still tell whether a submitted password is right or wrong, without having to know what the password is.
Using hashed passwords does mean you can't tell the user what their password was in a ‘recover password’ option. But you don't really want to do that anyway, especially over an insecure mechanism like e-mail. One-time, time-limited reset-password links serve the same purpose with less potential damage.
For passwords, one-way hashes are almost always the way to go. One-way hashes mean that there is far less likelihood that anyone but the user would be able to know their password.
If you choose the one-way route, then you'll need to set up a password reset method. If this is done correctly, it should be fairly secure for most purposes. To gain better security, you can add things like security questions (e.g., "What is your favorite color?") that the user would have to answer before receiving a password reset link in an email.
As for keys for AES_ENCRYPT/DECRYPT-- MySQL will accept variable lengths for the key parameter to the functions, but it will use a 128-bit key regardless, so it's to your advantage to pass at least 128 bits' worth.
One-way encryption means you can only encrypt. (For example, you encrypt a password and store the result. Whenever a user authenticates, you encrypt what the user enters and compare. There is no need for a decrypt function in such a scenario.)
Two-way encryption means, there is both an encrypt and decrypt function available. In PHP, that is accomplished through the mcrypt_encrypt() and mcrypt_decrypt() functions.
An update! mcrypt is deprecated in PHP 7.1 and removed in 7.2. See OpenSSL or Sodium instead for encrypt and decrypt functions.
Since this question is rather popular, I thought it useful to give it an update.
Let me emphasise the correct answer as given by AviD to this question:
You should not store any data that needs encrypting in your cookie. Instead, store a good sized (128 bits/16 bytes) random key in the cookie and store the information you want to keep secure on the server, identified by the cookie's key.
I'm looking for information about 'the best' encryption algorithm for encrypting cookies.
I hava the following requirements:
It must be fast
encrypting and decrypting the data will be done for (nearly) every request
It will operate on small data sets, typically strings of around 100 character or less
It must be secure, but it's not like we're securing banking transactions
We need to be able to decrypt the information so SHA1 and the like are out.
Now I've read that Blowfish is fast and secure, and I've read that AES is fast and secure.
With Blowfish having a smaller block size.
I think that both algorithms provide more than adequate security? so the speed would then become the decisive factor.
But I really have no idea if those algorithm are suited for small character string and if there are maybe better suited algorithm for encrypting cookies.
So my question is:
What encryption algorithm is best for encrypting cookie data?
Update
To be more precise, we want to encrypt 2 cookie: one with session information and the other with 'remeber me' information.
The platform is PHP as apache module on Linux on a VPS.
Update 2
I agree with cletus that storing any information in a cookie is insecure.
However, we have a requirement to implement a 'remeber me' feature. The accepted way to go about this is by setting a cookie. If the client presents this cookie, he or she is allowed access the system with (almost) equal rights as if he/she presented the valid username password combination.
So we at least want to encrypt all data in the cookie so that it:
a) malicious users can't read it's contents,
b) malicious users can't fabricate their own cookie or tamper with it.
(All data from cookies is sanitized and checked for validity before we do anything with it, but that's another story)
The session cookie contains a sessionId/timestamp nothing more. It could probably be used without encryption, but I see no harm in encrypting it? (other than computation time).
So given that we have to store some data on in a cookie, what is the best way to encrypt it?
Update 3
The responses to this question made me reconsider the chosen approach. I can indeed do the same without the need for encryption. Instead of encrypting the data, I should only send out data that is meaningless without it's context and cannot be guessed.
However, I'm also at a loss:
I thought that encryption enabled us send data out in to the BigBadWorld™, and still be (fairly) sure that nobody could read or tamper with the it...
Wasn't that the whole point of encryption?
But the reactions below push toward: Do not trust encryption to accomplish security.
What am I missing??
No real reason not to go with AES with 256 bits. Make sure to use this in CBC mode, and PKCS#7 padding.
As you said, fast and secure.
I have read (not tested) that Blowfish may be marginally faster... However Blowfish has a major drawback of long setup time, which would make it bad for your situation. Also, AES is more "proven".
This assumes that it really is necessary to symmetrically encrypt your cookie data. As others have noted, it really shouldnt be necessary, and there are only a few edge cases where there's no other choice but to do so. Commonly, it would better suit you to change the design, and go back to either random session identifiers, or if necessary one-way hashes (using SHA-256).
In your case, besides the "regular" random session identifier, your issue is the "remember me" feature - this should also be implemented as either:
a long random number, stored in the database and mapped to a user account;
or a keyed hash (e.g. HMAC) containing e.g. the username, timestamp, mebbe a salt, AND a secret server key. This can of course all be verified server-side...
Seems like we've gotten a little off topic of your original, specific question - and changed the basis of your question by changing the design....
So as long as we're doing that, I would also STRONGLY recommend AGAINST this feature of persistent "remember me", for several reasons, the biggest among them:
Makes it much more likely that someone may steal that user's remember key, allowing them to spoof the user's identity (and then probably change his password);
CSRF - Cross Site Request Forgery. Your feature will effectively allow an anonymous attacker to cause unknowing users to submit "authenticated" requests to your application, even without being actually logged in.
This is touching on two separate issues.
Firstly, session hijacking. This is where a third party discovers, say, an authenticated cookie and gains access to someone else's details.
Secondly, there is session data security. By this I mean that you store data in the cookie (such as the username). This is not a good idea. Any such data is fundamentally untrustworthy just like HTML form data is untrustworthy (irrespective of what Javascript validation and/or HTML length restrictions you use, if any) because a client is free to submit what they want.
You'll often find people (rightly) advocating sanitizing HTML form data but cookie data will be blindly accepted on face value. Big mistake. In fact, I never store any information in the cookie. I view it as a session key and that's all.
If you intend to store data in a cookie I strongly advise you to reconsider.
Encryption of this data does not make the information any more trustworth because symmetric encryption is susceptible to brute-force attack. Obviously AES-256 is better than, say, DES (heh) but 256-bits of security doesn't necessarily mean as much as you think it does.
For one thing, SALTs are typically generated according to an algorithm or are otherwise susceptible to attack.
For another, cookie data is a prime candidate for crib attacks. If it is known or suspected that a username is in the encrypted data will hey, there's your crib.
This brings us back to the first point: hijacking.
It should be pointed out that on shared-hosting environments in PHP (as one example) your session data is simply stored on the filesystem and is readable by anyone else on that same host although they don't necessarily know which site it is for. So never store plaintext passwords, credit card numbers, extensive personal details or anything that might otherwise be deemed as sensitive in session data in such environments without some form of encryption or, better yet, just storing a key in the session and storing the actual sensitive data in a database.
Note: the above is not unique to PHP.
But that's server side encryption.
Now you could argue that encrypting a session with some extra data will make it more secure from hijacking. A common example is the user's IP address. Problem is many people use the same PC/laptop at many different locations (eg Wifi hotspots, work, home). Also many environments will use a variety of IP addresses as the source address, particularly in corporate environments.
You might also use the user agent but that's guessable.
So really, as far as I can tell, there's no real reason to use cookie encryption at all. I never did think there was but in light of this question I went looking to be proven either right or wrong. I found a few threads about people suggesting ways to encrypt cookie data, transparently do it with Apache modules, and so on but these all seemed motivated by protecting data stored in a cookie (which imho you shouldn't do).
I've yet to see a security argument for encrypting a cookie that represents nothing more than a session key.
I will happily be proven wrong if someone can point out something to the contrary.
Security Warning: These two functions are not secure. They're using ECB mode and fail to authenticate the ciphertext. See this answer for a better way forward.
For those reading through wanting to use this method in PHP scripts. Here is a working example using 256bit Rijndael (not AES).
function encrypt($text, $salt)
{
return trim(base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $salt, $text, MCRYPT_MODE_ECB, mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB), MCRYPT_RAND))));
}
function decrypt($text, $salt)
{
return trim(mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $salt, base64_decode($text), MCRYPT_MODE_ECB, mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB), MCRYPT_RAND)));
}
Then to save the cookie
setcookie("PHPSESSION", encrypt('thecookiedata', 'longsecretsalt'));
and to read on the next page:
$data = decrypt($_COOKIE['PHPSESSION'], 'longsecretsalt');
Fast, Encrypted Cookies with Libsodium
If you need fast, secure encrypted cookies in PHP, check out how Halite implements them. Halite relies on the libsodium PECL extension to provide secure cryptography.
<?php
use \ParagonIE\Halite\Cookie;
use \ParagonIE\Halite\Symmetric\Key;
use \ParagonIE\Halite\Symmetric\SecretKey;
// You can also use Key::deriveFromPassword($password, $salt, Key::CRYPTO_SECRETBOX);
$encryption_key = new SecretKey($some_constant_32byte_string_here);
$cookie = new Cookie($encryption_key);
$cookie->store('index', $any_value);
$some_value = $cookie->fetch('other_index');
If you cannot install PECL extensions, ask your sysadmin or hosting provider to do it for you. If they refuse, you still have options.
Secure Encrypted Cookies in PHP, Hold the Salt Please
The other answers instruct you to encrypt your data with openssl or mcrypt, but they're missing a crucial step. If you want to safely encrypt data in PHP, you must authenticate your messages.
Using the OpenSSL extension, the process you would need to follow looks like this:
Preamble
(Before you even think about encryption) Generate a 128-bit, 192-bit, or 256-bit random string. This will be your master key.
Do not use a human-readable password. If you, for some reason, must use a human-readable password, ask Cryptography SE for guidance.
If you need special attention, my employer offers technology consulting services, including development of cryptography features.
Encryption
Generate a random Initialization Vector (IV) or nonce. e.g. random_bytes(openssl_cipher_iv_length('aes-256-cbc'))
Use HKDF or a similar algorithm for splitting your master key into two keys:
An encryption key ($eKey)
An authentication key ($aKey)
Encrypt your string with openssl_encrypt() with your IV and an appropriate modate (e.g. aes-256-ctr) using your encryption key ($eKey) from step 2.
Compute an authentication tag of your ciphertext from step 3, using a keyed hash function such as HMAC-SHA256. e.g. hash_hmac('sha256', $iv.$ciphertext, $aKey). It's very important to authenticate after encryption, and to encapsulate the IV/nonce as well.
Package the authentication tag, IV or nonce, and ciphertext together and optionally encode it with bin2hex() or base64_encode(). (Warning: This approach might leak cache-timing information.)
Decryption
Split your key, as per step 2 in encryption. We need the same two keys during decryption!
(Optionally, decode and) unpack the MAC, IV, and ciphertext from the packed message.
Verify the authentication tag by recalculating the HMAC of the IV/nonce and ciphertext with the user-provided HMAC by using hash_equals().
If and only if step 3 passes, decrypt the ciphertext using $eKey.
If you want to see how this all looks together, see this answer which has sample code.
If this sounds like too much work, use defuse/php-encryption or zend-crypt and call it a day.
Remember Me Cookies
However, we have a requirement to implement a 'remeber me' feature. The accepted way to go about this is by setting a cookie. If the client presents this cookie, he or she is allowed access the system with (almost) equal rights as if he/she presented the valid username password combination.
Encryption is actually not the correct tool for this job. You want to follow this process for secure remember me cookies in PHP:
Generating a Remember Me Token
Generate two random strings:
A selector which will be used for database lookups. (The purpose of a random selector instead of just a sequential ID is to not leak how many active users are on your website. If you're comfortable leaking this information, feel free to just use a sequential ID.)
A validator which will be used to authenticate the user automatically.
Calculate a hash of validator (a simple SHA-256 hash will suffice).
Store the selector and the hash of the validator in a database table reserved for automatic logins.
Store the selector and validator in a cookie on the client.
Redeeming a Remember Me Token
Split the incoming cookie into the selector and validator.
Perform a database lookup (use prepared statements!) based on selector.
If a row is found, calculate a hash of the validator.
Compare the hash calculated in step 3 with the hash stored in the database, once again using hash_equals().
If step 4 returns true, log the user in to the appropriate account.
This is the strategy that Gatekeeper adopted for long-term user authentication and it is the most secure strategy proposed to date for satisfying this requirement.
You can achieve what you want securely by using AES in EAX mode. The ciphertext will be larger than the plaintext; that's normal for secure encryption.
The attacker will of course know the length of your plaintext from the ciphertext, but they shouldn't be able to determine anything else.
Generate AES keys randomly.
Be sure and use a fresh nonce for each encryption, and use the "associated data" field to ensure that a thing you encrypted for one purpose isn't presented as being for another (so things like the user name and cookie name could go in there)
the reactions below push toward: Do
not trust encryption to accomplish
security.
More "if you're not an encryption expert you'll underestimate how easy it is to get wrong". For example, AFAICT no-one else in this thread has discussed chaining modes or message integrity, which covers two common beginner's mistakes.
While both a very strong ones, AES is a standard.
As for security of small chunks of data: the smaller - the better. The less encrypted data is exposed, the longer you can use the key. There is always a theoretical limit of how much data can be encrypted within one key of given algorithm without exposing system to risks.
As pointed out a few times in previous comments, you must apply integrity protection to any ciphertext that you send out to the user and accept back. Otherwise the protected data can be modified, or the encryption key recovered.
Especially the PHP world is full of bad examples that ignore this (see PHP cryptography - proceed with care) but this does apply to any language.
One of few good examples I've seen is PHP-CryptLib which uses combined encryption-authentication mode to do the job. For Python pyOCB offers similar functionality.
Why do you want to encrypt the cookie?
As I see it, there are two cases: either you give the client the key, or you don't.
If you don't give the key to the client, then why are you giving them the data? Unless you're playing some weird game with breaking weak encryption (which you're explicitly not), you might as well store the data on the server.
If you do hand the client the key, then why do you encrypt it in the first place? If you don't encrypt the communication of the key, then encrypting the cookie is moot: a MITM can look at the cookie and send you any cookie he wants. If you use an encrypted channel to the client, why the extra overhead of encrypting the stored data?
If you're worried about other users on the client's machine reading the cookie, give up and assume the browser sets good permission bits :)
If you encrypt the cookie, the server still has to decode it to read it (to check for same key), therefore any encrypted cookie is pointless, because if stolen (and un-edited) it will still lead the hacker right to your account. Its just as unsafe as no encrypted at all.
I believe the real issue of someone stealing your cookie is the connection between the server and client. Use SSL connection provided by your host.
As for your cookie, you need to make a long random id per user in the database, (have it change every log on) and just set that as the cookie or session. The cookie that contains the key can be checked via php and if it is equal to an account or table in your database, dump the data on the web page like normal.
AES (also known as Rijndael) is the most popular. The block size is 128-bits, that's only 16-bytes, and you're talking "around 100 characters".
I think that "giving away" any data even encrypted when it is about username and password is not good ...
There are many JS that can sniff it ...
I suggest you create in users DB table a field cookie_auth or whatever ...
after first login gather : current: browser, IP,ans some own salt key, plus your hostname var ...
create a hash and store in that field ...
set a cookie ...
when cookie "responds" compare all of these with the stored hash and done ...
even if someone "steal" a cookie they won't be able to use it :-)
Hope this helps :-)
feha
vision.to
In addition, I have tried the mcrypt_encrypt and one thing please keep in mind. If you do base64_encode(mcrypt_encrypt(...)).
and then later, you do base64_decode and output the encrypted data (echo). You probably will be screwed and not seeing anything. However, if you do mcrypt_decrypt( ... base64_decode($value) ). You will see the original data.
So many terrifying things been said, which is true though, but let's see the bright side, a little common sense and continuous watch over your site might save you all the time.
Saving cookies is an important part of web development so one can't ignore it. But also we should avoid as much as possible; I see the use of Cookies only if I want to extends the login session even after user close the browser. If ones don't want to extends the user session beyond browser closing, then Session component should be used. Even with Session component usage one should be aware of Session Hijacking.
Anyways, back to Cookie thing; In my opinion if one's follow the following precautionary measurement, I am pretty sure we can be on the safer side.
I divide the precautionary measurement in to two phase
Phase1: Development
Set path attribute
Set expiration_date
set secure, httpOnly attributes
Use latest encryption Algorithms
Use two algorithms: for instance use blowfish and then use base64_encode on top of it.
Phase 2: Operation/Audit
Periodically make site audit, using tools like burp.
I have a PHP app that needs to run bash scripts, and provide a username & password (for remote systems).
I need to store these credentials somewhere that is accessible by my PHP (web) app.
The logical place is the database (currently MySQL, but will be agnostic).
The problem with the "standard" way of hashing and storing the credentials, is that it is not reversible. I have to be able to get the credentials out as unencrypted clear text, to be able to insert the data into bash scripts.
Does anyone have any suggestions for a secure way to go about this ?
I thought maybe PKI'ing the credentials, and storing the result in the DB. Then use the private key to unencrypt (PHP can do that). Store the scripts to do this outside the web root.
Any thoughts much appreciated.
First, to state the (hopefully) obvious, if you can in any way at all avoid storing usernames and passwords do so; it's a big responsibility and if your credential store is breached it may provide access to many other places for the same users (due to password sharing).
Second, if you must store credentials prefer rather to stored passwords using a non-reversible, salted cryptographic hash, so if you data is compromised the passwords cannot easily be reverse-engineered and there's no need to store a decryption key at all.
If you must store decryptable credentials:
Choose a good encryption algorithm - AES-256, 3DES (dated), or a public key cipher (though I think that's unnecessary for this use). Use cryptographic software from a reputable trustworthy source - DO NOT ATTEMPT TO ROLL YOUR OWN, YOU WILL LIKELY GET IT WRONG.
Use a secure random generator to generate your keys. Weak randomness is the number one cause of encryption related security failures, not cipher algorithms.
Store the encryption/decryption key(s) separately from your database, in an O/S secured file, accessible only to your applications runtime profile. That way, if your DB is breached (e.g. through SQL injection) your key is not automatically vulnerable, since that would require access to to the HDD in general. If your O/S supports file encryption tied to a profile, use it - it can only help and it's generally transparent (e.g. NTFS encryption).
If practical, store the keys themselves encrypted with a primary password. This usually means your app. will need that password keyed in at startup - it does no good to supply it in a parameter from a script since if your HDD is breached you must assume that both the key file and the script can be viewed.
For each credential set, store a salt (unencrypted) along with the encrypted data; this is used to "prime" the encryption cipher such that two identical passwords do not produce the same cipher text - since that gives away that the passwords are the same.
If the username is not necessary to locate the account record (which in your case it is not), encrypt both the username and password. If you encrypt both, encrypt them as one encryption run, e.g
userAndPass=(user+":"+pass);
encryptInit();
encrypt(salt);
encrypt(userAndPass);
cipherText=encryptFinal();
and store the singular blob, so that there is less occurrence of short cipher texts, which are easier to break, and the username further salts the password.
PS: I don't program in PHP so cannot comment on suitable crypto s/w in that environment.
You'll need to look into good 2 way cryptographic methods, and my general rule of thumb is:
If you implement your own cryptographic code you will fail.
So, find a good implementation that is well verified, and utilize that.
There is probably some good info here:
http://phpsec.org/library/
Check this library: PECL gnupg it provides you methods to interact with gnupg. You can easily encrypt and decrypt data, using safe public-key cryptographic algorithms.
I would suggest you not store the passwords, but use passwordless ssh connection from the host to the remote system by generating a ssh key and storing your public key in the remote system's authorized_keys file. Then you would only need to establish connectivity during configuration. Admittedly not quite answering your question, but storing passwords in a reversible form is a slippery slope to a security breach imho, although I am sure smarter brains than mine can make it safe.
One easy way to get started is to use mysql's ENCODE() and DECODE() functions. I don't know what algorithm is used underneath, but it's easy enough to use:
INSERT INTO tbl_passwords SET encoded_pw = ENCODE('r00t', 'my-salt-string');
and
SELECT DECODE(encoded_pw, 'my-salt-string') FROM tbl_passwords;
If you go the PKI, and I would, make sure you safe guard your private keys! The strong encryption provided by PKI is only as secure as your keys.
I think you're on target. Look at GPG for a good, open encryption library
It looks like you pretty much have two methods of doing this:
1) Like you suggested use an encryption algorithm or algorithms which can then be decrypted and used for authentication in your scripts. You can use the MCrypt library in PHP to accomplish this.
2) Depending on the required level of security and your script's level of vulnerability, you could use a secure hash, key, or some other hard to guess unique identifier that you can use to hijack each user's account within the confines of the script.
As many stated you scenario requires that you encrypt username and password. I would recommend that you check out the mcrypt extension of php for encryption/decryption.
I think I am going to investigate compiling a PHP script with the credentials embedded, on the fly, from the web app.
I would ask for the credentials (for a given use), then create and compile a new PHP script, for this use only. That way, the script will only do what I need, and should not be "readable". I think this sounds like the safest way to do this.
Will try using Roadsend. http://www.roadsend.com/
Just to follow up on the suggestion to use MySQL encode and decode functions, the manual is vague on just how these work:
The strength of the encryption is based on how good the random generator is. It should suffice for short strings.
But what I'd suggest is that you can instead use the built-in MySQL 5.0 AES functions; AES_ENCRYPT() and AES_DECRYPT()
SELECT AES_ENCRYPT('secret squirrel', '12345678') AS encoded
=> ØA;J×ÍfOU»] É8
SELECT AES_DECRYPT('ØA;J×ÍfOU»] É8', '12345678') AS decoded
=> secret squirrel
These use 128-bit AES which should be strong enough for most purposes. As others commented, using a salt value and a key with a high entropy is a good practice.
For PHP, it is important to note that AES encryption is implemented via MCRYPT_RIJNDAEL functions. Don't go paying for a non-open implementation when PHP has them available.
See the PHP page discussing available ciphers for more information.