PHP 7.4.0RC6 Released!

password_hash

(PHP 5 >= 5.5.0, PHP 7)

password_hashErstellt einen Passwort-Hash

Beschreibung

password_hash ( string $password , int $algo [, array $options ] ) : string

password_hash() erstellt einen neuen Passwort-Hash und benutzt dabei einen starken Einweg-Hashing-Algorithmus. password_hash() ist kompatibel zu crypt(). Daher können Passwort-Hashes, die durch crypt() erzeugt wurden, mit password_hash() verwendet werden.

Die folgenden Algorithmen werden zur Zeit unterstützt:

  • PASSWORD_DEFAULT - Benutzt den bcrypt-Algorithmus (Standard in PHP 5.5.0). Beachte, dass sich diese Konstante mit der Zeit ändern wird, wenn stärkere Algorithmen in PHP implementiert werden. Aus diesem Grund kann sich die Länge des zurückgegebenen Strings mit der Zeit ändern. Es wird deshalb empfohlen das Ergebnis in einem Datenbankfeld zu speichern, das mehr als 60 Zeichen speichern kann. (z.B. 255 Zeichen).
  • PASSWORD_BCRYPT - Benutzt den CRYPT_BLOWFISH-Algorithmus zum Erstellen des Hashes. Dies erstellt einen crypt()-kompatiblen Hash und benutzt die "$2y$"-Kennung. Es wird immer ein 60 Zeichen langer String zurückgegeben, Im Fehlerfall wird FALSE zurückgegeben..
  • PASSWORD_ARGON2I - Use the Argon2i hashing algorithm to create the hash. This algorithm is only available if PHP has been compiled with Argon2 support.
  • PASSWORD_ARGON2ID - Use the Argon2id hashing algorithm to create the hash. This algorithm is only available if PHP has been compiled with Argon2 support.

Unterstützte Optionen für PASSWORD_BCRYPT:

  • salt (string) - to manually provide a salt to use when hashing the password. Note that this will override and prevent a salt from being automatically generated.

    If omitted, a random salt will be generated by password_hash() for each password hashed. This is the intended mode of operation.

    Warnung

    Die salt Option wurde von PHP 7.0.0 an missbilligt. Es wird nun empfohlen einfach das Salt zu verwenden, das standardmäßig erzeugt wird.

  • cost (integer) - which denotes the algorithmic cost that should be used. Examples of these values can be found on the crypt() page.

    If omitted, a default value of 10 will be used. This is a good baseline cost, but you may want to consider increasing it depending on your hardware.

Supported options for PASSWORD_ARGON2I and PASSWORD_ARGON2ID:

  • memory_cost (integer) - Maximum memory (in kibibytes) that may be used to compute the Argon2 hash. Defaults to PASSWORD_ARGON2_DEFAULT_MEMORY_COST.

  • time_cost (integer) - Maximum amount of time it may take to compute the Argon2 hash. Defaults to PASSWORD_ARGON2_DEFAULT_TIME_COST.

  • threads (integer) - Number of threads to use for computing the Argon2 hash. Defaults to PASSWORD_ARGON2_DEFAULT_THREADS.

Parameter-Liste

password

Das Passwort des Benutzers.

Achtung

Die Verwendung von PASSWORD_BCRYPT als Algorithmus führt dazu, dass der password Parameter auf eine Höchstlänge von 72 Zeichen gekürzt wird.

algo

Eine Konstante für den Passwort-Algorithmus, die den Algorithmus zum hashen des Passwortes angibt.

options

Ein assoziatives Array mit Optionen. Siehe auch Konstanten für Passwort-Algorithmen für Informationen zu den von dein jeweiligen Algorithmen unterstützten Optionen.

If omitted, a random salt will be created and the default cost will be used.

Rückgabewerte

Returns the hashed password, Im Fehlerfall wird FALSE zurückgegeben..

Der verwendete Algorithmus, der Aufwand und das Salt werden als Teil des Hashes zurückgegeben. Daher sind alle Informationen, die benötigt werden, um den Hash zu verifizieren, darin enthalten. Dies erlaubt es der Funktion password_verify() den Hash zu überprüfen, ohne dass eine separate Speicherung für das Salt oder die Algorithmus-Information erforderlich ist.

Beispiele

Beispiel #1 password_hash() example

<?php
/**
 * We just want to hash our password using the current DEFAULT algorithm.
 * This is presently BCRYPT, and will produce a 60 character result.
 *
 * Beware that DEFAULT may change over time, so you would want to prepare
 * By allowing your storage to expand past 60 characters (255 would be good)
 */
echo password_hash("rasmuslerdorf"PASSWORD_DEFAULT);
?>

Das oben gezeigte Beispiel erzeugt eine ähnliche Ausgabe wie:

$2y$10$.vGA1O9wmRjrwAVXD98HNOgsNpDczlqm3Jq7KnEd1rVAGv3Fykk1a

Beispiel #2 password_hash() example setting cost manually

<?php
/**
 * In this case, we want to increase the default cost for BCRYPT to 12.
 * Note that we also switched to BCRYPT, which will always be 60 characters.
 */
$options = [
    
'cost' => 12,
];
echo 
password_hash("rasmuslerdorf"PASSWORD_BCRYPT$options);
?>

Das oben gezeigte Beispiel erzeugt eine ähnliche Ausgabe wie:

$2y$12$QjSH496pcT5CEbzjD/vtVeH03tfHKFy36d4J0Ltp3lRtee9HDxY3K

Beispiel #3 password_hash() example finding a good cost

<?php
/**
 * This code will benchmark your server to determine how high of a cost you can
 * afford. You want to set the highest cost that you can without slowing down
 * you server too much. 8-10 is a good baseline, and more is good if your servers
 * are fast enough. The code below aims for ≤ 50 milliseconds stretching time,
 * which is a good baseline for systems handling interactive logins.
 */
$timeTarget 0.05// 50 Millisekunden 

$cost 8;
do {
    
$cost++;
    
$start microtime(true);
    
password_hash("test"PASSWORD_BCRYPT, ["cost" => $cost]);
    
$end microtime(true);
} while ((
$end $start) < $timeTarget);

echo 
"Appropriate Cost Found: " $cost;
?>

Das oben gezeigte Beispiel erzeugt eine ähnliche Ausgabe wie:

Appropriate Cost Found: 10

Beispiel #4 password_hash() example using Argon2i

<?php
echo 'Argon2i hash: ' password_hash('rasmuslerdorf'PASSWORD_ARGON2I);
?>

Das oben gezeigte Beispiel erzeugt eine ähnliche Ausgabe wie:

Argon2i hash: $argon2i$v=19$m=1024,t=2,p=2$YzJBSzV4TUhkMzc3d3laeg$zqU/1IN0/AogfP4cmSJI1vc8lpXRW9/S0sYY2i2jHT0

Anmerkungen

Achtung

It is strongly recommended that you do not generate your own salt for this function. It will create a secure salt automatically for you if you do not specify one.

As noted above, providing the salt option in PHP 7.0 will generate a deprecation warning. Support for providing a salt manually may be removed in a future PHP release.

Hinweis:

It is recommended that you test this function on your servers, and adjust the cost parameter so that execution of the function takes less than 100 milliseconds on interactive systems. The script in the above example will help you choose a good cost value for your hardware.

Hinweis: Updates to supported algorithms by this function (or changes to the default one) must follow the following rules:

  • Any new algorithm must be in core for at least 1 full release of PHP prior to becoming default. So if, for example, a new algorithm is added in 7.5.5, it would not be eligible for default until 7.7 (since 7.6 would be the first full release). But if a different algorithm was added in 7.6.0, it would also be eligible for default at 7.7.0.
  • The default should only change on a full release (7.3.0, 8.0.0, etc) and not on a revision release. The only exception to this is in an emergency when a critical security flaw is found in the current default.

Changelog

Version Beschreibung
7.3.0 Support for Argon2id passwords using PASSWORD_ARGON2ID was added.
7.2.0 Support for Argon2i passwords using PASSWORD_ARGON2I was added.

Siehe auch

add a note add a note

User Contributed Notes 13 notes

up
161
martinstoeckli
6 years ago
There is a compatibility pack available for PHP versions 5.3.7 and later, so you don't have to wait on version 5.5 for using this function. It comes in form of a single php file:
https://github.com/ircmaxell/password_compat
up
3
Anonymous
5 months ago
According to the draft specification, Argon2di is the recommended mode of operation:

> 9.4.  Recommendations
>
>   The Argon2id variant with t=1 and maximum available memory is
>   recommended as a default setting for all environments.  This setting
>   is secure against side-channel attacks and maximizes adversarial
>   costs on dedicated bruteforce hardware.

source: https://tools.ietf.org/html/draft-irtf-cfrg-argon2-06#section-9.4
up
40
nicoSWD
6 years ago
I agree with martinstoeckli,

don't create your own salts unless you really know what you're doing.

By default, it'll use /dev/urandom to create the salt, which is based on noise from device drivers.

And on Windows, it uses CryptGenRandom().

Both have been around for many years, and are considered secure for cryptography (the former probably more than the latter, though).

Don't try to outsmart these defaults by creating something less secure. Anything that is based on rand(), mt_rand(), uniqid(), or variations of these is *not* good.
up
2
phpnetcomment201908 at lucb1e dot com
2 months ago
Since 2017, NIST recommends using a secret input when hashing memorized secrets such as passwords. By mixing in a secret input (commonly called a "pepper"), one prevents an attacker from brute-forcing the password hashes altogether, even if they have the hash and salt. For example, an SQL injection typically affects only the database, not files on disk, so a pepper stored in a config file would still be out of reach for the attacker. A pepper must be randomly generated once and can be the same for all users. Many password leaks could have been made completely useless if site owners had done this.

Since there is no pepper parameter for password_hash (even though Argon2 has a "secret" parameter, PHP does not allow to set it), the correct way to mix in a pepper is to use hash_hmac(). The "add note" rules of php.net say I can't link external sites, so I can't back any of this up with a link to NIST, Wikipedia, posts from the security stackexchange site that explain the reasoning, or anything... You'll have to verify this manually. The code:

// config.conf
pepper=c1isvFdxMDdmjOlvxpecFw

<?php
// register.php
$pepper = getConfigVariable("pepper");
$pwd = $_POST['password'];
$pwd_peppered = hash_hmac("sha256", $pwd, $pepper);
$pwd_hashed = password_hash($pwd_peppered, PASSWORD_ARGON2ID);
add_user_to_database($username, $pwd_hashed);
?>

<?php
// login.php
$pepper = getConfigVariable("pepper");
$pwd = $_POST['password'];
$pwd_peppered = hash_hmac("sha256", $pwd, $pepper);
$pwd_hashed = get_pwd_from_db($username);
if (
password_verify($pwd_peppered, $pwd_hashed)) {
    echo
"Password matches.";
}
else {
    echo
"Password incorrect.";
}
?>

Note that this code contains a timing attack that leaks whether the username exists. But my note was over the length limit so I had to cut this paragraph out.

Also note that the pepper is useless if leaked or if it can be cracked. Consider how it might be exposed, for example different methods of passing it to a docker container. Against cracking, use a long randomly generated value (like in the example above), and change the pepper when you do a new install with a clean user database. Changing the pepper for an existing database is the same as changing other hashing parameters: you can either wrap the old value in a new one and layer the hashing (more complex), you compute the new password hash whenever someone logs in (leaving old users at risk, so this might be okay depending on what the reason is that you're upgrading).

Why does this work? Because an attacker does the following after stealing the database:

password_verify("a", $stolen_hash)
password_verify("b", $stolen_hash)
...
password_verify("z", $stolen_hash)
password_verify("aa", $stolen_hash)
etc.

(More realistically, they use a cracking dictionary, but in principle, the way to crack a password hash is by guessing. That's why we use special algorithms: they are slower, so each verify() operation will be slower, so they can try much fewer passwords per hour of cracking.)

Now what if you used that pepper? Now they need to do this:

password_verify(hmac_sha256("a", $secret), $stolen_hash)

Without that $secret (the pepper), they can't do this computation. They would have to do:

password_verify(hmac_sha256("a", "a"), $stolen_hash)
password_verify(hmac_sha256("a", "b"), $stolen_hash)
...
etc., until they found the correct pepper.

If your pepper contains 128 bits of entropy, and so long as hmac-sha256 remains secure (even MD5 is technically secure for use in hmac: only its collision resistance is broken, but of course nobody would use MD5 because more and more flaws are found), this would take more energy than the sun outputs. In other words, it's currently impossible to crack a pepper that strong, even given a known password and salt.
up
33
Cloxy
6 years ago
You can produce the same hash in php 5.3.7+ with crypt() function:

<?php

$salt
= mcrypt_create_iv(22, MCRYPT_DEV_URANDOM);
$salt = base64_encode($salt);
$salt = str_replace('+', '.', $salt);
$hash = crypt('rasmuslerdorf', '$2y$10$'.$salt.'$');

echo
$hash;

?>
up
15
Lyo Mi
3 years ago
Please note that password_hash will ***truncate*** the password at the first NULL-byte.

http://blog.ircmaxell.com/2015/03/security-issue-combining-bcrypt-with.html

If you use anything as an input that can generate NULL bytes (sha1 with raw as true, or if NULL bytes can naturally end up in people's passwords), you may make your application much less secure than what you might be expecting.

The password
$a = "\01234567";
is zero bytes long (an empty password) for bcrypt.

The workaround, of course, is to make sure you don't ever pass NULL-bytes to password_hash.
up
13
martinstoeckli
6 years ago
In most cases it is best to omit the salt parameter. Without this parameter, the function will generate a cryptographically safe salt, from the random source of the operating system.
up
8
Mike Robinson
5 years ago
For passwords, you generally want the hash calculation time to be between 250 and 500 ms (maybe more for administrator accounts). Since calculation time is dependent on the capabilities of the server, using the same cost parameter on two different servers may result in vastly different execution times. Here's a quick little function that will help you determine what cost parameter you should be using for your server to make sure you are within this range (note, I am providing a salt to eliminate any latency caused by creating a pseudorandom salt, but this should not be done when hashing passwords):

<?php
/**
* @Param int $min_ms Minimum amount of time in milliseconds that it should take
* to calculate the hashes
*/
function getOptimalBcryptCostParameter($min_ms = 250) {
    for (
$i = 4; $i < 31; $i++) {
       
$options = [ 'cost' => $i, 'salt' => 'usesomesillystringforsalt' ];
       
$time_start = microtime(true);
       
password_hash("rasmuslerdorf", PASSWORD_BCRYPT, $options);
       
$time_end = microtime(true);
        if ((
$time_end - $time_start) * 1000 > $min_ms) {
            return
$i;
        }
    }
}
echo
getOptimalBcryptCostParameter(); // prints 12 in my case
?>
up
0
ms1 at rdrecs dot com
1 month ago
Timing attacks simply put, are attacks that can calculate what characters of the password are due to speed of the execution.

More at...
https://paragonie.com/blog/2015/11/preventing-timing-attacks-on-string-comparison-with-double-hmac-strategy

I have added code to phpnetcomment201908 at lucb1e dot com's suggestion to make this possible "timing attack" more difficult using the code phpnetcomment201908 at lucb1e dot com posted.

$pph_strt = microtime(true);

//...
/*The code he posted for login.php*/
//...

$end = (microtime(true) - $pph_strt);

$wait = bcmul((1 - $end), 1000000);  // usleep(250000) 1/4 of a second

usleep ( $wait );

echo "<br>Execution time:".(microtime(true) - $pph_strt)."; ";

Note I suggest changing the wait time to suit your needs but make sure that it is more than than the highest execution time the script takes on your server.

Also, this is my workaround to obfuscate the execution time to nullify timing attacks. You can find an in-depth discussion and more from people far more equipped than I for cryptography at the link I posted. I do not believe this was there but there are others. It is where I found out what timing attacks were as I am new to this but would like solid security.
up
-1
hman
2 months ago
I believe a note should be added about the compatibility of crypt() and password_hash().

My tests showed that yes, password_verify can also take hashes generated by crypt - as well as those from password_hash. But vice versa this is not true...

You cannot put hashes generated by password_hash into crypt for comparing them themselves, when used as the salt for crypt, as was recommended years ago (compare user entry with user crypt(userentry,userentry). No big deal, but it means that password checking routines MUST immediately be rewritten to use password_hash...

You cannot start using password_hash for hash generation without also altering the password check routine!

So the word "compatible" should be, IMHO, ammended with a word of caution, hinting the reader, that compatibility here is a one-way street.
up
0
cottton
5 years ago
if you thought
"why is the salt included in the hash and is it save when i store it as it is in my db?"

Answer i found:
The salt just has to be unique. It not meant to be a secret.

As mentioned in notes and docu before: let password_hash() take care of the salt.

With the unique salt you force the attacker to crack the hash.
The hash is unique and cannot be found at rainbow tables.
up
-5
VladimirMozhenkov at yahoo dot com
4 years ago
Note that this function can return NULL. It does so if you provide an incorrect constant as an algorythm. I had the following:

    $password = password_hash($password1, PASSWORD_BDCRYPT, array( 'cost' => 10 ));

and i couldn't understand why i kept having NULL written in $password; it was a simple fact that the constant was PASSWORD_BCRYPT.
up
-11
anonymous
3 years ago
Pay close attention to the maximum allowed length of the password parameter!  If you exceed the maximum length, it will be truncated without warning.

If you prepend your own salt/pepper to the password, and that salt/pepper exceeds the maximum length, then this function will truncate the actual password.  That means password_verify() will return true with ANY password using the same salt/pepper.

It might be a good idea to append any salt/pepper to the end of the password instead.
To Top