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@ziadoz ziadoz/index.php
Last active Mar 28, 2019

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Simple PHP / jQuery CSRF Protection
<?php
// See: http://blog.ircmaxell.com/2013/02/preventing-csrf-attacks.html
// Start a session (which should use cookies over HTTP only).
session_start();
// Create a new CSRF token.
if (! isset($_SESSION['csrf_token'])) {
$_SESSION['csrf_token'] = base64_encode(openssl_random_pseudo_bytes(32));
}
// Check a POST is valid.
if (isset($_POST['csrf_token']) && $_POST['csrf_token'] === $_SESSION['csrf_token']) {
// POST data is valid.
}
?>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8" />
<title>PHP CSRF Protection</title>
<script>
window.csrf = { csrf_token: '<?php echo $_SESSION['csrf_token']; ?>' };
$.ajaxSetup({
data: window.csrf
});
$(document).ready(function() {
// CSRF token is now automatically merged in AJAX request data.
$.post('/awesome/ajax/url', { foo: 'bar' }, function(data) {
console.log(data);
});
});
</script>
</head>
<body>
<form action="index.php" method="post" accept-charset="utf-8">
<input type="text" name="foo" />
<input type="hidden" name="csrf_token" value="<?php echo $_SESSION['csrf_token']; ?>" />
<input type="submit" value="Submit" />
</form>
</body>
</html>
@energylevels

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commented Jan 8, 2016

I'm not using JQuery Library, how to send CSRF token in standard Javascript ?? ... Thanks

@pvictorlv

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commented Aug 10, 2016

thank you!

@ao

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commented Sep 17, 2016

Simple and effective, thanks!

@sinkaszab

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commented Sep 24, 2016

Maybe I am wrong, but:

  • If I can steal your cookie => I can steal your session (Session will set a session cookie, that's how you are connected to a server session, remember?)
  • If I can steal your session, I can steal your "hidden" token.

Instead

  • Regenerate session_id on a regular basis.
  • Delete obsolete sessions so that they cannot be revived.

I would not suggest relying on this code to anyone.

Some starting point

http://eddmann.com/posts/securing-sessions-in-php/

http://resources.infosecinstitute.com/fixing-csrf-vulnerability-in-php-application/

@idangoldman

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commented Feb 28, 2017

@sinkaszab your starting points are using session cookies....

@ziadoz, thanks looks good! :)

@AlekseyKorzun

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commented Apr 21, 2018

This implementation is missing a big security feature. The token must be cleared post validation, you can achieve that by executing unset($_SESSION['csrf_token']).

@sinkaszab your concerns are valid but what you are referring to is usually done upon privilege escalation. This doesn't apply here since the token is one-time use.

@AkinOlawale

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commented Jul 19, 2018

also you should use php's hash_equals to compare. Do not use ==. This is to prevent the timing attack

@banujan6

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@hdyangy

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commented Aug 22, 2018

thank you

@OscarKolsrud

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commented Mar 10, 2019

Maybe I am wrong, but:

  • If I can steal your cookie => I can steal your session (Session will set a session cookie, that's how you are connected to a server session, remember?)
  • If I can steal your session, I can steal your "hidden" token.

Instead

  • Regenerate session_id on a regular basis.
  • Delete obsolete sessions so that they cannot be revived.

I would not suggest relying on this code to anyone.

Some starting point

http://eddmann.com/posts/securing-sessions-in-php/

http://resources.infosecinstitute.com/fixing-csrf-vulnerability-in-php-application/

This is most likely a problem if you use correct time out of PHP sessions.

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