random_bytes() prevents me to log in if PHP is 5.3.5

[imath]

Since r35365, when i try to log in WordPress on a local WAMP stack using PHP 5.3.5 i get this fatal error :

Fatal error: Maximum execution time of 60 seconds exceeded in D:\path_to_wp\wp-includes\random_compat\random_bytes_openssl.php on line 64

xdebug is giving me these pieces of information :

Call Stack
#	Time	Memory	Function	Location
1	0.0072	689848	{main}( )	..\wp-login.php:0
2	0.3460	25607752	wp_signon( )	..\wp-login.php:776
3	0.3611	25695560	wp_set_auth_cookie( )	..\user-functions.php:94
4	0.3611	25696040	WP_Session_Tokens->create( )	..\pluggable.php:921
5	0.3611	25696648	wp_generate_password( )	..\session.php:147
6	59.2952	25697008	wp_rand( )	..\pluggable.php:2138
7	59.2952	25697168	random_int( )	..\pluggable.php:2185
8	59.2953	25697392	random_bytes( )	..\random_int.php:148

When i switch to PHP 5.4.9 i have no problem ??

As WordPress PHP required version is 5.2.4, i thought i should add this ticket. Maybe it's relative to my WAMP Stack, but just in case...

[dd32]

Hi @imath,
Thanks for reporting this! It's definitely not the intended behaviour.

Can you provide some more details about your server environment? Specifically the version of OpenSSL which you're running?

cc @sarciszewski

[dd32]

Noting it here, although it doesn't apply specifically to this case, in PHP 5.3.4 and earlier on Windows it's a known issue that openssl_random_pseudo_bytes() may block for a significant amount of time.

On later versions it's also known for being slow when running under CGI.

[imath]

Hi @dd32

Thanks a lot for your quick reply. It's probably this WAMP stack configuration that is getting old i guess :)

Openssl is 0.9.8o

And here's a truncated phpinfo if it can help ​https://cldup.com/KPPgwfVME2.html

But i'm not sure it's linked to the Openssl version as when i switch to php 5.4.9 it's the same.

[dd32]

Looks like although this function exists in the OpenSSL extension, on windows systems it doesn't use the OpenSSL provided function and instead prefers the Windows Crypto API instead, however that's ​only in PHP 5.4.1+.

[sarciszewski]

If I'm reading this correctly, we should probably prevent openssl_random_pseudo_bytes() from being invoked on PHP < 5.3.3; does that sound right to you @dd32?

[sarciszewski]

​https://github.com/paragonie/random_compat/releases/tag/1.0.10 - This should fix the known problem that Dion referred to on Windows.

If you change [this constant](​https://github.com/paragonie/random_compat/blob/2fa50aa2f17066fa74ba00d943e8cee1a98284af/lib/random.php#L114) from 50304 to 50401 does this performance problem evaporate?

(Note that OpenSSL is our last resort, so this means that you're not benefiting from a CSPRNG on outdated versions of PHP on Windows.)

[imath]

@sarciszewski

Well the file is a bit different in WP Core > https://core.trac.wordpress.org/browser/trunk/src/wp-includes/random_compat/random.php

But if i apply the attached patch (34409.patch) using the 50401 constant it's now possible to log in using PHP 5.3.5.

[sarciszewski]

Okay, I opened a ticket on random_compat to discuss our way forward: ​https://github.com/paragonie/random_compat/issues/73

[dd32]

In 35410:

Update Random_Compat to master.
This update mostly concerns OpenSSL being unusable on PHP 5.3~5.3.3.
See #28633, #34409

[dd32]

So far all i've been able to determine is that yes, random_int() can be slow with OpenSSL on windows under certain situations in <= php 5.3.8. Using ​XAMPP has shown that every call to random_int() takes roughly 1.2s using OpenSSL in those versions of PHP, which is about the same speed as PHP 5.3.0~5.3.3 in my testing.

PHP 5.4.7 is orders of magnitude faster (The XAMPP version which includes 5.4.4 is broken, and none include 5.4.0/5.4.1).

I'm going to bump the WP version to PHP 5.4.1+ for OpenSSL since that's when the last major change occurred, and we can't really risk it.

[dd32]

The builds directly from ​http://windows.php.net/ don't suffer the same problem when running as CLI scripts, so i suspect it's something to do with how they're used when run as mod_php.

[dd32]

In 35587:

Random_Compat: Bump the OpenSSL requirement for windows servers to 5.4.1 while the upstream issue is resolved.

Before PHP 5.4.1 the OpenSSL extension used a OpenSSL provided function which is seemingly slow under some circumstances, PHP 5.4.1+ uses the windows crypto API.

Fixes #34409

[dd32]

For reference, WP_Session_Tokens->create() calls wp_generate_password( 43 ) which calls random_int() 43 times, which if it's taking >1s is easy to hit timeouts for.

[dd32]

In 35600:

Update random_compat to master.
Clarifies strings, Merges [35587] upstream.
See #34409, #28633