General: Use functions that are more random to reduce likelihood of UUID collisions.

`mt_rand` produces not fully random numbers which makes it so `wp_generate_uuid4` was more likely to produce a uuid which collides with another uuid it produced. This attempts to make those collisions much less likely.

Since `wp_rand` is a pluggable function, it's not loaded until after plugins have been loaded. In order to make it so this function can still be used early, it falls back first to `random_int`, which will throw an exception if it can't find an appropriate source of randomness, and then to the existing, but flawed, `mt_rand`.

Props johnbillion, peterwilsoncc, westonruter, mukesh27, siliconforks, alexodiy, juanmaguitar, audrasjb, joppuyo, jorbin.
Fixes #59239.


git-svn-id: https://develop.svn.wordpress.org/trunk@62054 602fd350-edb4-49c9-b593-d223f7449a82

Author: aaronjorbin

src/wp-includes/functions.php

@@ -7990,20 +7990,34 @@ function wp_raise_memory_limit( $context = 'admin' ) {
  * Generates a random UUID (version 4).
  *
  * @since 4.7.0
+ * @since 7.0.0 Uses wp_rand if available.
  *
  * @return string UUID.
  */
 function wp_generate_uuid4() {
+	static $backup_randomizer = false;
+	$randomizer               = function_exists( 'wp_rand' ) ? 'wp_rand' : $backup_randomizer;
+
+	if ( false === $randomizer ) {
+		try {
+			random_int( 0, 15705 );
+			$backup_randomizer = 'random_int';
+		} catch ( Exception $e ) {
+			$backup_randomizer = 'mt_rand';
+		}
+		$randomizer = $backup_randomizer;
+	}
+
 	return sprintf(
 		'%04x%04x-%04x-%04x-%04x-%04x%04x%04x',
-		mt_rand( 0, 0xffff ),
-		mt_rand( 0, 0xffff ),
-		mt_rand( 0, 0xffff ),
-		mt_rand( 0, 0x0fff ) | 0x4000,
-		mt_rand( 0, 0x3fff ) | 0x8000,
-		mt_rand( 0, 0xffff ),
-		mt_rand( 0, 0xffff ),
-		mt_rand( 0, 0xffff )
+		$randomizer( 0, 0xffff ),
+		$randomizer( 0, 0xffff ),
+		$randomizer( 0, 0xffff ),
+		$randomizer( 0, 0x0fff ) | 0x4000,
+		$randomizer( 0, 0x3fff ) | 0x8000,
+		$randomizer( 0, 0xffff ),
+		$randomizer( 0, 0xffff ),
+		$randomizer( 0, 0xffff )
 	);
 }