From 0fe5a64e5645cf7769f9c6408bd349c517f148ca Mon Sep 17 00:00:00 2001
From: Gary Pendergast <pento@git.wordpress.org>
Date: Tue, 21 Apr 2015 05:10:11 +0000
Subject: [PATCH] WPDB: When deciding if a query needs extra sanity checking
 based on collation, we can quickly return if it's a query that will never
 return user data.

Fixes #32029.



git-svn-id: https://develop.svn.wordpress.org/trunk@32232 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-includes/wp-db.php          | 14 +++++++++++++-
 tests/phpunit/tests/db/charset.php | 13 ++++++++++++-
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/src/wp-includes/wp-db.php b/src/wp-includes/wp-db.php
index cdb9eda8c8..7dd81b89cc 100644
--- a/src/wp-includes/wp-db.php
+++ b/src/wp-includes/wp-db.php
@@ -2399,20 +2399,32 @@ class wpdb {
 			return true;
 		}
 
+		// We don't need to check the collation for queries that don't read data.
+		$query = ltrim( $query, "\r\n\t (" );
+		if ( preg_match( '/^(?:SHOW|DESCRIBE|DESC|EXPLAIN)\s/i', $query ) ) {
+			return true;
+		}
+
 		$table = $this->get_table_from_query( $query );
 		if ( ! $table ) {
 			return false;
 		}
 
 		$this->checking_collation = true;
-		$this->get_table_charset( $table );
+		$collation = $this->get_table_charset( $table );
 		$this->checking_collation = false;
 
+		// Tables with no collation, or latin1 only, don't need extra checking.
+		if ( false === $collation || 'latin1' === $collation ) {
+			return true;
+		}
+
 		$table = strtolower( $table );
 		if ( empty( $this->col_meta[ $table ] ) ) {
 			return false;
 		}
 
+		// If any of the columns don't have one of these collations, it needs more sanity checking.
 		foreach( $this->col_meta[ $table ] as $col ) {
 			if ( empty( $col->Collation ) ) {
 				continue;
diff --git a/tests/phpunit/tests/db/charset.php b/tests/phpunit/tests/db/charset.php
index dc5f428917..d55c750c66 100755
--- a/tests/phpunit/tests/db/charset.php
+++ b/tests/phpunit/tests/db/charset.php
@@ -505,6 +505,12 @@ class Tests_DB_Charset extends WP_UnitTestCase {
 			$value[0] = "CREATE TABLE $this_table_name {$value[0]}";
 			$value[2] = "SELECT * FROM $this_table_name";
 			$value[3] = "DROP TABLE IF EXISTS $this_table_name";
+			$value[4] = array(
+				"SHOW FULL TABLES LIKE $this_table_name",
+				"DESCRIBE $this_table_name",
+				"DESC $this_table_name",
+				"EXPLAIN SELECT * FROM $this_table_name",
+			);
 		}
 		unset( $value );
 
@@ -516,7 +522,7 @@ class Tests_DB_Charset extends WP_UnitTestCase {
 	 * @dataProvider data_table_collation_check
 	 * @ticket 21212
 	 */
-	function test_table_collation_check( $create, $expected, $query, $drop ) {
+	function test_table_collation_check( $create, $expected, $query, $drop, $always_true ) {
 		self::$_wpdb->query( $drop );
 
 		self::$_wpdb->query( $create );
@@ -524,6 +530,11 @@ class Tests_DB_Charset extends WP_UnitTestCase {
 		$return = self::$_wpdb->check_safe_collation( $query );
 		$this->assertEquals( $expected, $return );
 
+		foreach( $always_true as $true_query ) {
+			$return = self::$_wpdb->check_safe_collation( $true_query );
+			$this->assertTrue( $return );
+		}
+
 		self::$_wpdb->query( $drop );
 	}
 }