Ticket #45067: 45067.5.diff

src/wp-includes/kses.php

@@ -1687 +1687 @@
  * @return string            Filtered string of CSS rules.
  */
 function safecss_filter_attr( $css, $deprecated = '' ) {
-        if ( !empty( $deprecated ) )
+        if ( ! empty( $deprecated ) )
                 _deprecated_argument( __FUNCTION__, '2.8.1' ); // Never implemented
 
-        $css = wp_kses_no_null($css);
-        $css = str_replace(array("\n","\r","\t"), '', $css);
-
-        if ( preg_match( '%[\\\\(&=}]|/\*%', $css ) ) // remove any inline css containing \ ( & } = or comments
-                return '';
+        $css = wp_kses_no_null( $css );
+        $css = str_replace( array( "\n", "\r", "\t" ), '', $css );
+        $allowed_protocols = wp_allowed_protocols();
 
         $css_array = explode( ';', trim( $css ) );
 
@@ -1710 +1708 @@
         $allowed_attr = apply_filters( 'safe_style_css', array(
                 'background',
                 'background-color',
+                'background-image',
 
                 'border',
                 'border-width',
@@ -1778 +1777 @@
                 'list-style-type',
         ) );
 
-        if ( empty($allowed_attr) )
+
+        /*
+         * CSS attributes that accept URL data types.
+         *
+         * This is in accordance to the CSS spec and unrelated to
+         * the sub-set of supported attributes above.
+         *
+         * See: https://developer.mozilla.org/en-US/docs/Web/CSS/url
+         */
+        $css_url_data_types = array(
+                'background',
+                'background-image',
+
+                'cursor',
+
+                'list-style',
+                'list-style-image',
+        );
+
+        if ( empty( $allowed_attr ) ) {
                 return $css;
+        }
 
         $css = '';
         foreach ( $css_array as $css_item ) {
-                if ( $css_item == '' )
+                if ( $css_item == '' ) {
                         continue;
-                $css_item = trim( $css_item );
-                $found = false;
+                }
+
+                $css_item        = trim( $css_item );
+                $css_test_string = $css_item;
+                $found           = false;
+                $url_attr        = false;
+
                 if ( strpos( $css_item, ':' ) === false ) {
                         $found = true;
                 } else {
-                        $parts = explode( ':', $css_item );
-                        if ( in_array( trim( $parts[0] ), $allowed_attr ) )
+                        $parts = explode( ':', $css_item, 2 );
+                        $css_selector = trim( $parts[0] );
+
+                        if ( in_array( $css_selector, $allowed_attr, true ) ) {
                                 $found = true;
+                                $url_attr = in_array( $css_selector, $css_url_data_types, true );
+                        }
+                }
+
+                if ( $found && $url_attr ) {
+                        // Simplified: matches the sequence `url(*)`.
+                        preg_match_all( '/url\([^)]+\)/', $parts[1], $url_matches );
+
+                        foreach ( $url_matches[0] as $url_match ) {
+                                // Clean up the URL from each of the matches above.
+                                preg_match( '/^url\(\s*([\'\"]?)(.*)(\g1)\s*\)$/', $url_match, $url_pieces );
+                                $url = trim( $url_pieces[2] );
+
+                                if ( empty( $url ) || $url !== wp_kses_bad_protocol( $url, $allowed_protocols ) ) {
+                                        $found = false;
+                                        break;
+                                } else {
+                                        // Remove the whole `url(*)` bit that was matched above from the CSS.
+                                        $css_test_string = str_replace( $url_match, '', $css_test_string );
+                                }
+                        }
                 }
-                if ( $found ) {
-                        if( $css != '' )
+
+                if ( $found && ! preg_match( '%[\\\(&=}]|/\*%', $css_test_string ) ) {
+                        if ( $css != '' ) {
                                 $css .= ';';
+                        }
+
                         $css .= $css_item;
                 }
         }

tests/phpunit/tests/kses.php

@@ -718 +718 @@
 
                 $this->assertEquals( "<{$element}>", wp_kses_attr( $element, $attribute, array( 'foo' => false ), array() ) );
         }
+
+        /**
+         * Test URL sanitization in the style tag.
+         *
+         * @dataProvider data_kses_style_attr_with_url
+         *
+         * @ticket 45067
+         *
+         * @param $input string The style attribute saved in the editor.
+         * @param $expected string The sanitized style attribute.
+         */
+        function test_kses_style_attr_with_url( $input, $expected ) {
+                $actual = safecss_filter_attr( $input );
+
+                $this->assertSame( $expected, $actual );
+        }
+
+        /**
+         * Data provider testing style attribute sanitization.
+         *
+         * @return array Nested array of input, expected pairs.
+         */
+        function data_kses_style_attr_with_url() {
+                return array(
+                        /*
+                         * Valid use cases.
+                         */
+
+                        // Double quotes.
+                        array(
+                                'background-image: url( "http://example.com/valid.gif" );',
+                                'background-image: url( "http://example.com/valid.gif" )',
+                        ),
+
+                        // Single quotes.
+                        array(
+                                "background-image: url( 'http://example.com/valid.gif' );",
+                                "background-image: url( 'http://example.com/valid.gif' )",
+                        ),
+
+                        // No quotes.
+                        array(
+                                'background-image: url( http://example.com/valid.gif );',
+                                'background-image: url( http://example.com/valid.gif )',
+                        ),
+
+                        // Single quotes, extra spaces.
+                        array(
+                                "background-image: url( '  http://example.com/valid.gif ' );",
+                                "background-image: url( '  http://example.com/valid.gif ' )",
+                        ),
+
+                        // Line breaks, single quotes.
+                        array(
+                                "background-image: url(\n'http://example.com/valid.gif' );",
+                                "background-image: url('http://example.com/valid.gif' )",
+                        ),
+
+                        // Tabs not spaces, single quotes.
+                        array(
+                                "background-image: url(\t'http://example.com/valid.gif'\t\t);",
+                                "background-image: url('http://example.com/valid.gif')",
+                        ),
+
+                        // Single quotes, absolute path.
+                        array(
+                                "background: url('/valid.gif');",
+                                "background: url('/valid.gif')",
+                        ),
+
+                        // Single quotes, relative path.
+                        array(
+                                "background: url('../wp-content/uploads/2018/10/valid.gif');",
+                                "background: url('../wp-content/uploads/2018/10/valid.gif')",
+                        ),
+
+                        // Error check: valid property not containing a URL.
+                        array(
+                                "background: red",
+                                "background: red",
+                        ),
+
+                        /*
+                         * Invalid use cases.
+                         */
+
+                        // Attribute doesn't support URL properties.
+                        array(
+                                'color: url( "http://example.com/invalid.gif" );',
+                                '',
+                        ),
+
+                        // Mismatched quotes.
+                        array(
+                                'background-image: url( "http://example.com/valid.gif\' );',
+                                '',
+                        ),
+
+                        // Bad protocol, double quotes.
+                        array(
+                                'background-image: url( "bad://example.com/invalid.gif" );',
+                                '',
+                        ),
+
+                        // Bad protocol, single quotes.
+                        array(
+                                "background-image: url( 'bad://example.com/invalid.gif' );",
+                                '',
+                        ),
+
+                        // Bad protocol, single quotes.
+                        array(
+                                "background-image: url( 'bad://example.com/invalid.gif' );",
+                                '',
+                        ),
+
+                        // Bad protocol, single quotes, strange spacing.
+                        array(
+                                "background-image: url( '  \tbad://example.com/invalid.gif ' );",
+                                '',
+                        ),
+
+                        // Bad protocol, no quotes.
+                        array(
+                                'background-image: url( bad://example.com/invalid.gif );',
+                                '',
+                        ),
+
+                        // No URL inside url().
+                        array(
+                                'background-image: url();',
+                                '',
+                        ),
+                );
+        }
 }