Changeset 43781

Timestamp:

10/22/2018 04:03:07 AM (6 years ago)

Author:

pento

Message:

KSES: Allow url() to be used in inline CSS.

The cover image block uses the url() function in its inline CSS, to show the cover image. KSES didn't allow this, causing the block to not save correctly for Author and Contributor users. As KSES does already check each attribute name against an allowed list, we're able to add an extra check for certain attributes to be able to use the url() function, too.

Props peterwilsoncc, azaozz, pento, dd32.
See #45067.

Location:

branches/5.0

Files:

• src/wp-includes/kses.php (modified) (4 diffs)
• tests/phpunit/tests/kses.php (modified) (1 diff)
• tests/phpunit/tests/shortcode.php (modified) (1 diff)

branches/5.0/src/wp-includes/kses.php

@@ -1708 +1708 @@
  */
 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 ) );
@@ -1725 +1725 @@
      * @since 4.4.0 Added support for `min-height`, `max-height`, `min-width`, and `max-width`.
      * @since 4.6.0 Added support for `list-style-type`.
+     * @since 5.0.0 Added support for `background-image`.
      *
      * @param array $attr List of allowed CSS attributes.
@@ -1731 +1732 @@
         'background',
         'background-color',
+        'background-image',
 
         'border',
@@ -1799 +1801 @@
     ) );
 
-    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 ) {
-            if( $css != '' )
+
+        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 );
+
+                if ( empty( $url_pieces[2] ) ) {
+                    $found = false;
+                    break;
+                }
+
+                $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 );
+                }
+            }
+        }
+
+        // Remove any CSS containing containing \ ( & } = or comments, except for url() useage checked above.
+        if ( $found && ! preg_match( '%[\\\(&=}]|/\*%', $css_test_string ) ) {
+            if ( $css != '' ) {
                 $css .= ';';
+            }
+
             $css .= $css_item;
         }

branches/5.0/tests/phpunit/tests/kses.php

@@ -814 +814 @@
         );
     }
+
+    /**
+     * 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();',
+                '',
+            ),
+
+            // Malformed, no closing `)`.
+            array(
+                'background-image: url( "http://example.com" ;',
+                '',
+            ),
+
+            // Malformed, no closing `"`.
+            array(
+                'background-image: url( "http://example.com );',
+                '',
+            ),
+        );
+    }
 }

branches/5.0/tests/phpunit/tests/shortcode.php

@@ -493 +493 @@
             ),
             array(
-                '<div style="background:url([[gallery]])">',
-                '<div style="background:url([[gallery]])">',
+                '<div style="selector:url([[gallery]])">',
+                '<div style="selector:url([[gallery]])">',
             ),
             array(