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Opt-in to CORS mode for external font stylesheet links #1289

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merged 1 commit into from
Jul 31, 2018
Merged

Opt-in to CORS mode for external font stylesheet links #1289

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12 changes: 12 additions & 0 deletions includes/sanitizers/class-amp-style-sanitizer.php
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Original file line number Diff line number Diff line change
Expand Up @@ -590,6 +590,18 @@ private function process_link_element( DOMElement $element ) {
if ( $href !== $normalized_url ) {
$element->setAttribute( 'href', $normalized_url );
}

/*
* Opt-in to CORS Mode for the stylesheet. This ensures that a service worker caching the external
* stylesheet will not inflate the storage quota.
*
* See:
* - https://developers.google.com/web/tools/workbox/guides/storage-quota#beware_of_opaque_responses
* - https://developers.google.com/web/tools/workbox/guides/handle-third-party-requests#cross-origin_requests_and_opaque_responses
*/
if ( ! $element->hasAttribute( 'crossorigin' ) ) {
$element->setAttribute( 'crossorigin', 'anonymous' );
}
return;
}

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25 changes: 25 additions & 0 deletions tests/test-amp-style-sanitizer.php
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Original file line number Diff line number Diff line change
Expand Up @@ -1186,11 +1186,36 @@ public function test_font_urls( $url, $error_codes ) {
preg_replace( '#^(http:)?(?=//)#', 'https:', $url ),
$link->getAttribute( 'href' )
);
$this->assertEquals( 'anonymous', $link->getAttribute( 'crossorigin' ) );
} else {
$this->assertEmpty( $link );
}
}

/**
* Test addition of crossorigin attribute to external stylesheet links.
*
* @covers AMP_Style_Sanitizer::process_link_element()
*/
public function test_cors_enabled_stylesheet_url() {

// Test supplying crossorigin attribute.
$document = AMP_DOM_Utils::get_dom( '<html><head><link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Tangerine"></head></html>' ); // phpcs:ignore WordPress.WP.EnqueuedResources.NonEnqueuedStylesheet
$sanitizer = new AMP_Style_Sanitizer( $document, array( 'use_document_element' => true ) );
$sanitizer->sanitize();
$link = $document->getElementsByTagName( 'link' )->item( 0 );
$this->assertInstanceOf( 'DOMElement', $link );
$this->assertEquals( 'anonymous', $link->getAttribute( 'crossorigin' ) );

// Test that existing crossorigin attribute is not overridden.
$document = AMP_DOM_Utils::get_dom( '<html><head><link rel="stylesheet" crossorigin="use-credentials" href="https://fonts.googleapis.com/css?family=Tangerine"></head></html>' ); // phpcs:ignore WordPress.WP.EnqueuedResources.NonEnqueuedStylesheet
$sanitizer = new AMP_Style_Sanitizer( $document, array( 'use_document_element' => true ) );
$sanitizer->sanitize();
$link = $document->getElementsByTagName( 'link' )->item( 0 );
$this->assertInstanceOf( 'DOMElement', $link );
$this->assertEquals( 'use-credentials', $link->getAttribute( 'crossorigin' ) );
}

/**
* Test CSS imports.
*
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