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<?php |
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|
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/** |
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* @copyright © Melograno Venture Studio. All rights reserved. |
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* @licence See COPYING.md for license details. |
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*/ |
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|
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namespace IvyForms\Common\Sanitizer; |
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|
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class CssSanitizer |
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{ |
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/** |
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* Patterns matched per declaration (not whole style string — `;` separates declarations). |
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* |
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* @return array<int, string> |
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*/ |
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private static function declarationDangerousPatterns(): array |
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{ |
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return [ |
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'/expression\s*\(/i', |
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'/javascript\s*:/i', |
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'/vbscript\s*:/i', |
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'/<\s*script/i', |
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'/on\w+\s*=/i', |
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'/import\s+/i', |
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'/<!--/i', |
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'/-->/i', |
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'/behavior\s*:/i', |
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'/-moz-binding\s*:/i', |
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'/\{/', |
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'/\}/', |
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'/\/\*/', |
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'/\*\//', |
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'/\\\\/i', |
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]; |
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} |
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|
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private static function logBlockedDeclaration(string $declaration, string $pattern): void |
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{ |
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$cssHash = substr(hash('sha256', $declaration), 0, 12); |
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error_log( |
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'🚨 BLOCKED dangerous CSS declaration' . |
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' | pattern=' . $pattern . |
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' | css_hash=' . $cssHash . |
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' | css_len=' . strlen($declaration) |
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); |
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} |
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|
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private static function isDangerousCssDeclaration(string $declaration): bool |
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{ |
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foreach (self::declarationDangerousPatterns() as $pattern) { |
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if (preg_match($pattern, $declaration)) { |
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self::logBlockedDeclaration($declaration, $pattern); |
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return true; |
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} |
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} |
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|
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return false; |
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} |
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|
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/** |
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* @param array<int, string> $matches |
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*/ |
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private static function rewriteSingleCssUrlMatch(array $matches): string |
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{ |
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$url = trim($matches[1]); |
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|
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if (preg_match('/[;{}]|\/\*|\*\//', $url)) { |
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$urlHash = substr(hash('sha256', $url), 0, 12); |
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error_log( |
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'🚨 BLOCKED unsafe CSS url() rule fired' . |
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' | rule=declaration_breaking_tokens' . |
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' | url_hash=' . $urlHash . |
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' | url_len=' . strlen($url) |
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); |
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return ''; |
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} |
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|
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if (preg_match('/^(https?:|data:image\/)/i', $url)) { |
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return 'url("' . esc_url_raw($url) . '")'; |
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} |
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|
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$urlHash = substr(hash('sha256', $url), 0, 12); |
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error_log( |
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'🚨 BLOCKED unsafe CSS url() rule fired' . |
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' | rule=allowed_url_protocol' . |
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' | url_hash=' . $urlHash . |
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' | url_len=' . strlen($url) |
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); |
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|
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return ''; |
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} |
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|
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private static function rewriteUrlFunctionsInDeclaration(string $declaration): string |
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{ |
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$out = preg_replace_callback( |
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'/url\s*\(\s*["\']?([^"\')]+)["\']?\s*\)/i', |
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/** |
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* Explicit call so PHPMD counts `rewriteSingleCssUrlMatch` as used (callable array is not traced). |
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* |
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* @param array<int, string> $matches |
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*/ |
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static function (array $matches): string { |
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return self::rewriteSingleCssUrlMatch($matches); |
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}, |
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$declaration |
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); |
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|
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return $out === null ? '' : trim((string) $out); |
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} |
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|
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/** |
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* Sanitize CSS value to prevent XSS attacks while allowing safe color/function values. |
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* |
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* After structural checks and `url()` handling, the result is passed through `esc_attr()` |
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* so it is safe to embed in double-quoted HTML `style` attributes (matches legacy behavior). |
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* |
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* @param string $css Raw inline style declaration string. |
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* |
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* @return string Safe for use inside `style="..."`. |
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*/ |
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public static function sanitizeCssValue(string $css): string |
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{ |
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$sanitizedDeclarations = self::sanitizeCssDeclarationList($css); |
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if ($sanitizedDeclarations === '') { |
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return ''; |
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} |
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|
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return esc_attr($sanitizedDeclarations); |
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} |
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|
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/** |
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* Sanitize a semicolon-separated declaration list for use inside a stylesheet rule block. |
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* |
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* Unlike sanitizeCssValue(), this returns raw CSS (not HTML-escaped) so it can be injected |
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* into a <style> tag safely after declaration-level sanitization. |
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* |
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* @param string $css Raw CSS declaration list. |
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* @return string |
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*/ |
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public static function sanitizeCssDeclarationList(string $css): string |
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{ |
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$css = trim($css); |
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if ($css === '') { |
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return ''; |
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} |
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|
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$safeDeclarations = []; |
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foreach (explode(';', $css) as $chunk) { |
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$declaration = trim($chunk); |
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if ($declaration === '') { |
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continue; |
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} |
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if (self::isDangerousCssDeclaration($declaration)) { |
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continue; |
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} |
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$sanitized = self::rewriteUrlFunctionsInDeclaration($declaration); |
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if ($sanitized !== '') { |
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$safeDeclarations[] = $sanitized; |
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} |
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} |
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|
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if ($safeDeclarations === []) { |
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return ''; |
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} |
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|
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return implode('; ', $safeDeclarations); |
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} |
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|
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/** |
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* Sanitize a single CSS class name. |
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* |
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* @param mixed $value |
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* @return string |
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*/ |
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public static function sanitizeCssClass($value): string |
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{ |
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if (!is_string($value)) { |
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return ''; |
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} |
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|
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return sanitize_html_class($value); |
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} |
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|
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/** |
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* Sanitize a comma-separated list of CSS classes. |
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* |
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* @param mixed $value |
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* @return string |
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*/ |
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public static function sanitizeCssClassList($value): string |
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{ |
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if (!is_string($value)) { |
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return ''; |
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} |
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|
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$parts = preg_split('/[,\s]+/', $value) ?: []; |
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$uniqueClasses = []; |
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|
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foreach ($parts as $part) { |
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$sanitized = sanitize_html_class($part); |
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if ($sanitized !== '') { |
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$uniqueClasses[$sanitized] = true; |
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} |
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} |
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return implode(', ', array_keys($uniqueClasses)); |
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} |
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|
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/** |
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* Sanitize CSS unit value (px, rem, em, %, etc.) |
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* |
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* @param string $value |
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* @return string |
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*/ |
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public static function sanitizeCssUnit(string $value): string |
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{ |
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if (preg_match('/^-?[0-9.]+(?:px|rem|em|%|vh|vw|pt)?$/i', trim($value))) { |
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return sanitize_text_field($value); |
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} |
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|
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return ''; |
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} |
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|
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/** |
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* Sanitize a CSS length or the keyword "auto" (e.g. width / height). |
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* |
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* @param string $value |
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* @return string |
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*/ |
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public static function sanitizeCssUnitOrAuto(string $value): string |
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{ |
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$trimmed = trim($value); |
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if ('' === $trimmed) { |
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return ''; |
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} |
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if (preg_match('/^auto$/i', $trimmed)) { |
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return 'auto'; |
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} |
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return self::sanitizeCssUnit($trimmed); |
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} |
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|
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/** |
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* @return array<int, string> |
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*/ |
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private static function strictColorFunctionPatterns(): array |
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{ |
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return [ |
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'/^rgba?\([0-9,.\s%]+\)$/i', |
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'/^hsla?\([\d\s.,%\/-]+\)$/i', |
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'/^hwb\([\d\s.,%\/-]+\)$/i', |
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'/^var\(--[-\w]+\)$/i', |
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]; |
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} |
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|
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private static function matchStrictHexColor(string $color): ?string |
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{ |
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if (!preg_match('/^#([a-f0-9]{3}|[a-f0-9]{6}|[a-f0-9]{8})$/i', $color)) { |
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return null; |
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} |
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|
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return strlen($color) === 9 ? strtolower($color) : $color; |
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} |
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|
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private static function matchStrictFunctionColor(string $color): ?string |
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{ |
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foreach (self::strictColorFunctionPatterns() as $pattern) { |
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if (preg_match($pattern, $color)) { |
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return sanitize_text_field($color); |
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} |
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} |
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return null; |
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} |
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|
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private static function matchStrictNamedColor(string $color): ?string |
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{ |
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if (!preg_match('/^[a-z]+$/i', $color) || strlen($color) > 20) { |
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return null; |
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} |
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return sanitize_text_field($color); |
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} |
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|
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private static function matchKnownStrictColorFormat(string $color): ?string |
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{ |
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if (strcasecmp($color, 'transparent') === 0) { |
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return 'transparent'; |
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} |
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|
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$hexColor = self::matchStrictHexColor($color); |
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if ($hexColor !== null) { |
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return $hexColor; |
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} |
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|
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$functionColor = self::matchStrictFunctionColor($color); |
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if ($functionColor !== null) { |
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return $functionColor; |
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} |
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|
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return self::matchStrictNamedColor($color); |
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} |
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|
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/** |
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* Sanitize color value for advanced style settings — rejects values unsafe for CSS output. |
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* |
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* @param string $color |
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* @return string |
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*/ |
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public static function sanitizeStrictColor(string $color): string |
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{ |
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$color = trim($color); |
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if ($color === '') { |
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return ''; |
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} |
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|
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return self::matchKnownStrictColorFormat($color) ?? ''; |
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} |
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} |
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|
