44 lines
1.5 KiB
TypeScript
44 lines
1.5 KiB
TypeScript
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/**
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* Regular expression for safe style values.
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*
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* Quotes (" and ') are allowed, but a check must be done elsewhere to ensure
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* they're balanced.
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*
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* ',' allows multiple values to be assigned to the same property
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* (e.g. background-attachment or font-family) and hence could allow
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* multiple values to get injected, but that should pose no risk of XSS.
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*
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* The rgb() and rgba() expression checks only for XSS safety, not for CSS
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* validity.
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*
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* This regular expression was taken from the Closure sanitization library.
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*/
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const SAFE_STYLE_VALUE = /^([-,."'%_!# a-zA-Z0-9]+|(?:rgb|hsl)a?\([0-9.%, ]+\))$/;
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/**
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* Checks that quotes (" and ') are properly balanced inside a string. Assumes
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* that neither escape (\) nor any other character that could result in
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* breaking out of a string parsing context are allowed;
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* see http://www.w3.org/TR/css3-syntax/#string-token-diagram.
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*
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* This code was taken from the Closure sanitization library.
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*/
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function hasBalancedQuotes(value: string) {
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let outsideSingle = true;
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let outsideDouble = true;
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for (let i = 0; i < value.length; i++) {
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let c = value.charAt(i);
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if (c === '\'' && outsideDouble) {
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outsideSingle = !outsideSingle;
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} else if (c === '"' && outsideSingle) {
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outsideDouble = !outsideDouble;
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}
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}
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return outsideSingle && outsideDouble;
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}
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export function sanitizeStyle(value: string): string {
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if (String(value).match(SAFE_STYLE_VALUE) && hasBalancedQuotes(value)) return value;
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return 'unsafe';
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}
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