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feat: improve default html sanitizer (fix #733) #1010

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Jun 3, 2020
Merged

feat: improve default html sanitizer (fix #733) #1010

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4a68b06
feat: improve default html sanitizer (fix #733)
seonim-ryu May 29, 2020
91f8421
feat: apply code review
seonim-ryu Jun 3, 2020
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19 changes: 0 additions & 19 deletions apps/editor/src/js/convertor.js
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Original file line number Diff line number Diff line change
Expand Up @@ -51,8 +51,6 @@ class Convertor {
* @private
*/
_markdownToHtmlWithCodeHighlight(markdown) {
markdown = this._replaceImgAttrToDataProp(markdown);

return this.renderHTML(this.mdReader.parse(markdown));
}

Expand All @@ -68,27 +66,10 @@ class Convertor {
markdown = markdown.replace(HTML_TAG_RX, (match, $1, $2, $3) =>
match[0] !== '\\' ? `${$1}${$2} data-tomark-pass ${$3}` : match
);
markdown = this._replaceImgAttrToDataProp(markdown);

return this.renderHTML(this.mdReader.parse(markdown));
}

/**
* Replace 'onerror' attribute of img tag to data property string
* @param {string} markdown markdown text
* @returns {string} replaced markdown text
* @private
*/
_replaceImgAttrToDataProp(markdown) {
const onerrorStripeRegex = /(<img[^>]*)(onerror\s*=\s*[\\"']?[^\\"']*[\\"']?)(.*)/i;

while (onerrorStripeRegex.exec(markdown)) {
markdown = markdown.replace(onerrorStripeRegex, '$1$3');
}

return markdown;
}

/**
* Remove BR's data-tomark-pass attribute text when br in code element
* @param {string} renderedHTML Rendered HTML string from markdown editor
Expand Down
88 changes: 44 additions & 44 deletions apps/editor/src/js/htmlSanitizer.js
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Expand Up @@ -36,15 +36,14 @@ const SVG_ATTR_LIST_RX = new RegExp(
'g'
);

const ATTR_VALUE_BLACK_LIST_RX = {
href: /^(javascript:).*/g
};
const XSS_ATTR_RX = /href|src|background/gi;
const XSS_VALUE_RX = /((java|vb|live)script|x):/gi;

/**
* htmlSanitizer
* @param {string|Node} html html or Node
* @param {boolean} [needHtmlText] pass true if need html text
* @returns {string|DocumentFragment} result
* @param {string|Node} html - html or Node
* @param {boolean} [needHtmlText] - pass true if need html text
* @returns {string|DocumentFragment} - result
* @ignore
*/
function htmlSanitizer(html, needHtmlText) {
Expand All @@ -59,20 +58,19 @@ function htmlSanitizer(html, needHtmlText) {

removeUnnecessaryTags(root);
leaveOnlyWhitelistAttribute(root);
removeInvalidAttributeValues(root);

return domUtils.finalizeHtml(root, needHtmlText);
}

/**
* Remove unnecessary tags
* Removes unnecessary tags.
* @param {HTMLElement} html - root element
* @private
* @param {HTMLElement} html root element
*/
function removeUnnecessaryTags(html) {
const removedTags = domUtils.findAll(
html,
'script, iframe, textarea, form, button, select, meta, style, link, title, embed, object, details, summary'
'script, iframe, textarea, form, button, select, input, meta, style, link, title, embed, object, details, summary'
);

removedTags.forEach(node => {
Expand All @@ -81,49 +79,51 @@ function removeUnnecessaryTags(html) {
}

/**
* Leave only white list attributes
* Checks whether the attribute and value that causing XSS or not.
* @param {string} attrName - name of attribute
* @param {string} attrValue - value of attirbute
* @param {boolean} state
* @private
* @param {HTMLElement} html root element
*/
function leaveOnlyWhitelistAttribute(html) {
domUtils.findAll(html, '*').forEach(node => {
const attrs = node.attributes;
const blacklist = toArray(attrs).filter(attr => {
const isHTMLAttr = attr.name.match(HTML_ATTR_LIST_RX);
const isSVGAttr = attr.name.match(SVG_ATTR_LIST_RX);

return !isHTMLAttr && !isSVGAttr;
});
function isXSSAttribute(attrName, attrValue) {
return attrName.match(XSS_ATTR_RX) && attrValue.match(XSS_VALUE_RX);
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}

toArray(blacklist).forEach(attr => {
// Edge svg attribute name returns uppercase bug. error guard.
// https://developer.microsoft.com/en-us/microsoft-edge/platform/issues/5579311/
if (attrs.getNamedItem(attr.name)) {
attrs.removeNamedItem(attr.name);
}
});
/**
* Removes attributes of blacklist.
* @param {NamedNodeMap} nodeAttrs - all attributes of node
* @param {NamedNodeMap} blacklistAttrs - attributes of blacklist
* @private
*/
function removeBlacklistAttributes(nodeAttrs, blacklistAttrs) {
toArray(blacklistAttrs).forEach(({ name }) => {
// Edge svg attribute name returns uppercase bug. error guard.
// https://developer.microsoft.com/en-us/microsoft-edge/platform/issues/5579311/
if (nodeAttrs.getNamedItem(name)) {
nodeAttrs.removeNamedItem(name);
}
});
}

/**
* Remove invalid attribute values
* Leaves only white list attributes.
* @param {HTMLElement} html - root element
* @private
* @param {HTMLElement} html root element
*/
function removeInvalidAttributeValues(html) {
for (const attr in ATTR_VALUE_BLACK_LIST_RX) {
if (ATTR_VALUE_BLACK_LIST_RX.hasOwnProperty(attr)) {
domUtils.findAll(html, `[${attr}]`).forEach(node => {
const attrs = node.attributes;
const valueBlackListRX = ATTR_VALUE_BLACK_LIST_RX[attr];
const attrItem = attrs.getNamedItem(attr);

if (valueBlackListRX && attrItem && attrItem.value.toLowerCase().match(valueBlackListRX)) {
attrs.removeNamedItem(attr);
}
});
}
}
function leaveOnlyWhitelistAttribute(html) {
domUtils.findAll(html, '*').forEach(node => {
const { attributes } = node;
const blacklist = toArray(attributes).filter(attr => {
const { name, value } = attr;
const htmlAttr = name.match(HTML_ATTR_LIST_RX);
const svgAttr = name.match(SVG_ATTR_LIST_RX);
const xssAttr = htmlAttr && isXSSAttribute(name, value);

return (!htmlAttr && !svgAttr) || xssAttr;
});

removeBlacklistAttributes(attributes, blacklist);
});
}

export default htmlSanitizer;
69 changes: 52 additions & 17 deletions apps/editor/test/unit/htmlSanitizer.spec.js
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Original file line number Diff line number Diff line change
Expand Up @@ -8,18 +8,19 @@ import htmlSanitizer from '@/htmlSanitizer';

describe('htmlSanitizer', function() {
describe('tags', function() {
it('Remove unnecessary tags', function() {
it('removes unnecessary tags', function() {
expect(htmlSanitizer('<script>alert("test");</script>', true)).toBe('');
expect(htmlSanitizer('<embed>child alive</embed>', true)).toBe('child alive');
expect(htmlSanitizer('<object>child die</object>', true)).toBe('');
expect(htmlSanitizer('<details><summary>foo</summary></details>', true)).toBe('');
expect(htmlSanitizer('<input type="image" />', true)).toBe('');
});
});

describe('attributes', () => {
it('Remove all attritube but white list', () => {
it('removes all attritube but white list', () => {
const html =
'<img style="display:inline" class="V" title="V" data-custom="V" src="http://www.nhn.com/renewal/img/ci_nhn.png" onload="dd=1" />';
'<img style="display:inline" class="V" title="V" data-custom="V" src="http://www.nhn.com/renewal/img/ci_nhn.png" onload="dd=1" onerror="javascript:alert();"/>';
const dom = htmlSanitizer(html);

const $img = $(dom).find('img');
Expand All @@ -31,9 +32,10 @@ describe('htmlSanitizer', function() {
expect($img.attr('data-custom')).toBeTruthy();

expect($img.attr('onload')).not.toBeDefined();
expect($img.attr('onerror')).not.toBeDefined();
});

it('Leave svg attributes', function() {
it('leaves svg attributes', () => {
const html =
'<svg width="100" height="100"><circle cx="50" cy="50" r="40" stroke="green" stroke-width="4" fill="yellow" /></svg>';
const dom = htmlSanitizer(html);
Expand All @@ -47,19 +49,52 @@ describe('htmlSanitizer', function() {
expect($circle.attr('fill')).toBeTruthy();
});

it('Remove attributes with invalid value', function() {
expect(htmlSanitizer('<a href="javascript:alert();">xss</a>', true)).toBe('<a>xss</a>');
expect(htmlSanitizer('<a href="JaVaScRiPt:alert();">xss</a>', true)).toBe('<a>xss</a>');
expect(htmlSanitizer('<a href="#">benign</a>', true)).toBe('<a href="#">benign</a>');
expect(htmlSanitizer('<a href="http://example.com">http</a>', true)).toBe(
'<a href="http://example.com">http</a>'
);
expect(htmlSanitizer('<a href="https://example.com">https</a>', true)).toBe(
'<a href="https://example.com">https</a>'
);
expect(htmlSanitizer('<a href="ftp://example.com">ftp</a>', true)).toBe(
'<a href="ftp://example.com">ftp</a>'
);
describe('removes attributes with invalid value including xss script', () => {
it('table', () => {
expect(htmlSanitizer(`<TABLE BACKGROUND="javascript:alert('XSS')">`, true)).toBe(
'<table></table>'
);
expect(htmlSanitizer(`<TABLE><TD BACKGROUND="javascript:alert('XSS')">`, true)).toBe(
'<table><tbody><tr><td></td></tr></tbody></table>'
);
});

it('href attribute with a tag', () => {
expect(htmlSanitizer('<a href="javascript:alert();">xss</a>', true)).toBe('<a>xss</a>');
expect(htmlSanitizer('<a href=" JaVaScRiPt: alert();">xss</a>', true)).toBe('<a>xss</a>');
expect(htmlSanitizer('<a href="vbscript:alert();">xss</a>', true)).toBe('<a>xss</a>');
expect(htmlSanitizer('<a href=" VBscript: alert(); ">xss</a>', true)).toBe('<a>xss</a>');
expect(htmlSanitizer('<a href="livescript:alert();">xss</a>', true)).toBe('<a>xss</a>');
expect(htmlSanitizer('<a href=" LIVEScript: alert() ;">xss</a>', true)).toBe('<a>xss</a>');
expect(htmlSanitizer(`123<a href=' javascript:alert();'>xss</a>`, true)).toBe(
'123<a>xss</a>'
);
expect(htmlSanitizer(`<a href='javas<!-- -->cript:alert()'>xss</a>`, true)).toBe(
'<a>xss</a>'
);
});

it('src attribute with img tag', () => {
expect(htmlSanitizer('<img src="javascript:alert();">', true)).toBe('<img>');
expect(htmlSanitizer('<img src=" JaVaScRiPt: alert();">', true)).toBe('<img>');
expect(htmlSanitizer('<img src="vbscript:alert();">', true)).toBe('<img>');
expect(htmlSanitizer('<img src=" VBscript: alert(); ">', true)).toBe('<img>');
expect(htmlSanitizer('<img src=" LIVEScript: alert() ;">', true)).toBe('<img>');
expect(htmlSanitizer('<img src="java<!-- -->script:alert();">', true)).toBe('<img>');
});

it('src and onerror attribute with img tag', () => {
expect(
htmlSanitizer(
'<img src = x onerror = "javascript: window.onerror = alert; throw XSS">',
true
)
).toBe('<img src="x">');
expect(htmlSanitizer('"><img src="x:x" onerror="alert(XSS)">', true)).toBe('"&gt;<img>');
expect(htmlSanitizer('<img src=x:alert(alt) onerror=eval(src) alt=0>', true)).toBe(
'<img alt="0">'
);
});
});
});
});