HackMD/public/js/render.js

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/* eslint-env browser, jquery */
/* global filterXSS */
// allow some attributes
var whiteListAttr = ['id', 'class', 'style']
window.whiteListAttr = whiteListAttr
// allow link starts with '.', '/' and custom protocol with '://', exclude link starts with javascript://
var linkRegex = /^(?!javascript:\/\/)([\w|-]+:\/\/)|^([.|/])+/i
// allow data uri, from https://gist.github.com/bgrins/6194623
var dataUriRegex = /^\s*data:([a-z]+\/[a-z0-9-+.]+(;[a-z-]+=[a-z0-9-]+)?)?(;base64)?,([a-z0-9!$&',()*+;=\-._~:@/?%\s]*)\s*$/i
// custom white list
var whiteList = filterXSS.whiteList
// allow ol specify start number
whiteList['ol'] = ['start']
// allow li specify value number
whiteList['li'] = ['value']
// allow style tag
whiteList['style'] = []
// allow kbd tag
whiteList['kbd'] = []
// allow ifram tag with some safe attributes
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whiteList['iframe'] = ['allowfullscreen', 'name', 'referrerpolicy', 'sandbox', 'src', 'width', 'height']
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// allow summary tag
whiteList['summary'] = []
var filterXSSOptions = {
allowCommentTag: true,
whiteList: whiteList,
escapeHtml: function (html) {
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// allow html comment in multiple lines
return html.replace(/<(?!!--)/g, '&lt;').replace(/-->/g, '__HTML_COMMENT_END__').replace(/>/g, '&gt;').replace(/__HTML_COMMENT_END__/g, '-->')
},
onIgnoreTag: function (tag, html, options) {
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// allow comment tag
if (tag === '!--') {
// do not filter its attributes
return html
}
},
onTagAttr: function (tag, name, value, isWhiteAttr) {
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// allow href and src that match linkRegex
if (isWhiteAttr && (name === 'href' || name === 'src') && linkRegex.test(value)) {
return name + '="' + filterXSS.escapeAttrValue(value) + '"'
}
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// allow data uri in img src
if (isWhiteAttr && (tag === 'img' && name === 'src') && dataUriRegex.test(value)) {
return name + '="' + filterXSS.escapeAttrValue(value) + '"'
}
},
onIgnoreTagAttr: function (tag, name, value, isWhiteAttr) {
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// allow attr start with 'data-' or in the whiteListAttr
if (name.substr(0, 5) === 'data-' || window.whiteListAttr.indexOf(name) !== -1) {
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// escape its value using built-in escapeAttrValue function
return name + '="' + filterXSS.escapeAttrValue(value) + '"'
}
}
}
function preventXSS (html) {
return filterXSS(html, filterXSSOptions)
}
window.preventXSS = preventXSS
module.exports = {
preventXSS: preventXSS
}