Fix purify and highlight
- purify: apply target=_blank to links - purify: remove ALLOWED_URI_REGEXP - this breaks external links in anchor elements - purify: return a DOM fragment instead of a string - postprocess: only highlight pre - postprocess: remove nested code inside pre - better style messages with css
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4 changed files with 82 additions and 28 deletions
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@ -2,8 +2,16 @@ const {ElemJS} = require("../basic")
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const {lazyLoad} = require("../lazy-load-module")
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class HighlightedCode extends ElemJS {
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constructor(code) {
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super(code)
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constructor(element) {
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super(element)
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if (this.element.tagName === "PRE" && this.element.children.length === 1 && this.element.children[0].tagName === "CODE") {
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// we shouldn't nest code inside a pre. put the text in the pre directly.
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const code = this.element.children[0]
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this.clearChildren()
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for (const child of code.childNodes) {
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this.element.appendChild(child)
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}
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}
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lazyLoad("./static/hljs.js").then(hljs => hljs.highlightBlock(this.element))
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}
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}
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@ -12,61 +12,80 @@ purifier.addHook("uponSanitizeAttribute", (node, hookevent, config) => {
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const allowedElementAttributes = {
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"FONT": ["data-mx-bg-color", "data-mx-color", "color"],
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"SPAN": ["data-mx-bg-color", "data-mx-color", "color"],
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"SPAN": ["data-mx-bg-color", "data-mx-color"],
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"A": ["name", "target", "href"],
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"IMG": ["width", "height", "alt", "title", "src", "data-mx-emoticon"],
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"OL": ["start"],
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"CODE": ["class"],
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}
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const allowed_attributes = allowedElementAttributes[node.tagName] || []
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hookevent.keepAttr = allowed_attributes.indexOf(hookevent.attrName) > -1;
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const allowedAttributes = allowedElementAttributes[node.tagName] || []
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hookevent.keepAttr = allowedAttributes.indexOf(hookevent.attrName) > -1
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})
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purifier.addHook("uponSanitizeElement", (node, hookevent, config) => {
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// Remove bad classes from our code element
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if (node.tagName == "CODE") {
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if (node.tagName === "CODE") {
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node.classList.forEach(c => {
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if (!c.startsWith("language-")) {
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node.classList.remove(c)
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}
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})
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}
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if (node.tagName == "A") {
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node.setAttribute("rel", "noopener")
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if (node.tagName === "A") {
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node.setAttribute("rel", "noopener") // prevent the opening page from accessing carbon
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node.setAttribute("target", "_blank") // open in a new tab instead of replacing carbon
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}
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return node
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})
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function cleanHTML(html) {
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const config = {
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ALLOWED_URI_REGEXP: /^mxc:\/\/[a-zA-Z0-9\.]+\/[a-zA-Z0-9]+$/, // As per the spec we only allow mxc uris
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ALLOWED_TAGS: ['font', 'del', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'blockquote', 'p', 'a', 'ul', 'ol', 'sup', 'sub', 'li', 'b', 'i', 'u', 'strong', 'em', 'strike', 'code', 'hr', 'br', 'div', 'table', 'thead', 'tbody', 'tr', 'th', 'td', 'caption', 'pre', 'span', 'img'],
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ALLOWED_TAGS: [
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"font", "del", "h1", "h2", "h3", "h4", "h5", "h6", "blockquote", "p",
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"a", "ul", "ol", "sup", "sub", "li", "b", "i", "u", "strong", "em",
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"strike", "code", "hr", "br", "div", "table", "thead", "tbody", "tr",
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"th", "td", "caption", "pre", "span", "img",
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// matrix tags
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"mx-reply"
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],
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// In case we mess up in the uponSanitizeAttribute hook
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ALLOWED_ATTR: ["data-mx-bg-color", "data-mx-color", "color",
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"name", "target", "href",
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"width", "height", "alt", "title", "src", "data-mx-emoticon",
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"start", "class"],
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ALLOWED_ATTR: [
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"color", "name", "target", "href", "width", "height", "alt", "title",
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"src", "start", "class", "noreferrer", "noopener",
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// matrix attrs
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"data-mx-emoticon", "data-mx-bg-color", "data-mx-color"
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],
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// Return a DOM fragment instead of a string, avoids potential future mutation XSS
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// should also be faster than the browser parsing HTML twice
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// https://research.securitum.com/mutation-xss-via-mathml-mutation-dompurify-2-0-17-bypass/
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RETURN_DOM_FRAGMENT: true,
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RETURN_DOM_IMPORT: true
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}
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return purifier.sanitize(html)
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return purifier.sanitize(html, config)
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}
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// Here we put all the processing of the messages that isn't as likely to potentially lead to security issues
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function postProcessElements(rootNode) {
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const element = rootNode.element
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element.querySelectorAll("code").forEach((n) => rootNode.child(new HighlightedCode(n)))
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element.querySelectorAll("img").forEach((n) => {
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element.querySelectorAll("pre").forEach(n => {
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new HighlightedCode(n)
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})
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element.querySelectorAll("img").forEach(n => {
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let src = n.getAttribute("src")
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if (src) src = resolveMxc(src)
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n.setAttribute("src", src)
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})
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element.querySelectorAll("font, span").forEach((n) => {
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element.querySelectorAll("font, span").forEach(n => {
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const color = n.getAttribute("data-mx-color") || n.getAttribute("color")
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const bgColor = n.getAttribute("data-mx-bg-color")
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if (color) n.style.color = color;
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if (bgColor) n.style.backgroundColor = bgColor;
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if (color) n.style.color = color
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if (bgColor) n.style.backgroundColor = bgColor
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})
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}
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@ -78,8 +97,8 @@ class HTMLMessage extends MatrixEvent {
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let html = this.data.content.formatted_body
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const content = ejs("div")
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html = cleanHTML(html)
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content.html(html)
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const fragment = cleanHTML(html)
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content.element.appendChild(fragment)
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postProcessElements(content)
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this.child(content)
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@ -89,24 +108,23 @@ class HTMLMessage extends MatrixEvent {
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static canRender(event) {
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const content = event.content
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return event.type == "m.room.message" && content.msgtype == "m.text" && content.format == "org.matrix.custom.html" && content.formatted_body
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return event.type === "m.room.message" && content.msgtype === "m.text" && content.format === "org.matrix.custom.html" && content.formatted_body
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}
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canGroup() {
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return true
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}
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}
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class TextMessage extends MatrixEvent {
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render() {
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this.clearChildren()
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this.text(this.data.content.body)
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return super.render()
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super.render()
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}
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static canRender(event) {
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return event.type == "m.room.message"
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return event.type === "m.room.message"
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}
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canGroup() {
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@ -5,3 +5,4 @@ $mild: #393c42
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$milder: #42454a
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$divider: #4b4e54
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$muted: #999
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$link: #57bffd
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@ -1,6 +1,6 @@
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@use "../colors" as c
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.c-event-groups *
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.c-event-groups > *
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overflow-anchor: none
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.c-message-group, .c-message-event
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@ -67,6 +67,33 @@
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&:hover
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background-color: c.$darker
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// message formatting rules
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code, pre
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border-radius: 4px
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font-size: 0.9em
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pre
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background-color: c.$darkest
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padding: 8px
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border: 1px solid c.$divider
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code
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background-color: c.$darker
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padding: 2px 4px
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a
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color: c.$link
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p, pre
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margin: 16px 0px
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&:first-child
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margin-top: 0px
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&:last-child
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margin-bottom: 0px
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.c-message-event
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padding-top: 10px
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padding-left: 6px
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