proxmox-mirrors/proxmox-widget-toolkit
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markdown: make sanitizer more strict

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The href, and in some browser also the src attrs on img, or a tags
can be made to execute JS rather easily, catch thoseand just remove
the attr if, after creating an URL object from it, it does not looks
like it's a http(s) request.

Further, filter out the style tag completely, as that can be misused
too, even if only to break cosmetics.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
This commit is contained in:
Thomas Lamprecht 2021-07-04 20:06:26 +02:00
parent 71bc0913bd
commit f2c4f9bdc2
1 changed files with 17 additions and 2 deletions
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19
src/Parser.js
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@ -10,19 +10,34 @@ Ext.define('Proxmox.Markdown', {
if (!input) { if (!input) {
return input; return input;
} }
let _isHTTPLike = value => value.match(/^\s*https?:/i); // URL's protocol ends with :
let _sanitize; let _sanitize;
_sanitize = (node) => { _sanitize = (node) => {
if (node.nodeType === 3) return; if (node.nodeType === 3) return;
if (node.nodeType !== 1 || /^(script|iframe|object|embed|svg)$/i.test(node.tagName)) { if (node.nodeType !== 1 || /^(script|style|iframe|object|embed|svg)$/i.test(node.tagName)) {
// could do node.remove() instead, but it's nicer UX if we keep the (encoded!) html // could do node.remove() instead, but it's nicer UX if we keep the (encoded!) html
node.outerHTML = Ext.String.htmlEncode(node.outerHTML); node.outerHTML = Ext.String.htmlEncode(node.outerHTML);
return; return;
} }
for (let i=node.attributes.length; i--;) { for (let i=node.attributes.length; i--;) {
const name = node.attributes[i].name; const name = node.attributes[i].name;
const value = node.attributes[i].value;
// TODO: we may want to also disallow class and id attrs // TODO: we may want to also disallow class and id attrs
if (!/^(class|id|name|href|src|alt|align|valign|disabled|checked|start|type)$/i.test(name)) { if (
!/^(class|id|name|href|src|alt|align|valign|disabled|checked|start|type)$/i.test(name)
) {
node.attributes.removeNamedItem(name); node.attributes.removeNamedItem(name);
} else if ((name === 'href' || name === 'src') && !_isHTTPLike(value)) {
try {
let url = new URL(value, window.location.origin);
if (_isHTTPLike(url.protocol)) {
node.attributes[i].value = url.href;
} else {
node.attributes.removeNamedItem(name);
}
} catch (e) {
node.attributes[i].removeNamedItem(name);
}
} }
} }
for (let i=node.childNodes.length; i--;) _sanitize(node.childNodes[i]); for (let i=node.childNodes.length; i--;) _sanitize(node.childNodes[i]);