1 files changed, 53 insertions, 0 deletions
diff --git a/app/assets/javascripts/lib/dompurify.js b/app/assets/javascripts/lib/dompurify.js
new file mode 100644
index 00000000000..d9ea57fbbce
--- /dev/null
+++ b/app/assets/javascripts/lib/dompurify.js
@@ -0,0 +1,53 @@
+import { sanitize as dompurifySanitize, addHook } from 'dompurify';
+import { getBaseURL, relativePathToAbsolute } from '~/lib/utils/url_utility';
+
+// Safely allow SVG <use> tags
+
+const defaultConfig = {
+  ADD_TAGS: ['use'],
+};
+
+// Only icons urls from `gon` are allowed
+const getAllowedIconUrls = (gon = window.gon) =>
+  [gon.sprite_file_icons, gon.sprite_icons].filter(Boolean);
+
+const isUrlAllowed = url => getAllowedIconUrls().some(allowedUrl => url.startsWith(allowedUrl));
+
+const isHrefSafe = url =>
+  isUrlAllowed(url) || isUrlAllowed(relativePathToAbsolute(url, getBaseURL()));
+
+const removeUnsafeHref = (node, attr) => {
+  if (!node.hasAttribute(attr)) {
+    return;
+  }
+
+  if (!isHrefSafe(node.getAttribute(attr))) {
+    node.removeAttribute(attr);
+  }
+};
+
+/**
+ * Sanitize icons' <use> tag attributes, to safely include
+ * svgs such as in:
+ *
+ * <svg viewBox="0 0 100 100">
+ *   <use href="/assets/icons-xxx.svg#icon_name"></use>
+ * </svg>
+ *
+ * @param {Object} node - Node to sanitize
+ */
+const sanitizeSvgIcon = node => {
+  removeUnsafeHref(node, 'href');
+
+  // Note: `xlink:href` is deprecated, but still in use
+  // https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/xlink:href
+  removeUnsafeHref(node, 'xlink:href');
+};
+
+addHook('afterSanitizeAttributes', node => {
+  if (node.tagName.toLowerCase() === 'use') {
+    sanitizeSvgIcon(node);
+  }
+});
+
+export const sanitize = (val, config = defaultConfig) => dompurifySanitize(val, config);