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authorWojtek Kosior <koszko@koszko.org>2022-03-05 15:54:53 +0100
committerWojtek Kosior <koszko@koszko.org>2022-03-05 15:54:53 +0100
commit96efcc335bbd9f2ad098e694d6cff6c1c22b4ce8 (patch)
treecf8120ca6658c04c62e63dc66a8a5b39dbec4c2d /content
parent709238294ea83525e62476ce59d734c57c11fd3f (diff)
downloadbrowser-extension-96efcc335bbd9f2ad098e694d6cff6c1c22b4ce8.tar.gz
browser-extension-96efcc335bbd9f2ad098e694d6cff6c1c22b4ce8.zip
improve script blocking in non-HTML documents (XML)
Diffstat (limited to 'content')
-rw-r--r--content/policy_enforcing.js114
1 files changed, 92 insertions, 22 deletions
diff --git a/content/policy_enforcing.js b/content/policy_enforcing.js
index 29990b8..53f418f 100644
--- a/content/policy_enforcing.js
+++ b/content/policy_enforcing.js
@@ -45,6 +45,9 @@
#FROM common/misc.js IMPORT gen_nonce, csp_header_regex
+const html_ns = "http://www.w3.org/1999/xhtml";
+const svg_ns = "http://www.w3.org/2000/svg";
+
document.content_loaded = document.readyState === "complete";
const wait_loaded = e => e.content_loaded ? Promise.resolve() :
new Promise(c => e.addEventListener("DOMContentLoaded", c, {once: true}));
@@ -203,6 +206,10 @@ function sanitize_element_urls(element) {
*/
if (some_attr_blocked) {
const replacement_elem = document.createElement("a");
+
+ /* Prevent this node from being processed by our observer. */
+ replacement_elem.haketilo_trusted_node = true;
+
element.replaceWith(replacement_elem);
replacement_elem.replaceWith(element);
}
@@ -221,8 +228,8 @@ function sanitize_element_onevent(element) {
element.haketilo_sanitized_onevent = true;
for (const attribute_node of [...(element.attributes || [])]) {
- const attr = attribute_node.localName, attr_lo = attr.toLowerCase();;
- if (!/^on/.test(attr_lo) || !(attr_lo in element.wrappedJSObject))
+ const attr = attribute_node.localName, attr_lo = attr.toLowerCase();
+ if (!/^on/.test(attr_lo) || !(attr_lo in element))
continue;
/*
@@ -246,20 +253,69 @@ function sanitize_tree_onevent(root) {
}
#ENDIF
-function start_mo_sanitizing(doc) {
- if (!doc.content_loaded) {
- function mutation_handler(mutation) {
- mutation.addedNodes.forEach(sanitize_element_urls);
+/*
+ * Sanitize elements on-the-fly as they appear using MutationObserver.
+ *
+ * Under Abrowser 97 it was observed that MutationObserver does not always work
+ * as is should. When trying to observe nodes of an XMLDocument the behavior was
+ * as if the "subtree" option to MutationObserver.observe() was ignored. To work
+ * around this we avoid using the "subtree" option altogether and have the same
+ * code work in all scenarios.
+ */
+function MOSanitizer(root) {
+ this.root = root;
+
+ this.recursively_sanitize(root);
+
+ this.mo = new MutationObserver(ms => this.handle_mutations(ms));
+}
+
+MOSanitizer.prototype.observe = function() {
+ let elem = this.root;
+ while (elem && !elem.haketilo_trusted_node) {
+ this.mo.observe(elem, {childList: true});
+ elem = elem.lastElementChild;
+ }
+}
+
+MOSanitizer.prototype.handle_mutations = function(mutations) {
+ for (const mut of mutations) {
+ for (const new_node of mut.addedNodes)
+ this.recursively_sanitize(new_node);
+ }
+
+ this.mo.disconnect();
+ this.observe();
+}
+
+MOSanitizer.prototype.recursively_sanitize = function(elem) {
+ const to_process = [elem];
+
+ while (to_process.length > 0) {
+ const current_elem = to_process.pop();
+
+ if (current_elem.haketilo_trusted_node ||
+ current_elem.nodeType !== this.root.ELEMENT_NODE)
+ continue;
+
+ to_process.push(...current_elem.children);
+
+ sanitize_element_urls(current_elem);
#IF MOZILLA
- mutation.addedNodes.forEach(sanitize_element_onevent);
+ sanitize_element_onevent(current_elem);
#ENDIF
- }
- const mo = new MutationObserver(ms => ms.forEach(mutation_handler));
- mo.observe(doc, {childList: true, subtree: true});
- wait_loaded(doc).then(() => mo.disconnect());
}
}
+MOSanitizer.prototype.start = function() {
+ this.recursively_sanitize(this.root);
+ this.observe();
+}
+
+MOSanitizer.prototype.stop = function() {
+ this.mo.disconnect();
+}
+
#IF MOZILLA
/*
* Normally, we block scripts with CSP. However, Mozilla does optimizations that
@@ -270,8 +326,7 @@ function start_mo_sanitizing(doc) {
* applying this CSP to non-inline `<scripts>' in certain scenarios.
*/
function prevent_script_execution(event) {
- if (!event.target.haketilo_payload)
- event.preventDefault();
+ event.preventDefault();
}
#ENDIF
@@ -285,19 +340,32 @@ function prevent_script_execution(event) {
* javascript execution.
*/
async function sanitize_document(doc, policy) {
+ const root = doc.documentElement;
+ const substitute_doc =
+ new DOMParser().parseFromString("<!DOCTYPE html>", "text/html");
+
#IF MOZILLA
/*
* Blocking of scripts that are in the DOM from the beginning. Needed for
* Mozilla.
*/
const listener_args = ["beforescriptexecute", prevent_script_execution];
+
doc.addEventListener(...listener_args);
+ substitute_doc.addEventListener(...listener_args);
+
wait_loaded(doc).then(() => doc.removeEventListener(...listener_args));
sanitize_tree_urls(doc.documentElement);
sanitize_tree_onevent(doc.documentElement);
#ENDIF
+ if (!doc.content_loaded) {
+ const sanitizer = new MOSanitizer(doc.documentElement);
+ sanitizer.start();
+ wait_loaded(doc).then(() => sanitizer.stop());
+ }
+
/*
* Ensure our CSP rules are employed from the beginning. This CSP injection
* method is, when possible, going to be applied together with CSP rules
@@ -322,8 +390,14 @@ async function sanitize_document(doc, policy) {
* Root node gets hijacked now, to be re-attached after <head> is loaded
* and sanitized.
*/
- const root = doc.documentElement;
root.replaceWith(temporary_html);
+#IF MOZILLA
+ /*
+ * To be able to handle the onbeforescriptexecute event for scripts that
+ * appear under detached document.
+ */
+ substitute_doc.documentElement.replaceWith(root);
+#ENDIF
/*
* When we don't inject payload, we neither block document's CSP `<meta>'
@@ -336,15 +410,11 @@ async function sanitize_document(doc, policy) {
.forEach(m => sanitize_meta(m, policy));
}
- sanitize_tree_urls(root);
- root.querySelectorAll("script").forEach(s => sanitize_script(s, policy));
+ const scripts = [...root.getElementsByTagNameNS(html_ns, "script"),
+ ...root.getElementsByTagNameNS(svg_ns, "svg")];
+ scripts.forEach(s => sanitize_script(s, policy));
temporary_html.replaceWith(root);
- root.querySelectorAll("script").forEach(s => desanitize_script(s, policy));
-#IF MOZILLA
- sanitize_tree_onevent(root);
-#ENDIF
-
- start_mo_sanitizing(doc);
+ scripts.forEach(s => desanitize_script(s, policy));
}
async function _disable_service_workers() {