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-rw-r--r--background/webrequest.js136
1 files changed, 114 insertions, 22 deletions
diff --git a/background/webrequest.js b/background/webrequest.js
index a523772..5ec7b7f 100644
--- a/background/webrequest.js
+++ b/background/webrequest.js
@@ -3,7 +3,7 @@
*
* Function: Modify HTTP traffic usng webRequest API.
*
- * Copyright (C) 2021 Wojtek Kosior <koszko@koszko.org>
+ * Copyright (C) 2021, 2022 Wojtek Kosior <koszko@koszko.org>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
@@ -41,53 +41,145 @@
* proprietary program, I am not going to enforce this in court.
*/
-#IMPORT common/indexeddb.js AS haketilodb
+#IMPORT common/indexeddb.js AS haketilodb
+
#IF MOZILLA
#IMPORT background/stream_filter.js
#ENDIF
#FROM common/browser.js IMPORT browser
-#FROM common/misc.js IMPORT is_privileged_url, csp_header_regex
+#FROM common/misc.js IMPORT is_privileged_url, csp_header_regex, \
+ sha256_async AS sha256
#FROM common/policy.js IMPORT decide_policy
#FROM background/patterns_query_manager.js IMPORT tree, default_allow
let secret;
-function on_headers_received(details)
-{
+#IF MOZILLA
+/*
+ * Under Mozilla-based browsers, responses are cached together with headers as
+ * they appear *after* modifications by Haketilo. This means Haketilo's CSP
+ * script-blocking headers might be present in responses loaded from cache. In
+ * the meantime the user might have changes Haketilo settings to instead allow
+ * the scripts on the page in question. This causes a problem and creates the
+ * need to somehow restore the response headers to the state in which they
+ * arrived from the server.
+ * To cope with this, Haketilo will inject some additional headers with private
+ * data. Those will include a hard-to-guess value derived from extension's
+ * internal ID. It is assumed the internal ID has a longer lifetime than cached
+ * responses.
+ */
+
+const settings_page_url = browser.runtime.getURL("html/settings.html");
+const header_prefix_prom = sha256(settings_page_url)
+ .then(hash => `X-Haketilo-${hash}`);
+
+/*
+ * Mozilla, unlike Chrome, allows webRequest callbacks to return promises. Here
+ * we leverage that to be able to use asynchronous sha256 computation.
+ */
+async function on_headers_received(details) {
+#IF NEVER
+} /* Help auto-indent in editors. */
+#ENDIF
+#ELSE
+function on_headers_received(details) {
+#ENDIF
const url = details.url;
if (is_privileged_url(details.url))
return;
let headers = details.responseHeaders;
+#IF MOZILLA
+ const prefix = await header_prefix_prom;
+
+ /*
+ * We assume that the original CSP headers of a response are always
+ * preserved under names of the form:
+ * X-Haketilo-<some_secret>-<original_name>
+ * In some cases the original response may contain no CSP headers. To still
+ * be able to tell whether the headers we were provided were modified by
+ * Haketilo in the past, all modifications are accompanied by addition of an
+ * extra header with name:
+ * X-Haketilo-<some_secret>
+ */
+
+ const restore_old_headers = details.fromCache &&
+ !!headers.filter(h => h.name === prefix).length;
+
+ if (restore_old_headers) {
+ const restored_headers = [];
+
+ for (const h of headers) {
+ if (csp_header_regex.test(h.name) || h.name === prefix)
+ continue;
+
+ if (h.name.startsWith(prefix)) {
+ restored_headers.push({
+ name: h.name.substring(prefix.length + 1),
+ value: h.value
+ });
+ } else {
+ restored_headers.push(h);
+ }
+ }
+
+ headers = restored_headers;
+ }
+#ENDIF
+
const policy =
decide_policy(tree, details.url, !!default_allow.value, secret);
- if (policy.allow)
- return;
- if (policy.payload)
- headers = headers.filter(h => !csp_header_regex.test(h.name));
+ if (!policy.allow) {
+#IF MOZILLA
+ const to_append = [{name: prefix, value: ":)"}];
+
+ for (const h of headers.filter(h => csp_header_regex.test(h.name))) {
+ if (!policy.payload)
+ to_append.push(Object.assign({}, h));
+
+ h.name = `${prefix}-${h.name}`;
+ }
- headers.push({name: "Content-Security-Policy", value: policy.csp});
+ headers.push(...to_append);
+#ELSE
+ if (policy.payload)
+ headers = headers.filter(h => !csp_header_regex.test(h.name));
+#ENDIF
+
+ headers.push({name: "Content-Security-Policy", value: policy.csp});
+ }
#IF MOZILLA
- let skip = false;
- for (const header of headers) {
- if (header.name.toLowerCase().trim() !== "content-disposition")
- continue;
-
- if (/^\s*attachment\s*(;.*)$/i.test(header.value)) {
- skip = true;
- } else {
- skip = false;
- break;
+ /*
+ * When page is meant to be viewed in the browser, use streamFilter to
+ * inject a dummy <script> at the very beginning of it. This <script>
+ * will cause extension's content scripts to run before page's first <meta>
+ * tag is rendered so that they can prevent CSP rules inside <meta> tags
+ * from blocking the payload we want to inject.
+ */
+
+ let use_stream_filter = !!policy.payload;
+ if (use_stream_filter) {
+ for (const header of headers) {
+ if (header.name.toLowerCase().trim() !== "content-disposition")
+ continue;
+
+ if (/^\s*attachment\s*(;.*)$/i.test(header.value)) {
+ use_stream_filter = false;
+ } else {
+ use_stream_filter = true;
+ break;
+ }
}
}
- skip = skip || (details.statusCode >= 300 && details.statusCode < 400);
+ use_stream_filter = use_stream_filter &&
+ (details.statusCode < 300 || details.statusCode >= 400);
- if (!skip)
+ if (use_stream_filter)
headers = stream_filter.apply(details, headers, policy);
#ENDIF