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authorWojtek Kosior <koszko@koszko.org>2021-08-23 11:05:51 +0200
committerWojtek Kosior <koszko@koszko.org>2021-08-23 11:05:51 +0200
commit6b53d6c840140fc5df6d7638808b978d96502a35 (patch)
tree87a76576824c49b65b1aa9f4213b63926ba7d243 /background
parentd09b7ee10541b5a81430d2e11abb3a9a09643ade (diff)
downloadbrowser-extension-6b53d6c840140fc5df6d7638808b978d96502a35.tar.gz
browser-extension-6b53d6c840140fc5df6d7638808b978d96502a35.zip
use StreamFilter under Mozilla to prevent csp <meta> tags from blocking our injected scripts
Diffstat (limited to 'background')
-rw-r--r--background/main.js60
-rw-r--r--background/policy_injector.js61
-rw-r--r--background/stream_filter.js176
3 files changed, 247 insertions, 50 deletions
diff --git a/background/main.js b/background/main.js
index 7c50fd5..85f8ce8 100644
--- a/background/main.js
+++ b/background/main.js
@@ -11,18 +11,21 @@
* IMPORT get_storage
* IMPORT start_storage_server
* IMPORT start_page_actions_server
- * IMPORT start_policy_injector
* IMPORT browser
+ * IMPORT is_privileged_url
+ * IMPORT query_best
+ * IMPORT gen_nonce
+ * IMPORT inject_csp_headers
+ * IMPORT apply_stream_filter
+ * IMPORT is_chrome
* IMPORTS_END
*/
start_storage_server();
start_page_actions_server();
-start_policy_injector();
async function init_ext(install_details)
{
- console.log("details:", install_details);
if (install_details.reason != "install")
return;
@@ -44,4 +47,53 @@ async function init_ext(install_details)
browser.runtime.onInstalled.addListener(init_ext);
-console.log("hello, hachette");
+
+let storage;
+
+function on_headers_received(details)
+{
+ const url = details.url;
+ if (is_privileged_url(details.url))
+ return;
+
+ const [pattern, settings] = query_best(storage, details.url);
+ const allow = !!(settings && settings.allow);
+ const nonce = gen_nonce();
+ const policy = {allow, url, nonce};
+
+ let headers = details.responseHeaders;
+ let skip = false;
+ for (const header of headers) {
+ if ((header.name.toLowerCase().trim() === "content-disposition" &&
+ /^\s*attachment\s*(;.*)$/i.test(header.value)))
+ skip = true;
+ }
+
+ headers = inject_csp_headers(details, headers, policy);
+
+ skip = skip || (details.statusCode >= 300 && details.statusCode < 400);
+ if (!skip) {
+ /* Check for API availability. */
+ if (browser.webRequest.filterResponseData)
+ headers = apply_stream_filter(details, headers, policy);
+ }
+
+ return {responseHeaders: headers};
+}
+
+async function start_webRequest_operations()
+{
+ storage = await get_storage();
+
+ const extra_opts = ["blocking", "responseHeaders"];
+ if (is_chrome)
+ extra_opts.push("extraHeaders");
+
+ browser.webRequest.onHeadersReceived.addListener(
+ on_headers_received,
+ {urls: ["<all_urls>"], types: ["main_frame", "sub_frame"]},
+ extra_opts
+ );
+}
+
+start_webRequest_operations();
diff --git a/background/policy_injector.js b/background/policy_injector.js
index 3398b53..1d4db6f 100644
--- a/background/policy_injector.js
+++ b/background/policy_injector.js
@@ -8,36 +8,21 @@
/*
* IMPORTS_START
- * IMPORT get_storage
- * IMPORT browser
- * IMPORT is_chrome
- * IMPORT gen_nonce
- * IMPORT is_privileged_url
* IMPORT sign_data
* IMPORT extract_signed
- * IMPORT query_best
* IMPORT sanitize_csp_header
* IMPORT csp_rule
* IMPORT is_csp_header_name
* IMPORTS_END
*/
-var storage;
-
-function headers_inject(details)
+function inject_csp_headers(details, headers, policy)
{
const url = details.url;
- if (is_privileged_url(url))
- return;
-
- const [pattern, settings] = query_best(storage, url);
- const allow = !!(settings && settings.allow);
- const nonce = gen_nonce();
let orig_csp_headers;
let old_signature;
let hachette_header;
- let headers = details.responseHeaders;
for (const header of headers.filter(h => h.name === "x-hachette")) {
const match = /^([^%])(%.*)$/.exec(header.value);
@@ -50,7 +35,7 @@ function headers_inject(details)
/* Confirmed- it's the originals, smuggled in! */
orig_csp_headers = old_data.csp_headers;
- old_signature = old_data.policy_signature;
+ old_signature = old_data.policy_sig;
hachette_header = header;
break;
@@ -65,21 +50,20 @@ function headers_inject(details)
headers.filter(h => is_csp_header_name(h.name));
/* When blocking remove report-only CSP headers that snitch on us. */
- headers = headers.filter(h => !is_csp_header_name(h.name, !allow));
+ headers = headers.filter(h => !is_csp_header_name(h.name, !policy.allow));
if (old_signature)
headers = headers.filter(h => h.name.search(old_signature) === -1);
- const policy_object = {allow, nonce, url};
- const sanitizer = h => sanitize_csp_header(h, policy_object);
+ const sanitizer = h => sanitize_csp_header(h, policy);
headers.push(...orig_csp_headers.map(sanitizer));
- const policy = encodeURIComponent(JSON.stringify(policy_object));
- const policy_signature = sign_data(policy, new Date());
+ const policy_str = encodeURIComponent(JSON.stringify(policy));
+ const policy_sig = sign_data(policy_str, new Date());
const later_30sec = new Date(new Date().getTime() + 30000).toGMTString();
headers.push({
name: "Set-Cookie",
- value: `hachette-${policy_signature}=${policy}; Expires=${later_30sec};`
+ value: `hachette-${policy_sig}=${policy_str}; Expires=${later_30sec};`
});
/*
@@ -87,37 +71,22 @@ function headers_inject(details)
* These are signed with a time of 0, as it's not clear there is a limit on
* how long Firefox might retain headers in the cache.
*/
- let hachette_data = {csp_headers: orig_csp_headers, policy_signature, url};
+ let hachette_data = {csp_headers: orig_csp_headers, policy_sig, url};
hachette_data = encodeURIComponent(JSON.stringify(hachette_data));
hachette_header.value = sign_data(hachette_data, 0) + hachette_data;
/* To ensure there is a CSP header if required */
- if (!allow)
- headers.push({name: "content-security-policy", value: csp_rule(nonce)});
+ if (!policy.allow)
+ headers.push({
+ name: "content-security-policy",
+ value: csp_rule(policy.nonce)
+ });
- return {responseHeaders: headers};
-}
-
-async function start_policy_injector()
-{
- storage = await get_storage();
-
- let extra_opts = ["blocking", "responseHeaders"];
- if (is_chrome)
- extra_opts.push("extraHeaders");
-
- browser.webRequest.onHeadersReceived.addListener(
- headers_inject,
- {
- urls: ["<all_urls>"],
- types: ["main_frame", "sub_frame"]
- },
- extra_opts
- );
+ return headers;
}
/*
* EXPORTS_START
- * EXPORT start_policy_injector
+ * EXPORT inject_csp_headers
* EXPORTS_END
*/
diff --git a/background/stream_filter.js b/background/stream_filter.js
new file mode 100644
index 0000000..2dce811
--- /dev/null
+++ b/background/stream_filter.js
@@ -0,0 +1,176 @@
+/**
+ * Hachette modifying a web page using the StreamFilter API
+ *
+ * Copyright (C) 2018 Giorgio Maone <giorgio@maone.net>
+ * Copyright (C) 2021 Wojtek Kosior
+ * Redistribution terms are gathered in the `copyright' file.
+ *
+ * Derived from `bg/ResponseProcessor.js' and `bg/ResponseMetaData.js'
+ * in LibreJS.
+ */
+
+/*
+ * IMPORTS_START
+ * IMPORT browser
+ * IMPORTS_END
+ */
+
+function validate_encoding(charset)
+{
+ try {
+ new TextDecoder();
+ return charset;
+ } catch(e) {
+ return undefined;
+ }
+}
+
+function is_content_type_header(header)
+{
+ header.name.toLowerCase().trim() === "content-type";
+}
+
+const charset_reg = /;\s*charset\s*=\s*([\w-]+)/i;
+
+function properties_from_headers(headers)
+{
+ const properties = {};
+
+ for (const header of headers.filter(is_content_type_header)) {
+ const match = charset_reg.exec(header.value);
+ if (!properties.detected_charset && validate_encoding(match[1]))
+ properties.detected_charset = match[1];
+
+ if (/html/i.test(header.value))
+ properties.html = true;
+ }
+
+ return properties;
+}
+
+const UTF8_BOM = [0xef, 0xbb, 0xbf];
+const BOMs = [
+ [UTF8_BOM, "utf-8"],
+ [[0xfe, 0xff], "utf-16be"],
+ [[0xff, 0xfe], "utf-16le"]
+];
+
+function charset_from_BOM(data)
+{
+ for (const [BOM, charset] of BOMs) {
+ if (BOM.reduce((ac, byte, i) => ac && byte === data[i], true))
+ return charset;
+ }
+
+ return "";
+}
+
+const charset_attrs =
+ ['charset', 'http-equiv="content-type"', 'content*="charset"'];
+const charset_meta_selector =
+ charset_attrs.map(a => `head>meta[${a}]`).join(", ");
+
+function charset_from_meta_tags(doc)
+{
+ for (const meta of doc.querySelectorAll(charset_meta_selector)) {
+ const maybe_charset = meta.getAttribute("charset");
+ if (maybe_charset && validate_encoding(maybe_charset))
+ return maybe_charset;
+
+ const match = charset_reg.exec(meta.getAttribute("content"));
+ if (match && validate_encoding(match[1]))
+ return match[1];
+ }
+
+ return undefined;
+}
+
+function create_decoder(properties, data)
+{
+ let charset = charset_from_BOM(data) || properties.detected_charset;
+ if (!charset && data.indexOf(0) !== -1) {
+ console.debug("Warning: zeroes in bytestream, probable cached encoding mismatch. Trying to decode it as UTF-16.",
+ properties);
+ return new TextDecoder("utf-16be");
+ }
+
+ /* Missing HTTP charset, sniffing in content... */
+ /*
+ * TODO: I recall there is some standard saying how early in the doc the
+ * charset has to be specified. We could process just this part of data.
+ */
+ const text = new TextDecoder("latin1").decode(data, {stream: true});
+ properties.html = properties.html || /html/i.test(text);
+
+ if (properties.html) {
+ const tmp_doc = new DOMParser().parseFromString(text, "text/html");
+ charset = charset_from_meta_tags(tmp_doc);
+ }
+
+ return new TextDecoder(charset || "latin1");
+}
+
+function filter_data(properties, event)
+{
+ const data = new Uint8Array(event.data);
+ let first_chunk = false;
+ if (!properties.decoder) {
+ first_chunk = true;
+ properties.decoder = create_decoder(properties, data);
+ properties.encoder = new TextEncoder();
+ /* Force UTF-8, this is the only encoding we can produce. */
+ properties.filter.write(new Uint8Array(UTF8_BOM));
+ }
+
+ let decoded = properties.decoder.decode(data);
+
+ if (first_chunk) {
+ /*
+ * HAX! Our content scripts that execute at `document_start' will always
+ * run before the first script in the document, but under Mozilla some
+ * `<meta>' tags might already be loaded at that point. Here we inject a
+ * dummy `<script>' at the beginning (before any `<meta>' tags) that
+ * will force `document_start' to happen earlier. This way our content
+ * scripts will be able to sanitize `http-equiv' tags with CSP rules
+ * that would otherwise stop our injected scripts from executing.
+ */
+ const dummy_script =
+ `<script data-hachette-deleteme="${properties.policy.nonce}" nonce="${properties.policy.nonce}">null</script>`;
+ const doctype_decl = /^(\s*<!doctype[^<>"']*>)?/i.exec(decoded)[0];
+ decoded = doctype_decl + dummy_script +
+ decoded.substring(doctype_decl.length);
+ }
+
+ properties.filter.write(properties.encoder.encode(decoded));
+
+ if (properties.decoder.encoding === "utf-8")
+ properties.filter.disconnect();
+}
+
+function apply_stream_filter(details, headers, policy)
+{
+ if (policy.allow)
+ return headers;
+
+ const properties = properties_from_headers(headers);
+ properties.policy = policy;
+
+ properties.filter =
+ browser.webRequest.filterResponseData(details.requestId);
+
+ properties.filter.ondata = event => filter_data(properties, event);
+ properties.filter.onstop = () => properties.filter.close();
+
+ /*
+ * In the future we might consider modifying the headers that specify
+ * encoding. For now we are not yet doing it, though. However, we
+ * prepend the data with UTF-8 BOM which should be enough.
+ */
+ return headers;
+}
+
+/*
+ * EXPORTS_START
+ * EXPORT apply_stream_filter
+ * EXPORTS_END
+ */