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/**
* Hachette miscellaneous operations refactored to a separate file
*
* Copyright (C) 2021 Wojtek Kosior
* Copyright (C) 2021 jahoti
* Redistribution terms are gathered in the `copyright' file.
*/
/*
* IMPORTS_START
* IMPORT sha256
* IMPORT browser
* IMPORT is_chrome
* IMPORT TYPE_NAME
* IMPORT TYPE_PREFIX
* IMPORTS_END
*/
/* Generate a random base64-encoded 128-bit sequence */
function gen_nonce()
{
let randomData = new Uint8Array(16);
crypto.getRandomValues(randomData);
return btoa(String.fromCharCode.apply(null, randomData));
}
/*
* generating unique, per-site value that can be computed synchronously
* and is impossible to guess for a malicious website
*/
/* Uint8toHex is a separate function not exported as (a) it's useful and (b) it will be used in crypto.subtle-based digests */
function Uint8toHex(data)
{
let returnValue = '';
for (let byte of data)
returnValue += ('00' + byte.toString(16)).slice(-2);
return returnValue;
}
function gen_nonce(length) // Default 16
{
let randomData = new Uint8Array(length || 16);
crypto.getRandomValues(randomData);
return Uint8toHex(randomData);
}
function get_secure_salt()
{
if (is_chrome)
return browser.runtime.getManifest().key.substring(0, 50);
else
return browser.runtime.getURL("dummy");
}
function extract_signed(signature, data, times)
{
const now = new Date();
times ||= [[now], [now, -1]];
const reductor =
(ok, time) => ok || signature === sign_data(data, ...time);
if (!times.reduce(reductor, false))
return undefined;
try {
return JSON.parse(decodeURIComponent(data));
} catch (e) {
/* This should not be reached - it's our self-produced valid JSON. */
console.log("Unexpected internal error - invalid JSON smuggled!", e);
}
}
/* csp rule that blocks all scripts except for those injected by us */
function csp_rule(nonce)
{
const rule = `'nonce-${nonce}'`;
return `script-src ${rule}; script-src-elem ${rule}; script-src-attr 'none'; prefetch-src 'none';`;
}
/*
* Print item together with type, e.g.
* nice_name("s", "hello") → "hello (script)"
*/
function nice_name(prefix, name)
{
return `${name} (${TYPE_NAME[prefix]})`;
}
/* Open settings tab with given item's editing already on. */
function open_in_settings(prefix, name)
{
name = encodeURIComponent(name);
const url = browser.runtime.getURL("html/options.html#" + prefix + name);
window.open(url, "_blank");
}
/* Check if url corresponds to a browser's special page */
function is_privileged_url(url)
{
return !!/^(chrome(-extension)?|moz-extension):\/\/|^about:/i.exec(url);
}
/* Sign a given string for a given time */
function sign_data(data, now, hours_offset) {
let time = Math.floor(now / 3600000) + (hours_offset || 0);
return sha256(get_secure_salt() + time + data);
}
/* Parse a CSP header */
function parse_csp(csp) {
let directive, directive_array;
let directives = {};
for (directive of csp.split(';')) {
directive = directive.trim();
if (directive === '')
continue;
directive_array = directive.split(/\s+/);
directive = directive_array.shift();
/* The "true" case should never occur; nevertheless... */
directives[directive] = directive in directives ?
directives[directive].concat(directive_array) :
directive_array;
}
return directives;
}
/* Make CSP headers do our bidding, not interfere */
function sanitize_csp_header(header, rule, allow)
{
const csp = parse_csp(header.value);
if (!allow) {
/* No snitching */
delete csp['report-to'];
delete csp['report-uri'];
delete csp['script-src'];
delete csp['script-src-elem'];
csp['script-src-attr'] = ["'none'"];
csp['prefetch-src'] = ["'none'"];
}
if ('script-src' in csp)
csp['script-src'].push(rule);
else
csp['script-src'] = [rule];
if ('script-src-elem' in csp)
csp['script-src-elem'].push(rule);
else
csp['script-src-elem'] = [rule];
const new_policy = Object.entries(csp).map(
i => `${i[0]} ${i[1].join(' ')};`
);
return {name: header.name, value: new_policy.join('')};
}
/* Regexes and objest to use as/in schemas for parse_json_with_schema(). */
const nonempty_string_matcher = /.+/;
const matchers = {
sha256: /^[0-9a-f]{64}$/,
nonempty_string: nonempty_string_matcher,
component: [
new RegExp(`^[${TYPE_PREFIX.SCRIPT}${TYPE_PREFIX.BAG}]$`),
nonempty_string_matcher
]
};
/*
* EXPORTS_START
* EXPORT gen_nonce
* EXPORT extract_signed
* EXPORT sign_data
* EXPORT csp_rule
* EXPORT nice_name
* EXPORT open_in_settings
* EXPORT is_privileged_url
* EXPORT sanitize_csp_header
* EXPORT matchers
* EXPORTS_END
*/
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