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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
* 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 gen_unique(url)
{
return sha256(get_secure_salt() + url);
}
function get_secure_salt()
{
if (is_chrome)
return browser.runtime.getManifest().key.substring(0, 50);
else
return browser.runtime.getURL("dummy");
}
/*
* stripping url from query and target (everything after `#' or `?'
* gets removed)
*/
function url_item(url)
{
let url_re = /^([^?#]*).*$/;
let match = url_re.exec(url);
return match[1];
}
/*
* Assume a url like:
* https://example.com/green?illuminati=confirmed#<injected-policy>#winky
* This function will make it into an object like:
* {
* "base_url": "https://example.com/green?illuminati=confirmed",
* "target": "#<injected-policy>",
* "target2": "#winky",
* "policy": <injected-policy-as-js-object>,
* "current": <boolean-indicating-whether-policy-url-matches>
* }
* In case url doesn't have 2 #'s, target2 and target can be set to undefined.
*/
function url_extract_target(url)
{
const url_re = /^([^#]*)((#[^#]*)(#.*)?)?$/;
const match = url_re.exec(url);
const targets = {
base_url: match[1],
target: match[3] || "",
target2: match[4] || ""
};
if (!targets.target)
return targets;
/* %7B -> { */
const index = targets.target.indexOf('%7B');
if (index === -1)
return targets;
const now = new Date();
const sig = targets.target.substring(1, index);
const policy = targets.target.substring(index);
if (sig !== sign_policy(policy, now) &&
sig !== sign_policy(policy, now, -1))
return targets;
try {
targets.policy = JSON.parse(decodeURIComponent(policy));
targets.current = targets.policy.base_url === targets.base_url;
} catch (e) {
/* This should not be reached - it's our self-produced valid JSON. */
console.log("Unexpected internal error - invalid JSON smuggled!", e);
}
return targets;
}
/* csp rule that blocks all scripts except for those injected by us */
function csp_rule(nonce)
{
let rule = `script-src 'nonce-${nonce}';`;
if (is_chrome)
rule += `script-src-elem 'nonce-${nonce}';`;
return rule;
}
/*
* 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 policy for a given time */
function sign_policy(policy, now, hours_offset) {
let time = Math.floor(now / 3600000) + (hours_offset || 0);
return gen_unique(time + policy);
}
/* 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, block)
{
const csp = parse_csp(header.value);
if (block) {
/* 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('')};
}
/*
* EXPORTS_START
* EXPORT gen_nonce
* EXPORT gen_unique
* EXPORT url_item
* EXPORT url_extract_target
* EXPORT sign_policy
* EXPORT csp_rule
* EXPORT nice_name
* EXPORT open_in_settings
* EXPORT is_privileged_url
* EXPORT sanitize_csp_header
* EXPORTS_END
*/
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