Haketilo

/**

 * 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

 */