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/**
* This file is part of Haketilo.
*
* Function: Determining what to do on a given web page.
*
* Copyright (C) 2021 Wojtek Kosior
*
* 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
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* As additional permission under GNU GPL version 3 section 7, you
* may distribute forms of that code without the copy of the GNU
* GPL normally required by section 4, provided you include this
* license notice and, in case of non-source distribution, a URL
* through which recipients can access the Corresponding Source.
* If you modify file(s) with this exception, you may extend this
* exception to your version of the file(s), but you are not
* obligated to do so. If you do not wish to do so, delete this
* exception statement from your version.
*
* As a special exception to the GPL, any HTML file which merely
* makes function calls to this code, and for that purpose
* includes it by reference shall be deemed a separate work for
* copyright law purposes. If you modify this code, you may extend
* this exception to your version of the code, but you are not
* obligated to do so. If you do not wish to do so, delete this
* exception statement from your version.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*
* I, Wojtek Kosior, thereby promise not to sue for violation of this file's
* license. Although I request that you do not make use of this code in a
* proprietary program, I am not going to enforce this in court.
*/
#IMPORT common/patterns_query_tree.js AS pqt
#FROM common/sha256.js IMPORT sha256
/*
* CSP rule that either blocks all scripts or only allows scripts with specified
* nonce attached.
*/
function make_csp(nonce) {
const rule = nonce ? `'nonce-${nonce}'` : "'none'";
const csp_list = [
["prefetch-src", "'none'"],
["script-src-attr", "'none'"],
["script-src", rule, "'unsafe-eval'"],
["script-src-elem", rule]
];
return csp_list.map(words => `${words.join(" ")};`).join(" ");
}
function decide_policy(patterns_tree, url, default_allow, secret)
{
const policy = {allow: default_allow};
try {
var payloads = pqt.search(patterns_tree, url).next().value;
} catch (e) {
console.error("Haketilo:", e);
policy.allow = false;
policy.error = {haketilo_error_type: "deciding_policy"};
}
if (payloads !== undefined) {
/*
* mapping will be either the actual mapping identifier or "~allow" if
* we matched a simple script block/allow rule.
*/
policy.mapping = Object.keys(payloads).sort()[0];
const payload = payloads[policy.mapping];
if (policy.mapping === "~allow") {
/* Convert 0/1 back to false/true. */
policy.allow = !!payload;
} else /* if (payload.identifier) */ {
policy.allow = false;
policy.payload = payload;
/*
* Hash a secret and other values into a string that's unpredictable
* to someone who does not know these values. What we produce here
* is not a true "nonce" because it might get produced multiple
* times given the same url and mapping choice. Nevertheless, this
* is reasonably good given the limitations WebExtension APIs and
* environments give us. If we were using a true nonce, we'd have no
* reliable way of passing it to our content scripts.
*/
const nonce_source = [
policy.mapping,
policy.payload.identifier,
url,
secret
];
policy.nonce = sha256(nonce_source.join(":"));
}
}
if (!policy.allow)
policy.csp = make_csp(policy.nonce);
return policy;
}
#EXPORT decide_policy
#EXPORT () => ({allow: false, csp: make_csp()}) AS fallback_policy
#IF NEVER
/*
* Note: the functions below were overeagerly written and are not used now but
* might prove useful to once we add more functionalities and are hence kept...
*/
function relaxed_csp_eval(csp) {
const new_csp_list = [];
for (const directive of csp.split(";")) {
const directive_words = directive.trim().split(" ");
if (directive_words[0] === "script-src")
directive_words.push("'unsafe-eval'");
new_csp_list.push(directive_words);
}
new_policy.csp = new_csp_list.map(d => `${d.join(" ")}';`).join(" ");
}
function relax_policy_eval(policy) {
const new_policy = Object.assign({}, policy);
return Object.assign(new_policy, {csp: relaxed_csp_eval(policy.csp)});
}
#EXPORT relax_policy_eval
#ENDIF
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