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/**
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* This file is part of Haketilo.
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*
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* Function: Determining what to do on a given web page.
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*
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* Copyright (C) 2021 Wojtek Kosior
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* As additional permission under GNU GPL version 3 section 7, you
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* may distribute forms of that code without the copy of the GNU
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* GPL normally required by section 4, provided you include this
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* license notice and, in case of non-source distribution, a URL
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* through which recipients can access the Corresponding Source.
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* If you modify file(s) with this exception, you may extend this
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* exception to your version of the file(s), but you are not
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* obligated to do so. If you do not wish to do so, delete this
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* exception statement from your version.
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*
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* As a special exception to the GPL, any HTML file which merely
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* makes function calls to this code, and for that purpose
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* includes it by reference shall be deemed a separate work for
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* copyright law purposes. If you modify this code, you may extend
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* this exception to your version of the code, but you are not
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* obligated to do so. If you do not wish to do so, delete this
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* exception statement from your version.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*
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* I, Wojtek Kosior, thereby promise not to sue for violation of this file's
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* license. Although I request that you do not make use of this code in a
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* proprietary program, I am not going to enforce this in court.
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*/
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#IMPORT common/patterns_query_tree.js AS pqt
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#FROM common/sha256.js IMPORT sha256
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/*
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* CSP rule that either blocks all scripts or only allows scripts with specified
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* nonce attached.
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*/
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function make_csp(nonce)
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{
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const rule = nonce ? `nonce-${nonce}` : "none";
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const csp_list = [
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["prefetch-src", "none"],
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["script-src-attr", "none"],
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["script-src", rule],
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["script-src-elem", rule]
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];
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return csp_list.map(([a, b]) => `${a} '${b}';`).join(" ");
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}
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function decide_policy(patterns_tree, url, default_allow, secret)
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{
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const policy = {allow: default_allow};
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try {
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var payloads = pqt.search(patterns_tree, url).next().value;
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} catch (e) {
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console.error("Haketilo:", e);
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policy.allow = false;
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policy.error = {haketilo_error_type: "deciding_policy"};
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}
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if (payloads !== undefined) {
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/*
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* mapping will be either the actual mapping identifier or "~allow" if
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* we matched a simple script block/allow rule.
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*/
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policy.mapping = Object.keys(payloads).sort()[0];
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const payload = payloads[policy.mapping];
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if (policy.mapping === "~allow") {
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/* Convert 0/1 back to false/true. */
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policy.allow = !!payload;
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} else /* if (payload.identifier) */ {
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policy.allow = false;
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policy.payload = payload;
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/*
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* Hash a secret and other values into a string that's unpredictable
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* to someone who does not know these values. What we produce here
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* is not a true "nonce" because it might get produced multiple
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* times given the same url and mapping choice. Nevertheless, this
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* is reasonably good given the limitations WebExtension APIs and
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* environments give us. If we were using a true nonce, we'd have no
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* reliable way of passing it to our content scripts.
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*/
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const nonce_source = [
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policy.mapping,
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policy.payload.identifier,
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url,
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secret
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];
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policy.nonce = sha256(nonce_source.join(":"));
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}
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}
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if (!policy.allow)
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policy.csp = make_csp(policy.nonce);
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return policy;
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}
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#EXPORT decide_policy
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#EXPORT () => ({allow: false, csp: make_csp()}) AS fallback_policy
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