/**
 * Hachette injecting policy to page using webRequest
 *
 * Copyright (C) 2021 Wojtek Kosior
 * Copyright (C) 2021 jahoti
 * Redistribution terms are gathered in the `copyright' file.
 */

/*
 * IMPORTS_START
 * IMPORT TYPE_PREFIX
 * IMPORT get_storage
 * IMPORT browser
 * IMPORT is_chrome
 * IMPORT is_mozilla
 * IMPORT gen_unique
 * IMPORT gen_nonce
 * IMPORT is_privileged_url
 * IMPORT url_item
 * IMPORT url_extract_target
 * IMPORT sign_policy
 * IMPORT query_best
 * IMPORT sanitize_csp_header
 * IMPORTS_END
 */

var storage;

const csp_header_names = new Set([
    "content-security-policy",
    "x-webkit-csp",
    "x-content-security-policy"
]);

/* TODO: variable no longer in use; remove if not needed */
const unwanted_csp_directives = new Set([
    "report-to",
    "report-uri",
    "script-src",
    "script-src-elem",
    "prefetch-src"
]);

const report_only = "content-security-policy-report-only";

function url_inject(details)
{
    if (is_privileged_url(details.url))
	return;

    const targets = url_extract_target(details.url);
    if (targets.current)
	return;

    /* Redirect; update policy */
    if (targets.policy)
	targets.target = "";

    let [pattern, settings] = query_best(storage, targets.base_url);
    /* Defaults */
    if (!pattern)
	settings = {};

    const policy = encodeURIComponent(
	JSON.stringify({
	    allow: settings.allow,
	    nonce: gen_nonce(),
	    base_url: targets.base_url
	})
    );

    return {
	redirectUrl: [
	    targets.base_url,
	    '#', sign_policy(policy, new Date()), policy,
	    targets.target,
	    targets.target2
	].join("")
    };
}

function headers_inject(details)
{
    const targets = url_extract_target(details.url);
    /* Block mis-/unsigned requests */
    if (!targets.current)
	return {cancel: true};

    let orig_csp_headers = is_chrome ? null : [];
    let headers = [];
    let csp_headers = is_chrome ? headers : [];

    const rule = `'nonce-${targets.policy.nonce}'`;
    const block = !targets.policy.allow;

    for (const header of details.responseHeaders) {
	if (!csp_header_names.has(header)) {
	    /* Remove headers that only snitch on us */
	    if (header.name.toLowerCase() === report_only && block)
		continue;
	    headers.push(header);

	    /* If these are the original CSP headers, use them instead */
	    /* Test based on url_extract_target() in misc.js */
	    if (is_mozilla && header.name === "x-orig-csp") {
		let index = header.value.indexOf('%5B');
		if (index === -1)
		    continue;

		let sig = header.value.substring(0, index);
		let data = header.value.substring(index);
		if (sig !== sign_policy(data, 0))
		    continue;

		/* Confirmed- it's the originals, smuggled in! */
		try {
		    data = 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);
		}

		orig_csp_headers = csp_headers = null;
		for (const header of data)
		    headers.push(sanitize_csp_header(header, rule, block));
	    }
	} else if (is_chrome || !orig_csp_headers) {
	    csp_headers.push(sanitize_csp_header(header, rule, block));
	    if (is_mozilla)
		orig_csp_headers.push(header);
	}
    }

    if (orig_csp_headers) {
	/** Smuggle in the original CSP headers for future use.
	  * These are signed with a time of 0, as it's not clear there
	  * is a limit on how long Firefox might retain these headers in
	  * the cache.
	  */
	orig_csp_headers = encodeURIComponent(JSON.stringify(orig_csp_headers));
	headers.push({
	    name: "x-orig-csp",
	    value: sign_policy(orig_csp_headers, 0) + orig_csp_headers
	});

	headers = headers.concat(csp_headers);
    }

    /* To ensure there is a CSP header if required */
    if (block) {
	headers.push({
	    name: "content-security-policy",
	    value: `script-src ${rule}; script-src-elem ${rule}; ` +
		"script-src-attr 'none'; prefetch-src 'none';"
	});
    }

    return {responseHeaders: headers};
}

async function start_policy_injector()
{
    storage = await get_storage();

    let extra_opts = ["blocking", "responseHeaders"];
    if (is_chrome)
	extra_opts.push("extraHeaders");

    browser.webRequest.onBeforeRequest.addListener(
	url_inject,
	{
	    urls: ["<all_urls>"],
	    types: ["main_frame", "sub_frame"]
	},
	["blocking"]
    );

    browser.webRequest.onHeadersReceived.addListener(
	headers_inject,
	{
	    urls: ["<all_urls>"],
	    types: ["main_frame", "sub_frame"]
	},
	extra_opts
    );
}

/*
 * EXPORTS_START
 * EXPORT start_policy_injector
 * EXPORTS_END
 */