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| 'use strict';
const fs = require('fs');
const config = require(__dirname + '/../config');
const uce_maps = require(__dirname + '/uce-maps');
const net = require('net');
// So far the classifiers are treating the arrays as matching any, not all.
// When such a requirement arises, we will add support for that.
// These functions return objects with an indicator of whether a match was
// found. If match is truthy, it must also contain a splits array indicating
// where in the input string the match or matches were found.
/**
* @function equals
* @desc Evaluates whether a given execution context field value equals any of
* the strings.
* @param {string} field - the value; may be falsy
* @param {array} names - the list of strings to match
* @return {object} match set to truthy, if field can be found in names, and
* sets splits reflecting the match
*/
function equals(field, names) {
const res = {
match: field && names.find(n => field === n)
};
Iif (res.match) {
res.splits = ['', res.match];
}
return res;
}
/**
* @function endsWith
* @desc Evaluates whether a given execution context field value ends with any
* of the strings.
* @param {string} field - the value; may be falsy
* @param {array} names - the list of strings to match
* @return {object} match set to truthy, if field ends with one of the
* substrings found in names, and sets splits reflecting the match
*/
function endsWith(field, names) {
const res = {
match: field && names.find(n => field.endsWith(n))
};
if (res.match) {
res.splits = [field.substring(0, field.length - res.match.length),
res.match];
}
return res;
}
/**
* @function domainEndsWith
* @desc Evaluates whether a given hostname ends with any of the domain names.
* @param {string} field - the value; may be falsy
* @param {array} names - the list of strings to match
* @return {object} match set to truthy, if field as a domain name ends with one
* of the substrings found in names, and sets splits reflecting the match
*/
function domainEndsWith(field, names) {
const r = endsWith(field, names.map(s => '.' + s));
Iif (r.match) {
return r;
}
return equals(field, names);
}
/**
* @function contains
* @desc Evaluates whether a given execution context field value contains any of
* the strings.
* @param {string} field - the value; may be falsy
* @param {array} names - the list of strings to match
* @return {object} match set to truthy, if field contains any one of the names,
* and sets splits reflecting the first match
*/
function contains(field, names) {
const res = {
match: field && names.find(n => field.indexOf(n) >= 0)
};
if (res.match) {
const idx = field.indexOf(res.match);
res.splits = [ field.substring(0, idx),
res.match,
field.substring(idx+res.match.length)
];
}
return res;
}
/**
* @function count
* @desc Counts the number of occurrences of substr in str.
* @param {string} str - the value; may be falsy
* @param {string} substr - the substring to look for
* @return {object} match set to an integer number of occurrences; if non-zero,
* sets splits reflecting all the occurrences of substr in str.
*/
function count(str, substr) {
const splits = str && str.split(substr);
if (!splits || splits.length === 1) {
return {match: 0};
}
const res = {
splits: splits.slice(1)
.reduce((a,b) => a.concat([substr, b]), [splits[0]])
};
// split will return at least one string
res.match = splits.length - 1;
return res;
}
/**
* @function isIP
* @desc Tests if a given string is a IP address.
* @param {string} host - the string representing a host name
* @return {object} match set to true, if it is a IP address, and sets splits
* to reflect the whole string matched
*/
function isIP(host) {
const res = {
match: net.isIP(host)
};
Iif (res.match) {
res.splits = ['', host];
}
return res;
}
/**
* @function* splitsToExplain
* @desc Flattens a tree of splits into an array of pairs ['plain'|'bold', s].
* This is to support explainURL, which combines plaintext URL parts with URL
* parts with splits. Nesting the parts of URLs is a natural way to represent
* the URL structure as described at
* https://nodejs.org/api/url.html#url_url_strings_and_url_objects
* - for example, query is a part of search, which is a part of path, which is a
* part of href.
*
* @param {array{subtree|string}} splits - an array of either strings
* representing the splits of the part of the URL, or subtrees, which get
* flattened recursively
*/
function* splitsToExplain(splits) {
let plain = true;
for(let s of splits) {
if (typeof s !== 'object') {
yield [plain, s];
} else {
yield* splitsToExplain(s);
}
plain = !plain;
}
}
/**
* @function explainURL
* @desc Given a object representing a part of URL that was analysed,
* reconstructs the text, making the selected part bold.
*
* Assumes this points to the env with the URL parts.
*
* Technically, explainURL supports arbitrary number of URL parts, but
* the use case is for just one part, since at the moment not more than one
* split can be stored in the global namespace.
*
* @param {object} orig - the original URL
* @param {object} url - parts of the URL that were split.
* @return {array} - plain and bold parts of the URL
*/
function explainURL(orig, url) {
// helper functions taking the splits from the given object,
// or, if that is not specified, from the original URL in the execution
// context
const field = n => url[n] || [orig[n] || ''];
const separator = (n, s) => [url[n] || orig[n] ? s: ''];
if (!url.href) {
if (!url.host && (url.hostname || url.port)) {
url.host = [
field('hostname'),
separator('port', ':'),
field('port')
];
}
if (!url.path) {
Iif (!url.search && url.query) {
url.search = [['?'], url.query];
}
Iif (url.pathname || url.search) {
url.path = [
field('pathname'),
field('search')
];
}
}
url.href = [
field('protocol'),
separator('protocol', '//'),
field('auth'),
separator('auth', '@'),
field('host'),
field('path'),
field('hash')
];
}
// flatten the tree to an array of plain and bold
const splits = Array.from(splitsToExplain(url.href));
// now reduce to a chain of tokens with alternating style:
// concatenate consecutive tokens of the same style
const res = [''];
let plain = true;
for(let s of splits) {
if (s[0] === plain) {
res[res.length - 1] += s[1];
} else {
res.push(s[1]);
}
plain = s[0];
}
return res;
}
const classifiers = {
uce_classifiers: {
/**
* @function uce_cats
* @desc Given the config of UCE categories to score map and a UCE
* response, computes the score. Additionally to the score and explain,
* maintains a trace indicating how much each category scored for logging
* purposes.
*/
uce_cats: (env, uce_response) => {
const trace = {};
const culprits = uce_response.webroot_cats
.map((c) => {
const score = env.scoreMap[c.name] || 0;
trace[c.name] = score;
return [c.name, score];
})
.filter((c) => c[1]);
const score = culprits.reduce((score, c) => score + c[1], 0);
return {
score: score,
trace: trace,
explain: score &&
{
cats: {
type: 'array',
val: culprits
.sort((a,b) => b[1] - a[1])
.reduce((acc, c) => {
const n =
uce_maps.webrootMailRiskCategoriesMap[c[0]] ||
c[0];
Eif (acc.indexOf(n) < 0) {
acc.push(n);
}
return acc;
}, []) // unique culprits
}
}
};
},
/**
* @function uce_reputation
* @desc Given the config and the UCE response, computes the score based
* on reputation.
*/
uce_reputation: (env, uce_response) => {
const reputations = uce_response.reputation &&
uce_maps.ipReputation(uce_response.reputation) ||
[];
Eif (reputations.find(r => r[0] === 'ok')) {
return {score: 0};
}
if (reputations.find(r =>
['dns timeout','dns error'].indexOf(r[0]) >= 0
)) {
return {score: env.uncertainty_weight};
}
return {
score: env.weight,
explain: {reputation: {
type: 'array',
val: Array.from(new Set(reputations.map(r => r[1])))
}}
};
},
/**
* @function uce_malware
* @desc Given the config and the UCE response, computes the score based
* on the malware indicator.
*/
uce_malware: (env, uce_response) => {
const score = uce_response.malware === 'ok'? 0: env.weight;
return {
score: score,
explain: score && {
malware: [uce_maps.mdbCategories(uce_response.malware)]
}
};
},
dynamicDNS: (env, uce_response) => {
const dynDNS = uce_response.risk_factors &&
uce_response.risk_factors.dynDNS || {};
return {
score: dynDNS.explain ? env.weight: 0,
explain: dynDNS.explain && {
url: dynDNS.explain
}
};
},
/**
* @function alexaRank
* @desc Given a classification configuration with ranks sorted in
* descending order, and a UCE response with risk_factors, produces a
* score with explanation.
*/
alexaRank: (env, uce_response) => {
const rank = uce_response.risk_factors &&
uce_response.risk_factors.alexaRank || {};
const res = 'rank' in rank ?
env.ranks.find(a => a[0] <= rank.rank) || [0, 0]:
env.ranks[0];
return {
score: res[1],
explain: res[1] && {
rank: [res[2]]
}
};
}
},
/**
* A collection of URL classifiers that compute the score by looking at the
* URL as a string. They all take a parsed URL as the second argument.
*
* Their names are self-explanatory and correspond to the section in
* classification.json where config contains lists of strings to look for.
*/
url_classifiers: {
phishTarget: (env, url) => {
// NB: hostname component's classification overrides other factors.
// (e.g. 'http://www.ebay.com/?phish=google.com' is classified as
// non-phishing by virtue of 'www.ebay.com' being considered
// legitimate, despite the presence of '?phish=google.com')
let res = contains(url.hostname, env.value);
Iif (res.match) {
const parts = url.hostname.split('.').reverse();
const idx = parts.indexOf(res.match);
const secondary = ['co', 'com'];
// Ignore any matching gTLDs, second level domains, and a subset of
// third level domains.
if (idx === 0 || idx === 1 || (idx === 2 &&
secondary.indexOf(parts[1]) !== -1)) {
res.match = undefined;
}
return {
score: res.match? env.weight: 0,
explain: res.match &&
{url: explainURL(url, {hostname: res.splits})}
};
} else {
res = contains(url.href, env.value);
return {
score: res.match? env.weight: 0,
explain: res.match &&
{url: explainURL(url, {href: res.splits})}
};
}
},
exploitPath: (env, url) => {
const res = contains(url.path, env.value);
return {
score: res.match? env.weight: 0,
explain: res.match &&
{url: explainURL(url, {path: res.splits})}
};
},
dots: (env, url) => {
const res = count(url.hostname, '.');
const score = res.match < env.less_certain_threshold?
0:
res.match === env.less_certain_threshold?
env.less_certain_weight:
env.weight;
return {
score: score,
explain: score && {url: explainURL(url, {hostname: res.splits})}
};
},
dashes: (env, url) => {
const res = count(url.hostname, '-');
const score = res.match >= env.threshold? env.weight: 0;
return {
score: score,
explain: score && {url: explainURL(url, {hostname: res.splits})}
};
},
suspectCountry: (env, url) => {
const res = endsWith(url.hostname, env.value);
return {
score: res.match? env.weight: 0,
explain: res.match &&
{
url: explainURL(url, {hostname: res.splits}),
tld: [env.tldToCountry[res.splits[1]] || res.splits[1]]
}
};
},
badTLD: (env, url) => {
const res = endsWith(url.hostname, env.value);
return {
score: res.match? env.weight: 0,
explain: res.match &&
{
url: explainURL(url, {hostname: res.splits}),
tld: [res.splits[1]]
}
};
},
sketchyWebHost: (env, url) => {
const res = domainEndsWith(url.hostname, env.value);
const res1 = res.match? res: contains(url.hostname, env.cvalue);
return {
score: res1.match? env.weight: 0,
explain: res1.match &&
{
url: explainURL(url, {hostname: res1.splits})
}
};
},
hostIsIp: (env, url) => {
const res = isIP(url.hostname);
return {
score: res.match? env.weight: 0,
explain: res.match &&
{
url: explainURL(url, {hostname: res.splits})
}
};
},
httpInURL: (env, url) => {
const res = contains(url.path, env.value);
const res1 = !res.match && contains(url.hostname, env.value);
const score = res.match || res1.match? env.weight: 0;
const highlight = res.match?
{path: res.splits}:
{hostname: res1.splits};
return {
score: score,
explain: score &&
{
url: explainURL(url, highlight)
}
};
},
fakeTLD: (env, url) => {
let r = endsWith(url.hostname, env.value.map(tld => '-' + tld));
Eif (!r.match) {
for(let tld of env.value) {
r = contains(
url.hostname,
['-' + tld + '.', '-' + tld + '-', '.' + tld + '-']);
Iif (r.match) {
break;
}
}
}
return {
score: r.match? env.weight: 0,
explain: r.match && {
url: explainURL(url, {hostname: r.splits})
}
};
},
urlShorteners: (env, url) => {
const res = domainEndsWith(url.hostname, env.value);
return {
score: res.match? env.weight: 0,
explain: res.match &&
{
url: explainURL(url, {hostname: res.splits})
}
};
},
unusualPort: (env, url) => {
Eif (!url.port) {
return {score: 0};
}
const res = equals(url.port, env.value);
return {
score: !res.match? env.weight: 0,
explain: !res.match &&
{
url: explainURL(url, {port: ['', url.port]})
}
};
}
}
};
/**
* @function bind
* @desc A helper function performing common wrapping of classifiers. Given a
* classifier, a config, and the name to assign to it, wraps the processing to
* catch errors and reorganize the return value to include factor_name.
*
* If classifier throws an exception, it is propagated to the caller as an
* object with error, but no score.
*/
function bind(f, env, displayName) {
Iif (!f) {
throw new Error('Could not find a classifier for ' + displayName);
}
const risk_scorer = context => {
try {
const res = f(env, context);
if (res.score && res.explain) {
res.explain = {
factor_name: displayName,
attributes: res.explain
};
} else {
delete res.explain;
}
return res;
} catch(e) {
return {error: displayName + ': Not applicable: ' + e.message};
}
};
risk_scorer.displayName = displayName;
return risk_scorer;
}
const countryScore = env => {
const blacklist = new Set(env.blacklist);
return (env, countries) => {
const country_names = countries && countries.map(c => c.country.names.en);
const uniq = Array.from(new Set(country_names || []));
const res = uniq.filter(c => blacklist.has(c));
const score = res && res.length > 0 ? env.weight: 0;
return {
score: score,
explain: score && {
countries: res
}
};
};
};
/**
* @function init
* @desc The module initialization. It is done here, so that the module
* requiring it may choose non-default behaviour.
*
* Populates the contents of module.exports with the classification functions
* bound to config take from classificaiton.json (or the given stream).
*
* @param {object} cfg - the PnR-E config; will use the default, if omitted
* @param {string} stream - the classification.json contents; if omitted, will
* use the default file defined in cfg
*/
const init = (cfg, stream) => {
try {
delete exports.error;
cfg = cfg || config;
exports.MED_RISK_THRESHOLD =
parseInt(cfg.pnr_enforcement.med_risk_threshold, 10);
exports.HIGH_RISK_THRESHOLD =
parseInt(cfg.pnr_enforcement.high_risk_threshold, 10);
const CLASSIFICATION_JSON = cfg.pnr_enforcement
.url_classification_config;
const json = JSON.parse(
stream ||
fs.readFileSync(CLASSIFICATION_JSON).toString()
);
const c_uce_classifiers = classifiers.uce_classifiers;
const j_uce_classifiers = json.uce_classifiers;
exports.uceClassifiers = Object.keys(c_uce_classifiers)
.map(k => bind(c_uce_classifiers[k], j_uce_classifiers[k], k));
const c_url_classifiers = classifiers.url_classifiers;
const j_url_classifiers = json.url_classifiers;
exports.urlClassifiers = Object.keys(c_url_classifiers)
.map(k => bind(c_url_classifiers[k], j_url_classifiers[k], k));
exports.countryScore = bind(countryScore(json.countryScore),
json.countryScore,
'geolocation');
} catch(e) {
exports.error = e;
}
return exports;
};
module.exports = exports = {
init: init
};
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