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| 'use strict';
/**
Code partially adapted from node-cef logging library, used under
MPL 2.0 License.
*/
const _ = require('lodash');
const util = require('util');
const requiredParams = ['vendor', 'product', 'version', 'signature', 'name', 'severity'];
const CEF_VERSION = '0';
var Formatter = module.exports = function Formatter(config) {
config = config || {};
this.vendor = config.vendor || 'Menlo Security';
this.product = config.product || 'MSIP';
this.version = config.version || '1.0';
this.signature = config.signature || '100';
this.severity = config.severity || '5';
return this;
};
Formatter.prototype = {
/**
* Convert a string to a legal CEF string
*
* @param text
* (string) The text to filter
*
* According to the CEF:0 spec, page 4:
*
* - Escape pipes (|) in the prefix, but not necessarily the
* extension.
*
* - Escape backslashes (\) in the prefix, but not necessarily the
* extension.
*
* - Escape equal signs (=) in the extensions, but not necessarily
* the prefix.
*
* - Multi-line fields can be sent by Common Event Format (CEF) by
* encoding the newline character as \n or \r. Multiple lines
* are only allowed in the value part of the extensions.
*
* Therefore we have two text sanitizers:
*
* - sanitizePrefixField()
* - sanitizeExtensionValue()
*
*/
inputToString: function inputToString(input) {
if (typeof input === 'undefined') {
return typeof input;
}
else if (typeof input === 'object') {
return JSON.stringify(input, null, 2);
}
return input.toString();
},
/**
* Escape pipes and backslashes in the prefix. Equal signs are ok.
Newlines are forbidden.
*/
sanitizePrefixField: function sanitizePrefixField(input) {
input = this.inputToString(input);
var output = '';
var nextChar = '';
for (var i = 0; i < input.length; i++) {
// A backslash is already escaping the next char?
if (input[i] === '\\') {
nextChar = input[i+1];
if (/[\\|]/.test(nextChar)) {
output += '\\' + nextChar;
i += 1;
} else {
output += '\\\\';
}
// An unescaped backslash or pipe?
} else if (/[\\|]/.test(input[i])) {
if (input[i-1] !== '\\') {
output += '\\' + input[i];
}
// Replace newlines with a space to maintain some legibility
} else if (/[\r\n]/.test(input[i])) {
output += ' ';
} else {
output += input[i];
}
}
return output;
},
/**
* Escape equal signs in the extensions. Canonicalize newlines.
* CEF spec leaves it up to us to choose \r or \n for newline.
* We choose \n as the default.
*/
sanitizeExtensionValue: function sanitizeExtensionValue(input) {
input = this.inputToString(input);
var output = '';
for (var i = 0; i < input.length; i++) {
// Escape equal signs
if (input[i] === '=') {
if (input[i-1] !== '\\') {
output += '\\' + input[i];
} else {
output += input[i];
}
// Canonicalize whitespace
} else if (input[i] === '\r') {
// convert \r\n to \n
if (input[i+1] === '\n') {
output += '\n';
i += 1;
// convert plain \r to \n
} else {
output += '\n';
}
} else {
output += input[i];
}
}
return output;
},
/**
* Format log message extensions
*
* @param extensions
* (object) A dictionary of key/value pairs to format
*
* Returns a string like 'key1=value1 key2=value2'. Whitespace in
* values is preserved (with some possible modification of
* newlines).
*/
formatExtensions: function formatExtensions(extensions) {
if (typeof extensions !== 'object') {
return '';
}
// Convert extensions dictionary to a string like 'food=pie barm=42'
var extensionArray = [];
var value = '';
Object.keys(extensions).forEach(function(key) {
value = extensions[key];
extensionArray.push(util.format('%s=%s',
key, this.sanitizeExtensionValue(value)));
}.bind(this));
return extensionArray.join(' ');
},
/**
* Format KVP messages
*
* @param extensions
* (object) A dictionary of key/value pairs to format
*
* Returns a string like "key1='value1' key2='value2'". Whitespace in
* values is preserved (with some possible modification of
* newlines).
*/
formatExtensionsKVP: function formatExtensionsKVP(extensions) {
if (typeof extensions !== 'object') {
return '';
}
// Convert extensions dictionary to a string like 'food=pie barm=42'
var extensionArray = [];
var value = '';
var string_to_push = '';
Object.keys(extensions).forEach(function(key) {
value = this.sanitizeExtensionValue(extensions[key]);
if (value.indexOf(' ') !== -1) {
string_to_push = util.format("%s='%s'", //jshint ignore:line
key, value);
} else {
string_to_push = util.format('%s=%s',
key, value);
}
extensionArray.push(string_to_push);
}.bind(this));
return extensionArray.join(' ');
},
/*
* Find the event type from the payload.
*/
getEventType: function getEventType(payload) {
var potential_events = ['file_download', 'file_upload',
'flash', 'ssl_inspection_exception', 'page_request'];
var event_type = 'unknown_event_type';
_.forEach(potential_events, function(potential_event) {
if (payload[potential_event] === 'true') {
event_type = potential_event;
return false;
}
});
return event_type;
},
/*
* Accept dictionary containing log values. Create a key called extensions that
* correlates to the extension dictionary.
*/
transformPayloadKVP: function transformPayloadKVP(payload) {
//elements of the logs that could have multiple elements
var list_extensions = {'server_top_level_details': 'threats',
'top_level_risks': 'threat_types', 'cats': 'categories',
'dest_ips': 'dst'};
var necessary_fields = new Set(['pe_action', 'protocol', 'userid',
'request_type','browser_and_version',
'x-client-ip', 'url', 'event_time', 'referer', 'response_code',
'content-type', 'user-agent']);
var payload_info = {};
_.forEach(payload, function (value, key) {
if (key in list_extensions && value.length > 0) {
payload_info[list_extensions[key]] = value.join(', ');
} else if (necessary_fields.has(key) && value) {
payload_info[key] = value;
} else if (_.contains(requiredParams, key) && value) {
payload_info[key] = value;
}
});
payload_info.name = this.getEventType(payload);
return payload_info;
},
/*
* Accept dictionary containing log values. Create a key called extensions that
* correlates to the extension dictionary. Translate all possible keys to their
* CEF equivalent according to the HP Arcsight Standards.
* See Logging Document: https://goo.gl/ZNKzJc
*/
transformPayload: function transformPayload(payload) {
//elements of the logs that could have multiple elements
var list_extensions = {'server_top_level_details': 'threats',
'top_level_risks': 'threat_types', 'cats': 'categories',
'dest_ips': 'dst'};
var cef_changes = {'pe_action': 'act', 'protocol': 'app', 'userid': 'suid',
'request_type': 'requestMethod',
'browser_and_version': 'requestClientApplication',
'x-client-ip': 'src', 'url': 'request', 'event_time': 'end',
'referer': 'referer', 'response_code': 'responseCode',
'content-type': 'contentType', 'user-agent': 'requestClientApplication'};
var extensions = {};
var cef_info = {};
if (payload.browser_and_version !== 'undefined_undefined') {
payload['user-agent'] = payload.browser_and_version;
} else {
payload.browser_and_version = payload['user-agent'];
}
_.forEach(payload, function (value, key) {
if (key in list_extensions && value.length > 0) {
extensions[list_extensions[key]] = value.join(', ');
} else if (key in cef_changes && value) {
extensions[cef_changes[key]] = value;
} else if (_.contains(requiredParams, key) && value) {
cef_info[key] = value;
}
});
cef_info.extensions = extensions;
cef_info.name = this.getEventType(payload);
return cef_info;
},
addProductInfo: function addProductInfo(params) {
// If none supplied, use default vendor, product, version
if (! (params.vendor && params.product)) {
params.vendor = this.vendor;
params.product = this.product;
}
if (! params.version) {
params.version = this.version;
}
if (! params.severity) {
params.severity = this.severity;
}
if (! params.signature) {
params.signature = this.signature;
}
return params;
},
formatKVP: function formatKVP(params) {
params = this.transformPayloadKVP(params);
params = this.addProductInfo(params);
return this.formatExtensionsKVP(params);
},
formatCEF: function formatCEF(params) {
var err = null;
params = this.transformPayload(params);
var extensions = params.extensions;
params = this.addProductInfo(params);
// Check that required params are present and contain a value.
// If not, return an error.
var paramKeys = Object.keys(params);
requiredParams.forEach(function checkRequiredKeys(requiredKey) {
if (paramKeys.indexOf(requiredKey) === -1) {
err = new Error(util.format("Missing required key '%s' from params", //jshint ignore: line
requiredKey));
} else {
// Sanitize prefix fields
params[requiredKey] = this.sanitizePrefixField(params[requiredKey]);
}
}.bind(this));
if (err) {
return (err);
}
params.severity = parseInt(params.severity, 10);
// Build the CEF prefix
var output = util.format('CEF:%s|%s|%s|%s|%s|%s|%s',
CEF_VERSION,
params.vendor,
params.product,
params.version,
params.signature,
params.name,
params.severity);
// Add any extensions
if (extensions) {
output += '|' + this.formatExtensions(extensions);
}
return null, output;
}
};
|