Nmap scripting engine

Nmap Scripting Engine
(NSE)

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3 Sections Todays Agenda – NSE
1. Nmap Overview - 10 Mins

 Nmap ?
 Basic Scan Options

2. NSE Overview – 20 Mins
 Existing Categories
 How to use these available scripts ?
 Use of 2 sample scripts
3. How to write your own NSE script ?- 20 Mins

 Baiscs on writing NSE Script
 Write a script to find website title “Null”

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Nmap Overview

10 Mins

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Nmap (Network Mapper) – Overview
 Was written 15 years back as a port scanner by Gordon Lyon (Fyodor)
Port Scanner : Used to discover hosts and services on a computer network by sending specially crafted
packets to the target host and then analyzes the responses.

 Current Stable release : version 6.40 (Free)
 Have CLI and GUI interfaces. GUI called Zenmap/NmapFE/Xnmap(Mac)

 Linux, Mac OS X, Windows, Solaris, Free/Net/OpenBSD are supported.
 Why Nmap? – Fast, free, easy to use, flexible in scan options, portable with
multiple OS, large community support and neat documentation.

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How to use Nmap ? (As port scanner)
How to start with nmap ?
Single Host
# nmap 220.220.220.2xx
# nmap Target.Nmaptest.com

What i plan to scan ?
IP Address : 220.220.220.2xx
Subnet : /24
Host Name : Target.Nmaptest.com

Subnet
# nmap 220.220.220.2xx
Mulitple Targets
# nmap 220.220.220.2x1 220.220.220.2x5

IP Address Range
# nmap 220.220.220.2x1-100
Random Ip Address
(Make a list in text file - list.txt)
# nmap -sL list.txt
Sepcific ports
# nmap -p21,23,80,443 220.220.220.2xx
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Nmap Basic Scan Output

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Nmap Switches
Scan Options :
-sS/sT/sA: TCP SYN/Connect()/ACK/
-sU: UDP Scan
-sN/sF/sX: TCP Null, FIN, and Xmas
Specify Ports :
-p <port ranges>: scan specified ports
Eg: -p22; -p1-65535; -p U:53,111,137,
-F: Fast mode - Scan fewer ports
-r: Scan ports consecutively
--top-ports <number>:Scancommon ports
OS Detection :
-O: Enable OS detection

Host Discovery :
-sL: List Scan - simply list targets to scan
-sn: Ping Scan - disable port scan
-Pn: Treat hosts as online, skip H discovery
Time Change :
-T<0-5>: Set timing template (higher is faster)
IP version 6 scan :
-6 : Enable IPv6 scanning
Output:
-oN : Output scan in normal,
-oX : Output scan XML

How to use them together , just chain them :
# nmap [ <Scan Type> ...] [ <Options> ] { <target specification> }
e.g.
# nmap –sS –sU -T4 -A -v -Pn 220.220.220.211
#namp –T4 –randomize-host –iL list.txt –oX scanresults.xml

Cheet Sheet : http://pentestlab.wordpress.com/2012/08/17/nmap-cheat-sheet/
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Nmap Scripting Engine (NSE) – Introduction
 Nmap Scripting Engine (NSE) allows users to write simple scripts to automate
networking and pentesting tasks.

 NSE include network discovery, sophisticated version detection, vulnerability detection
and even for vulnerability exploitation.
 Uses Lua programming. Lua also used in Wireshark, snort and some Web App. F/W.
 Current download of nmap comes with 437 scripts.
 Scrips are categratized into various caterogies based on the usage. Every script needs
to be identified by a category. E.g. categories = {"intrusive", "auth"}
 Nmap.org also provides libary details for writting your own scripts.
NSE Docuemntation : http://nmap.org/nsedoc/
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NSE Script Categories
auth

These scripts deal with authentication credentials (or bypassing them)
on the target system. E.g. ftp-anon, oracle-enum-users

broadcast

Scripts in this category typically do discovery of hosts not listed on the
command line by broadcasting on the local network. E.g. newtargets

brute

Use brute force attacks to guess authentication credentials of a remote
server. E.g. http-brute, oracle-brute, snmp-brute

default

- A option with namp E.g. http-auth, ftp-anon

discovery

try to actively discover more about the network by querying public
registries, SNMP-enabled devices, directory services, and similar.
E.g. html-title, smb-enum-shares

dos

Denial of service scripts. E.g. broadcast-avahi-dos

Exploit

Scripts aim to actively exploit some vulnerability. E.g. http-fileuploadexploiter

external

Connects to 3rd party database to get info. E.g. Whois

fuzzer

Designed to fuzz. E.g. dns-fuzz

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NSE Script Categories
intrusive

Intrusive scripts E.g. snmp-brute, http-open-proxy

malware

Scripts test whether the target platform is infected by malware or
backdoors E.g. smtp-strangeport, auth-spoof

Safe

Most of these perform general network discovery. E.g. html-title, sshhostkey

Version

Works with –sV switch with nmap. E.g. skypev2-version, pptp-version

vuln

Check for specific known vulnerabilities and generally only report
results if they are found E.g. realvnc-auth-bypass and afp-path-vuln

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How to use existing NSE scripts?
Existing 437 scripts with v6.40
Every Script will have category defined by the author, this will also be used to use the
script with nmap scanning. E.g. domino-enum-users

Usage :
# nmap –sC (equivalent to --script=default; sC == script)
e.g #nmap x.x.x.x –sC
# nmap --script <filename>|<category>|<directory>|<expression>
e.g # nmap --script all x.x.x.x (Runs all avalable Scripts on ip x.x.x.x)
# namp –script safe,external, http-auth x.x.x.x
# nmap --script <scriptname> --script-args <args>
e.g. nmap --script snmp-sysdescr --script-args snmpcommunity=admin example.com
#nmap --script-help <scriptname > ( provides help on the script)
e.g. #nmap --script-help http-auth
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Sample Nmap NSE Scan Output

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January 2010
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How to write your own NSE script ?

20 Mins

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Writing your own NSE script !!
 Writing NSE script is simple !!!
 You write them in Lua
 Pretty set structure for the script.

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HR Portal Script (Oracle_Fussion.nse)
1.
description Field : The description field describes what a script is testing for and
any important notes the user should be aware of.
description = [[Attempts to retrieve HR Potral hosted on Oracle Fussion App.
]]

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]]
2. author Field : The author field contains the script authors' names and can also
contain contact information
author = “Sudhir Babu B <sudhir@securitytest.com >"

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]]
author = “Sudhir Babu B <sudhir@securitytest.com >“
3. categories Field : The categories field defines one or more categories to which a
script belongs.
categories = {"default", "discovery", "safe"}

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]]
categories = {"default", "discovery", "safe"}
4. license Field (Optional) – Provide appropriate licence.
license = "Same as Nmap--See http://nmap.org/book/man-legal.html”"

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]]
license = "Same as Nmap--See http://nmap.org/book/man-legal.html”“
categories = {"default", "discovery", "safe“}
----------------------------------------------------------------5. As it’s http app. we need the follwoing libary :
require “shortport” --- ???
require “hhtp”

Why we need short port ?
“portrule” defines when nmap when to trigger the script.
“shortport” module simplify the this process as common use for portrule

6. Portrule = shortport.port_or_service({80, 443, 8081},{“http”,”https”})
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]]
require “shortport”
require “hhtp”
Portrule = shortport.port_or_service({80, 443, 8081},{“http”,”https”})
7. Action funtion, what to do when portrule triggers.

action = function(host, port)
-- Define action
end

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]]
require “hhtp”
-- just checking if the directory exist with 200 OK response
local stats = http.get (host, port, ‘/Oracle_Fusion/’).status
end

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]]
require “hhtp”
-- just checking if the directory exist with 200 OK response
Need to add response : what if ?
if stats == 200 then
return “Internal HR Portal Found”
end
end
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]]
require “hhtp”
if stats == 200 then
return “Internal HR Portal Found”
end
end

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Thanks for your time & patience

babusudhirb@gmail.com

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NSE – Example Y ??

Slide 10

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Nmap scripting engine

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